Navigating the gestational surrogacy seas: the legalities and complexities of gestational carrier services

Abstract

This paper offers a comprehensive review of the gestational surrogacy process in the US, as well as internationally, focusing on the legal and ethical challenges that gestational carriers, intended parents, fertility providers, and OB/GYNs may face. The objective of this review article is to serve as an overview and provide information on legal, cultural, and ethical aspects of the decisions to pursue gestational surrogacy both for intended parents and gestational carriers in the US and globally. By understanding the surrogacy landscape and the obstacles, the surrogacy agencies and other involved parties can improve the surrogacy process to better serve all parties involved.

Introduction/background

Definitions/brief description of current practice

Gestational surrogacy is the process in which a gestational carrier (GC) gestates a pregnancy after transfer of an embryo from the intended parents (IPs) or donors. The embryo is created via the in vitro fertilization (IVF) process, which involves fertilization of an oocyte by sperm outside the body in an IVF laboratory. In contrast to gestational surrogacy in which the GC does not contribute their own oocyte to the implanted embryo, traditional surrogacy occurs when the surrogate is the genetic parent and provides their own oocyte to be fertilized via intrauterine insemination (IUI) or IVF with sperm from the IP father with subsequent transfer of the embryo back into their own uterus. It is increasingly rare to encounter a case of traditional surrogacy, so for the purposes of this paper the term surrogacy will be used to address gestational surrogacy. Depending on whether the surrogate is compensated for carrying the fetus, the surrogacy may be classified as commercial or altruistic; and the cost of surrogacy for IPs ranges accordingly. A contract needs to be drafted and signed by all parties involved, including GC, IP, partners, and spouses. It is both recommended and sometimes mandated for respective parties to have separate legal representation to negotiate the contract, understand the regulations around establishing parenthood, and avoid encountering conflict of interests [1]. A GC contract usually addresses issues such as parental rights, custody issues, health and life insurance, future contact between the parties, control over medical decisions during pregnancy, presence of IPs at doctors’ visits and delivery, financial considerations such as compensation, expenses, legal fees, child care during appointments, and even maternity clothes and diet/lifestyle during pregnancy.

Historical perspective and current trends

The practice of surrogacy is recorded historically across many cultures and time periods. Babylonian law and customs allowed this practice to avoid otherwise inevitable divorce [2]. In the biblical Book of Genesis, it is claimed that the servant Hagar served as a surrogate for the childless Sarah through her husband Abraham [3]. In addition, Rachel asked her maid Bilhah to carry a child with her husband Jacob. In Hindu mythology, Balram is considered the son of Devaki and elder brother of Lord Krishna despite being birthed by Rohini [4].

In modern times, with advancement of assisted reproductive technologies (ART), the feasibility and therefore the popularity of gestational surrogacy drastically increased. The first ever live birth through gestational surrogacy was in the United States (US), in 1985 [5]. Outside of the US, the first baby born via GC was in Australia in 1988 [6]. This event marked the beginning of surrogacy practices outside the US and contributed to the global development and acceptance of ART. In the US, the Center for Disease Control and Prevention (CDC) reports the number of GC cycles in the US increased from 727 in 1999 to 3432 in 2013, yielding more than 18,000 children over this period via gestational surrogacy [7]. Of the IVF clinics that reported to the CDC in 2020, 90% offer GC services [8].

One of the limiting factors is the high and continuously increasing cost associated with gestational surrogacy. In 2017, the cost of having a baby via GC in the US has surpassed $100,000. Compensation to the GC typically ranges from $25,000 to $45,000, excluding additional costs for travel, psychosocial, medical, legal, and administrative fees [9]. Families in need of a donor oocyte have the options to use a frozen or fresh donor eggs from a bank or live donor respectively, and this drives the prices up even further [9]. Given its considerable cost, pursuing gestational surrogacy may not be an option for families with lower socioeconomic status, especially in the US [10].

The challenges associated with gestational surrogacy are multifold. With this review, we aim to delineate current obstacles and challenges faced by IPs as well as GCs in the US and globally, as well as provide some guidance to the providers on working with IP-GC tandems.

Materials and methods

For the purposes of conducting this narrative review, a PubMed search was performed starting from 1985 (the first case of surrogacy in the US) using the following keywords: gestational surrogacy; commercial surrogacy; gestational carrier, LGBTQ + Surrogacy; third party reproduction; legal, ethical and cultural considerations in surrogacy. Then, 2507 articles were identified. After removal of irrelevant articles (1372), duplicates (35), manuscripts published in languages other than English (52), articles with missing full text (964), 84 articles were included in this review. Additionally, Google search was conducted to screen for international and US state legislatures and to identify the religions’ position on ART.

Ethical and legal considerations

Ethical challenges for intended parent and gestational carrier

There are several ethical considerations that complicate the practice of gestational surrogacy, including those that influence the legality of surrogacy and protections for surrogates and IPs, as well as varying degrees of expectations from the surrogates and IPs in terms of each parties’ role in this complicated collaboration [11]. Many countries and states cite ethical concerns as the primary reason for banning surrogacy [12]. Supporters of traditional family structures reject surrogacy altogether as an untraditional mode of reproduction [13]. Others raise concerns about the forced separation of the birth mother from the child, suggesting that a GC may not be capable of willfully preventing bonding with the child during pregnancy [14]. The principle of “mater semper certa est,” meaning “the mother of the child is always known,” is cited by anti-surrogacy proponents who argue that gestational surrogacy implies that a child’s mother is uncertain in non-traditional methods of reproduction [15]. Some opponents argue that commercial surrogacy is unethical as it commodifies the female body if surrogates receive compensation for “lending” their womb to a third party to carry their child [16]. Anti-commodification opponents of surrogacy often use language suggesting that surrogates lack choice or agency. For example, opponents have referred to the services that surrogates provide as “baby selling” or “renting their wombs” and argue that surrogates exercise no real “choice” if they are selling their body as a last resort to provide for their family [14, 17]. It is argued that in certain developing countries many women lack accessibility to the courts, and “unlike the United States,” the industry operates in the “shadow of the law” [18]. The argument continues that poor women are easier to take advantage of without the leverage of strict legal protections, such that women accept conditions and treatments that inherently benefit the receiving end of the party, specifically the IPs [18]. This supposedly allows for the exploitation of women with lower socioeconomic status, who are compelled by the compensation to be GCs without strict legal protections for their services. If surrogacy contracts are not comprehensive or adequately enforced, GCs face the possibility of only receiving compensation for favorable outcomes or desirable characteristics after carrying and delivering the child and might not receive the appropriate access to medical and psychiatric services during or after their pregnancy [19]. Providing payments for GCs may suggest that individual characteristics can be commodified by attributing a monetary value to preferences for weight, race, and willingness to engage in dietary practices, prenatal testing, pregnancy termination, multifetal reduction, or elective cesarean birth.

