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Overweight and Obese Women Deliver Fewer IVF Live Births

Major Finding: Compared with normal weight women undergoing

IVF, a live birth was significantly less likely among overweight

(adjusted OR, 0.96) and obese women in class I (0.63), class II (O.39),

and class III (0.32).

Data Source: Retrospective cohort study of 4,609 women undergoing initial IVF at a single center in Boston.

Disclosures: Dr. Jones said she had no relevant disclosures.


 

From the Annual Meeting of the American Society for Reproductive Medicine

ORLANDO – Obesity significantly lowers a woman's chance of delivering a live birth after in vitro fertilization, according to a retrospective study of more than 4,500 women.

Up to a 68% lower chance for a live birth was the major finding when researchers compared overweight and obese women to those with a normal body mass index (BMI). Women with a BMI greater than 25 kg/m

The live birth rate declined as BMI increased, Dr. Stephanie Jones said. Compared with women with a normal BMI (18.50-24.99), the adjusted odds ratio (OR) for a live birth was 0.96 among overweight women (25-29.99); 0.63 for obesity class I (30-34.99); 0.39 for obesity class II (35-39.99); and 0.32 for those in obesity class III (BMI of 40 kg/m

The clinical message is to counsel patients that even “a modest amount of weight loss might improve IVF success rates,” Dr. Jones said at the meeting.

Dr. Jones and her associates examined outcomes after the first, fresh, autologous procedure for 4,609 women treated at Boston IVF in Brookline, Mass. from 2006 to 2010. Patients were aged 20-45 years.

A secondary outcome, the likelihood of implantation, was significantly different by BMI, compared with those with a normal BMI. Chances dropped for underweight women (BMI less than 18 kg/m

The likelihood of clinical pregnancy dropped only slightly for underweight women (adjusted OR, 0.98). However, it decreased significantly for overweight women (0.90) and for women in obesity class I (0.70), class II (0.41), and class III (0.43).

Interestingly, the miscarriage rate did not differ significantly according to maternal BMI, said Dr. Jones, a third-year resident in the department of obstetrics and gynecology, Beth Israel Deaconess Medical Center, Boston.

The normal-weight reference group included 2,605 patients with a BMI of 18.5-24.99 kg/m

In addition to its large sample size, the single institution design of the study is an advantage, Dr. Jones said. Previous researchers reported an association between increasing obesity and lower IVF success, but most of these studies were small, unadjusted, and focused on pregnancy rates.

“The live birth rate is the outcome most significant to our patients,” she said.

A systematic literature review found a decreased chance of IVF pregnancy (OR, 0.71) for overweight or obese women compared with normal weight women (Hum. Reprod. Update 2007;13:433-44). “But they only compared women in two groups – those with a BMI of 25 or less versus 25 plus,” Dr. Jones said.

In another study reported at the 2009 ASRM meeting, researchers found a lower clinical pregnancy rate and lower birth weights as maternal BMI increased (Hum. Reprod. 2011;26:245-52). This report was multicenter “and they did not necessarily control for differences in provider factors,” she said.

Dr. Jones and her associates also controlled for multiple potential confounders, including maternal age, paternal age, baseline follicle stimulating hormone levels, duration of stimulation, mean daily gonadotropin dose, peak estradiol, number of oocytes retrieved, use of intracytoplasmic sperm injection, embryo quality and number, transfer day, and number of embryos transferred.

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