Table 2.

Characteristics of the studies included in the meta-analysis.

Study	Inclusion criteria	Exclusion criteria
Korsholm	(i) Women of reproductive age in a heterosexual relationship who had (ii) tried to conceive naturally or had an unplanned natural conception within 2 years after inclusion. All women included had (iii) a known duration of the pregnancy attempt, and (iv) AMH analyzed by the Elecsys® method	Hormonal contraceptive use at inclusion
Casadei	(1) Unexplained infertility, that is the lack of pregnancy after 1 year of unprotected sexual intercourse in women without apparent disorder of fertility; (2) normal or low ovarian reserve; (3) both ovaries present; (4) regular menstrual cycles	(1) PCOS according to the Rotterdam criteria (Rotterdam ESHRE/ASRM-Sponsored PCOS Consensus Workshop Group 2004); (2) congenital adrenal hyperplasia; (3) androgen secreting tumors; (4) Cushing syndrome; (5) male infertility; (6) tubal pathologies; (7) anovulation; (8) hyperprolactinemia; (9) hypothalamic amenorrhea; (10) previous ovarian surgery; (11) ovarian tumors; (12) anatomical abnormalities of the uterine cavity; (13) intraperitoneal adhesions; (14) endometriosis and other pelvic pathologies; (15) thyroid dysfunction and other endocrinological disorders such as diabetes mellitus; (16) recurrent pregnancy loss; (17) autoimmune diseases
Somigliana	Inclusion criteria for both cases and controls were: (i) age >18 years, (ii) natural conception (women conceiving with the use of controlled ovarian hyperstimulation with or without assisted reproductive techniques were excluded), and (iii) regular menstrual cycles (24–35 days). Controls were the subsequently referred women matched to cases on the basis of age (6 months, ratio 1:1).	-
Murugappan	Patients with a history of at least two prior pregnancy losses, defined as loss of pregnancy from conception through 20 weeks gestational age, were included.	-
Casadei	Age between 18 and 45 years; ultrasound diagnosis of uni- or bilateral ovarian cysts; absence of malignancy criteria by ultrasound; and absence of endocrine disorders such as thyroid dysfunction, hyperprolactinemia, or Cushing syndrome	Histologic diagnosis of malignancy and perform bilateral ovariectomy; previous adnexal and uterine surgery or chemotherapy; and premature ovarian failure (POF)
Steiner	Women between 30 and 44 years of age had been attempting to conceive for 3 months or less and were cohabitating with a male partner	Fertility problems (history of sterilization, diagnosis of polycystic ovarian syndrome, previous or current use of fertility treatments, known tubal blockage, surgically diagnosed endometriosis) or a partner with a history of infertility. Women who were currently breastfeeding or had used injectable hormonal contraception in the preceding year were also excluded
Zarek	Women in this cohort were attempting pregnancy; were aged 18–40 years, with regular menstrual cycles of 21–42 days in length; and had a history of one to two prior pregnancy losses	history of infertility, pelvic inflammatory disease, tubal occlusion, endometriosis, anovulation, uterine abnormality, or polycystic ovarian syndrome
Hagen	20–35 years old, lived with a partner, and had no children. Couples with no previous reproductive experience who intended to discontinue contraception to become pregnant were eligible for enrolment	-
Hvidman	Study group: infertile patients referred for fertility treatment at The Fertility Clinic, Rigshospitalet, at Copenhagen University Hospital from September 2011 to October 2013. From September 2011, the Fertility Clinic offered newly referred infertile patients an assessment of ovarian and endocrine parameters prior to the first treatment cycle. Patients identified as eligible for the present study were examined on Cycle Days (CD) 2–5 and interviewed to obtain relevant background information. Control group: non-users of hormonal contraception with no history of infertility recruited in a prospective cross-sectional study conducted at the Fertility Clinic, Rigshospitalet, from August 2008 to February 2010.		Study group: The following patients were considered non-eligible: (i) patients referred for preimplantation genetic diagnosis, (ii) patients referred due to HIV or contagious hepatitis B or C infection, and (iii) single and homosexual women, as they were per se not considered infertile. Furthermore, patients referred directly for oocyte donation (OD) from other fertility centers were not examined on CD 2–5 and thus not included as they had already been diagnosed with a diminished ovarian reserve and most had started hormone replacement therapy or treatment with estradiol to prepare for the OD. Control group: polycystic ovary syndrome (PCOS) defined as oligo- or amenorrhea in addition to AFC ≥12 and/or an ovarian volume.10 ml3 in at least one ovary in accordance with the Rotterdam Criteria
Khan	i) no history of gynecological and abdominal surgery, ii) having the normal sonographic texture of ovaries, and iii) with no signs of hyperandrogenemia.		i) Those having any communicable disease or metabolic syndrome, ii) patients referred for pre-implantation genetic testing, iii) patients with polycystic ovarian syndrome (PCOS) and oligo-amenorrhea, iv) patients using any contraceptives, v) those having iatrogenic and autoimmune conditions, vi) obese infertile patients over the age of 40.
Zhou	Patients with an age of 20 to 35 years and a plan to conceive after surgery		Any suspicious findings of malignant disease, recurrent endometriosis, and hormone therapy within 3 months before surgery