Evaluation of intraovarian injection of platelet-rich plasma for enhanced ovarian function and reproductive success in women with POI and POR: a systematic review and meta-analysis

Abstract

Objective

The objective of this study was to evaluate the effect of the intraovarian injection of platelet-rich plasma (PRP) on ovarian reserve and reproductive outcomes in patients with premature ovarian insufficiency (POI) and poor ovarian response (POR).

Methods and data sources

The study registered in the PROSPERO database adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. PubMed, Web of Science, Scopus, Google Scholar, and ClinicalTrials.gov databases were searched from inception to June 2024—23 studies included in the meta-analysis. A total of 1853 participants aged 29.8–45 years old were included in the meta-analysis. The human studies reporting the effect of intraovarian PRP injection on ovarian reserve indicators were included in the meta-analysis. The quality of the included studies was assessed using the Cochrane Handbook or the Newcastle–Ottawa scale. The primary outcomes were serum levels of anti-Mullerian hormone (AMH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), Estradiol, and antral follicle count (AFC), number of retrieved oocytes, metaphase II (M2) oocytes, and pregnancy and live birth rates.

Result(s)

The pooled analysis of the included studies showed that intraovarian PRP injection significantly increased oocyte number (WMD: 0.97, 95% CI 0.58, 1.35, P < 0.001), M2 oocyte number (WMD: 0.80, 95% CI 0.33, 1.27, P < 0.001), AFC (WMD: 1.64, 95% CI 0.90, 2.38, P < 0.001), and AMH levels (WMD: 0.12 ng/mL, 95% CI 0.07, 0.17, P < 0.001) in women with POR. Besides, in women with POI, PRP injection significantly improved AFC (WMD: 1.33, 95% CI 1.19, 1.47, P < 0.001) and serum levels of FSH (WMD: − 15.68 IU/mL, 95% CI − 24.12, − 7.24, P < 0.001), AMH (WMD: 0.29 ng/mL, 95% CI 0.08, 0.49, P = 0.006), and LH (WMD: − 9.87 IU/mL, 95% CI − 15.23, − 4.51, P < 0.001). The meta-analysis revealed a pregnancy ratio of 0.21 and a live birth ratio of 0.18 in women with poor ovarian reserve after PRP injection. In women with POI, the figures were marginally lower, recorded as 0.138 for pregnancy and 0.10 for live birth, respectively.

Conclusion

PRP may serve as an alternative therapy for POI and POR; however, further investigation is required to validate its efficacy and determine suitable candidates.

Introduction

Female infertility can be caused by a variety of conditions, such as endocrine dysfunction, implantation failure, endometriosis, and uterine fibroids, as well as ovarian pathologies, such as polycystic ovary syndrome (PCOS), premature ovarian insufficiency (POI), environmental factors, and inflammatory diseases [1].

The decline in the fertility in aging women, especially those with poor ovarian response (POR) or premature ovarian insufficiency (POI), is a significant concern for modern IVF centers. POI and POR are related to decreased ovarian reserve, but are distinct conditions with different clinical implications [2]. POI is a pathological condition characterized by the cessation of ovarian function prior to an individual attaining the age of 40 years [3].

It involves not just a decrease in ovarian reserve but a more significant reduction in ovarian function, often leading to irregular or absent menstrual cycles and infertility [3]. POI is diagnosed when a woman has few or no periods, her gonadotrophin levels are high (follicle-stimulating hormone (FSH) > 25 IU/L), while her estrogen (E2) levels are low. Ovarian insufficiency is not a specific, either/or state. Instead, it is a spectrum of ovarian dysfunction or ovarian aging. This condition can be temporary or worsen over time, leading to early menopause [4, 5].

POR refers to a suboptimal response to ovarian stimulation during fertility treatments like IVF. Women with POR typically have a lower number of oocytes retrieved after stimulation, which is often owing to decreased ovarian reserve [2]. POI is more severe and represents an earlier and more complete loss of function, while POR is a specific response observed during fertility treatments [2].

Advancements in assisted reproductive technologies (ARTs) has provided remedies for numerous infertility challenges. Nonetheless, these techniques are less efficacious for perimenopausal or postmenopausal women and those with reduced ovarian reserve, especially in the absence of donor oocytes, as they depend on the viable oocytes [6]. Assisted reproductive technologies (ARTs) do not completely resolve the fundamental ovarian and oocyte dysfunctions. The researchers have investigated various techniques to enhance results for women with poor ovarian response (POR) undergoing controlled ovarian hyperstimulation (COH). This encompasses pretreatments utilizing aromatase inhibitors, human chorionic gonadotropin, or androgens; adjuvant therapies involving estrogen agonists or luteinizing hormones; administering elevated initial gonadotropin dosages; and implementing various protocols such as microdose flare-up, short flare-up, agonist stop, antagonist (standard or delayed initiation), or luteal phase support with progesterone [7–13].

There is currently no conclusive medication available for women with POI to restore normal ovarian function [14]. However, therapies are available to address the symptoms associated with the condition and to minimize the associated hazards. Various practical interventions are being tested, some with a biologically reasonable theory and others with less biological plausibility. However, it is very challenging to define the population that needs to be treated and/or how to treat them [15, 16]. Platelet-rich plasma (PRP) is gaining popularity as a non-surgical treatment for various gynecological disorders, especially infertility [17].