Regardless of the disputes surrounding the practice of surrogacy, legal protections for GCs and IPs are necessary for any form of surrogacy to be ethically acceptable [20]. For example, after research in India demonstrated that GCs were often not consulted regarding decisions about their own medical care and their decisions were not honored by their physicians, India moved to ban compensated gestational surrogacy on ethical grounds in 2015 [21, 22]. Later, in 2020 this law was revised and commercial gestational surrogacy was allowed, however limited to couples with infertility for over 5 years and/or pregnancy posing unacceptable health threat to the IP [23]. In the US, where contracts are strongly enforced, supporters of payments for surrogacy emphasize reproductive autonomy, such that each party should have the right to make their own decisions surrounding procreation, including whether to participate as a GC and be accordingly reimbursed [24]. Some argue that it is unethical to withhold “fair and just compensation” for GCs, as banning compensation prevents women from choosing for themselves to engage in surrogacy as a source of income [25]. Denying a woman the opportunity to be a GC strips her of her own bodily autonomy, implying that women with adequate legal protections and medical counseling remain incapable of making these decisions [26]. Studies in the US and globally regarding the impact of these arrangements have shown that when adequate protections are enforced with contracts, both GCs and IPs view their experience as positive and rewarding [27, 28]. Advocates also argue that banning surrogacy discriminates against IPs who have limited options to build a family and prevent potential GCs from seeking this compensated surrogacy as a means toward fulfillment and income [29]. In emphasizing the protection and autonomy of the GC, some argue that contractual surrogacy is only permissible if the GC can choose to end the pregnancy and revoke the agreement at any time [30]. For IPs in countries that prohibit surrogacy, the international commercialization of parenthood has incited global inequalities and promoted fertility tourism, where IPs may choose to travel to countries that permit or poorly regulate gestational surrogacy, leading to the potential for the unethical treatment of GC [31, 32]. The data indicate that over the course of 4 years the number of non-US residents seeking ART services in the US has more than doubled, with increased utilization of donor oocytes, preimplantation genetic testing, gestational surrogacy, compared to US residents [32].

On the other hand, IPs’ intrinsic psychologic distress associated with the inability to carry own pregnancy, relative unavailability of gestational surrogacy, high financial burden, and social stigma associated with use of GC services all add to the lower self-esteem and increase in anxiety and depression [33] [34]. For heterosexual couples with uterine factor infertility, there are three main options for parenting (not all three readily available), such as adoption, gestational surrogacy, and uterine transplant. For couples who are looking to have genetically related offspring, gestational surrogacy and possibly uterine transplant are the only viable options, with uterine transplantation being associated with significant risks and limited availability; for majority of families looking for biological family, gestational surrogacy seems to be the only option [35].

Same-sex male couples: challenges and legal considerations

It is the recommendation of the American College of Obstetricians and Gynecologists (ACOG) that “that the use of gestational surrogacy be restricted to situations in which carrying a pregnancy is biologically impossible or medically contraindicated for the IP(s)” [36]. Similarly, ASRM has set out indications for IPs interested in seeking a surrogate, including medical conditions that decrease the chances of viable pregnancy or situations that disallow patients to carry pregnancy, as would be the case with same-sex male couples [7, 9]. In 2015 in the US, 9.7% of same-sex male couples reported having children. When assessing cycles of assisted reproduction between 2009 and 2013, there were 648,000 cycles; from these, 457,000 cycles resulted in embryo transfer. Out of those, 14,682 (2.3%) used GCs. Diving in deeper into the 14,682 cycles, only 701 cycles had a reasons for treatment listed, of which 10.5% were listed as same-sex couples or lacking female partners [9]. The financial, logistical, and emotional nature of surrogacy can make it daunting for same-sex couples as determined by Goldberg et al. [37–39]. Relative scarcity of fertility services available for same-sex couples further complicates the accessibility [38–40]. Analyzing 547 websites for their content revealed that about 62% of infertility clinics and 42% of surrogacy agencies do not advertise directly to gay men [41]. High cost and minimal coverage for fertility services especially for third party reproduction lead to disparity against the socioeconomically disadvantaged and people of color even though evidence suggests increased infertility rates among these groups [42–46].

The process of pursuing surrogacy for male couples involves determining the genetic contributor within the couple, selecting an egg donor, finding a surrogate, and navigating the social ramifications while facing varying degrees of support. These decisions create an inherent imbalance in genetic relatedness to the child [47]. Often, male IPs might choose to take turns, with one partner providing sperm for the first child and then the other partner providing sperm for the next attempt, utilizing eggs from the same donor [48].

Variation in legislation in the US and more so internationally adds to the challenges associated with surrogacy perceived by same-sex couples. In fact, in the US, same-sex couples will cross state lines to areas with favorable surrogacy regulations [47]. The National Assisted Reproductive Technology Surveillance System from 2010 to 2014 indicates that 29.1% of GC cycles by US residents were performed in a state other than the state of residence of the IP.

More legal proceedings need to take place after the GC arrangements are made and underway. Legal parentage in GC arrangement is often defined by the court using pre-birth or post-birth order. A pre-birth order is obtained before the child’s birth, defining the IPs as the child’s only legal parents and ordering the IPs to be named on the child’s birth certificate, whereas post-birth order is obtained after the child’s birth [49].

Ultimately, it is important for all parties involved to address the numerous obstacles in pursuing and establishing parenthood.

Religious considerations

As gestational surrogacy increases in popularity worldwide with the notable improvements in ARTs, the practice of gestational surrogacy remains a contentious topic across different religions.

With technological advancement and globalization, the idea of surrogacy is now more finessed, and there is an increased public awareness in part due to the publicity by celebrities who pursued the pathway of surrogacy. While surrogacy finds its place within the political and sociocultural realms, it is eliciting multilevel moral and ethical dilemmas rooted in traditional and historical beliefs.

