Why You’re Probably Gaining Too Much (or Too Little) Weight In Your Pregnancy

When it comes to normal weight gain during pregnancy, the Institute of Medicine (IOM) recommends a range—from 11 to 40 pounds—based on your pre-pregnancy body mass index (BMI). But according to a research review published in the Journal of the American Medical Association (JAMA), most women gain more or less than the IOM recommends. And it can have a significant health impact.

In their review of data on over 1 million pregnancies, the researchers found that 47 percent of women gained more weight during pregnancy than the IOM recommends, and 23 percent gained less. Being underweight led to a 5 percent higher chance of having a smaller-than-normal infant and a preterm birth. Being overweight meant a 4 percent higher chance of having a larger infant and higher chance of a C-section.

Improper weight gain can affect the size of the baby, which may contribute to problems with breathing or regulating blood sugar, according to time.com. A study published in JAMA in 2000 found that 1,000 babies who were on the smaller side experienced lower academic achievement than normal sized babies at birth, although they still went on to get married, have jobs, and be overall satisfied with life.

Emily Oster, a professor of economics at Brown University told Time, “If anything, you should probably be more concerned about gaining too little weight than too much.” Women are better off weighing slightly more because if they are underweight, they run the risk of their child being malnourished, according to americanpregnancy.org.

At the same time, it’s important not to let pressure to gain a certain amount of weight make you crazy, as stress has negative effects on a pregnancy too. When it comes to pregnancy weight gain, Oster says people need to “chill out.”

Weight is far from the only factor that influences the health of the baby, which is why keeping up with prenatal visits is critical if you want to help your baby have the best possible health. In particular, here’s what you need to know to help prevent birth defects.