Obesity and Assisted Reproduction

Peter Kovacs, MD, PhD


October 18, 2011

The Effect of Increasing Obesity on the Response to and Outcome of Assisted Reproductive Technology: A National Study

Luke B, Brown MB, Missmer SA, Bukulmez O, Leach R, Stern JE; Society for Assisted Reproductive Technology Writing Group
Fertil Steril. 2011;96:820-825. Epub 2011 Aug 6.


Obesity is a growing health issue in the developing world. Excess body weight is associated with increased morbidity and mortality. The incidences of cardiovascular disease, diabetes, certain types of cancers, and orthopaedic problems are all increased as well. The risk of becoming overweight or obese increases with age, but it is also seen with increasing frequency in young adults and even children.[1]

When present during the reproductive years, obesity affects reproduction. In obese men, the sperm count is lower, whereas obese women are more likely to have menstrual problems. Chronic anovulation affects the endometrium of obese women, and the risk for hyperplasia and even endometrial cancer is higher. Underlying medical problems associated with obesity may also reduce a woman's chance for successful reproduction. It is not surprising that overweight and obese couples are more likely to require assisted reproductive technology (ART) to achieve pregnancy. In this case, in addition to the usual infertility evaluation, a thorough medical screening is important to reduce prenatal complications. Testing should be done for diabetes, hypertension, and dyslipidemia. If a woman's cycles are irregular, testing for endometrial hyperplasia/cancer is needed to complete the workup. The approach should be multidisciplinary and usually requires consultation with a dietician and an internist.

Infertility treatment should be started only when the patient is medically cleared. Some patients manage to lose weight during the process, but many remain overweight or obese. This review by Luke and associates looked at ART outcomes for patients in various body mass index (BMI) categories.

Study Summary

The analysis was conducted on the basis of records from the 2007-2008 Society for Assisted Reproductive Technology (SART) database. Data were collected for BMI, age, baseline follicle stimulating hormone (FSH) level, infertility diagnosis, race, medication use, and treatment outcome. Categories were created for BMI (< 18.5 kg/m2; 18.5-24.9 kg/m2; 25-29.9 kg/m2; 30-34.9 kg/m2; 35-39.9 kg/m2; 40-44.9 kg/m2; 45-49.9 kg/m2; and > 50 kg/m2). The analysis adjusted for age, race, infertility diagnosis, and the number of embryos transferred. The results are based on the analysis of 152,500 started cycles. Comparisons were made with the normal BMI group (18.5-24.9 kg/m2).

The risk for ovulatory dysfunction and tubal or endometrial problems increased with higher BMI, whereas the risk for endometriosis decreased. Women in the higher BMI categories required more gonadotropin and/or clomiphene citrate during the stimulation phase. When using a woman's own oocytes, the risk for cycle cancellation increased progressively with increasing BMI and was twofold in women with a BMI > 50 kg/m2. The risk for low response to stimulation also increased with higher BMI. The odds ratio for failing to achieve a clinical pregnancy rose across BMI categories. The odds ratio for failing to achieve a live birth increased through BMI categories and was 2.3 when the BMI was > 50 kg/m2.


The findings of this study, based on more than 150,000 cycles of in vitro fertilization (IVF) or intracytoplasmic sperm injection, clearly show the negative impact of increasing BMI on ART outcomes. Women with BMI > 25 kg/m2 were more likely to have menstrual, tubal, and uterine problems leading to infertility. Despite the use of more medications for stimulation, overweight and obese women were more likely to have reduced response, were at greater risk for cycle cancellation, and were less likely to have successful outcomes. This information should be shared with the overweight/obese patient who is seeking infertility care to allow her to make the lifestyle adjustments needed to improve her chances of pregnancy.

This study did not evaluate the prenatal complications of these pregnancies. Diabetes and hypertensive complications are more likely to develop during pregnancy in overweight and obese women. Thromboembolic events are more frequent as well. Partly as a result of these medical problems, preterm labor, preterm delivery, and the need for operative delivery are also more common in overweight and obese women. This affects not only the mothers but also their newborns.[2,3]These complications are associated with several-fold increased healthcare costs, and therefore have an impact on the healthcare system and society as a whole.

It is challenging to manage overweight or obese couples. We know that their chances are better if the woman loses weight, but often these couples want to enter treatment as soon as possible. They do not necessarily understand the implications of obesity. In general, IVF is associated with few risks, but the risks for inadequate monitoring, problems during sedation, bleeding, and infectious complications are all more frequent in patients with higher BMIs. In addition, we have to consider the reduced chances overweight/obese women have of achieving a successful pregnancy and live birth.[4,5,6] Most infertility specialists no longer practice obstetrics; therefore, they do not see the obesity-associated prenatal and perinatal complications on an everyday basis.

ART is expensive, and couples need to be made aware that their money may not be well spent when the treatment is started under suboptimal conditions. However, we also have to be realistic about what to expect from patients. Most women with BMIs of 45 kg/m2 and higher will not be able to reduce their BMIs to 25 kg/m2 to optimize their pregnancy success. As long as the overweight or obese patient makes a real effort to manage her weight, has no complicating medical problems, and is able to lose some weight, she should be permitted to start a cycle following appropriate counseling, even if her BMI is not yet in the normal range.



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