Catholicism

Over the years, Catholicism has offered a variety of perspectives surrounding ARTs and surrogacy, as contextualized from teachings in the Bible and interpreted among different Catholic theologists and figureheads. With the increased popularity of surrogacy over the past century, the Catholic Church’s views on surrogacy and ARTs emphasize the ethical implications surrounding the transmission of life. Pope Paul VI who served as head of the Catholic Church from 1963 to 1978 teaches that “The transmission of life is a most serious role in which married people collaborate freely and responsibly with God the creator” [50]. The Catholic Church confines the transmission of life to only occur within the marriage of husband and wife, such that artificial reproduction removes procreation from the unity of marriage and prevents the consummation of the marital bond [51]. In 1992, Catechism of Catholic Church stated that “techniques that entail the dissociation of husband and wife, by the intrusion of a person other than the couple (donation of sperm or ovum, surrogate uterus), are gravely immoral” and “[establish] the domination of technology over the origin and destiny of the human person” [50, 52]. Accordingly, Catholicism morally opposes both ARTs and surrogacy in upholding the unity of marriage as responsible for procreation without conflicting views of maternal identity [53].

Islam

Sharia law, the heart of Islamic religion, is considered the primary source toward which Muslims look for guidance. Although the Sharia law does not mention artificial reproduction, Islam supports treatment of infertility and pathway toward successful delivery of babies. The Shi’a guidelines permit surrogacy and third party donations. However, the current Sunni guidelines do not permit use of third party egg, spermatozoon, embryo, or uterus. IVF-embryo transfer is acceptable but the embryo must be a result of the husband and wife’s gametes. Using the husband’s spermatozoa is not permitted if the marriage ends through a divorce or the death of a husband. Donation of oocytes and embryos is not permitted [54–56].

Judaism

Judaism allows for artificial insemination with husband’s sperm. It does not permit artificial insemination with donor sperm as it raises the question of adultery and the legitimacy of the offspring. Some communities such as the halakhic Jewish permit Non-Jewish donor spermatozoa since the Jewish status is based in the maternal lineage. Jewish majority groups are supportive of IVF and embryo transfer; however, rabbinical authorities continue to debate on which factor to weigh more for establishing Jewish status: the egg donors or surrogates [54, 57]. According to the Maimonides, the intended mother is the mother, while some rabbinical authorities define motherhood as fixed on the removal of the child from the womb [57]. There is no complete consensus on surrogacy, but Israel legalized gestational surrogacy, and the process is regulated by the government. Jewish individuals living outside of Israel are also subject to Jewish tradition.

Hinduism

Hinduism is liberal when concerning artificial reproductive technologies. The acceptance could be rooted in sociocultural pressures related to infertility. Hindu literature, specifically the story of Mahabharata, depicts individuals resorting to surrogacy and extra-uterine manipulation in attempts to circumvent infertility and to propagate their lineage. In India, where 966.3 million Hindu’s reside, several popular celebrity couples have been transparent about the role gestational surrogacy played in welcoming their offspring [58]. The openness of Hindu society to surrogacy resulted in rapid growth of villages and institutions eager to supply the increasing demand for surrogates across the world [59]. Before banning entirely commercial surrogacy for foreigners in 2015 and for the domestic market in late 2021, the Indian surrogacy industry was estimated to be worth $375 million [60]. To be noted however, India consists of a population practicing more than 6 different religions including Hinduism, Jainism, Zoroastrianism, Buddhism, Christianity, Islam, and Judaism. The motivation behind this law is likely rooted in protecting rights of the vulnerable Indian surrogates as opposed to religion.

Buddhism

There are about 507 million individuals around the world who practice Buddhism. Generally, Buddhism, due to variation in practicing style based on geographic and sociocultural factors, has no consensus in regard to surrogacy, but tends to be liberal. Buddhism permits individuals, not just married ones, to utilize IVF and allows for sperm donation. The tradition emphasizes the right of such offspring, born through donated genetic material, to meet their genetic parents [50].

The above reflects various lines of thought and directives within each of the world’s major religions. Practices widely vary depending on the culture and political climate in each location. Given multicultural nature of modern societies, particularly in the US, familiarity with the principles of main religions potentially governing patient decision-making in regard to various ways for family building is important for personalized and respectful patient care.

Legislation

Trends in the US and globally

United States

Tables 1 and 2 illustrate global legislature trends by continent and separates 6 categories that most countries/states’ laws fall into: countries/regions that permit commercial gestational surrogacy for all couples, those that only permit commercial gestational surrogacy for select couples/individuals, countries/states that only permit altruistic gestational surrogacy for all, those that only permit altruistic gestational surrogacy for select couples/individuals, countries/states that do not permit any gestational surrogacy, and those that do not have distinct legislature around the gestational surrogacy.

Table 1.

