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Pregnancy Weight Gain: When the Guidelines Might Not Be Right for You

Monday, May 19th, 2014

When you find out you’re pregnant, one of the first things your doctor will probably want to discuss with you is how much weight you should gain over the course of your pregnancy. The guidelines say that most pregnant women should gain between 25 and 35 pounds – more if they start out underweight, less if they are overweight to begin with. How does that weight gain break down?

  • 1  pound for the placenta
  • 2 pounds for amniotic fluid
  • 2  pounds for the increased weight of the uterus
  • 1 pound for increased breast size
  • 3 ½ pounds for increased blood volume
  • 6 ½ pounds for maternal fat stores
  • 6-7 ½ pounds for the full-term baby

All of this adds up to between 22 to 24 pounds that a healthy woman of normal weight can safely gain during her pregnancy.  The operative term here is “normal weight”.

However, many women don’t start pregnancy at their ideal weights. For a woman who is very underweight, somewhat more weight gain may be optimal, and may be the natural outcome of eating enough nutritious food to nourish herself and her growing fetus.

A much more common problem, though, is that of the woman who starts her pregnancy overweight. One in five pregnant women (20%) are obese at the start their pregnancy.   Gaining too much weight during pregnancy is one of the most preventable causes of complications, ranging from gestational diabetes to preeclampsia to overly large babies that require cesarean deliveries.

A woman who is overweight or obese can safely gain less than 25 pounds during her pregnancy as long as she eats a healthy diet. Keep in mind that “eating for two” should mean that you are eating twice as well, not twice as much.  The fetus usually weighs less than 1/20 of its Mom’s weight. So for an overweight or obese woman, switching to the healthy diet she needs for pregnancy may actually mean a reduction in calories, and gaining less than the recommended amount or even losing weight may be the natural result.  And, an obese pregnant woman shouldn’t get overly concerned about it.  If you are obese, you already have a fluffy substrate or matrix upon which your pregnancy will grow.  A numerical end-point, i.e., weight gain or loss, should not be used in obese pregnant women, but rather a healthy, balanced nutritional intake should take priority. 

This is perfectly fine as long as your doctor agrees (always discuss matters related to your pregnancy with your own doctor, because your situation is unique), and as long as your diet contains all the necessary nutrients and fluids you and your baby need.  I, as the principle investigator, have done the original research and have published the first and, to date, the only randomized clinical trial regarding the outcomes of nutritionally monitored obese pregnant women.  A well-balanced diet is the way to go resulting in less problems during the pregnancy.

A pregnant woman should be drinking lots of water – at least eight cups a day – and another four cups of skim milk, leaving very little room for soda or fruit juice (which are both mostly sugar). And eating all the fresh fruits, vegetables, lean meats, fish, and whole grains you need does not, for the most part, leave room for junk food.

The occasional treat is fine. A cup of coffee, a small serving of chocolate, and the like do not have to be abandoned entirely for nine months, and trying to do so would most likely set you up for failure anyway as the temptation to “cheat” would be too great. Tell yourself you can have treats – just not every day and not in large amounts.

Exercise will also help you feel better and keep your weight in check during pregnancy. Walking, swimming, and using a stationary bicycle are excellent exercises now. Keeping track of everything you eat and which exercise you perform each day and for how long can help you stay accountable and motivated.

Just because countless people – even strangers – will tell you that you “should” be gaining 25-35 pounds does not make this necessarily right for you. They don’t even know you!  Talk to your doctor to determine whether you can safely gain less; delivering a baby in better shape than they were in nine months ago is a very real possibility for many women. See my book, Inside Information for Women, for much more information on this and other women’s health issues.

– Yvonne S. Thornton, M. D., M. P. H