"A lot of studies on fertility and body composition have focused on the female partner, but our findings underscore the importance of including both partners," said Rajeshwari Sundaram, a researcher at the US National Institute of Child Health and Human Development.
"Our results also indicate that fertility specialists may want to consider couples' body compositions when counselling patients," said Sundaram.
The study enrolled 501 couples in the US from 2005 to 2009. The women ranged from 18 to 44 years of age, and the men were over 18 years old.
The couples were followed until pregnancy or for up to one year of trying to conceive.
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Scientists also calculated body mass index (BMI) for each participant, categorising 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 researchers 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 researchers found that the class II couples took much longer to achieve pregnancy than couples not struggling with obesity.
The findings appear in the journal Human Reproduction.