Research | Open | Open Peer Review | Published:
The correlation between raised body mass index and assisted reproductive treatment outcomes: a systematic review and meta-analysis of the evidence
Reproductive Healthvolume 15, Article number: 34 (2018)
Public funding for fertility services within the United Kingdom is limited, and therefore, strict guidance exists regarding who can be offered treatment under the National Health Service (NHS). Body mass index (BMI) is a universal criteria adopted by both the public and private sector.
This study addresses an important aspect of the impact of a raised BMI on fertility treatment outcomes. We standardise the analysis of the data by only including studies incorporating the WHO BMI criteria; the current reference point for clinicians and clinical commissioning groups in ascertaining which group of patients should receive treatment. This study is an update of the previous systematic review performed in 2010, with the inclusion of a larger number of cycles from central databases such as the Society for Assisted Reproductive Technology (SART).
An electronic literature search was conducted through the Cochrane, Medline and Embase libraries. Data extraction for each outcome measure was pooled and expressed as an odds ratio with 95% confidence intervals. Where clinical heterogeneity was evident, the random effects model was used to calculate the risk ratio and a fixed effects model was used for the remaining studies. A p value < 0.05 was considered statistically significant.
A total of 49 studies have been identified and included in this systematic review. Overweight and obese (BMI ≥ 25 kg/m2) women have a statistically significant lower live birth rate (OR 0.81, 95% CI 0.74–0.89, p < 0.00001) following Assisted Reproductive Technology (ART) when comparisons are drawn to women with a normal BMI. An increase is also demonstrated in the number of miscarriages experienced by women with a BMI ≥ 30 kg/m2 (OR 1.52, 95% CI 1.28–1.81, p < 0.00001).
Although this review concludes that a clear impact of BMI on ART outcomes is demonstrated, there remains questions as to the pathophysiology underlying these differences. This review supports the government’s stringent criteria regarding BMI categories under which NHS funding is made available for ART, through a clear description of poor reproductive outcomes in women with a BMI ≥ 30 kg/m2.
Plain English summary
This study highlights the impact of an overweight or obese female partner on fertility treatment outcomes, in particular focusing on IVF. Women who are overweight or obese have been shown to be less likely to have a life birth outcome from an IVF cycle. They are also more likely to suffer from early miscarriages whilst undergoing fertility treatments.
The correlation between raised body mass index and assisted reproductive treatment outcomes: A systematic review and meta-analysis of the evidence.
Obesity is a major challenge for today’s clinicians. In 2016, the World Health Organisation (WHO)  stated that a staggering 39% of adults aged > 18 years fell into the overweight category, of which 40% were accounted for by women. Furthermore, 13% of the adult population were documented to be obese, with women accounting for 15% (WHO Global Health Observatory Data 2016). A raised body mass index (BMI) has been linked to a number of medical comorbidities, as well as being implicated in having a detrimental impact on the reproductive capacity of women in particular. Women who fall into high BMI categories can present with hypothalamic-pituitary ovarian dysfunction and thus, low fecundity rates. In 2011, Rittenberg et al.,  concluded that women with a BMI ≥ 25.0 kg/m2 had a lower live birth rate through assisted reproductive treatments (ART) compared with women of a normal BMI. This has been further supported by multiple large studies evaluating the impact of BMI on ART outcomes.
The WHO classification of BMI is widely referred to, and provides standardisation for comparison of research outcomes. A documented BMI of 18.5–24.9 kg/m2 is considered normal and healthy and the preferred range. A BMI of 25–29.9 kg/m2 refers to overweight and a BMI ≥ 30 kg/m2 is considered obese. The latter range is further subdivided into Class 1 (30.0–34.9 kg/m2), Class 2 (35.0–39.9 kg/m2) and Class 3 (≥ 40.0 kg/m2).
This paper, considers the current evidence regarding the impact of raised BMI on outcomes following ART treatment. A systematic review and meta-analysis of the available evidence will help provide or refute the current recommendations from the government regarding the allocation of resources for fertility treatment.
Literature searches were conducted through the Cochrane, Embase and Medline libraries (1966–2017). The medical subject headings (MeSH) were generated for two categories: 1. Body mass index (BMI, overweight, obesity); 2. in vitro fertilisation (IVF)/ intracytoplasmic sperm injection (ICSI) (embryo, embryo transfer, ART). All identified papers were reviewed by two authors (PRS and MM) independently. All discrepancies, regarding inclusion or exclusion of the data were discussed with a final decision mutually agreed upon.
