Do Big Moms Make Big Babies?

There are a lot of stories and old wives’ tales surrounding pregnancy and birth, and each and every possible factor of having a baby is subject of discussion. The potential size of your baby is no different, and whether or not you’ll have a large baby is a question on many people’s lips. Thanks to recent research though, that question can now be answered – at least for some people. Studies show that mothers who are overweight or obese during pregnancy are much more likely to have big babies than smaller mothers.

A recent co-operative review study between universities in the UK looked at research involving more than 30,000 women of European ancestry and their babies. The studies examined the mother’s body mass index (BMI), blood sugar levels, and blood pressure as well as the weight of the resulting babies. The results, published in the Journal of American Medical Association, demonstrated that not only will larger moms have larger babies, but moms with high blood sugar levels (whether overweight or not) will also have bigger babies. Conversely, moms with high blood pressure will have smaller babies[1].

Big Babies

The size of the average baby is around 6-7 pounds[2], but the amount of babies being born at 9.9 pounds or more has increased over the last ten years[3]. These are known as LGA babies, or ‘large for gestational age’. The American Journal of Obstetrics and Gynecology suggests that overweight moms are twice as likely to have an LGA baby and obese moms are three times as likely. What’s more, a study by the Kaiser Permanente Center for Health Research shows that women who gain 40 pounds or more actually during the pregnancy are also twice as likely to have LGA babies[4], even if they started out with a healthy BMI. So the statistics show that this increase in baby size is there, but the questions we’re left with are why are babies getting bigger? And why does it matter?

Bigger Babies

The fact that babies are getting bigger is not only due to the size of the mother, of course. One of the most obvious reasons that babies are getting bigger is that we are getting healthier in terms of pregnancy development. Mothers generally don’t smoke and drink during pregnancy any longer, for example, and these factors influence the resulting size of the baby. That however would only explain a small growth, rather than why babies are increasingly being born LGA.