For all of its wonders, pregnancy is a time with a lot of restrictions too. There are certain foods you’re not supposed to eat, medications or supplements you shouldn’t take, activities to avoid because they can increase the risk of falling, and of course you need to refrain from smoking and drinking alcohol. One of the things many pregnant women still enjoy, however, is getting to indulge in second helpings and dessert. After all, they often reason, those extra calories are necessary when you’re eating for two. And it’s just that type of thinking that may explain why new research has determined that many women go above and beyond medical recommendations for weight during pregnancy.

The study, which took place at the Centers for Disease Control and Prevention in Atlanta, Georgia, found that almost half of pregnant women gain an excessive amount of weight over that nine-month period.¹ Haelle, Tara. “Many Women Gain Too Much Weight While Pregnant.” WebMD. 11 March 2015. Accessed 18 March 2015. http://www.webmd.com/baby/news/20150311/many-women-gain-too-much-weight-while-pregnant-study-finds The subjects were more than 44,000 women from across 28 states, each of whom gave birth to a single, full-term baby during 2010 or 2011.

The scientists used the women’s body mass index (BMI) calculated with their pre-pregnancy weight to determine whether they were at a healthy weight prior to conception. Those with a BMI under 18.5 are underweight, 18.5 to 24.9 represents a normal weight, 25 to 29.9 is considered overweight, 30 to 34.9 is obese, and 35 and above is deemed severely obese. This categorizing was performed because medical guidelines vary based on a woman’s BMI before pregnancy. The recommendations were developed by the Institute of Medicine, a nonprofit organization that is a subsidiary of the National Academy of Science. The healthy recommended amount to gain for a woman of normal weight is 25 to 35 pounds, while underweight women are encouraged to gain between 28 and 40 pounds. Overweight women should limit weight gain to 15 to 25 pounds, and obese women to 11 to 20 pounds.

But the results showed the reality was quite different from these recommendations. Less than one-third of the women–32 percent–gained within the range of the guidelines. Nearly half of them–just over 47 percent–gained more than the recommended amount. The researchers did not specify how much excessive weight on average they totaled, but chances are pretty good that they did not overshoot by just a pound or two in most cases. And the remaining 20 percent actually did not gain enough weight during pregnancy, which is not healthy either.

Certain factors appear to have had an effect on the participant’s risk of gaining too much weight. Those with pre-existing high blood pressure, those who exercised regularly prior to pregnancy, and those who quit smoking because of conceiving were all found to be more likely to put on too high a number of pounds. The physically active women were a somewhat surprising group, because it might be assumed they would continue working out to some extent and were aware of the value of a healthy lifestyle. Then again, perhaps the problem was that they stopped exercising–but continued to eat as though they still were.

Weight gain is expected and necessary when your body is doing the work of nourishing a growing baby. Yet clearly, many women are not getting the message or are ignoring their obstetricians as to how many pounds they really need to put on. The extra weight is not just from the increasingly growing baby, but also from increased blood volume, amniotic fluid, the placenta, uterine expansion, and natural fat stores. In fact, a 2013 study at the University of Maryland in College Park found that gaining too little weight during pregnancy is associated with an increased risk of infant mortality.² “Inadequate Pregnancy Weight Gain a Risk Factor for Infant Mortality.” University of Maryland. 20 December 2013. Accessed 19 March 2015. http://www.umdrightnow.umd.edu/news/inadequate-pregnancy-weight-gain-risk-factor-infant-mortality

But the findings of the current study show overabundant weight gain during pregnancy to clearly be a far more common problem, and that brings up a whole different set of dangers. One issue is gestational diabetes, which occurs when blood sugar levels become elevated while you are pregnant. It puts the baby at risk for a large birth weight, making premature labor or Caesarean section more likely and has been linked with a higher likelihood that the child will develop ADHD. And excessive weight gain also can result in pre-eclampsia, a form of hypertension that can restrict the flow of blood and oxygen to the baby and do damage to the mother’s liver and kidneys. Note: for those of you concerned about getting your figure back after the baby is born, a lot of the extra weight, particularly the weight from increased blood volume, amniotic fluid, the placenta, and uterine expansion, will simply “drop off” after the baby is born. The weight that’s going to give you a problem is the “extra” weight that comes from an “overabundance” of stored fat. That’s the weight that’s tough to get rid of, but that’s also the weight that you over-store in the first place.

So if you are pregnant, make an effort to keep your weight gain in the recommended range. You can certainly eat more if you’re hungry, but stick with nutritious foods that will benefit your baby much more than a huge slice of cake will. And get some exercise daily, even if the only thing you are comfortable doing is walking. In the end, both you and your little bundle of joy will be healthier for it.