Study inclusion and exclusion criteria
All relevant published studies reporting on the effects of BMI on IVF and ICSI pregnancy outcomes were included. Studies that reported donor cycles, conception by natural cycles, intrauterine insemination, waist hip ratio, and non-WHO classification of BMI were excluded. In addition, studies reporting on the effects of paternal body mass index on IVF/ ICSI outcomes were also excluded.
The primary outcome measure assessed was live birth rate following an IVF/ ICSI cycle. Secondary outcome measures included: clinical pregnancy rate; and, miscarriage rate. The presence of a gestational sac on an ultrasound scan at least four weeks following on from an embryo transfer was used as confirmation for a clinical pregnancy. The clinical pregnancy rate was calculated per IVF/ ICSI cycle. For the purpose of this review, miscarriage was defined as pregnancy loss ≤ 20 weeks gestation. The miscarriage rate was calculated per clinical pregnancy.
Data extraction for each outcome measure was pooled and expressed as an odds ratio (OR) with a 95% confidence interval (CI). Clinical heterogeneity (I2)  was considered significant when the I2 value was < 50%. Where clinical heterogeneity was evident, the random effects model (DerSimonian and Laird, 1986) was used to calculate the risk ratio, and clinical heterogeneity was explored by comparing the variation in studies, such as, study design, study quality and interventions. Particular care was taken to further evaluate studies with similar first authors to avoid heterogeneity in the study population. For the remaining pooled data, the fixed effect model  was used to calculate the risk ratio. Statistical analysis was performed using the RevMan 5.3 software. A p value < 0.05 was considered statistically significant.
The search strategy yielded 7458 electronic citations (Fig. 1). Of this, 2830 were removed secondary to duplications. Titles and abstracts were reviewed for the remaining 4628 publications. After screening of the titles and abstracts, 4508 publications were further excluded. Full manuscripts were obtained for the remaining 120 articles. A further 16 articles were excluded as they did not use the WHO classification for BMI categories. A further 55 articles were excluded as per the inclusion exclusion criteria. The remaining 49 articles met all requirements and were included in this systematic review and meta-analysis (Table 1).
Primary outcome measure
Life birth rate per IVF/ ICSI cycle
In women with a BMI ≥25 kg/m2 versus BMI < 25 kg/m2, a total of 14 studies were pooled and a statistically significant reduction in the live birth rate (OR 0.81, 95% CI 0.74–0.89, p < 0.00001; Fig. 2a) was seen. There was significant heterogeneity between the included studies (I2 = 65%).
A total of 11 studies compared women with a normal BMI against those who were overweight (BMI 25–29.9 kg/m2). An analysis of the pooled data showed a statistically significant reduction in the live birth rate in women with a BMI 25–29.9 (OR 0.92, 95% CI 0.86–0.97, p = 0.005; Fig. 2b). No significant heterogeneity (I2 = 18%) was documented.
Data for women with a normal BMI versus BMI ≥ 30 kg/m2 came from the pooling of 10 studies. The live birth rate for women with a BMI ≥30 kg/m2 was statistically significantly lower than for women with a normal BMI (OR 0.81, 95% CI 0.79–0.82, p < 0.00001; Fig. 2c). No significant heterogeneity (I2 = 0%) was detected in the data source.
Secondary outcome measures
Clinical pregnancy rate
A total of 37 studies were pooled for BMI < 25 kg/m2 versus BMI ≥25 kg/m2. A statistically significant reduction in the clinical pregnancy rate was demonstrated for women with a BMI ≥25 kg/m2 (OR 0.82, 95% CI 0.77–0.88, p < 0.00001; Fig. 3a). However, there was significant heterogeneity (I2 = 58%, p < 0.00001) between the studies analysed.
A statistically significant reduction in the clinical pregnancy rate was demonstrated for women with a BMI between 25 and 29.9 kg/m2 when compared to women with a normal BMI (19 studies pooled, OR 0.89, 95% CI 0.84–0.94, p < 0.00001; Fig. 3b). No significant heterogeneity (I2 = 31%) was seen between the studies.
Pooled analysis from 18 studies demonstrated a statistically significant reduction in the clinical pregnancy rate for women with a BMI ≥30 kg/m2 when compared to women with a normal BMI (OR 0.80, 95% CI 0.74–0.87, p < 0.00001; Fig. 3c). There was no significant heterogeneity (I2 = 32%) present between the studies.