PRP is a natural substance that contains highly concentrated platelets with growth factors three to five times higher than those found in plasma [18]. Platelets contain many growth factors (PDGF, IGF, VEGF, FGF, and TGF-β), coagulation factors, and differentiation factors that help with different processes like blood vessel growth, immune system suppression, and tissue repair [19–23]. Platelet-rich plasma (PRP) therapy for the ovaries may represent a promising novel intervention for patients with unfavorable fertility prognoses. The primary etiological factor of ovarian failure is diminished ovarian function, which results from an insufficient number of stimulable primordial follicles [24]. PRP therapy is a viable method for increasing the number of accessible oocytes. The molecular network that promotes angiogenesis is markedly impaired in patients with ovarian insufficiency [6]. The application of PRP for ovarian rejuvenation has been investigated owing to its regenerative and anti-inflammatory characteristics [25, 26]. Research has shown that PRP comprises growth factors and cytokines that facilitate angiogenesis, cell migration, differentiation, and proliferation [27]. Studies have demonstrated that PRP enhances tissue regeneration and healing [28–31]. Significant clinical experience regards PRP as a safe alternative more readily available than stem cells [11–13]. These qualities may improve ovarian function and the response to therapies for ovarian dysfunction. Reproductive medicine first utilized PRP to enhance endometrial thickness in patients undergoing in vitro fertilization (IVF) [32]. Pantos et al. provided the initial account of PRP for ovarian rejuvenation in 2016. Their research indicated that PRP, a blood component, may facilitate the restart of menstrual periods in women exhibiting climacteric symptoms when administered directly into the ovary [15, 16]. Several observational studies showed that ovarian PRP treatment reduced Follicle Stimulating Hormone (FSH) levels and increased anti-Müllerian Hormone (AMH), which led to more spontaneous pregnancies and better IVF outcomes, as shown by a clinical trial involving a group of women with very poor prognoses [26]. Despite the positive outcomes, ovarian PRP treatment remains unknown and is therefore not commonly used in clinical practice. Reliable clinical evidence about the efficacy of ovarian PRP treatment is insufficient. This study aimed to gather all relevant clinical data regarding the impact of ovarian PRP treatment and synthesize the results to formulate definitive conclusions about its efficacy. Six meta-analyses recently have been reported on the effects of intraovarian platelet-rich plasma (PRP) injection on pregnancy outcomes in women with premature ovarian insufficiency (POI), poor ovarian response (POR), and reduced ovarian reserve (DOR). Two meta-analyses concentrated on women with DOR, but their target populations were different from those of the current work. Two studies focused just on women with POR. One study aggregated data on women with POR and POI despite these two disorders being different and needing different analysis. One meta-analysis on women with POR and POI contrasted these two groups but omitted to document the findings for any one group individually. Moreover, all of the above listed studies omitted some pertinent papers, therefore violating the basic need of a systematic review to include all pertinent publications. Thus, considering the aforesaid reasons, this meta-analysis was carried out with the intention of separately examining the efficacy of intraovarian PRL injection on pregnancy outcomes in women with POR and POI.

Methods

Study design

This systematic review and meta-analysis used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol, which was registered in the international prospective register for systematic reviews PROSPERO (Registration number: CRD42023437723).

Eligibility criteria

Human studies evaluating the effects of PRP injection on fertility outcomes were included in this meta-analysis. The studies were considered eligible if they met the inclusion criteria: clinical trials, case-series, and observational studies; assessed the effect of intraovarian PRP injection on fertility outcomes in women with POR and POI [POI definition based on ESHRE criteria: onset < 40 years, oligo-/amenorrhea ≥ 4 months, and FSH > 25 IU/l, POR definition based on Bologna criteria: age > 40 years, history of POR ≤ 3 oocytes in previous stimulation, and low ovarian reserve tests (anti Mullerian hormone (AMH) < 1.1 ng/ml) or antral follicle count (AFC) < 5)]; reported mean and standard deviations (SDs), or other data to estimate these values for before and after the study. We excluded the studies in which the effect of intraovarian PRP was evaluated in women with DOR if there was insufficient data to categorize the participants either in POI or POR. Reviews, case report studies, conference abstracts, and nonresearch letters were also excluded from the study.

Search strategy and data extraction

A comprehensive literature search was performed in PubMed, Scopus, ISI Web of Science, Google Scholar, and ClinicalTrials.gov (Clinicalrial.gov was searched comprehensively, and only one study titled Ovarian PRP (Platelet Rich Plasma) Injection for Follicular Activation was found, which is in Recruiting stage) databases to find articles investigating the effect of intraovarian PRP injection on fertility outcomes using search terms until June 2024. Keywords were: “In Vitro Fertilization” OR “IVF” OR “oocyte” OR “Intracytoplasmic sperm injection” OR “ICSI” OR “Embryo transfer” OR “implantation failure” OR “fertility” OR “reproductive hormones” OR “FSH” OR “LH” OR “AMH” OR “E2” AND “Platelet-rich plasma” OR “PRP” OR “Autologous platelet-rich plasma”. Two investigators independently screened retrieved studies' titles and/or abstracts based on inclusion criteria. The same reviewers appraised the full texts separately to select the eligible articles for data extraction. The data included first author/publication year/country, PRP dose, participant’s characteristics such as health status, age, body mass index (BMI), number of participants, study design, and study outcomes. Any discrepancies were resolved by consulting the third investigator.

Study quality

The study quality was evaluated using criteria of the Cochrane Handbook for Systematic Reviews of Interventions, which assigns up to low, unclear, or high risk of bias to each study based on the seven items, including the sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, selective outcome reporting, incomplete outcome data, and other sources of bias. A study was considered to provide high quality if it had a low risk of bias for all key domains. To evaluate the quality of the observational studies, the Newcastle–Ottawa scale was applied, which encompasses the following areas: the selection of participants, comparability of the groups, and ascertainment of exposure and outcome.

