February 6, 2017Fertility
According to an article published online in Human Reproduction (3 February 2017), couples in which both partners are obese may take from 55 to 59% longer to achieve pregnancy, compared to their normal weight counterparts. According to the authors, a lot of studies on fertility and body composition have focused on the female partner, but these new findings underscore the importance of including both partners.
The couples in the study were part of the Longitudinal Investigation of Fertility and the Environment (LIFE) Study, which examined the relationship between fertility and exposure to environmental chemicals. The study enrolled 501 couples from Michigan and Texas from 2005 to 2009. The women ranged from 18 to 44 years of age, and the men were over 18 years old. Women kept journals to record their monthly menstrual cycles, intercourse and the results of home pregnancy tests. The couples were followed until pregnancy or for up to one year of trying to conceive. The study also calculated body mass index (BMI) for each participant, categorizing couples with obesity into two subgroups: obese class I (with a BMI from 30 to 34.9) and the most obese group, obese class II (a BMI of 35 or greater). The authors compared the average time to achieve a pregnancy among couples in the non- obese group (84 men and 228 women) to that of the couples in the obese class II group (75 men and 69 women). The authors then calculated the probability that a couple would achieve pregnancy by using a statistical measure called the fecundability odds ratio (FOR). The measure estimates couples’ probability of pregnancy each menstrual cycle while trying for pregnancy, relative to their BMIs. Results showed that the class II couples took much longer to achieve pregnancy than couples not struggling with obesity. Couples in the non-obese group had a FOR of 1. Obese class II couples had a FOR of .45 — indicating that they took 55% longer to achieve pregnancy than their normal weight counterparts. When the study took into account other factors known to influence fertility — such as age, smoking status, physical activity level and cholesterol level — the ratio for obese class II couples dropped to .41, or a 59% longer time to achieve pregnancy.
The authors concluded that couples’ obesity may reduce fertility chances and that fertility specialists may want to take couples’ weight status into account when counseling them about achieving pregnancy. In addition to the health benefits of a healthy weight for reducing risk of other diseases such as Type 2 diabetes, heart disease and cancer, taking steps to lose weight may help reduce the time needed to conceive.