Obesity and Fertility

Obesity & Fertility Treatment

Should a high body mass index (BMI) be enough to prevent a woman from undergoing fertility treatment? While the question is controversial, this is the official policy in several countries. For example, women with a BMI > 32 kg/m2 are banned from fertility therapy in New Zealand. In British Columbia, egg retrieval under sedation is not allowed in women with a BMI > 32 kg/m2.


Obesity has been associated with an impaired ability to conceive, primarily due to hormonal causes such as polycystic ovarian syndrome (PCOS). Brewer et al (2010) reported that women with abdominal obesity have a decreased pregnancy rate per cycle during each treatment cycle. Obesity impairs the response of women during assisted reproduction by affecting ultrasound imaging and subsequent egg retrieval. Obesity also provokes a poor response to super ovulation lowering overall pregnancy rates. Shah et al (2011) compared normal weight versus women with class III obesity (BMI > 40 kg/m2) and noted that the birth rate was 50% lower in the class III obesity group. Research also links obesity to complications during pregnancy such as hypertension, gestational diabetes, prolonged labor, increased blood loss, unexplained still birth, and increased neonatal admissions.

However, there is an ongoing debate over whether the medical evidence is conclusive enough to withhold fertility treatment. Balen (2006) reported that BMI did not affect the overall outcome of ovulation induction in women with PCOS and a BMI as high as 35 kg/m2. Dokras (2006) showed the success of in vitro fertilization outcomes were not affected by obesity up to a BMI of 40 kg/m2 although the cycle cancellation in the obese group was 25% compared to 11% in the normal BMI group. Maheshwari et al (2009) reported that there were no differences between women with normal BMI and high BMI in terms of associated costs: the cost per IVF cycle, cost of prenatal care, cost per positive pregnancy test, or cost per ongoing pregnancy. However, the researchers concluded that women should lose weight due to the increased obstetric complications associated with obesity.

In conclusion, educating infertile women who are obese on the benefits of losing weight is important. Infertile women who are obese should be counseled that a high BMI may negatively affect the likelihood of becoming pregnant and is correlated with complications during pregnancy.

References Balen, A.H. et al. (2006). British Journal of Gynecology, 113, 1195-1202. Brewer, C.J. et al. (2010). Reproduction, 140, 347-364. Dokras, A. et al. (2006). Obstetrics & Gynecology, 108, 61-69. Maheshwari, A. et al. (2009). Human Reproduction, 24, 633-639. Shah, D.K. et al. (2011). Obstetrics & Gynecology, 118, 63-70.