Weight, race affect success of fertility treatment

Obese and minority women have less success with treatment for infertility than normal-weight women and Caucasian women, new research from Michigan State University suggests.

A historical cohort study of 31,672 embryo transfers at United States clinics in 2007-nearly 25,000 in Caucasian women-found that obese women were about 20% more likely to fail fertility treatment than normal-weight women and that minority women, regardless of weight, had lower success rates than Caucasian women. Overall, 45% of Caucasian women became pregnant compared with 43% of Hispanic women, 38% of Asian women, and 36% of African American women. Among women who carried their babies for at least 22 weeks, 85% of Caucasian women gave birth compared with about 80% of Asian and Hispanic women and 76% of African American women.

“These findings indicate significant disparities in pregnancy and live birth rates, even within BMI [body mass index] categories,” the authors write. Failure to conceive was significantly more likely among obese women overall (adjusted odds ratio [AOR], 1.22), obese and normal-weight Asian women (AOR, 1.36 and 1.73, respectively), normal-weight Hispanic women AOR, 1.21), and overweight and obese African American women (AOR, 1.34 and 1.47, respectively. Failure to achieve live birth among women who conceived was markedly greater in overweight and obese women overall (AOR, AOR, 1.56 and 2.20, respectively) and Hispanic women (AOR, 1.57 and 1.76, respectively), and normal-weight and obese African American women (AOR, 1.45 and 1.84, respectively).

The cause of the disparities is unclear, say the researchers led by Dr. Barbara Luke, ScD, MPH. Racial differences may arise in part from body fat distribution, the researchers suggest, because African American women tend to carry more weight in the upper body, where it may cause greater inflammation and health risks, and they are more likely to have uterine fibroids. The researchers speculate that vitamin D deficiency, more prevalent in darker skinned people, could play a role by increasing the risk of bacterial vaginosis and attendant pregnancy complications. Variables such as age and type of infertility didn’t explain racial differences in the findings.

The study was published online January 27 in Fertility and Sterility.