Jurisdictions regarding gestational surrogacy per US state

US state	Notes	Jurisdictions permit commercial and altruistic surrogacy for all couples	Jurisdictions permit commercial and altruistic surrogacy for selected couples*	Jurisdictions permit altruistic surrogacy for all couples	Jurisdictions permit altruistic surrogacy for selected couples*	Jurisdictions ban all forms of surrogacy for everyone	Jurisdictions without surrogacy laws or regulation	Legislature and case laws
Alabama (AL)	No law prohibiting GS	x						AL Code § 26–17-801 (2012)
Alaska (AK)							x
Arizona (AZ)	Residents are prohibited to enter into GS contracts. The contracts are unenforceable					x		Ariz. Rev. Stat. Ann. § 25–218
Arkansas (AR)		x						Arkansas Code § 9–10-201
California (CA)		x						Cal. Fam. Code §§ 7960–7962
Colorado (CO)		x						HOUSE BILL 21–1022
Connecticut (CT)		x						2014-R-0074
Delaware (DE)		x						Gestational Carrier Agreement Act
Florida (FL)	IPs must be married, 18 years of age or older		x					Chapter 742
Georgia (GA)	No law prohibiting GS	x
Hawaii (HI)	No law prohibiting GS. Genetically unrelated IP required to complete adoption of the child	x						Report on Surrogacy and Gestational Carrier Agreements
Idaho (ID)	No law prohibiting GS. Genetically unrelated IP required to complete adoption of the child	x
Illinois (IL)		x						(750 ILCS 47/) Gestational Surrogacy Act
Indiana (IN)	GS contracts are unenforceable and against public policy					x		Article 20-FAMILY LAW: HUMAN REPRODUCTION (§§ 31–20-1–1—31–20-1–3)
Iowa (IA)		x					x
Kansas (KS)	No law prohibiting GS. Genetically unrelated married IP required to complete adoption of the child	x					x
Kentucky (KY)	No law prohibiting GS. Genetically unrelated married IP required to complete adoption of the child	x						Ky. Rev. Stat. § 199.590
Louisiana (LA)	GS contracts are allowed and limited to heterosexual married couples, genetically related to the child		x					HOUSE BILL NO. 1102
Maine (ME)		x						Title 19-A: DOMESTIC RELATIONS
Maryland (MD)		x						In re Roberto d.B., 399 Md. 267 (2007)
Massachusetts	Pre-birth parentage orders to be obtained by genetically related IPs	x						Hodas v. Morin (2004)
Michigan (MI)	As of 4/1/24, commercial surrogacy is supported by law	x						Michigan Family Protection Act
Minnesota (MN)	No law prohibiting GS						x
Mississippi (MS)	No law prohibiting GC						x
Missouri (MO)	No law prohibiting GS						x
Montana (MT)	No law prohibiting GS						x
Nebraska (NE)	GS contracts are unenforceable and against public policy Post birth parental orders may be granted to genetically related fathers					x		Neb. Rev. Stat. 6 25–21,200
Nevada (NV)		x						NRS 126.500–126.810
New Hampshire (NH)		x						N.H. Rev. Stat. § 168-B
New Jersey (NJ)		x						New Jersey Gestational Carrier Agreement Act
New Mexico (NM)	Single IPs may face difficulties obtaining parentage		x					NM Stat. Ann. § 40-11A-801
New York (NY)	Limited to married or unmarried heterosexual couple or single IPs who are genetically related to the child				x			NY Family Court Act §§ 581–203, 581–401, 581–406
North Carolina (NC)	Stepparent adoption is allowed, second parent adoptions are not allowed						x
North Dakota (ND)	GS allowed if at least one IP is genetically related to the child		x					N.D. Cent. Code §§14–18
Ohio (OH)		x						J.F. v. D.B., 116 Ohio St.3d 363, 2007-Ohio-6750
Oklahoma (OK)	GS agreement to be validated by court prior to embryo transfer	x						Oklahoma Gestational Agreement Act
Oregon (OR)	Pre-birth parentage orders available if at least one IP is genetically related to the child		x					Rights and obligations of children resulting from assisted reproduction
Pennsylvania (PA)	No law prohibiting GS; two unpublished case laws permit GS							J.F., Appellant v. D.B., Appellee. (2008)
Rhode Island (RI)	No law prohibiting GS; pre-birth parentage orders are readily available	x						RI Gen L § 15–8.1–801 (2020)
South Carolina (SC)		x						Mid-South Ins. Co. v Doe (2003)
South Dakota (SD)	No law prohibiting GS; pre-birth parentage orders are readily available						x
Tennessee (TN)	Pre-birth parentage orders available if at least one intended parent is genetically related to the child		x					2010 Tennessee Code Title 36-Domestic Relations Chapter 1-Adoption Part 1-General Provisions 36–1-102-Part definitions
Texas (TX)	GS agreements are available for married couples. Those must be validated by court prior to embryo transfer		x					“Tex. Fam. Code § 160.7” Tex. Fam. Code § 160.754
Utah (UT)	GS permitted for married intended parents		x					Utah Code Ann. §§ 78B-15–801 to 78B-15–809
Vermont (VT)		x						Title 15C: Parentage Proceedings
Virginia (VA)	Either court preapproval needed prior to embryo transfer or surrogate consent and report form filed by the IP with the birth registered within 3 days of child birth	x						Va. Code Ann. §§ 20–156 to 20–165
Washington DC		x						DC Law § 21–0255
Washington (WA)		x						2018 c 6 § 711
West Virginia (WV)		x						§61–2-14 h. Prohibition of purchase or sale of child; penalty; definitions; exceptions
Wisconsin (WI)		x						Paternity of F.T.R., Rosecky v. Schissel
Wyoming (WY)	Insufficient data regarding GC laws in the state of Wyoming						x	WY Stat § 14–2-403. (2015)

GS gestational surrogacy, GC gestational carrier, IP intended parent

^*Select couples may include heterosexual married couples, but not others (e.g., singles and same-sex couples)

Table 2.