Statistical analysis

Data synthesis was performed using STATA version 17 software. The pooled results for retrieved oocyte number, M2 oocyte number, AFC and serum levels of FSH, luteinizing hormone (LH), AMH, E2, and peak E2 were expressed as weighted mean difference (WMD) and its 95% confidence interval (CI). A random-effects model was used to estimate pooled WMDs and their 95%CI for the overall effect of PRP injection on study outcomes. The inter-study heterogeneity was assessed by the I-squared (I²) index and the Cochran Q test (considered significant for P values < 0. 05). Stratified analyses were carried out to detect possible sources of inter-study heterogeneity based on PRP dosage, participants’ age, PRP injection time, using activator, and prp preparation stage. Publication bias was determined by Begg’s or Egger’s regression tests. If there were any significant publication bias, we applied trim-and-fill analysis to adjust the bias detected. The robustness of the results was assessed by a sensitivity analysis using the removal of each study from the overall analysis.

Results

The flow diagram of study identification and selection is indicated in Fig. 1. Of the 2789 articles identified from the database search, 952 duplicate articles were removed. 1837 remaining records were reviewed based on title and abstract, of which 1796 articles did not meet the eligibility criteria and were excluded. After reviewing full-text articles, 23 studies met our inclusion criteria and were included in the meta-analysis. There was only one randomized clinical trial investigating the effect of ovarian injection of PRP on women with POR, while the design of most studies was before–after. However, the use of randomized clinical trial design is the gold standard in clinical research; using a control group is not always acceptable because of ethical or practical issues. Considering that the results of the randomized clinical trial cannot be merged with before–after studies, only data from the PRP group was extracted from this clinical trial. Where we couldn’t have access to the article or the sufficient data for the meta-analysis were not reported, we contacted the relevant authors.

Fig. 1.

Flow diagram of the literature search and study selection process

Characteristics of included studies

Table 1 presents the characteristics of the included trials. Three studies were case-series, two were prospective cohort studies, one was a retrospective study, and 17 were clinical trials. Of 23 studies, 15 conducted on women with POR, Sixon women with POI, and two on both conditions. A total of 1853 participants aged 29.8–45 years old were included in the meta-analysis from all 23 studies. The infertility duration of included participants was between 2.6 and 13 years. However, only 16 studies reported data on infertility duration. Regarding BMI values, nine studies didn’t report BMI, and the mean BMI of the remaining studies was 25.15 kg/m². Dosages of PRP ranged from 0.7 to 6 mL, while one study did not report the PRP dosage. Studies were published between 2019 and 2024. These 23 studies originated from Iran (n = 7), USA (n = 3), Turkey (n = 3), and single studies from Australia, Switzerland, Greece, Ukraine, Egypt, Romania, Taiwan, Iraq, Bangladesh, and Bulgaria. All clinical trials that used before–after design have a high risk of bias because of not performing random sequence generation, allocation concealment, and blinding.

Table 1.

An overview of the characteristics and main findings of the studies is included in the systematic review

Author/date/Country/ year	Study design	Condition	Sample size	Mean age of subjects (years)	Mean BMI of subjects (kg/m2)	Duration of infertility (years)	Dose of PRP (mL)	Fertility	Live birth	Main outcomes
Abdullah et al./Iraq/[33]	Before–after clinical trial	POI	50	39.7	26.5	5.2	1.25	NR	NR	AFC, FSH, and AMH
Farimani et al./Iran/[34]	Before–after clinical trial	POR	12	35.5	NR	6.5	2	3	3	Retrieved oocyte number
Cakiroglu et al./Turkey/[35]	Before–after clinical trial	POI	311	34.8	NR	6.8	2–4	36	25	FSH, AMH, and AFC
Petryk et al./Ukraine/[36]	Before–after clinical trial	POI	38	31–45	NR	NR	0.7	10	6	FSH, LH, E2, and AMH
Sfakianoudis et al./Greece/[26]	Case-series study	POR and POI	30 Women with POR; 30 Women with POI	38.4	23.1	5.8	4	14 (Women with POR) 3 (Women with POI)	12 (Women with POR) 3 (Women with POI)	Retrieved oocyte number, 2 pronuclear embryo, M2 oocyte number, FSH, AMH, LH, E2, Peak E2, and AFC
Sills et al./USA/[37]	Case-series study	POR	48 Patients < 42 years old and 134 patients ≥ 42 years old	Patients < 42 years old) and patients ≥ 42 years old	23.6 in the patients < 42 years old and 23.3 in the patients ≥ 42 years old	NR	NR	NR	NR	FSH, E2, and AMH
Aflatoonian et al./Iran/[38]	Before–after clinical trial	POR and POI	17 women with POR and 9 women with POI	35.4 (in women with POR) and 33.6 (in women with POI)	25.1 (in women with POR) and 26.6 (in women with POI)	4.4 (Poor responder women) 6.3 (Women with the premature ovarian insufficiency)	4	9 (Women with POR) 0 (Women with POI)	4 (Women with POR) 0 (Women with POI)	FSH, LH, E2, and AMH
Farimani et al./Iran/[39]	Retrospective study	POR	96	38.3	NR	NR	2	14	NR	Retrieved oocyte number, M2 oocyte number, FSH, LH, E2, AMH, and AFC
Hsu et al./Taiwan/[40]	Before–after clinical trial	POI	12	44.4	NR	13	3	1	0	FSH and LH
Pacu et al./Romania/[41]	Before–after clinical trial	POR	20	37.4	NR	NR	2–4	2	2	Retrieved oocyte number, M2 oocyte number, FSH, LH, AMH, Peak E2, and AFC
Tülek et al./Turkey/[42]	Before–after clinical trial	POR	50	38.1	25	NR	2	6	4	Retrieved oocyte number, M2 oocyte number, and E2
Barad et al./USA/[43]	Prospective cohort study	POR	26	44.1	23.6	NR	1.5	0	0	Retrieved oocyte number, FSH, E2, Peak E2, AMH, and AFC
Cakiroglu et al./Turkey/[44]	Before–after clinical trial	POR	510	40.3	25.7	7.4	2–4	105	66	Retrieved oocyte number, 2 pronuclear embryo, Blastocyte number, M2 oocyte number, FSH, AMH, and AFC
Keikha et al./Iran/[45]	Before–after clinical trial	POR	12	40	22.5	2.79	4	NR	NR	Retrieved oocyte number, FSH and AMH
Navali et al./Iran/[46]	Before–after clinical trial	POR	35	40.6	NR	NR	2	3	NR	Retrieved oocyte number, FSH, LH, E2, and AMH
Parvanov et al./Bulgaria/[47]	Before–after clinical trial	POR	66	40.5	23.5	NR	1	NR	NR	M2 oocyte number, FSH, AMH, and AFC
Rezk et al./ Egypt/[48]	Before–after clinical trial	POI	50	31.1	31.1	2.6	1	NR	NR	FSH, E2, and AMH
Tremellen et al./Australia/[49]	Case-series study	POR	20	40	25.4	3	3	6	6	Retrieved oocyte number, Embryo number, and Peak E2
Setudeh et al./Iran/ [50]	Before–after clinical trial	POR	20	41.8	25.8	9.7	6	1	NR	M2 oocyte number, Retrieved oocyte number, FSH and AMH
Garavelas et al./Switzerland/[51]	Before–after clinical trial	POI	100	29.8	NR	NR	4	6	6	FSH, LH, E2, and AMH
Najafian et al./Iran/[52]	Before–after clinical trial	POR	50	39	25.3	4	4	10	NR	AMH and FSH
Tickoo et al./India/[53]	Prospective cohort study	POR	66	NR	NR	NR	4	NR	NR	AFC and AMH
Herlihy et al./USA/[54]	Randomized clinical trial	POR	41	34.4	26.3	NR	4	NR	NR	AMH and AFC, M2 oocyte

