Pregnancy & Weight

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If mothers had untreated tooth decay, their children had four times the risk of decay compared with children of other mothers. If mothers consumed large amounts of sugar, their children had four times the risk of tooth decay compared with children of mothers with low sugar consumption.

Weight Gain in Pregnancy: A Major Factor in the Development of Obesity in Childbearing Women?

The prevalence of overweight in women of childbearing age has nearly doubled since the 1960s (Gunderson et al.). Data from the Third National Health and Nutrition Examination Survey (NHANES III) indicate that 23% of women ages 25 to 55 years of age are overweight and 26% are obese using the most recent weight classification system for Body Mass Index (BMI) (Must et al.).

Average weight gain in pregnancy (gestational weight gain) increased from 10 kg to 15 kg [22 to 33 pounds] in approximately the same time period.

In 1990, the Institute of Medicine (IOM) issued new gestational weight gain guidelines that were generally higher than previous recommendations. These are shown in Table 1 below. Two physicians, Johnson and Yancey, have criticized the IOM guidelines as potentially contributing to the development of obesity in women. While indicating that the evidence suggests an average of 1 kg or 2.2 pounds of weight retention per birth beyond that due to aging, the IOM Committee also indicated that this figure may be an underestimate because it is based on older studies and the higher gestational weight gains seen in women in recent years could not be considered.

In a recent review of the literature on the topic, Gunderson and Abrams state that six studies have reported significant positive relationships between gestational weight gain and postpartum weight retention. Further two studies using self-reported weight data from the 1988 National Maternal and Infant Health Survey have found significantly greater weight retention among women who had weight gains in pregnancy that exceeded the IOM guidelines (Keppel et al., Parker et al.).

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A Cornell-Bassett Healthcare Study on the Topic

A team of researchers (including myself) from the Division of Nutritional Sciences at Cornell University and the Research Institute of Bassett Healthcare in Cooperstown, NY were interested in determining whether weight gain in pregnancy that exceeded the IOM gestational weight gain guidelines was related to postpartum weight retention in a contemporary sample of pregnant women and whether excessive gestational weight gain is an important factor in the development of obesity surrounding childbearing. With funding from the National Institutes of Health, we undertook the "Bassett Mothers Health Project" to investigate these issues. (NIH grant number HD29549)

A sample of 622 women who enrolled for prenatal care at Bassett Healthcare were followed from early pregnancy until one year postpartum. Women completed mailed questionnaires during pregnancy and at 6 and 12 months postpartum; information was extracted from their medical records; and they were weighted during pregnancy and at one year postpartum. One year weights were available for 577 women.

Our Findings

Table 1 shows the proportion of women in each body mass index (BMI) category at the beginning of pregnancy as well as the proportion of women gaining more than what IOM recommends during their pregnancies. Results show 37.5% of the women in the normal BMI group, 67.7% in the high (overweight) BMI group, and 46.3% in the obese group gained more than the upper limit of the IOM recommended range. The low BMI group was the only group in which the majority of women (56%) stayed within the recommended weight gain range of 12.5 to 18 kg [28 to 40 lb].

Table 1. Body Weight Characteristics of Women in Sample at One Year Postpartum (N=577)

Forty-one percent of women were at the same weight or lighter at one year postpartum compared to early pregnancy, but 25.1% of women were 4.55 kg [10 lb] or more heavier.

Figure 1 shows weight retained at one year by initial BMI and gestational weight gain groups. Several general trends are clear. Women in all BMI groups who gained less than is recommended weighed the same or less at one year postpartum than they did in early pregnancy. For all but the low BMI group, women who gained more than is recommended were heavier at one year postpartum than women who gained the recommended amount or less. Women in the normal, high and obese BMI groups who gained more than is recommended retained significantly more (p<0.01) than normal BMI women who gained the recommended amount.

Figure 1. Mean Weight Retention at One Year Postpartum by Initial Body Mass Index (BMI) Category and Gestational Weight Gain Group

In the sample, there were 38 incident cases of obesity. In other words, 38 women who had not been obese in early pregnancy according to the IOM classification system (BMI >29), were obese at one year postpartum. Twenty-eight of these women were among the 181 women who gained more than was recommended, while only 10 came from the group of 261 women who gained at or below the recommended amount. Thus the relative risk of becoming obese that is associated with excessive gestational weight gain in this population-based sample was 4.

The population attributable risk is the maximum proportion of a disease that can be attributed to the etiological factor. In this study, the factor of interest is excessive gestational weight gain, that is, gaining more weight in pregnancy than is recommended by the IOM. The population attributable risk in this sample was 56%, meaning 56% of the incident cases of obesity could have been prevented by staying below the upper limit of the IOM ranges for gestational weight gain. This result is due in part to the high prevalence of excessive gestational weight gain with an average of 42% of pregnant women gaining more than is recommended.

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Conclusions

Excessive gestational weight gain appears to be a very important factor in the development of obesity in this primarily rural, White population of women in Upstate New York. Health care providers should make every effort to encourage pregnant women to "stay in the range" of weight gain recommended by the Institute of Medicine. It is best for both infants and their mothers.

Note to Providers

Full-sized BMI and Weight Gain Charts are included in a publication called "Supplementary Materials for Nutrition During Pregnancy and Lactation: An Implementation Guide". This publication is available free of charge by ordering from the National Maternal and Child Health Catalog.

Two of the charts, are included here:

View "Chart for estimating Body Mass Index (BMI) Category and BMI (Pounds and Inches)"

View "Prenatal Weight Gain Chart in Pounds".

Both charts can be printed using Microsoft Word:

Print "Chart for estimating Body Mass Index (BMI) Category and BMI (Pounds and Inches)"

Print "Prenatal Weight Gain Chart in Pounds"

References

Gunderson EP, Abrams B. Epidemiology of gestational weight gain and body weight changes after pregnancy. Epidemiol Rev. 1999;21:261-275.

Must A, Spadano J, Coakley EH, et al. The disease burden associated with overweight and obesity. JAMA. 1999;282:1523-1529.

Institute of Medicine. Nutrition during Pregnancy. Part I, Weight Gain. Washington, D.C.: National Academy Press; 1990:10.

Johnson JWC, Yancey MK. A critique of the new recommendations for weight gain in pregnancy. Am J Obstet Gynecol. 1996;174:254-258.

Keppel KG, Taffel SM. Pregnancy-related weight gain and retention: Implications of the 1990 Institute of Medicine guidelines. Am J Public Health 1993;83:1100-3.

Parker JD, Abrams B. Differences in postpartum weight retention between black and white mothers. Obstet Gynecol 1993;81:768-74.

Source: Cornell, Food and Nutrition, Christine M. Olson, Ph.D., R.D. Professor,
Division of Nutritional Sciences, Cornell University

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