International gestational surrogacy jurisdictions

Country	Notes	Jurisdictions permit commercial and altruistic surrogacy for all couples	Jurisdictions permit commercial and altruistic surrogacy for selected couples*	Jurisdictions permit altruistic surrogacy for all couples	Jurisdictions permits altruistic surrogacy for selected couples*	Jurisdictions ban all forms of surrogacy for everyone	Jurisdictions without surrogacy laws or regulation	Legislature and case laws
North America
Canada				x				Assisted Human Reproduction Act
Quebec Canada	GS contracts are unenforceable and void					x
Mexico	In 2021, the supreme court endorsed GS for Mexican and foreign nationals	x
Central and Southern America
Argentina						x		Assisted Reproduction Law No. 26.862
Brazil					x
Chile	Permitted only for married heterosexual infertile couples after 5 years of marriage				x			Law No. 20.418 on Assisted Reproduction
Colombia							x
Ecuador	Illegal to adopt a child for same-sex couples						x
Guatemala							x
Paraguay							x
Peru							x
Uruguay					x			Law No. 18.426 on Assisted Reproduction
Venezuela							x
Europe
Austria						x		Austrian Act on Reproductive Medicine
Belgium	No legal protection for IP, GC, or the future child						x	Law of 1 July 2021 on Surrogacy (Wet van 1 juli 2021 betreffende draagmoederschap)
Bulgaria						x		Bulgarian Family Code
Cyprus	There is no law prohibiting GS; the contracts between the IP and GC are unenforceable and lack validity						x	Law Regulating the Application of Medically Assisted Reproduction, Embryo, and Gamete Donation (69(I)/2015)
Denmark	Starting January 1, 2025, commercial surrogacy will be legalized			x				The Assisted Human Reproduction Act (AHRC)
Estonia	A transfer of ovarian tissue or a genetically unrelated embryo to a woman is punishable under a Penal Code					x		The Artificial Insemination and Embryo Protection Act
Finland						x		Assisted Fertility Treatments Act (1237/2006)
France						x		Civil Code, Bioethics Law
Germany						x		The Embryo Protection Act
Greece	Heterosexual couple or a single mother				x			Law 4272/2014
Iceland						x		Act on Artificial Fertilisation No. 55/1996
Ireland							x	A Supreme Court ruling in May 2023 noted the lack of legislation around surrogacy in Ireland
Italy						x		Law No. 40/2004 (Assisted Reproduction Techniques Act)(133)
Malta						x		Embryo Protection Act (Chapter 513 of the Laws of Malta)
Netherlands					x			Promoting commercial surrogacy is prohibited by law under articles 151b and 151c of the Criminal Code (in Dutch)
Norway	Not practiced/not addressed legally						x
Portugal	Since 2019, the prior permissive law was suspended					x		Law No. 25.2016
Poland	Family Code Law states that the mother of a child is the person who gave birth to them						x	Act on Family Planning, Human Embryo Protection, and Conditions of Legal Termination of Pregnancy
Serbia	Carrying pregnancy for another person is punishable with criminal sentence 3–10 years					x		Law on Biomedically Assisted Fertilization
Spain						x		Article 10(1) Law 14/2006 on Assisted Human Reproduction Techniques
Sweden						x		Swedish Parental Code
Switzerland	Egg, embryo donation, and GS are illegal					x		Bundesgesetz über die medizinisch unterstützte Fortpflanzung (Fortpflanzungsmedizingesetz, FMedG) vom 18. Dezember 1998
Ukraine		x						Family Code of Ukraine and Order No. 787
UK	The GS agreements are unenforceable			x
Asia
Cambodia						x		Proclamation on the Principles for Managing the Process of Surrogacy, 2016(135)
China	Despite the ban, reports of underground surrogacy agencies have flourished as the ban was limited to only medical personnel (134)					x		National Health and Family Planning Commission Notice, 2001
Hong Kong					x			Human Reproductive Technology Ordinance
India	Restricted to married couples of at least 5 years with documented infertility				x			Surrogacy (Regulation) Act, 2021
Israel	Permitted if at least one IP is genetically related to the child and GC is not related to the child		x					The Surrogacy Law (5746–1996)
Iran	Permitted for heterosexual married local and foreign couples		x					Iranian Civil Code and Medical Ethics Council Guidelines (136, 137)
Japan						x		Article 4–2 of the Act on the Prohibition of Human Cloning and Other Practices (Hourei 143 of 2001)
Kazakhstan	Permitted for heterosexual married local and foreign couples		x					Law on the Rights of the Child (2002) and Civil Code (1999)
Malaysia	ART services are not permitted for unmarried/same-sex couples						x	No specific law
Nepal	Altruistic GS is only allowed for infertile heterosexual married residents				x			Surrogacy (Regulation) Act 2064
Philippines							x
Republic of Georgia	Permitted only for residents of Georgia and financial compensation is illegal				x			Law on Gestational Surrogacy June 2023
Russian Federation		x						Family Code of the Russian Federation (Federal Law No. 143-FZ)
Saudi Arabia						x		Fatwa No. 240, issued by the Permanent Committee for Scholarly Research and Ifta (citation 64)
Singapore						x		Human Reproductive Technology Act, 2017
South Korea							x
Thailand	Restricted to altruistic GS for married couples of at least 3 years with documented infertility				x			Protection of Children Born from Assisted Reproductive Technologies Act B.E. 2558
Vietnam					x			Law on Marriage and Family 2014
Africa
Nigeria							x
Kenya	One of few countries with legally allowed commercial surrogacy	x						Assisted Reproductive Technology Act (No. 33 of 2020)
South Africa	Judicial confirmation of GS agreement required prior to initiation of pregnancy	x						Children’s Act of 2005
Australia and Oceania
Australia	Majority of the states allow altruistic surrogacy for all couples			x				Australia Surrogacy Act 2008
New Zealand				x

GS gestational surrogacy, GC gestational carrier, IP intended parent

^*Select couples may include heterosexual married couples, but not others (e.g., singles and same-sex couples)

In the US, each state determines its surrogacy law, resulting in mixed laws and regulations across the country (Table 1). Overall, the legislative trend is toward legalizing surrogacy where it is illegal or providing a comprehensive framework for industries that operate without legal regulation [61]. Baby M’s case in 1988 set the precedent for New York’s ban on compensated surrogacy, while Johnson vs. Calvert in 1993 determined California’s surrogacy laws permitting compensation [62]. In February 2021, New York legalized gestational surrogacy through the Child-Parent Security Act and established guidelines for surrogate compensation [63].

While states such as Maryland have no regulation surrounding gestational surrogacy, it was implicitly approved by the highest court in Maryland in the Roberto d.B case. Since 2011, legislation has been introduced in the Maryland legislature to regulate surrogacy, and every year it becomes more gestational surrogacy friendly [64].

In fact, in 2019, Nevada passed a bill prohibiting discrimination by insurance companies based on how the person became pregnant, thus ensuring coverage for surrogates [65]. Iowa’s Supreme Court upheld a commercial surrogacy contract in 2018, establishing the state as surrogacy friendly [66]. In 2013, Iowa’s Supreme Court in Gartner vs Iowa Department of Health ruled for the non-biological IP to be listed on the birth certificate regardless of sex [67].

Under the Gestational Surrogacy Act 2005, Illinois permits compensated surrogacy, and birth orders are not necessary to establish parentage as long as at least one IP is genetically related [68]. If the surrogate is married, then the Gestational Surrogacy Act requires the spouse to have agreed to take on the obligations required of the surrogacy and relinquish parental rights immediately upon birth [68].

Since 2008, under Utah Code Part 78B-15–8, compensated gestational surrogacy is valid and enforceable. The language in the code includes “her” and “husband” for gestational surrogate but keeps the pronouns for the IPs vague leading to assumption that same-sex IPs are protected under this law [69].

Wisconsin’s Supreme Court in ROSECKY V. SCHISSEL in 2015 upheld that surrogacy contracts were valid and enforceable but the contracts could not include termination of parental rights [70]. Wisconsin generally allows for pre-birth orders for married heterosexual IPs or single IP who can prove their genetic relationship to the child but it is not official until after birth.

West Virginia grants legal parenthood to opposite sex and same-sex IPs if at least one of them is genetically related to the child and has a preference for married IPs. In 2003, Texas Governor Rick Perry signed House Bill 729 making gestational surrogacy contracts enforceable. IPs do not have to be Texans or biologically related to the child to enter into a gestational surrogacy agreement and can be married to the opposite sex or same sex. Unmarried IPs are not protected under the bill, but the Texan court may grant legal parenthood regardless [71]. However, in 2022, after Roe v Wade was overturned, there is increasing uncertainty about how it might impact IVF treatments and surrogacy [72].

