Ideal Weight Gain in Pregnancy

Abstract & Commentary

By John C. Hobbins, MD, Professor and Chief of Obstetrics, University of Colorado Health Sciences Center, Denver, is Associate Editor for OB/GYN Clinical Alert

Dr. Hobbins reports no financial relationship to this field of study.

Synopsis: Evaluation of gestational weight gain guidelines for women with normal prepregnancy body mass index.

Source: DeVader S, et al. Evaluation of gestational weight gain guidelines for women with normal pre-pregnancy body mass index. Obstet Gynecol. 2007;110:745-751.

Last month an article was featured in the OB/GYN Clinical Alert from the October issue of Obstetrics & Gynecology. Since the issue was rich in good material, I will go back to it to review information pertaining to one of the most common questions asked of providers—"How much weight should I gain in my pregnancy?"

Although I will focus on the first of three papers dealing with an answer to this question, material from the other two will be folded in.

De Vader et al reviewed Missouri birth certificate data from 1999-2001. Using only those women with a normal body mass index (BMI) who delivered term infants, the patients were broken up into 3 groups: 1) those who gained less than 25 lbs.; 2) those whose weight gain was within recommended guidelines; 25-35 lbs. (37,292); and 3) those who exceeded 35 lbs. (40,552).

Those in the lower weight gain category had significantly lower rates of preeclampsia (OR=0.56), cephalopelvic disproportion (OR=0.64), failed induction (OR=.68), cesarean section (OR=.82), and large-for-gestation (LGA) babies (OR=0.4) than those gaining the recommended weight. The downside was that they had a higher rate of small-for-gestation (SGA) babies (OR=2.14). Those in the upper weight gain category had a significantly lower rate of SGA (OR=0.48), but increased odds for preeclampsia (OR=1.88), LGA (OR=2.43), failed induction (OR=1.5), and cesarean section (OR=1.35) compared with those in the "normal" weight gain category.

This study indicated that with those with normal BMIs, gaining more than or less than recommended weight had higher rates of adverse outcome, as well as some interesting trade-offs. However, all in all, the recommendation of 25-35 lbs seemed to be a reasonable guideline. I did find it interesting that more (42%) Missouri women gained more than 35 lbs than those falling into the "recommended" category (37%).

The second article dealt with Missouri patients who were in the high BMI category (>30). As classified by the NIH definition, these obese patients were further broken down into Class I (30-35), Class II 35-40, and Class III (>40). The perinatal outcomes were assessed according to weight gain. The most important finding was that for every class of obesity, if the patient gained less than 15 lbs., the risk of LGA infants, preeclampsia and cesarean section was significantly lower than for those gaining more than 15 lbs. However, the incidence of SGA infants was higher in this group.

In the last article from Sweden, Cedergren analyzed perinatal outcome data from almost 300,000 pregnancies and came up with ideal weight gains for women with various body types. The results are laid out in the table below.

BMI
Ideal Weight Gain
<20
9-22 LBS
20-24.9
5-22 LBS
25-29.9
<20 LBS
≥30
<13 LBS

Commentary

In so many aspects of medicine, the pendulum swings back and forth, sometimes very quickly. In the 1950's and 1960's, it was in vogue to recommend that patients restrict their weight gain since it seemed to make sense (without real proof at the time), that this would decrease the risk of preeclampsia and make it easier to attain their pre-pregnant weight after delivery. Then there was a major swing during the "I'm OK, You're OK" era toward a laissez-faire approach to weight gain (backed again by lack of data to support restrictive measures, but with no real evidence that extra weight gain was good for the fetus and mother). Now, we do have data to indicate that if one has a "normal" pre-pregnant weight, gaining more than 35 lbs (something that was done in 40% of Missouri gravidas) increased the risk of adverse outcome. Also, if patients were categorized as obese (BMI >30), their best outcomes came with some weight gain restriction (less than the lowest previously recommended level of 25 lbs).

Last, although it is clear from the Swedish study that we may be dealing with "apples and oranges" regarding body habitus, life styles and diet, it is clear that when it comes to food "some" is good but "more" is not necessarily better and "less" in some cases may not be necessarily bad.