The incidence of obesity in the United States has reached epidemic proportions. The prevalence of obesity is increasing in both sexes, all age groups, all racial groups, and among all educational levels. According to the 2004 National Health and Nutritional Examination Surveys, the prevalence of obesity among adults 20–74 years of age has increased from 15% in the 1976–1980 survey to 32.9% in the 2003–2004 survey.1
According to the 1999–2002 National Health and Nutrition Examination Survey, the prevalence of overweight or obesity in adults aged older than 20 years was 65.0%, and the prevalence of obesity was 30.0%.2 Associated with an increase in obesity is a concomitant increase in the prevalence of many chronic health conditions, such as diabetes mellitus, hypertension, and cardiovascular disease. In women of reproductive age, obesity has also been associated with an increased rate of preeclampsia, operative vaginal deliveries, cesarean delivery, and postoperative complications.3 Therefore, obesity is a major concern in pregnancy.
The Institute of Medicine (IOM) recommends that underweight women (body mass index [BMI] less than 19.8) gain 35–45 lb during pregnancy, normal-weight women (BMI 19.8–26.0) 25–35 lb, overweight women (BMI 26.1–29.0) 15–25 lb, obese women (BMI 29.1–39.0) less than 15 lb, and that morbidly obese women (BMI higher than 39.0) gain no weight (BMI is calculated as weight (kg)/[height (m)]2). Weight gain within these guidelines has been associated with healthy fetal and maternal outcomes. Weight gain below these goals is associated with low neonatal birth weight, and weight gain above these goals is with neonatal macrosomia.4
Unfortunately, the prevalence of excessive gestational weight gain is increasing. Based on data from the National Maternal and Infant Health Survey, which includes a representative sample of women in the United States who had live births in 1988, 36% of women exceed the IOM recommendations. Only 20% of underweight women exceeded the goals, but 37% of normal-weight women and 64% of overweight women gained more weight than recommended.5
According to Shieve and colleagues in 1998, two thirds of women gain more weight in pregnancy than is recommended by the IOM.6
Not only is excessive gestational weight gain responsible for complications during pregnancy, it also contributes to increased postpartum weight retention. Women who gain more weight than recommended retain twice as much weight after pregnancy as women who gain within the IOM recommendations.5 In the National Maternal and Infant Health Survey, white women who gained above the IOM guidelines retained 2.2 kg (4.8 lb) at 10–18 months postpartum, whereas those who gained within the IOM guidelines retained only 0.7 kg (1.5 lb). African-American women who exceeded the recommended level of weight gain retained 5.8 kg (12.8 lb), whereas those who gained within the recommended levels retained 3.3 kg (7.3 lb).
Therefore, excessive weight gain in pregnancy may contribute to the development of obesity and its associated complications in women later in life. Given the evidence that excessive gestational weight gain is associated with increased complications in pregnancy, increased postpartum weight retention, and potentially with increased obesity in the nonpregnant state, this study examines an intervention aimed at reducing excessive gestational weight gain.
We designed a randomized controlled trial comparing a program of intensive counseling regarding diet and lifestyle during pregnancy with routine prenatal care. We specifically chose an inexpensive intervention that could be introduced easily into any obstetric practice. The intervention provided education and feedback about weight gain, appropriate exercise in pregnancy, and pregnancy-specific dietary counseling. We examined whether the intervention would reduce the number of women who exceed the IOM recommendations.
MATERIALS AND METHODS
This study was approved by the institutional review board of Carolinas Medical Center and was funded through a grant from the Carolinas Healthcare Foundation. The randomized controlled trial included women who presented to the Resident Obstetric Clinic in Charlotte, North Carolina, for prenatal care between October 2005 and April 2007. Inclusion criteria included: 1) prenatal care established at 6–16 weeks of gestation, 2) age 18–49 years, 3) all prenatal care received at the Resident Obstetrics Clinic, 4) English-speaking, Spanish-speaking, or both, and 5) singleton pregnancy. Exclusion criteria included: 1) prenatal care established at more than 16 weeks of gestation, 2) non–English-speaking or non–Spanish-speaking, 3) multiple pregnancy, 4) BMI higher than 40, 5) preexisting diabetes, untreated thyroid disease, or hypertension requiring medication or other medical conditions that might affect body weight, 6) delivery at institution other than Carolinas Medical Center-Main, 7) pregnancy ending in premature delivery (less than 37 weeks), and 8) limited prenatal care (fewer than four visits).