An increased risk of miscarriage is demonstrated in women with a BMI ≥25 kg/m2 when compared to women with a BMI < 25 kg/m2 (26 studies pooled, OR 1.30, 95% CI 1.15–1.48, p < 0.0001; Fig. 4a). However, significant heterogeneity (I2 = 53%, p = 0.0001) was seen between the studies.
Women with a BMI 25–29.9 kg/m2 were also more likely to have a miscarriage when compared to women with a normal BMI (18 studies pooled, OR 1.15 95% CI 1.05–1.26, p = 0.002; Fig. 4b). There was no significant clinical heterogeneity (I2 = 16%) in this group.
The risk of miscarriage is further increased in women with a BMI ≥30 kg/m2 when compared to women who fall into a normal BMI category (17 studies pooled, OR 1.52, 95% CI 1.28–1.81, p < 0.00001; Fig. 4c). No significant heterogeneity (I2 = 46%) was demonstrated between the studies.
Dosage of gonadotrophin stimulation
Women with a BMI ≥25 kg/m2 required significantly larger total gonadotrophin dosages than women with a BMI < 25 kg/m2 (15 studies pooled, weighted mean difference [WMD] 196.03iu, 95% CI 131.91–260.16, p < 0.00001; Fig. 5a). However, significant heterogeneity (I2 = 75%, p < 0.00001) was present between the studies.
Women with a BMI 25–29.9 kg/m2 were demonstrated to require significantly higher total gonadotrophin dosages than women with a normal BMI (12 studies pooled, WMD 83.67iu, 95% CI 24.54–142.80, p = 0.006; Fig. 5b). However, significant heterogeneity (I2 = 80%, p < 0.00001) existed between the studies.
Furthermore, increased total dosages of gonadotrophin was documented for women with a BMI ≥30 kg/m2 when compared to women whose BMI fell into the normal category (13 studies pooled, WMD 363.58iu, 95% CI 252.99–474.17, p < 0.00001; Fig. 5c). However, significant heterogeneity (I2 = 81%, p < 0.00001) was present between the studies.
Duration of gonadotrophin stimulation
No significant difference in duration of stimulation therapy was documented between women with a BMI < 25 kg/m2 or ≥25 kg/m2 (13 studies pooled, WMD 0.10, 95% CI -0.10-0.31, p = 0.32; Fig. 6a), however significant heterogeneity (I2 = 95%, p < 0.00001) existed between the included studies.
Furthermore, no significant difference was seen for duration of gonadotrophin stimulation between women with a BMI 25–29.9 kg/m2 versus a normal BMI (8 pooled studies, WMD 0.02, 95% CI -0.10-0.13, p = 0.79, I2 = 48%; Fig. 6b) or for women with a BMI ≥30 kg/m2 versus a normal BMI (12 pooled studies, WMD 0.12 95% CI -0.24-0.47, p = 0.52; Fig. 6c), however significant heterogeneity (I2 = 96%, p < 0.00001) was noted between the studies for the latter comparison.
Public funding for fertility services within the United Kingdom is limited, and therefore, strict guidance exists regarding who can be offered treatment under the National Health Service (NHS). Body mass index (BMI) is a universal criteria adopted by both the public and private sector. This study addresses an important aspect of the impact of a raised BMI on fertility treatment outcomes.
We standardise the analysis of the data by only including studies incorporating the WHO BMI criteria; the current reference point for clinicians and clinical commissioning groups in ascertaining which group of patients should receive treatment. This study is an update of the previous systematic review performed in 2010, with the inclusion of a larger number of cycles from central databases such as the Society for Assisted Reproductive Technology (SART).
This systematic review and meta-analysis has clearly highlighted the negative impact of a raised BMI on the outcomes following ART treatment, with documented lower success rates and higher rates of miscarriages as well as higher total dosage of gonadotrophin usage with no effect on the duration of stimulation. The latter may have been balanced by higher dosages of treatment which can also have a cost implication. However, as most studies have included a BMI category of < 25 kg/m2, which would also include underweight women with a BMI < 18 kg/m2, the detrimental effects of which have been addressed in a number of previous studies, a risk of bias cannot be confidently excluded. This has been addressed through the inclusion of studies allowing for a sub-group analysis of women with a normal BMI with overweight and obese women.
The presented data is able to demonstrate statistical significance with low clinical heterogeneity for a number of factors reflective of success through ART treatment. Despite this, caution is advised for interpretation of the presented information as only a few of the included studies controlled for confounding factors such as age, smoking and duration of infertility. In order to reduce further clinical heterogeneity, studies not incorporating the WHO classification for BMI and paternal BMI were excluded.