AFC Antral Follicle Count, AMH Anti-Mullerian Hormone, BMI body mass index, FSH Follicle-stimulating hormone, M2 oocyte Metaphase 2 oocyte, E2 Estradiol, LH Luteinizing hormone, POI premature ovarian insufficiency, POR Poor ovarian response

Meta-analysis

A total of 12 studies reported the effect of PRP injection on pregnancy in women with POR. The pregnancy ratio following PRP injection was 0.21, with 95% CI at 0.08 and 0.34. Besides, eight studies reported live birth numbers following PRP injection. The live birth ratio was 0.18 with 95% CI 0.05, 0.19. Six studies reported pregnancy rate and live birth numbers following PRP injection. Pregnancy ratio in women with POI was 0.138 with 95% CI: 0.05, 0.22. The live birth ratio was 0.10 with 95% CI 0.04, 0.10.

Retrieved oocyte number

The pooled analysis of 12 studies indicated a significant increase in retrieved oocyte number following PRP injection in women with POR (Fig. 2; WMD: 0.97, 95% CI 0.58, 1.35, P < 0.001). The I² index (70.5%) and Cochrane Q test (P < 0.001) showed a high interstudy heterogeneity. No significant difference was detected between participants aged < 40 and ≥ 40 or prp preparation stage for the overall effect of PRP injection, while the studies in which PRP was prepared at one stage showed better effects on retrieved oocyte number as compared to two-stage preparation. Begg's (P = 0.945) test did not confirm publication bias (Table 2).

Fig. 2.

Forest plot of the effect of PRP on retrieved oocyte number in women with POR

Table 2.

Subgroup analyses for the effects of PRP on retrieved oocytes, M2 oocytes, and AFC in the participants of included studies (Women with POR)

	Effect sizes, n	WMD (95% CI)	P-between	I2	P-heterogeneity
Subgroup analysis for retrieved oocytes
Overall	12	0.97 (0.58, 1.35)		70.50	< 0.001
Participant’s age
< 40	6	1.24 (0.69, 1.79)	0.204	61.8	0.022
≥ 40	6	0.71 (0.12, 1.31)		77.5	< 0.001
Injection time
Follicular phase	7	0.95 (0.44, 1.46)	0.926	73.9	< 0.001
Puncture day	4	1.00 (− 0.02, 2.03)		78.4	0.003
prp preparation stage
One-stage preparation	5	1.11 (0.71, 1.52)	0.033	44.9	0.123
Two-stage preparation	5	0.41 (− 0.09, 0.91)		29.1	0.227
Subgroup analysis for M2 oocytes
Overall	8	0.80 (0.33, 1.27)		84.4	< 0.001
Participant’s age
< 40	5	0.98 (0.21, 1.75)	0.375	85.8	< 0.001
≥ 40	3	0.50 (− 0.24, 1.24)		87.2	< 0.001
prp preparation stage
One-stage preparation	3	0.53 (− 0.13, 1.20)	0.738	79.1	0.008
Two-stage preparation	3	0.76 (− 0.40, 1.92)		88.9	< 0.001
Subgroup analysis for AFC
Overall	8	1.64 (0.90, 2.38)		88.3	< 0.001
PRP dosage
< 2 mL	2	0.82 (− 0.35, 2.00)	0.160	52.3	0.148
≥ 2 mL	6	1.87 (1, 2.74)		90.2	< 0.001
Participant’s age
< 40	3	1.61 (0.02, 3.21)	0.511	89.5	< 0.001
≥ 40	4	1.02 (0.27, 1.77)		79.5	0.002
prp preparation stage
One-stage preparation	2	1.61 (1.37, 1.84)	0.844	0.0	0.728
Two-stage preparation	4	1.78 (0.06, 3.50)		91.7	< 0.001

