The present prospective study evaluated the prevalence of FSH-R receptor polymorphisms among infertile and fertile women of Indian-Asian ethnicity. The study concluded that GG (Ser/Ser) is the most common genotypes among fertile Indian women at SNP 680. The genotypes did not significantly affect the ART outcomes on sub-group analysis of infertile cases into normo-responders and unexpected poor-responders at both SNPs.

The first study from India on FSH- R genotypes was done by Achrekar et al. [8] in 2009, which showed heterozygous genotype were most common at both 680 and 307 position among fertile and infertile women. Also, the distribution of different sub-types was comparable among cases and controls. In our study, GG (Ser/Ser) at position 680 was the most common genotype among fertile controls. Rest distribution of all genotypes at both positions showed heterozygous genotype (Asn/Ser (AG) at 680; Ala/Thr (AG) at 307) to be most common with infertile women having significantly higher genotypes with allele “A”(p < 0.01). Previous studies have reported similar observations [13, 15].

The interesting genotype; Asn/Ser at position 680 has been studied extensively, and different conclusions have been reported in different studies from different ethnic populations. Latest Delphi consensus statement by Conforti A et al. [16] and previous studies [17,18,19,20] have reported that Ser/Ser (position 680) is associated with higher basal FSH levels; higher requirement of gonadotrophins and less number of oocytes. Similarly in report by Nenonen et al. [7], the relative risk of development of ovarian hyperstimulation syndrome (OHSS) was significantly higher in women with SNP AA and AG at position 680 as compared to those with GG. Recently, Baldini et al. studied the effect of FSH-R 680 on ovarian response in ART cycles and further divided them into abnormal and normal responders. He concluded that in abnormal responders, a significant prevalence of the amino acid serine at position 680 was detected (p < 0.05) [20]. Similar to the above study; Bayraktar et al. [21] also observed more number of poor-responders in Ser/Ser group among Turkish women.

There are two studies published till date which are in concordance with our study. First study which reported the findings against Perez Mayorga et al. was by Klinkert et al. who studied SNP 680 and its relation with IVF response and IVF outcomes. The ovarian response was comparable between patients with different FSH receptor genotypes, and patients with polymorphism Ser/Ser (GG) had implantation and pregnancy rates three times higher compared with patients with polymorphism Asn/Asn [22].

A previous study on Indian ethnicity by Achrekar et al. evaluated the combined effect of the polymorphisms at positions −29 and 680 of FSH-R with the type of ovarian response and receptor expression. Various clinical parameters revealed that 75% of the subjects with A/A–Asn/Asn (AA) genotype were poor ovarian responders (odds ratio 7.92; P = 0.009). The study speculated that the A allele at position −29 and the Asn allele at position 680 (AA) might be more susceptible to poor ovarian response. Although our study evaluated only SNP 680 polymorphism, we have reported that Ser/Ser (GG) at 680 is most common among fertile controls, and least risk of poor oocyte yield and least association with EFS. Despite this, it did not affect the CLBR, which was comparable among all the genotypes.

EFS is one unpredictable outcome in IVF cycles with wide range of prevalence reported upto of 0.045–7% of aspirated IVF cycles [23]. Lazaros et al. reported that lower serum FSH levels, higher follicle and oocyte numbers, increased numbers of large follicles as well as decreased empty follicle numbers in Thr307Thr/Asn680Asn (AA) women as compared to Thr307 Ala/Asn680Ser (AG) and Ala307Ala/Ser680Ser (GG) women (p < 0.006, p < 0.01, p < 0.008, p < 0.01, p < 0.005, respectively). Contradictory to this study, most of the patients in our cohort with EFS despite high serum hCG levels, had either AA or AG genotype both at 680 and 307 positions; implying that presence of ‘A’ allele in Indian-Asian women may cause resistance to FSH action. Also lowest peak oestradiol levels (<1000 pg/ml) were observed among AA genotype at both SNP 680 and 307.

Despite these differences, most of the studies have reported comparable IVF outcomes among different genotype subgroups. Jun et al. [24] found highest pregnancy rate per transfer with AA genotype and the lowest with GG genotype at SNP 680. While Klinkert et al. [22] reported that Ser680Ser was associated with higher pregnancy rates and implantation rates. Konig et al. [13] reported comparable CLBR among different genotypes despite Ser/Ser having higher basal FSH levels and a significantly lower number of oocytes and embryos. Lindgren et al. [25] found that women homozygous for Ser at both FSH-R and LHR had ~40% higher chance of live birth in the first IVF cycle with a doubled chance in cumulative cycles. CLBR in the present study although numerically higher in the heterozygous group (Asn/Ser and Ala/Thr), but the difference was not statistically significant among three genotypes similar to those published by Konig et al. [13].

Studies have evaluated the effect of 307 SNP polymorphism and reported Ala/Ala (GG) genotype to be significantly associated with the use of higher doses of recombinant FSH; suggesting lower sensitivity of ‘G’ allele to r-FSH but CLBR was comparable among three genotypes, at 307 position [5].

The strengths of our study are the largest study cohort of Indian ethnicity along with fertile control group where we had IVF details available for 46 controls (voluntary oocyte donors). This is the first study to divide the IVF cohort into normal-responders and unexpected poor responders and POSEIDON I and II stratification according to IVF response. This is the first study from India to stratify all unexpected poor-responders according to POSEIDON stratification and correlation of different genotypes with different POSEIDON groups. Patients with GG genotype showed the lowest risk of low-oocyte-yield in IVF/ICSI cycles at both SNPs. The results are similar to previous studies by Achrekar et al. and Klinkert et al. and not in concordance with other reports and meta-analyses. This is the first study elaborating the EFS cases and their relation to polymorphisms and was found maximum in women with allele A at both positions.

Limitations are that not all the women recruited could undergo IVF during COVID pandemic. COVID also affected oocyte donor recruitments. Dose selection and adjustments were according to clinician discretion which may have affected oocyte yield. Although our centre is tertiary referral centre, future prospective studies with different centres in the country may give more generalisable information.

To conclude; GG genotype in Indian-Asian women (Ser/Ser 680 and Ala/Ala 307) is characterised by lower basal FSH levels and is more common among fertile women. The effects of these polymorphisms on IVF parameters are small and negligible, with no significant effect on oocyte yield and CLBR. The presence of allele “A” (asparagine and threonine) may be responsible for genuine EFS and unexpected low estradiol levels in IVF cycles in Indian women. The results pave the way for new studies based on pharmacogenomics, randomised controlled prospective, and multi‐centre studies from different geographical areas before utilising FSH-R polymorphism as a confounder for the deficient ovarian response in ART.