Mid-South Ins. Co. v Doe in 2003 established South Carolina as a gestational surrogacy friendly state. The GC must be a South Carolina resident, but IPs do not have to be South Carolina residents. Pre-birth orders are granted by South Carolina courts to IPs regardless of marital, biological, and sexual orientation [73]. Arkansas permits surrogacy; however, the surrogate is named the legal parent of the child. IPs must obtain birth orders to establish legal parenthood.

Massachusetts does not have specific laws but three cases have shaped the practice of surrogacy in this state. These cases include Hodas v Morin in 1998, Culliton v Beth Israel Deaconess Med. Ctr., and R.R. v. M.H. in 2001 [74, 75].

Since 2016, Louisiana’s Surrogacy Bill HB 1102 recognizes altruistic gestational surrogacy contracts but limits them to only married heterosexual couples and requires IPs, defined as a “man” and “woman,” to use their own gametes. These restrictions make it challenging for same-sex couples to pursue parenthood, especially gay couples. It is possible for non-biological married lesbian IPs to complete Intrafamily Adoption 6 months after the birth of the child to state their parentage [76].

Nebraska’s R.R.S Neb 25–21, 200 declared in 1988 compensated surrogacy contracts to be unenforceable and void and states that the biological father has all the rights with respect to the child. Residents, however, continue to participate in altruistic surrogacy and use post-birth orders to establish parentage. Interestingly, only the biological father can obtain post-birth order and intended mother must obtain stepparent adoption. For married same-sex couples, both parents cannot be listed on the birth certificate, but non-biological IP can adopt the child. This violates the rights for married same-sex couples established by Obergefell vs. Hodges and in Pavon vs. Smith in 2015, which reaffirmed equal access to all marriage-related rights including being listed on the birth certificate. In 2020, a 61-year-old Nebraskan woman gave birth to the child she carried for her son and his husband, the non-biological parent, who later adopted the child. In 2021, Nebraska Supreme Court protected the rights of married same-sex couples by permitting a married lesbian couple to adopt a 3-year-old child.

As of April 1, 2024, Michigan state repealed the law criminalizing surrogacy, and under the house bill 5207 “The Assisted Reproduction and Surrogacy Parentage Act,” altruistic and commercial gestational surrogacy are currently legal in the State [77].

Even though in 2022 Article 20 of Title 31 of the Indiana Code states gestational surrogacy contracts to be void and unenforceable, gestational surrogacy is practiced with courts granting pre-birth orders to IPs as long as they are genetically related to the child. Same-sex couples can establish parentage by proving genetic relation to the child or through stepparent or second parent adoption for the non-biological same-sex IP [78].

Arizona’s statute A.R.S 25–218 prohibits a person from entering a “surrogate parentage contract,” which is defined as “contract, agreement or arrangement where an individual agrees to implantation of a foreign embryo or conceive a child through natural or artificial insemination.” This statute determines the surrogate to be the legal parent, and if she’s married, then assigns her husband as the biological father, which is rebuttable. Landmark case Soos vs. The Superior Court (1994) established the ability of IPs to rebut the automatic assumption of GC’s parenthood, thus allowing IPs to obtain pre-birth orders as long as both are genetically related to the child [79]. While same-sex couples in Arizona can participate in gestational surrogacy, the individual without a genetic link to the child cannot establish parentage as of 2022. Currently, Arizona permits single members of LBTQ + and married same-sex couples to adopt regardless of gender and sexual orientation [80].

Alabama allows for post-birth orders, and parentage is reviewed on a case by case basis. Georgia courts are considered surrogacy friendly, and pre-birth orders are granted to IPs in Georgia regardless of the marital status, sexual orientation, or genetic relationship to the child. In Idaho, IPs must obtain post birth orders to establish parenthood, and non-biological IP can obtain parenthood through second-parent adoption, granted they have been residents of Idaho for greater than 6 months. North Carolina grants pre-birth orders; however, it is preferred for the IPs to be married, especially when it comes to establishing legal parenthood with a non-biological IP. Kentucky specifically prohibits compensated traditional surrogacy, and couples can obtain pre-birth orders as long as IP is genetically related to the child. The certificate can list same-sex IPs as parent-parent, father and mother, father or mother. Minnesota grants pre-birth orders and will recognize legal parentage of the IP genetically related to the child, and the non-biological IP must obtain legal parenthood via second parent adoption or stepparent adoption. In Hawaii, Chapter 584, HRS (Hawaii Revised Statutes) establishes that the woman, who gives birth, is the legal parent of the child, and if she’s married, then her husband is considered the legal father. As of 2018, there were 8 recorded cases of surrogacy adoptions in Hawaii since January 2016 [81].

Oregon recognizes both IPs as legal parents as long as one IP is genetically related to the child regardless of the IPs’ marital status and sexual orientation. Given lack of sufficient surrogacy data in Wyoming, IPs and surrogates should approach with caution in regard to compensation and post and pre-birth orders, especially, for same-sex couples. In 2020, the South Dakota House of Representatives introduced House Bill 1096 to prohibit commercial surrogacy. The bill did not pass the state’s Senate Health and Human Services committee [82]. Tennessee grants pre-birth orders to IPs as long as at least one IP shares a genetic relationship with the child. The non-biological IP can obtain legal parenthood through stepparent adoptions. Unmarried IPs may face challenges in establishing parenthood because Tennessee only allows for married couples to undergo stepparent adoptions.

International trends

Worldwide surrogacy has gained significant popularity and visibility, attracting the attention of affluent individuals and celebrities. However, this surge in interest and participation by prominent figures has also brought to light the complex and varied landscape of surrogacy legislation around the world. Despite the increasing prominence of surrogacy in the public eye, the regulatory response remains diverse, with some countries opting to prohibit surrogacy altogether, others lacking specific regulations, and some allowing for altruistic or commercial surrogacy arrangements. This patchwork of global regulations creates uncertainty for both IPs and potential surrogates, highlighting the need for comprehensive and consistent frameworks to address the ethical and legal aspects of surrogacy. In an effort to provide clarity, a comprehensive table has been compiled, offering guidance to patients, doctors, GCs, and surrogacy agencies navigating the complex legal and regulatory aspects of surrogacy (Table 2).