AFC Antral Follicle Count, M2 oocyte Metaphase 2 oocyte, POR Poor ovarian response, PRP Platelet-rich plasma

M2 oocyte number

Eight studies investigated the effect of PRP injection on M2 oocyte number in women with POR. The pooled estimations of these studies revealed that PRP injection significantly enhanced M2 oocyte number (Fig. 3; WMD: 0.80, 95% CI 0.33, 1.27, P < 0.001), with evidence of high inter-study heterogeneity (I² index = 84.4% and P < 0.001). Subgrouping analyses stratified by participants’ age and number of prp preparation stage did not change the effect of PRP on M2 oocyte number (Table 2). Egger’s (P = 0. 311) test did not confirm publication bias.

Fig. 3.

Forest plot of the effect of PRP on M2 oocyte number in women with POR

Antral follicle count

Combining eight WMD on the effect of PRP injection on AFC in women with POR indicated a significant increase of AFC in participants (Fig. 4; WMD: 1.64, 95% CI 0.90, 2.38, P < 0.001). Considering the I² index (88.3%) and the Cochrane Q test (P < 0.001), a high heterogeneity was observed between studies. Besides, the pooled estimates of three studies showed a significant positive effect on AFC of women with POI (Fig. 4; WMD: 1.33, 95% CI 1.19, 1.47, P < 0.001). The inter-study heterogeneity was not significant (I² index = 49.2%, P = 0.139). Subgrouping based on PRP dosage or participants’ age and number of prp preparation stage did not show significant changes in the results (Table 2). Publication bias results for the studies, including women with POR (P _{Begg's test} = 0.371) or POI (P _{Egger's test} = 0.837), were not significant.

Fig. 4.

Forest plot of the effect of PRP on antral follicle count (A.POR, B.POI)

Serum hormone levels

Of the included studies, 11 and eight provided adequate data on serum levels of FSH in women POR and POI, respectively. The pooled estimates did not show a significant reduction in serum levels of FSH in women with POR (Fig. 5; WMD: 1.78 IU/mL, 95% CI − 0.91, 4.48, P = 0.359), while PRP significantly decreased FSH level in women with POI (Fig. 5; WMD: − 15.68 IU/mL, 95% CI − 24.12, − 7.24, P < 0.001). A high degree of heterogeneity was detected among the studies (I² index 98.2%, P < 0.000 for POR and I2 index 95.9%, P < 0.000 for POI). The findings from the subgroup analysis based on the participant’s age, PRP dosage, PRP injection time and number of prp preparation stage did not show a significant beneficial effect on FSH in women with POR, while the studies that did not use an activator for PRP decreased FSH level significantly compared to the studies that used calcium gluconate as an activator (Table 3). Regarding women with POI, PRP had a significant effect on FSH levels in subgroups of dosages ≥ 2 mL PRP, two-stage PRP preparation, and ages ≥ 40 years (Table 4). Publication bias results for the studies, including women with POR (P Begg’s test = 0.064) or POI (P Egger’s test = 0.614), were not significant. Of the included studies, five provided sufficient data on LH levels and indicated no significant decrease in LH levels following PRP injection in women with POR (Fig. 6; WMD: − 0.86 IU/mL, 95% CI − 2.30, 0.58, P = 0.241). The I² index (97.8%) and Cochrane Q test (P < 0.001) revealed a high heterogeneity among studies. Pooling five effect sizes showed a significant decrease in LH levels of women with POI (Fig. 6; WMD: − 9.87 IU/mL, 95% CI − 15.23, − 4.51, P < 0.001). Besides, there was a significant heterogeneity between the studies (I² index = 94.6% and Cochrane Q test, P < 0.001). The results from the subgroup analysis based on PRP injection time in women with POR showed that PRP injection at follicular phase led to a more reduction in LH level compared to the studies that injected PRP at puncture day. Based on Egger’s test, we found no evidence of publication bias in the studies, including women with POR (P = 0.444) or POI (P = 0.462). The pooled analysis of 13 studies, with 14 effect sizes, indicated that PRP injection significantly increased AMH levels in women with POR (Fig. 7; WMD: 0. 12 ng/mL, 95% CI 0. 07, 0. 17, − < 0.001). Considering the I² index (90.2%) and the Cochrane Q test (− < 0.001), there was a high heterogeneity among studies. Pooling seven effect sizes on the effect of PRP on the women with POI showed a significant increase in AMH level (Fig. 7; WMD: 0.29 ng/mL, 95% CI 0.08, 0.49, P = 0.006). There was considerable heterogeneity between the studies (I² index = 99.6% and P < 0.000). Publication bias results for the studies, including women with POR (P Begg’s test = 0.584) or POI (P Egger’s test = 0.429), were not significant. No significant changes were detected in serum levels of AMH in women with POR and POI based on PRP dosage, using activator, number of PRP injection time, and age, while the studies that injected PRP to women with POR at follicular phase significantly increased AMH compared to the studies that injected PRP at puncture day (Tables 3 and 4). Combining seven and five effect sizes on the effect of PRP injection on plasma levels of E2 in women with POR and POI respectively did not reveal significant changes in E2 level (Fig. 8; Women with POR; WMD: 34.61 pg/mL, 95% CI − 16.9, 86.12, P = 0.188 and Figure; Women with POI; WMD: 28.7 pg/mL, 95% CI − 4.69, 62.10, P = 0.092). Considering the I² index (99.8%) and the Cochrane Q test (P < 0.000), there was high heterogeneity between the studies, including women with POR. Inter-study heterogeneity was also high between the studies in which women with POI were the target group (I² index = 99.9% and P < 0.001). Subgrouping based on participants' age, injection time, using activator, and number of prp preparation stage did not show significant changes in E2 levels of women with POR (Table 3). Subgroup analyses based on PRP dosage could not change the overall effect of PRP on E2 level in women with POI (Table 4). Egger's test did not show significant publication bias for POR (P = 0.129) or POI (P = 0.584). Four studies measured peak E2 levels following PRP injection in women with POR. The meta-analysis indicated no significant changes in peak E2 levels following PRP injection (Fig. 9; WMD: 257.2 pg/mL; 95% CI − 157.1, 671.5; P = 0.224), and the heterogeneity between the studies was high (I² = 94.2%, P < 0.001). Egger's test (P = 0.464) did not confirm publication bias evidence.

