New York, Feb 3 (IANS): Couples in which both partners are obese may take over 50 per cent longer to achieve pregnancy, compared to their non-obese counterparts, say researchers, including one of Indian-origin.

"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 from US National Institutes of Health's Eunice Kennedy Shriver 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," Sundaram said of the study that appeared online in the journal Human Reproduction.

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 kept a record of 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 researchers compared the average time to achieve a pregnancy among couples in the non- obese group to that of the couples in the obese group with a BMI of 35 or greater.

The researchers 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.

The researchers found that the obese couples took 55 percent longer to achieve pregnancy than their normal weight counterparts. 

The findings suggest that taking steps to lose weight may help reduce the time needed to conceive.