After completion of the usual care provided at the initial obstetrical appointment, the health care providers explained the study in full to each eligible patient. After giving written informed consent, study participants were stratified based on BMI (calculated based on participants’ self-report of prepregnancy weight and height measured in clinic) into three categories. Group 1 included underweight and normal-weight patients (BMI less than 26). Group 2 included overweight patients (BMI between 26 and 30). Group 3 included obese patients (BMI higher than 30). After this stratification, the patients were assigned randomly to either the control group, who received routine prenatal care for the remainder of the pregnancy, or to the intervention group, who received the standardized protocol of dietary and lifestyle counseling. Randomization was performed using computer-generated random allocation. Study randomization was numbered and sealed in an opaque envelope. Randomization occurred in consecutive order at the time of the new obstetrical visit.
The control group received routine prenatal care, including an initial physical examination and history, routine laboratory tests, and routine visits per American College of Obstetricians and Gynecologists standards. The only counseling on diet and exercise during pregnancy was that included in our standard prenatal booklet “What to do When You’re Having a Baby,” by Gloria Mayer (Institute for Health Advancement, 2003, La Habra, CA). At each routine obstetrical appointment, the participant’s weight was measured using a balance beam scale and recorded in the medical chart. The health care provider did not counsel the participant regarding any changes in diet or lifestyle.
The intervention group underwent a complete history and physical examination with specific attention paid to prepregnancy weight, current weight, height, and BMI. At the initial visit, the study group met with a registered dietician to receive a standardized counseling session, including information on pregnancy-specific dietary and lifestyle choices. The counseling consisted of recommendations for a patient-focused caloric value divided in a 40% carbohydrate, 30% protein, and 30% fat fashion. Patients were instructed to engage in moderate-intensity exercise at least three times per week and preferably five times per week. They also received information on the appropriate weight gain during pregnancy using the IOM guidelines. Each participant met with the dietician only at the time of enrollment.
At each routine obstetrical appointment, the participant’s weight was measured using a balance beam scale and charted on an IOM Gestational Weight Gain Grid in front of the participant. The health care provider (physician or nurse practitioner) informed the participant whether her weight gain was at the appropriate level. If her weight gain was within the IOM guidelines, the patient was praised and encouraged to continue her current diet and exercise regimen. If her weight gain was not within the IOM guidelines, the participant’s diet and exercise regimen was reviewed and she was advised on increasing or decreasing her intake and increasing or decreasing exercise.
Both groups of participants had their weight recorded shortly before delivery on arrival at Carolinas Medical Center. The total weight gain and the BMI change from prepregnancy to just before delivery were examined and compared between the study and control groups to deduce the efficacy of the intervention.
Before the initiation of the study, health care providers were educated on the goals of the study as well as the study protocol. The providers underwent training regarding the appropriate dietary and lifestyle counseling for each specific change in weight to standardize counseling technique.
The main study hypothesis was that an organized, consistent program of dietary and lifestyle counseling would prevent excessive gestational weight gain. The sample size was chosen based on several criteria. The current literature states that 30–35% of women gain within the IOM guidelines. Our theory was that 30% of the women in the routine care group would gain within the IOM guidelines and that an increase of 25% (from 30% to 55%) of women in the intensive counseling group gaining within the IOM guidelines would be clinically significant. Therefore, using an 80% power and an alpha of 0.05, this required 61 participants in each treatment arm to achieve overall statistical significance.
Demographic characteristics were described using frequencies, percents, means, and standard deviations. Potential differences between the two groups were analyzed using χ2 tests and t-tests (or Fisher exact tests and Mann-Whitney tests for sparse and nonnormally distributed data, respectively). We estimated odds ratios and 95% confidence intervals for the relationship between gestational weight gain category and treatment group using multivariable logistic regression models. A P value of less than .05 was used to define statistical significance in all cases. All analyses were performed using SAS 8 (SAS Institute, Inc., Cary, NC).