Fig. 5.

Forest plot of the effect of PRP on FSH level (A.POR, B.POI)

Table 3.

Subgroup analyses for the effects of PRP on serum levels of hormones in the participants of included studies (Women with POR)

	Effect sizes, n	WMD (95% CI)	P-between	I2	P-heterogeneity
Subgroup analysis for FSH
Overall	12	1.78 (− 0.91, 4.48)		98.2	< 0.001
PRP dosage
< 2 mL	2	− 0.07 (− 2.17, 2.04)	0.448	0	0.325
≥ 2 mL	8	− 1.01 (− 2.21, 0.20)		85.3	< 0.001
Participant's age
< 40	5	− 0.75 (− 2.14,0.65)	0.388	67.6	0.015
≥ 40	6	2.08 (− 4.17, 8.33)		99.0	< 0.001
Injection time
Follicular phase	9	2.57 (− 2.97, 8.11)	0.424	98.5	< 0.001
Puncture day	3	0.31 (0.17, 0.44)		0.0	0.889
Using activator
Yes	3	12.06 (10.94, 13.18)	< 0.001	4.9	0.350
No	9	− 0.90 (− 2.00, 0.21)		83.5	< 0.001
prp preparation stage
One-stage preparation	5	3.46 (− 3.31, 10.22)	0.343	99.3	< 0.001
Two-stage preparation	5	0.16 (− 0.63, 0.96)		0.0	0.843
Subgroup analysis for AMH
Overall	13	0.12 (0.07, 0.17)		90.2	< 0.001
PRP dosage
< 2 mL	3	0.11 (0.01, 0.22)	0.711	17.7	0.297
≥ 2 mL	9	0.14 (0.04, 0.24)		93.6	< 0.001
Participant’s age
< 40	6	0.12 (− 0.09, 0.33)	0.725	85.2	< 0.001
≥ 40	6	0.08 (0.02, 0.04)		93	< 0.001
Injection time
Follicular phase	11	0.15 (0.06, 0.24)	< 0.001	90.0	< 0.001
Puncture day	3	− 0.01 (− 0.03, 0.01)		0.0	0.834
Using activator
Yes	5	0.10 (0.0, 0.19)	0.672	53.5	0.072
No	9	0.13 (0.01, 0.25)		93.5	< 0.001
prp preparation stage
One-stage preparation	6	0.07 (0.02, 0.13)	0.431	92.6	< 0.001
Two-stage preparation	6	0.11 (0.03, 0.20)		16.0	0.311
Subgroup analysis for E2
Overall	7	34.61 (− 16.90, 86.12)		99.8	< 0.001
Participant’s age
< 40	3	20.60 (− 28.59, 69.79)	0.643	76.1	0.015
≥ 40	3	54.29 (− 20.12, 123.03)		99.9	< 0.001
Injection time
Follicular phase	4	− 12.95 (− 33.71, 7.81)	0.257	97.3	< 0.001
Puncture day	2	82.7 (− 81.35, 246.7)		99.9	< 0.001
Using activator
Yes	3	− 18.84 (− 43.01, 5.32)	0.079	98.1	< 0.001
No	4	85.8 (− 28.27, 199.8)		99.7	< 0.001
prp preparation stage
One-stage preparation	4	64.88 (− 15.84, 145.6)	0.115	99.9	< 0.001
Two-stage preparation	3	− 0.21 (− 6.74, 6.32)		0.0	0.808
Subgroup analysis for LH
Overall	5	− 0.86 (− 2.30, 0.58)	0.241	97.8	< 0.001
Injection time
Follicular phase	3	− 1.98 (− 3.72, − 0.24)	0.017	73.8	0.022
Puncture day	2	0.13 (0.02, 0.25)		0.0	0.771

AFC Antral Follicle Count, M2 oocyte Metaphase 2 oocyte, POR Poor ovarian response, PRP Platelet-rich plasma

Table 4.