The included studies were considered relevant if they conformed to the WHO classification of BMI, despite this, a considerable amount of methodological and clinical heterogeneity existed. The level of statistical heterogeneity for the primary outcome measure live birth rate and secondary outcome measures clinical pregnancy rate and miscarriage rate were limited. However, despite a significant increase in total gonadotrophin dosage requirements with increasing BMI categories, the studies demonstrated significant statistical heterogeneity, limiting their value.
The presented data can act as an aid in the counselling of subjects secondary to a clear impact on ART outcomes being demonstrated across all BMI categories. The evidence supports the government’s stringent allocation of funding when resources are significantly limited.
A raised BMI impacts reproductive health at the pre and post embryological stage of development, affecting oocyte quality and the endometrial environment .
A recent meta-analysis and systematic review by Best et al.,  has demonstrated that weight loss can improve pregnancy rate and ovulatory status with a trend favouring spontaneous conception. However, these effects have not been seen through ART. Of note, miscarriage rates were unaltered with a change in weight.
Besides the reproductive health effects of a raised BMI, clinicians should also be aware of the increased rate of pregnancy complications such as pregnancy induced hypertension, pre-eclampsia and gestational diabetes in women with a raised BMI. Women are also at an increased risk of an emergency caesarean section with increasing BMI [6, 7].
A holistic approach should be used when counselling patients seeking ART treatments using an open discussion method to inform patients of the effects of raised BMI on ART and obstetric care. This will allow couples to make an informed decision and to take ownership of their well-being.
This systematic review and meta-analysis further emphasises the negative impact of a raised BMI on ART outcomes. However, the underlying pathophysiology is beyond the scope of this systematic review and will need to be evaluated in future studies. The quality of this systematic review would be further improved if future study designs included the WHO classification of BMI and controlled for confounding variables.
Assisted reproductive technology
Body Mass Index
Follicle stimulation hormone
Gamete intra-Fallopian transfer
Human chorionic gonadotrophin
Intracytoplasmic sperm injection
In vitro fertilization
Medical subject headings
National Health Service
Ovarian hyperstimulation syndrome
Society for Assisted Reproductive Technology
WHO. Obesity and overweight. Geneva: World Health Organization. Fact Sheet 311. Available from http://www.who.int/mediacentre/factsheets/fs311/en/.
Rittenberg V, Seshadri S, Sunkara SK, Sobaleva S, Oteng-Ntim E, El-Toukhy T. Effect of body mass index on IVF treatment outcome: an updated systematic review and meta-analysis. Reprod BioMed Online. 2011;23(4):421–39.
Higgins JPT, Thompson SG. Quantifying heterogeneity in a meta-analysis. Stat Med. 2002;21(11):1539–58.
Mantel N, Haenszel W. Statistical aspects of the analysis of data from retrospective studies of disease. J Natl Cancer Inst. 1959;22:719–48.
Best D, Avenell A, Bhattacharya S. How effective are weight-loss interventions for improving fertility in women and men who are overweight or obese? A systematic review and meta-analysis of the evidence. Hum Reprod Update. 2017;23(6):681–705.
Aly H, Hammad T, Nada A, Mohamed M, Bathgate S, El-Mohandes A. Maternal obesity, associated complications and risk of prematurity. J Perinatol. 2010;30(7):447–51.
Bhattacharya S, Campbell DM, Liston WA, Bhattacharya S. Effect of body mass index on pregnancy outcomes in nulliparous women delivering singleton babies. BMC Public Health. 2007;7:168.
Fedorcsak P, et al. Obesity is a risk factor for early pregnancy loss after IVF or ICSI. Acta Obstet Gynecol Scand. 2000;79(1):43–8.
Wittemer C, et al. Does body mass index of infertile women have an impact on IVF procedure and outcome? J Assist Reprod Genet. 2000;17(10):547–52.
Wang JX, Davies M, Norman RJ. Body mass and probability of pregnancy during assisted reproduction treatment: retrospective study. Br Med J. 2000;321(7272):1320–1.
Loveland JB, et al. Increased body mass index has a deleterious effect on in vitro fertilization outcome. J Assist Reprod Genet. 2001;18(7):382–6.
Wang JX, Davies MJ, Norman RJ. Polycystic ovarian syndrome and the risk of spontaneous abortion following assisted reproductive technology treatment. Hum Reprod. 2001;16(12):2606–9.
