Children of obese women could be less fertile than children born to women of a healthier body weight, a new study from the Yale School of Medicine has found.

The research, conducted by obstetrics and gynecology professor Hugh Taylor, investigated the relationship between obesity and fertility in mice. The researchers found that when women are obese and have low levels of a hormone that stimulates hunger, called ghrelin, their daughters are at a higher risk for infertility because they have not been exposed to sufficient quantities of the hunger hormone in their mothers’ wombs.

“People know that it’s not healthy to be obese, but they didn’t necessarily know it was affecting their children and their children’s fertility,” Taylor said.

The research centered around mice that were heterozygous for the ghrelin gene — meaning that they carried two different forms of the gene — and had low levels of ghrelin. The research team bred these mice and compared the offspring to their parents, by implanting embryos into the female offspring.

Female offspring showed a decreased reproductive ability, Taylor said, due to “really abnormal” gene expression in the uterus, and, as a result, healthy embryos did not implant as well in these mice, rendering these mice less likely to reproduce. The daughters differed from their mothers only in this gene expression.

The results show that obesity in mothers affects the well-being of future generations, Taylor said

“The effects may not even be realized until 20, 30 years later,” he said. “They may not even relate it back to the obesity of their mother.”

In the case of ghrelin, infertility is preventable, Taylor said, because only women who are obese during pregnancy will be affected. A woman who was obese when she was younger but at a normal weight during her pregnancy, produces fertile offspring who have normal levels of ghrelin, he said. Similarly, if a woman gained weight and became obese after she gave birth and did not have any more children, her offspring would not be at risk for infertility.

MeMe Roth, founder and president of the advocacy group National Action Against Obesity, said the findings of Taylor’s study demonstrates the necessity of maintaining a healthy weight.

“If we fail to reverse obesity, then it appears natural selection will exact her cruel correction for us,” she said. “This study further underscores our obligation to be healthy before ever conceiving.”

Taylor said he and his research team plan to conduct a follow-up study that investigates whether dieting prior to pregnancy changes the effects of a ghrelin deficiency. They also plan to test the effects of injecting ghrelin into obese mice so that they have normal levels of the hormone.

According to the Centers for Disease Control, 34 percent of American adults are classified as obese.