Subgroup analyses for the effects of PRP on serum levels of hormones in the participants of included studies (Women with POI)

	Effect sizes, n	WMD (95% CI)	P-between	I2	P-heterogeneity
Subgroup analysis for FSH
Overall	8	− 15.68 (− 24.12, − 7.24)		95.9	< 0.001
PRP dosage
< 2 mL	4	− 8.68 (− 15.93, − 1.43)	0.019	84.5	< 0.001
≥ 2 mL	4	− 23.54 (− 33.67, − 13.41)		93.4	< 0.001
Participant’s age
< 40	5	− 8.55 (− 15.26, − 1.85)	0.016	87.5	< 0.001
≥ 40	2	− 33.01 (− 51.68, − 14.35)		83.1	0.015
Using activator
Yes	3	− 19.96 (− 49.23, 9.32)	0.707	90.5	< 0.001
No	5	− 14.02 (− 23.99, − 4.05)		97.1	< 0.001
prp preparation stage
One-stage preparation	2	− 3.32 (− 9.50, 2.86)	< 0.001	76.1	0.041
Two-stage preparation	5	− 22.59 (− 30.95, − 14.23)		79.1	< 0.001
Subgroup analysis for AMH
Overall	7	0.29 (0.08, 0.49)		99.6	< 0.001
PRP Dosage
< 2 mL	3	0.28 (0.12, 0.44)	0.940	97.5	< 0.001
≥ 2 mL	4	0.29 (-0.04, 0.63)		99.8	< 0.001
Using activator
Yes	2	0.18 (-0.27, 0.63)	0.581	99.1	< 0.001
No	5	0.33 (0.06, 0.60)		99.7	< 0.001
prp preparation stage
One-stage preparation	2	0.23 (-0.12, 0.58)	0.835	99.7	< 0.001
Two-stage preparation	4	0.28 (-0.08, 0.64)		99.6	< 0.001
Subgroup analysis for E2
Overall	5	28.7 (− 4.69, 62.10)		99.8	< 0.001
PRP dosage
< 2 mL	2	16.69 (− 14.36, 47.75)	0.295	96.5	< 0.001
≥ 2 mL	3	39.12 (10.86, 67.39)		99.6	< 0.001

AFC Antral Follicle Count, M2 oocyte Metaphase 2 oocyte, POI Premature ovarian insufficiency, PRP Platelet-rich plasma

Fig. 6.

Forest plot of the effect of PRP on LH level (A.POR, B.POI)

Fig. 7.

Forest plot of the effect of PRP on AMH level (A.POR, B.POI)

Fig. 8.

Forest plot of the effect of PRP on E2 level (A.POR, B.POI)

Fig. 9.

Forest plot of the effect of PRP on peak E2 level in women with POR

Sensitivity analyses

Sensitivity analysis revealed that the effect of PRP on retrieved oocyte number, M2 oocyte number, AFC and serum levels of FSH, LH, AMH, E2, and peak E2 in the women with POR did not depend on the individual study, as the exclusion of each study from the analysis had no significant effect on their overall effect sizes. However, excluding the studies conducted by Sills et al. can shift the results for the effect of PRP into the significance level. In addition, excluding the study conducted by Tremellen et al. significantly increased peak E2 levels following PRP injection. Sensitivity analysis in the women with POI showed that the results for AFC, LH, and FSH did not depend on the individual study. In contrast, the effect of PRP on AMH and E2 levels depended on the studies conducted by Sfakianoudis et al. and Rezk et al., respectively.

Discussion

The present meta-analysis found a beneficial effect of intraovarian PRP injection on AFC, the number of retrieved oocytes, and M2 oocytes in women with POR. Although there was an improvement in hormones such as AMH, FSH, and E2 after intraovarian injection of PRP, this improvement failed to reach statistical significance except for serum AMH. The effect of PRP on AFC and the number of retrieved oocytes is more evident than its effect on hormonal assessment. This may be explained by the physical recovery of the ovarian tissue that may precede its functional and hormonal recovery. Longer follow-up duration may detect a functional recovery with improved ovarian reserve hormone markers. In the subjects with POI, intraovarian injection of PRP led to significant improvements in AFC, AMH, FSH, and LH levels, while E2 levels remained unchanged.

The relatively higher pregnancy and live birth ratios in POR compared to POI may be attributed to the residual ovarian function in POR patients, which is typically more responsive to regenerative therapies like PRP. Subgrouping based on participants' age did not change the results for oocytes, M2 and AFC, and serum levels of FSH, AMH, and E2 in the participants with POR. Subgroup analysis based on PRP dosage did not also show significant changes in AFC, FSH, and AMH levels in these participants. In the individuals with POI, PRP decreased FSH levels much more effectively at the dosage of ≥ 2 mL and studies that recruited subjects aged ≥ 40 years than comparators, while subgrouping based on participant's age could not change the results for AMH and E2 levels.

These results indicate that PRP may have a stimulatory effect on the ovaries, leading to enhanced follicular development and a possible increase in available oocytes. In recent years, numerous research has focused on the effect of intraovarian PRP on ovarian reserve markers [55]. Ovarian reserve, which refers to the quantity and quality of oocytes, is crucial in determining fertility potential and the efficacy of assisted reproductive techniques [56].

Considering the beneficial effects of PRP on ovarian reserve, it may be a promising therapeutic option for infertility. Advantages of autologous PRP intraovarian infusion include simple manipulation, excellent storage characteristics, and low immunogenicity [57]. Intraovarian PRP treatment is hypothesized to improve ovarian function by augmenting both the quantity (by stimulating dormant follicles in the aging ovary) and quality (by promoting the differentiation of potential ovarian stem cells into new young oocytes); however, some experts contend that the existence of potential ovarian stem cells remains contentious [58].

Although the exact mechanisms are unclear, these results may be due to the effect of platelet-derived cytokines, which may improve the ovarian microenvironment, enhance ovarian vascular activation, stabilization or even de novo development of oocytes from precursor stem cells, stimulate angiogenesis, improve blood flow to the ovaries, and promote follicular development, tissue regeneration, cell proliferation, extracellular matrix remodeling, apoptosis, differentiation, angiogenesis and its close association with inflammatory signaling [59, 60]. Pantos et al. were the first author to describe PRP for ovarian rejuvenation in 2016. The beneficial effects of PRP on ovarian reserve parameters and pregnancy outcomes may be attributable to PRP’s numerous soluble mediators that orchestrate cellular repair following tissue injury [61, 62].