Altruistic or uncompensated surrogacy is practiced in various countries worldwide, each with its own unique legal framework.

In Europe, countries such as Greece and the Netherlands have comprehensive legislation that allows for valid and enforceable altruistic surrogacy contracts [83–85]. The United Kingdom (UK) follows a model where IPs cover the medical and welfare expenses, while the surrogate is legally recognized as the mother at birth, regardless of genetic connection [12, 86–89].

In Switzerland, surrogacy is prohibited by the Law on Assisted Reproductive Technologies, but Swiss court rulings have started to recognize non-biological IPs [61, 90–92].

France and Italy have criminalized surrogacy. In France, the Court of Cassation denounced surrogacy in 1991, leading to the enactment of Article 16–7 of the Civil Code in 1994, which made surrogacy illegal [93]. The French Court of Appeals allows biological intended fathers to claim legal parenthood, but non-biological intended mothers face challenges [94]. Italy categorizes surrogacy as a criminal offense, lacks explicit regulations for birth certificate registration, and has faced criticism from the European Court of Human Rights. Notably, Italy acknowledges same-sex parenting through IVF procedures and foreign adoptions by same-sex couples [95–97]. The Constitutional Court of Italy concluded that female same-sex parenting conforms to public order, while male same-sex parenting contravenes the 40/2004 surrogacy ban [98]. Notably, in 2018, a female same-sex couple in Turin, Italy, was acknowledged as parents on their child’s birth certificate following an IVF procedure. Italy permits civil unions for same-sex couples, affording them equivalent privileges to married heterosexual couples. In terms of adoption, Italy recognized foreign adoptions by same-sex couples in 2021 [95, 99, 100].

Spain declares surrogacy contracts null and void, and international surrogacy contracts are not recognized. Spanish citizens seeking surrogacy arrangements abroad have led to the emergence of for-profit intermediary agencies, tolerated by authorities as long as no complaints arise overseas [94, 101]. The Spanish Supreme Court allows the biological intended father to claim parenthood, while legal establishment of motherhood remains unaddressed. Attempts to legalize altruistic surrogacy have faced opposition.

Despite surrogacy being illegal and considered a criminal offense in Iceland, there are provisions in Icelandic law that allow women in same-sex relationships to undergo fertility treatments and pursue joint adoption since 2006. However, Iceland’s Act on Artificial Fertilization explicitly prohibits surrogacy, and a proposed legislation for altruistic surrogacy did not pass [102, 103]. Notably, a recent case in 2021 saw the Icelandic government refusing to register a child as the son of an Icelandic female same-sex couple who had the child through surrogacy in the US [104]. This decision raised significant questions about the recognition of parental rights for same-sex couples and the importance placed on genetic connection when determining legal parentage in surrogacy cases.

In Asia, Vietnam and Hong Kong have specific regulations governing altruistic surrogacy. Vietnam’s revised Marriage and Family Law legalized altruistic surrogacy, limited to close relatives of the IPs and restricted to one surrogate arrangement [105]. However, despite the illegality of commercial surrogacy in Vietnam, reports suggest an increasing underground network facilitating such contracts. In Hong Kong, altruistic surrogacy is restricted to married heterosexual couples who have no other viable options, with the additional requirement that the surrogate be a relative [106].

Surrogacy legislation in Asia has witnessed a varied landscape, driven by apprehensions surrounding the potential exploitation of women, especially in economically disadvantaged regions. Consequently, several Asian countries have implemented more stringent regulations or complete bans on surrogacy, aiming to address these concerns and safeguard the rights and welfare of women involved, particularly when foreign couples are involved in the process [107].

In China, government restrictions on surrogacy have led to the emergence of an underground market, as highlighted in a 2014 New York Times article. Chinese residents resorted to services like “Baby Plan” which involved sending IPs and a Chinese surrogate to Thailand where surrogacy was legal [108]. However, the surrogates faced isolation and lack of legal protection while being separated from their loved ones in China, disproportionately affecting rural Chinese surrogates who were paid more than their non-Chinese counterparts. Despite strict regulations and a ban on commercial surrogacy, the demand for surrogates in China persists, contributing to the growth of an underground market and exacerbating the exploitation of women involved. The recent scandal involving a Chinese actress accused of abandoning her surrogate babies has sparked a broader discussion on surrogacy laws and ethics in China [108].

In 2003, the Japanese Society of Obstetrics and Gynecology (JSOG) established guidelines against practicing surrogacy and discouraged its members from assisting IPs with surrogacy services. A landmark ruling by the Japanese Supreme Court in 2007 recognized the child born to celebrity IPs through surrogacy in the US as the legitimate offspring, but subsequent reports in 2008 from the ART Review Committee called for a ban on surrogacy. These guidelines and limited access to reproductive technology for same-sex couples in Japan have contributed to a minimal number of reported surrogacy cases [109].

In other regions, Australia and New Zealand have established legal frameworks that support altruistic surrogacy, prioritizing the protection of all parties involved. South Africa also accepts altruistic surrogacy, providing a regulated environment for IPs and surrogates. It is important to highlight that certain countries enforce stringent regulations that explicitly forbid commercial surrogacy, imposing potential criminal penalties on individuals involved in transnational surrogacy arrangements.

Canada’s Assisted Human Reproduction Act (AHRA) outlaws commercial surrogacy while allowing reimbursements for pregnancy-related expenses. In South America, Brazil and Uruguay are the only countries that have developed legislation permitting altruistic surrogacy. The influence of Catholicism in the region has led to restrictions on commercial surrogacy and a preference for altruistic models, driven by theological and ethical concerns about separating biological and social parenthood [110, 111].

Due to concerns surrounding ethical considerations, potential exploitation of women, and the necessity for strong legal frameworks to govern surrogacy practices, several countries including India, Nepal, Thailand, Cambodia, and Laos have implemented comprehensive bans on compensated surrogacy. As a consequence, previously thriving unregulated transnational gestational surrogacy initiatives have experienced a decline. Cases like Baby Gammy, an abandoned male twin born with Down syndrome to a Thai surrogate and Australian IPs, highlight the urgency for industry regulation to ensure accountability among all parties involved. India’s previous permissive approach to commercial surrogacy, driven by accessibility and affordability, led to regulatory reforms with the implementation of the Surrogacy (Regulation) Act in 2021, which prohibits commercial surrogacy while promoting altruistic arrangements and stronger safeguards for surrogate mothers [60, 112].