Wang X, Davies J, Norman J. Obesity increases the risk of spontaneous abortion during infertility treatment. Obes Res. 2002;10(6):551–4.
Winter E, Wang J, Davies MJ, Norman RJ. Early pregnancy loss following assisted reproductive technology treatment. Hum Reprod. 2002;12:3220–3.
Doody KM, Langley MT, Marek DE, Nackley AC, Doody KJ. Morbid obesity adversely impacts outcomes with IVF. Fertility Sterility. 2003;80:S160.
Fedorcsák P, Dale PO, Storeng R, Ertzeid G, Bjercke S, Oldereid N, Omland AK, Abyholm T, Tanbo T. Impact of overweight and underweight on assisted reproduction treatment. Hum Reprod. 2004;19(11):2523–8.
Ryley DA, Bayer SR, Eaton J, Zimon A, Klipstein S, Reindollar. Influence of body mass index (BMI) on the outcome of 6,827 IVF cycles. Fertil Steril. 2004;82(Supplement 2):S38–9.
Van ECAM, et al. Obesity and clomiphene challenge test as predictors of outcome of in vitro fertilization and intracytoplasmic sperm injection. Gynecol Obstet Investig. 2005;59(4):220–4.
Hammadeh ME, Sykoutris A, Amer AS, Schmidt. Relationship between body mass index (BMI) and plasma lipid concentration and their effect on IVF/ICSI outcome. Fertil Steril. 2005;84(Supplement 1):S422.
Dechaud H, et al. Obesity does not adversely affect results in patients who are undergoing in vitro fertilization and embryo transfer. European Journal of Obstetrics Gynecology and Reproductive Biology. 2006;127(1):88–93.
Dokras A, et al. Obstetric outcomes after in vitro fertilization in obese and morbidly obese women. Obstet Gynecol. 2006;108(1):61–9.
Mitwally MF, Leduc MM, Ogunleye O, Albuarki H, Diamond MP, Abuzeid M. The effect of body mass index (BMI) on the outcome of IVF and embryo transfer in women of different ethnic backgrounds. Fertility Sterility. 2006;86:S68–9.
Metwally M, Cutting R, Tipton A, Skull J, Ledger WL, Li TC. Effect of increased body mass index on oocyte and embryo quality in IVF patients. Reprod BioMed Online. 2007;15:532–8.
Esinler I, Bozdag G, Yarali H. Impact of isolated obesity on ICSI outcome. Reprod BioMed Online. 2008;17(4):583–7.
Martinuzzi K, et al. Elevated body mass index (BMI) does not adversely affect in vitro fertilization outcome in young women. J Assist Reprod Genet. 2008;25(5):169–75.
Moini A, et al. The effect of body mass index on the outcome of IVF/ICSI cycles in non polycystic ovary syndrome women. International Journal of Fertility and Sterility. 2008;2(2):82–5.
Sneed ML, et al. Body mass index: impact on IVF success appears age-related. Hum Reprod. 2008;23(8):1835–9.
Ozgun MT, et al. The influence of body mass index on FSH dose and pregnancy rate in women undergoing ICSI-embryo transfer. Journal of the Turkish German Gynecology Association. 2009;10(1):1–5.
Sathya A, et al. Effect of body mass index on in vitro fertilization outcomes in women. Journal of Human Reproductive Sciences. 2010;3(3):135–8.
Zhang D, et al. Overweight and obesity negatively affect the outcomes of ovarian stimulation and in vitro fertilisation: a cohort study of 2628 Chinese women. Gynecol Endocrinol. 2010;26(5):325–32.
Bellver J, et al. Female obesity impairs in vitro fertilization outcome without affecting embryo quality. Fertil Steril. 2010;93(2):447–54.
Vilarino Lima F, et al. Body mass index and fertility: is there a correlation with human reproduction outcomes? Gynecol Endocrinol. 2011;27(4):232–6.
Farhi J, et al. High-quality embryos retain their implantation capability in overweight women. Reprod BioMed Online. 2010;21(5):706–11.
Davies D, et al. Are the negative effects of being overweight on reproductive potential evident in FET cycles? Reprod BioMed Online. 2010;20(Supplement S2):S58.
Funabiki M, et al. The influence of body mass index (BMI) on pregnancy outcomes among Japanese infertile women. Fertil Steril. 2011;96(3 Supplement 1):S115.
Hill MJ, Hong S, Frattarelli JL. Body mass index impacts in vitro fertilization stimulation. ISRN Obstetrics and Gynecology. 2011;2010:1–5.