We randomized a total of 144 women for this study between October 2005 and April 2007. Forty-four women were excluded secondary to not fulfilling all inclusion criteria or meeting the exclusion criteria. Of these 44 women, one was excluded after it was determined that she was not pregnant. Additionally, eight women were excluded because they had not delivered as of the final analysis, two were excluded because their BMIs were higher than 40, eight delivered at an outside institution, two established prenatal care at more than 16 weeks of gestation, 13 had fewer than four prenatal visits, one had a preexisting medical condition, and nine delivered prematurely. Therefore, a total of 100 women completed the study and were available for analysis. Specifically, 57 women were assigned to the intensive counseling group and 43 to the routine care group (Fig. 1).
No statistically significant difference was detected in demographic composition between the intensive counseling group and the routine care group (Table 1). Furthermore, the study arms were not statistically different with respect to age, prepregnancy weight, height, and BMI (Table 2).
Our primary outcome was the rate of adherence to the IOM guidelines between our study groups. Participants in the intensive counseling group gained significantly less weight (28.7±12.5 lb compared with 35.6±15.5 lb, P=.01) than those in the routine care group. However, even though those the intensive counseling group gained less weight, we did not identify any difference in the rate of adherence to the IOM guidelines between groups. In the intensive counseling group, 61.4% of patients were adherent to the IOM guidelines; 48.8% were adherent in the routine care group (P=.21) (Table 3).
Our study group also was analyzed based on initial BMI group. Women in the overweight (BMI 26–29) and obese (BMI higher than 29) BMI groups were less likely to adhere to the IOM guidelines. Overweight women in each of the groups were adherent 30.0% (intensive counseling) and 25.0% (routine care) of the time. Obese women in each of the groups were adherent 33.3% (intensive counseling) and 20.0% (routine care) of the time, compared with 80.0% (intensive counseling) and 68.8% (routine care) among participants with healthy BMIs. There was no statistically significant difference in adherence across BMI groups between the intensive counseling and routine care groups when adjusted for BMI (Table 4). The most predictive factor of IOM adherence was having a normal prepregnancy BMI (Table 5).
A secondary outcome analyzed was the effect of weight gain on mode of delivery. Other secondary outcomes included rate of operative vaginal delivery, neonatal weight, and the incidence of preeclampsia, gestational diabetes mellitus, vaginal/perineal lacerations, and shoulder dystocia.
Although not reaching statistical significance, the cesarean delivery rate in the routine care group (27.9%) was greater than that in the intensive counseling group (14.0%, P=.09). The routine care group had significantly more cesarean deliveries due to “failure to progress” (routine care 58.3% compared with intensive counseling 25.0%, P=.02). Furthermore, women who gained more weight in pregnancy, regardless of counseling group, had higher rates of cesarean delivery. The average weight gained by those who delivered vaginally (30.4±13.4 lb) was less than the average weight gained by those who delivered via cesarean (36.8±16.3 lb) (P=.07).
Across the study population, nulliparous participants gained significantly more weight than did parous participants (36.5±14.5 compared with 27.7±12.7 lb) (P<.01). This remained true across BMI groups and regardless of intensive counseling compared with routine care group, with the exception of obese nulliparous women gaining less weight than obese multiparous women (14.3±15.3 compared with 20.6±12.6, not statistically significant) (Table 6). Parous women were nearly six times as likely to adhere to the IOM guidelines as were nulliparous women (odds ratio 6.2, confidence interval 1.6–24.1, P<.01) (Table 5).
We performed a secondary analysis to identify differences between women who were adherent to the IOM guidelines and those who were not. Women who were heavier prepregnancy were more susceptible to excessive weight gain in pregnancy. Patients who were not adherent to the IOM guidelines had an average prepregnancy weight of 154.3±33.4 lb, whereas IOM-adherent women had an average prepregnancy weight of 134.2±32.2 lb. (P<.01) (Table 7). Across groups, patients who were not adherent to the IOM guidelines had significantly heavier neonates (adherent 3,203.2±427.2 g compared with not adherent 3,517.4±572.4 g, P<.01).
No statistically significant differences were noted between the groups in adherence to IOM guidelines, rate of cesarean delivery, preeclampsia, gestational diabetes mellitus, operative vaginal delivery, or vaginal lacerations.
Our program of intensive counseling regarding appropriate dietary and lifestyle habits during pregnancy did reduce weight gain in comparison with a control population receiving routine prenatal care. However, the intervention did not result in a significant increase in adherence to IOM guidelines. Nevertheless, we feel that any weight loss achieved by our intervention could result in a decrease in antepartum, intrapartum, and postpartum complications. Furthermore, reduced pregnancy weight gain should result in a reduction in postpartum weight retention and obesity in the nonpregnant state, which should reduce the overall burden of obesity-related diseases such as diabetes mellitus and cardiovascular disease.