The process of intraovarian PRP injection carries low risks; however, these risks have not been documented in the relevant research. Complications such as vascular injury, organ perforation, infection, abscess formation, and oocyte tissue necrosis have been postulated, although there is no definitive evidence linking these directly to the treatment. An additional significant theoretical consideration is the malignant potential associated with strong cellular proliferation and differentiation in the ovary following the surgery. This, however, remains a subject of contention about PRP. This presents a significant issue in the infusion treatment of stem cells (as opposed to PRP) into the ovary, as the undifferentiated cells are multipotent and may lead to neoplasia [63].

Women with POI frequently exhibit small and fibrotic ovaries, complicating the intraovarian injection of 2–4 mL of PRP. However, this procedure can be enhanced through distention, which may involve the creation of new tissue planes and the administration of injections at multiple ovarian sites [35].

Our meta-analysis has shown that intraovarian PRP injection significantly enhances the quantity of M2 oocytes in women with POR. This matches the clinical trial by Barrenetxea et al., which showed a slight increase in the total number of mature oocytes collected in the group receiving PRP therapy [64]. This agreement supports our idea that PRP might increase the number of oocytes available for fertilization, but we still need to investigate how it works, whether through growth factors from platelets or some other physical effect. Nonetheless, a significant disparity arises when evaluating reproductive outcomes. The meta-analysis revealed a pregnancy ratio of 0.21 and a live birth ratio of 0.18 in women with poor ovarian reserve after PRP injection. In women with POI, the figures were marginally lower, recorded as 0.138 for pregnancy and 0.10 for live birth, respectively. The research by Barrenetxea et al. did not show any important improvements in key areas, such as the number of blastocysts formed, the number of normal blastocysts, or the rates of clinical and full-term pregnancies [64]. The clinical pregnancy rate in the PRP group of their experiment was markedly inferior to that of the control group. This paradox indicates that just augmenting the quantity of oocytes may not inherently lead to enhanced oocyte quality, superior embryo development, or, ultimately, elevated pregnancy success rates. This discrepancy may arise from various sources, including variability in PRP preparation techniques and timing of injections. As previously mentioned, discrepancies in PRP preparation and administration among various research can markedly affect findings. Our study findings demonstrate that one-step PRP preparation resulted in a superior increase in oocyte yield compared to two-step preparation in both POI and POR patients. Moreover, the absence of an activator led to a reduction in FSH levels in women with POR. In studies where PRP was injected during the follicular phase in women with POR, there was an elevation in AMH levels and a reduction in LH levels.

Multiple methods exist for processing whole blood to generate PRP [65]. The speed and duration of centrifugation, together with the separation method employed (utilizing mechanical or manual pipettes), may differ between studies. After preparing PRP, one can either activate it with chemicals or leave it unaltered to facilitate the release of its natural granules and growth factors. Upon injection into soft tissue, PRP is inherently triggered by the collagen present in the tissue [66]. Moreover, platelets are further stimulated by the mechanical stress induced during centrifugation. Chemical activation necessitates the utilization of calcium gluconate, calcium chloride, or an anticoagulant like thrombin. Some researchers believe that chemical activation is necessary for PRP to work fully, while others think it's an unnecessary step and that just using mechanical activation is enough to ensure degranulation.

It should be noted that depending on the methods and processes used to make the PRP, the concentrations of bioactive factors are also different since the growth factors content of PRP has a very short half life, and the effects of PRP continue for only a short time. Our meta-analysis suggests that intraovarian PRP injection could be tried in all women with POI and POR in whom other measurements to improve their ovarian response failed.

Strength and limitations

This systematic review and meta-analysis evaluated the impact of intraovarian injection of PRP in patients with POR or POI. Despite being a relatively recent method, this meta-analysis included 23 studies on intraovarian PRP injection. A comprehensive search strategy and separate analyses of the studies that included individuals with POI and POR were the strengths of this study. However, there are some limitations. Most studies used a before-and-after treatment design with relatively small sample sizes, which increases the risk of bias. Most studies did not include data on important outcomes, such as pregnancy and live birth rates. Significant heterogeneity existed between studies, so we employed the random-effects methodology to assess and account for this heterogeneity. The studies included in the analysis exhibit significant variation in terms of patient's age and the dosage of PRP used. Besides, variations in PRP preparation methods, patient selection criteria, and timing of PRP administration may be the sources of high heterogeneity between the studies. Although we anticipated these limitations due to the newness of this treatment method in the field of infertility, the positive results of our study encourage conducting well-designed randomized controlled trials.

Conclusion

Our systematic review and meta-analysis revealed that intraovarian injection of PRP improves ovarian reserve in women with POR and POI. This systematic review found nonsignificant improvements in FSH or E2 levels and significant improvements in AMH, AFC, the number of retrieved oocytes, and M2 oocytes. The PRP injection may enhance pregnancy, although randomized clinical trials are required to confirm its accuracy. This novel therapy seems to have the potential to put an end to our lengthy search for a solution to insufficient ovarian reserve. Finally, autologous intraovarian PRP injection needs to be studied on a larger scale in a clinical trial setting with standardized preparation, injection, and follow-up techniques.

Author contributions

All authors have contributed to the conducting of this study. F.SH, F.M., and H.Gh.B. participated in the study design, data extraction and search for articles, and interpretation of data, and read and approved the final manuscript. F.SH participated in the analysis and interpretation of data and assisted in drafting the manuscript. S. S. participated in editing the article and drafting the manuscript. All authors read and approved the final manuscript.

Funding

The authors received no financial support or grants for this project.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

Not applicable.

Competing interests

The authors declare no competing interests.