In countries where various religions intersect with legal frameworks, such as Malaysia, surrogacy laws vary. In Malaysia, there is no civil law legislation governing surrogacy for children born to non-Muslim parents, resulting in the surrogate mother being recognized as the legal mother if she is married and thus receiving adequate recognition and protection under Malaysian law. However, under Islamic law, surrogacy is not permitted if parties involved are Muslim [113].

Georgia’s surrogacy market has thrived due to its supportive stance on gestational surrogacy, attracting international IPs seeking affordable options. Surrogacy costs in Georgia are significantly lower than in the US, ranging from approximately US$38,000 to US$52,000. The country’s legal framework, encompassing the Law on Healthcare and the Civil Code, provides clear guidelines for establishing parentage and protecting the rights of IPs, contributing to its growing popularity among same-sex couples and individuals seeking surrogacy services. In addition to Georgia, commercial surrogacy is legal in Iran, Kazakhstan, Poland, Russia, and Ukraine, each with varying levels of regulation and legal frameworks. Despite the ongoing conflict in Ukraine, surrogates have continued to carry babies for foreign clients, and surrogacy agencies have adapted by relocating surrogates to safer locations and providing financial compensation [114–117].

Israel allows for gestational surrogacy under strict regulations, with the state medical commission verifying the couple’s infertility. The practice was regulated in 1996 to address the needs of infertile couples and provide a legal framework for surrogacy arrangements. Surrogacy has become a popular practice among Israelis, driven by a combination of factors such as high infertility rates, advanced reproductive technologies, and a supportive legal environment. While religious perspectives, particularly within Judaism, may influence individual beliefs and practices, the prevalence of surrogacy in Israel indicates that it is widely accepted within the society despite potential variations in personal religious views [54, 61].

Cross-border commercial surrogacy

Each year, the continuous increase in demand for surrogacy and stringent laws force many families to look for cross-border commercial surrogacy. This raises ethical, legal, and social issues, including surrogacy in unregulated regions, inadequate legal protection and representation of GCs and IPs, lack of communication among the counterparts that can lead to dissatisfaction, sensation of being used/betrayed/mistreated [11] Particularly ethically challenging is the care for LGBTQ + individuals, who not only face more restrictions when it comes to surrogacy but may experience other barriers such as healthcare provider lack of knowledge in care for LGBTQ + individuals [118].

Generally, destinations with better surrogacy laws and regulations may be associated with higher financial cost, potentially forcing some couples to look for surrogacy services in less regulated regions. Additionally, cross-border surrogacy has raised legal concerns at the time of COVID-19 pandemic, when due to restricted international travel IPs and their newborn children were in different countries with limited travel availability. Swain and Rogerson delineated the best practice for IPs and GCs residing both outside and within the US with the considerations and recommendations regarding the legal aspect of international surrogacy services [119]. Additionally, ASRM has updated its recommendations regarding legal as well as medical and psychoeducational care for IPs and GCs [120].

Practitioners globally have raised concerns regarding the need for universal laws protecting and representing the rights of surrogates and IPs in order to decrease the cross-border surrogacy and improve the ethical and legal representation of all parties involved in surrogacy [11, 98, 121].

Provider perspective

The contract between GC and IP can lead to conflict between parties, and that can complicate the role of the physicians involved in care for the GCs and IPs; in particular, the obstetrician gynecologist (OB/GYN) is ultimately obligated to provide competent medical care for the GC [122]. This poses the ethical dilemma of whether the OB/GYN must uphold the terms of the contract between GC and IPs by sharing pregnancy-related medical care with the IPs or serve the GC’s right to confidentiality with their physician. Though many contracts waive the GC’s right to confidentiality with regard to pregnancy-related medical care, additionally, contract provisions often require the GC to avoid caffeine, nicotine, alcohol, deli meats, and fish high in mercury content and to maintain a high-protein, low-sugar diet [123]. However, since the contract is between IPs and the GC, the physician is not a party to the contract and is not legally bound by the terms of the contract, including disclosure of medical care. Although the surrogate signs a release of information in their contract, which authorizes the physician to disclose information to the IPs, the surrogate maintains the right to revoke the release of information shared with their physician to outside parties. Ultimately, the physician should remind the GC that regardless of what a contract specifies, the GC maintains autonomy in medical decision-making and information sharing, and the OB/GYN provider serves the GC first and foremost [36]. The American Society for Reproductive Medicine (ASRM) states that “GC arrangements are ethically permissible so long as the parties undergo appropriate psychological, medical, and legal counseling. The GC retains all rights to direct her medical care, including any decisions regarding prenatal testing, pregnancy termination, or multifetal pregnancy reduction. Financial compensation is ethical but should not create an undue inducement or risk of exploitation” [20].

Conclusion

As the utilization of GC services, commonly known as gestational surrogacy, assumes a prominent position within our contemporary society, it becomes imperative to subject this practice and its associated procedures to a comprehensive evaluation within the framework of sociocultural and economic systems. With the journey of surrogacy being embarked upon by patients and physicians alike, it is our fervent aspiration that they avail themselves of this article as a valuable resource, offering deeper insights into the prevailing laws and regulations within their desired jurisdiction, supplemented by a concise historical account of the policies and prevailing attitudes surrounding this intricate matter. It is crucial to acknowledge that this article is by no means intended to replace the indispensable legal consultations that all involved parties are compelled to seek, but rather serves as an introductory educational guide to facilitate a better understanding of the vast ocean of multifaceted considerations, traditions, laws, and regulations that intricately encompass the surrogacy process.

Take home points

• Despite continuous improvements in international and US laws protecting GCs and IPs, gestational surrogacy remains to be inaccessible for many couples seeking parenthood.

• Fertility tourism, or cross-border reproductive care (CBRC), continues to attract couples from areas where gestational surrogacy is unlawful or complicated to the areas where it may be accessible and relatively more affordable.

• It is crucial to continue improving the country and state-specific legislature to protect all the parties involved in gestational surrogacy.

• It is important to understand the particular challenges that same-sex male couples may experience since the access to gestational surrogacy is more limited for this patient population.

• To provide personalized and respectful patient care, healthcare providers should familiarize themselves with the key principles of major religions that may influence patient decisions regarding different approaches to family building.

Declarations

Competing interests

The authors declare no competing interests.