Failing to Lose Weight a Danger to Next Baby

It can be hard to shed the baby weight, but a new study suggests it's best to do so before baby #2—even if you were a healthy weight and only gained 15 pounds.

Failing to Lose Weight a Danger to Next Baby Osadchaya Olga/Shutterstock

With all that new moms have to deal with, losing excess baby weight isn't always top priority. But a recent study published in the journal The Lancet gives busy first-time mothers a reason to make time for themselves to get healthy before getting pregnant again. Alarmingly, the findings showed that women who put on pounds between their first and second pregnancies had an increased risk for stillbirth and infant death.

Risk greatest for women of previously healthy weight

The researchers looked at more than 450,000 women in the Swedish Medical Birth Register who gave birth to their first and second children. Regardless of how much they initially weighed, women who gained between pregnancies had an increase in the risk of stillbirth. "Weight gain between pregnancies increases risks of obesity-related complications, including preeclampsia, gestational diabetes, and preterm birth," study author Sven Cnattingius, M.D., Ph.D., an OBGYN and professor at the Karolinska Institutet in Stockholm, tells Fit Pregnancy. "Weight gain appears to increase these risks especially in women who start off with a normal weight."

Exactly how many pounds are we talking? Mothers of average height and a previously healthy weight who gained two to four BMI points (13 to 24 pounds) had a 27 percent risk of infant death, and those who gained more than 4 BMI units increased the risk by 60 percent. The more gained, the greater the risk. "The increased risk was more prominent in women who started off with a healthy weight in their first pregnancy and then gained before the second, than in women who were already overweight or obese in their first pregnancy and gained additional weight," co-author Eduardo Villamor, M.D., M.P.H., Dr.P.H., a professor at the University of Michigan's School of Public Health, tells Fit Pregnancy. This is probably because of a proportionately greater increase in fat mass. On the other hand, the good news is that women who started out overweight and then lost at least 13 pounds had a 50 percent reduced risk.

How does mom's weight impact baby?

The study authors suspect that connection between mom's BMI and baby's negative outcomes has to do with pregnancy complications more common in overweight and obese women. "This is the focus of ongoing research," Dr. Villamor says. "Thus far it is known that maternal obesity is related to some types of preterm delivery, and preterm delivery is the strongest risk factor for infant mortality. Maternal obesity is also related to pregnancy complications," and to problems with the baby after birth. The increase in stillbirth is "harder to explain," Dr. Cnattingius says, but is probably also linked to the same pregnancy complications. "We speculate that obese women may also, due to [increased fat in blood] and inflammation, have reduced circulation across the placenta," he says, which could also heighten the risk.

Slimming down after baby

Unfortunately, many women find it hard to slim down after having a baby. "We suspect that a lot of what we call inter-pregnancy weight gain corresponds to 'baby weight' from the previous pregnancy that women are not able to shed off after delivery," Dr. Villamor says. "The reasons why such a large proportion of women cannot go back to their pre-pregnant weight are not fully understood."

Because the study compared the women's BMIs at the start of their first and their second pregnancies, Cnattingius says his research didn't separate weight gained during the first pregnancy and weight gained afterward. But gaining only the appropriate amount of pounds during the first pregnancy could help moms go back to their pre-baby weight sooner. "Monitoring weight gain during the initial pregnancy might be helpful, especially if women start off overweight or obese," Dr. Villamor adds. After the first baby is born, Cnattingius suggests trying to shed the pounds before conceiving again. "I would advise women to try to regain their weight they had before getting pregnant the first time, and women who started off as overweight or obese to reduce their weight even more," he says.