DENVER — Among couples using assisted reproductive technology, an overweight male partner may lower the chances of pregnancy, a retrospective study showed.
After controlling for several factors, including the mother's body mass index, every 5-unit increase in the father's BMI was associated with a 28 percent decrease in the likelihood of clinical pregnancy, according to Dr. Zaher Merhi of Albert Einstein College of Medicine and Montefiore Medical Center in New York City.
As there were no differences in the quality or concentration of sperm or day-three embryo quality between couples with an overweight male partner and those with a normal-weight male, some unknown factor must explain the association, Merhi said at the American Society for Reproductive Medicine here.
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He said his group plans on evaluating the quality of the day-five embryos to see whether there is a difference there.
Also, he said, the relationship may involve a factor that cannot be seen at the embryo stage with a microscope, perhaps an increase in sperm DNA fragmentation, which has been demonstrated previously in obese men.
If further research confirms the findings of the current study, clinicians may need to start counseling men as well as women about losing weight before undergoing in vitro fertilization, rather than focusing on female BMI, Merhi said.
To evaluate the association between an overweight male partner and the success of assisted reproductive technology, Merhi and his colleagues analyzed data from cycles performed at their center from 2007 to 2008.
The analysis was limited to 251 fresh in vitro fertilization/intracytoplasmic sperm injection embryo transfer cycles using a woman's own oocytes and her partner's sperm.
Overall, 37.5 percent of the cycles resulted in clinical pregnancy, with a lower rate in couples with an overweight male partner (BMI of at least 25) compared with those with a normal-weight man.
Couples with an overweight male also had a higher female BMI and more embryos transferred.
Sperm concentration, the total number of motile sperm, and the percentage of men with low sperm count were similar in couples with an overweight male and those with a normal-weight male.
Embryo quality on day three also did not differ based on the male partner's BMI.
In a multivariate analysis adjusting for potential confounders, including female BMI, female age, semen concentration, type of assisted reproductive technology, and number of embryos transferred, only an increase in male BMI and the number of embryos transferred were associated with odds of clinical pregnancy.