So Much For Child-Bearing Hips: Study Finds Obesity In Black Women May Hinder Fertility

July 30, 2012  |  

Weight may be a cause for infertility in black women.

According to the Black Women’s Health Study (conducted by Boston University), young black women who are obese or heavy through the hips were less likely to become pregnant:

Fecundity [the ability to reproduce] was significantly reduced in a dose-response fashion for women who were overweight, obese and very obese after adjustment for age, education, smoking history, alcohol intake, physical activity, parity, region, and waist-to-hip ratio.

A large waist-to-hip ratio, also was significantly associated with lower fecundity, with fecundity ratios less than 1 indicating reduced fecundity or longer time to pregnancy (TTP).

“Overall and central [obesity] are associated with reduced fecundability in black women,” Lauren Wise, Sc.D., said at the annual meeting of the Society for Pediatric and Perinatal Epidemiologic Research.

This isn’t necessarily a “black women are doomed to failure” study, considering they did this study before on White women and found the same thing.

The substudy is the first TTP study in black women, and its results largely agree with previous studies consistently linking high body mass index and reduced fertility in white women.

Little is known about the determinants of fertility in black women, who are disproportionately affected by the obesity epidemic in the United States. Studies of central obesity and fertility in whites have been inconclusive, with some suggesting that obesity may interfere with estrogen metabolism, increase insulin resistance, and change the quality and pH of cervical mucus, said Dr. Wise of the Slone Epidemiology Center at Boston University.

So how did they come to this conclusion about black women?

The substudy cohort was drawn from 59,000 women in the Black Women’s Health Study, the largest study of U.S. black women’s health yet conducted and now in its 17th year of follow-up. A total of 15,500 women completed a Web-based survey in 2011 reporting the TTP for each planned pregnancy. There were 10,272 births, of which only 4,315 births (43%) were planned. The researchers excluded both the unplanned pregnancies and women who had incomplete data, a history of infertility, and age older than 40 years either in 1995 or while they attempted pregnancy; the final sample included 2,084 births and 209 unsuccessful pregnancy attempts among 1,706 women, aged 21-40 years.

The fact that only 43% of those pregnancies were planned seems like the bigger story (and problem) here, but apparently that wasn’t the focus considering they excluded them from the study.

The average age was 34 years for all BMI groups including those classified as overweight (BMI, 25-29 kg/m2), obese (BMI, 30-34) and very obese (BMI, 35 or greater).

BMI was inversely associated with education and vigorous exercise, and was positively associated with waist-to-hip ratio, waist circumference, and current smoking status, reported Dr. Wise and her colleagues.

After adjusting for all previous covariates plus BMI, researchers found that a waist circumference of 33-35 inches – but not beyond – was significantly associated with lower fecundity.

Fecundity was not lower in women who were underweight (BMI less than 18.5; FR, 1.11).

Not surprisingly, these results are controversial with many believing that blaming obesity in black women for infertility is too simplistic.

During a discussion of the results, one attendee pointed out that asking participants about marital status, which the investigators did, is not the same as asking about relationship status or frequency of intercourse.

Another audience member observed that male obesity is proving to be just as important as female obesity in terms of a couple’s inability to conceive.

That audience member was right. It’s not just obese women who can have problems with infertility. Men can have the same issue.

Indeed, a recent systematic review involving 14 studies and 9,779 men reported that overweight and obese men are at increased risk of oligozoospermia [semen with a low concentration of sperm and a common finding in male infertility] or azoospermia [not having any measurable level of sperm in his semen and associated with very low levels of fertility or even sterility], compared with normal-weight men.

Of course “BMI” is contentious among black women. Many believe that the chart is too general and doesn’t account for different races and body types while others believe that overweight is overweight regardless of weight. Most can agree though that even an adjusted BMI chart would still deem some women obese and, for those trying to conceive, that obesity could be a problem.

However, it’s not impossible for a woman struggling with obesity to get pregnant. Dr. Loralei L. Thornburg wrote in Seminars in Perinatology:

Just like everybody else, women considering pregnancy or currently pregnant should get a healthy mix of fruits and vegetables, lean proteins and good quality carbohydrates. Unfortunately, these are not the foods people lean towards when they overeat. Women also need to be sure they are taking vitamins containing folic acid before and during pregnancy.

If a woman starts her pregnancy overweight or obese, not gaining a lot of weight can actually improve the likelihood of a healthy pregnancy. Talking with your doctor about appropriate weight gain for your pregnancy is key.

Unchecked obesity in black women is problematic, but it doesn’t have to be a death sentence to her dreams of getting pregnant.

What do you think of this study?

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