Pinborg A, et al. Influence of female bodyweight on IVF outcome: a longitudinal multicentre cohort study of 487 infertile couples. Reprod BioMed Online. 2011;23(4):490–9.
Parker K, et al. Does body mass index (BMI) affect IVF outcomes? Fertil Steril. 2011;96(3 Supplement 1):S124.
Rittenberg V, Sobaleva S, et al. Influence of BMI on risk of miscarriage after single blastocyst transfer. Hum Reprod. 2011;26(10):2642–50.
Singh N, et al. Correlation of body mass index with outcome of in vitro fertilization in a developing country. Arch Gynecol Obstet. 2012;285(1):259–63.
Luke B, et al. Female obesity adversely affects assisted reproductive technology (ART) pregnancy and live birth rates. Hum Reprod. 2011;26(1):245–52.
Chavarro JE, et al. Body mass index and short-term weight change in relation to treatment outcomes in women undergoing assisted reproduction. Fertil Steril. 2012;98(1):109–16.
Galal AF, Elhelaly DN. Higher body mass index significantly affects intracytoplasmic sperm injection success rate. Fertil Steril. 2012;97(3 Supplement 1):S9–S10.
Werner M, et al. Body mass index (BMI) does not impact endometrial receptivity in fresh IVF cycles: evaluation of implantation rates (IR) and ongoing pregnancy rates (PR) following the transfer of euploid blastocysts. Fertil Steril. 2012;98(3 Supplement 1):S286–7.
Zander-Fox DL, et al. Does obesity really matter? The impact of BMI on embryo quality and pregnancy outcomes after IVF in women aged <38 years. Aust N Z J Obstet Gynaecol. 2012;52(3):270–6.
Ozgun MT, et al. Effect of body mass index on the risk of miscarriage after ICSI. Int J Gynecol Obstet. 2012;119:S535.
Ramezanzadeh F, et al. Impact of body mass index versus physical activity and calorie intake on assisted reproduction outcomes. European Journal of Obstetrics Gynecology and Reproductive Biology. 2012;163(1):52–6.
Moragianni VA, Jones SML, Ryley DA. The effect of body mass index on the outcomes of first assisted reproductive technology cycles. Fertil Steril. 2012;98(1):102–8.
Bailey AP, et al. Effect of body mass index on in vitro fertilization outcomes in women with polycystic ovary syndrome. Am J Obstet Gynecol. 2014;211(2):163.e1–6.
Schliep KC, et al. Effect of male and female body mass index on pregnancy and live birth success after in vitro fertilization. Fertil Steril. 2015;103(2):388–95.
Cai J, Liu L, Zhang J, Qiu H, Jiang X, Li P, Sha A, Ren J. Low body mass index compromises live birth rate in fresh transfer in vitro fertilization cycles: a retrospective study in a Chinese population. Fertility Sterility. 2017;107(2):422–9.
Ozekinci M, Seven A, Olgan S, Sakinci M, Keskin U, Akar ME, Ceyhan ST, Ergun A. Does obesity have detrimental effects on IVF treatment outcomes? BMC Womens Health. 2015;15:61. https://doi.org/10.1186/s12905-015-0223-0.
Caillon H, Fréour T, Bach-Ngohou K, Colombel A, Denis MG, Barrière P, Masson D. Effects of female increased body mass index on in vitro fertilization cycles outcome. Obesity Research & Clinical Practice. 2015;9:382–8.
Provost MP, Acharya KS, Acharya CR, Yeh JS, Steward JG, Eaton JL, Goldfarb JM, Muasher SJ. Pregnancy outcomes decline with increasing body mass index: analysis of 239,127 fresh autologous in vitro fertilization cycles from the 2008-2010 Society for Assisted Reproductive Technology registry. Fertil Steril. 2016;105(3):663–9.
Russo M, Ates S, Shaulov T, Dahan MH. Morbid obesity and pregnancy outcomes after single blastocyst transfer: a retrospective, north American study. J Assist Reprod Genet. 2017; https://doi.org/10.1007/s10815-017-0883-9.
Christensen MW, Ingerslev HJ, Degn B, Kesmodel US. Effect of female body mass index on oocyte quantity in fertility treatments (IVF): treatment cycle number is a possible effect modifier. A Register-Based Cohort Study PLoS ONE. 2016;11(9):e0163393. https://doi.org/10.1371/journal.
Availability of data and materials
All data generated or analysed during this study are included in this published article.
Ethics approval and consent to participate
Consent for publication
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.