Women who were heavier prepregnancy were more susceptible to increased weight gain during pregnancy and, therefore, were less adherent to the IOM guidelines. We hypothesize that women who watch their dietary intake and weight prepregnancy are more likely to remain focused on maintaining their weight during pregnancy. The most predictive factor of IOM adherence was having a normal prepregnancy BMI. Although we recommend counseling all women regarding weight management, it is important to pay special attention to overweight and obese nulliparous women.
Few studies have examined the effects of specific antenatal interventions on weight gain in pregnancy. Olson et al found that an intervention consisting of gestational weight gain monitoring by health care providers and a by-mail patient education program reduced the risk of excessive weight gain only in a low-income subgroup of their total study population.7
Polley et al8 compared a stepped-care behavioral intervention with usual care in decreasing the percentage of women who gained more weight than the IOM recommendations. The intervention group received education about weight gain, healthy eating, and exercise and individual graphs of their weight gain. Those exceeding weight-gain goals were given more intensive intervention using a registered dietician. They found that the intervention significantly decreased the percentage of normal-weight women who exceeded the IOM recommendations (33% compared with 58%, P<.05). However, there was a nonsignificant effect in the opposite direction among overweight women (59% on intervention and 32% of control gained more than recommended).8
The studies by Olson et al7 and the Polley et al8 are similar to our study design in that the respective interventions are designed to encourage pregnant women to gain an amount of weight during pregnancy that is within the range recommended by the IOM. However, the intervention in the Olson et al7 study used a by-mail patient nutrition education program only and clinical guidance was given by obstetric health care providers. The Polley et al8 study intervention is similar to ours in consisting of regularly scheduled counseling by a nutritional health professional; however, the nutritional health professional was a master-level or doctoral-level student in nutrition or clinical psychology. We believe that few obstetrical offices can provide this level of nutritional instruction in clinical practice. Therefore, our study, using a single visit with a registered dietician, was designed to provide patient education and counseling in a manner that could be introduced easily and inexpensively into any obstetrical practice.
Our study has several limitations. First, it is limited by our inability to achieve our predetermined power. Recruitment for this study was terminated secondary to the time restrictions involved with completing a resident research project. Second, we cannot exclude a potential Hawthorne effect. Participants selected for a study in which they are counseled on weight gain, nutrition, and exercise are more likely to pay specific attention to these factors in their life and modify behaviors accordingly. This could be viewed as a positive effect that universal counseling would bring out in all of our patients. A third limitation is the potential for the healthy volunteer bias. People who are healthier in general tend to volunteer for research studies. Finally, we were unable to control strictly the content of the counseling that actually took place at each clinic visit.
This study lends one to consider further research in several areas. A study with the same intervention and design as the present study with only one health care provider doing the counseling would be of great interest. One health care provider would not only ensure consistent counseling, but also would make participants feel more responsible to their provider and likely be more compliant. Another study of interest would involve implementation of a preconception counseling protocol and examine its effect on weight loss or weight gain prepregnancy and subsequent weight gain in pregnancy.
In conclusion, an organized, consistent program of dietary and lifestyle counseling did reduce weight gain in pregnancy. Nulliparous women as well as women who are heavier prepregnancy are most likely to gain excessive weight during pregnancy. Therefore, it is essential at each office visit to counsel all women on the importance of diet and lifestyle in weight management, but spend even more time with heavier nulliparous women.
1. National Health and Nutrition Examination Survey, 2004.
3. Kabiru W, Raynor BD. Obstetric outcomes associated with increase in BMI category during pregnancy. Am J Obstet Gynecol 2004;191:928–32.
4. Parker JD, Abrams B. Prenatal weight gain advice: an examination of the recent prenatal weight gain recommendations of the Institute of Medicine. Obstet Gynecol 1992;79:664–9.
5. 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.
6. Schieve LA, Cogswell ME, Scanlon KS. Trends in pregnancy weight gain within and outside ranges recommended by the Institute of Medicine in a WIC population. Matern Child Health J 1998;2:111–6.
7. Olson CM, Strawderman MS, Reed RG. Efficacy of an intervention to prevent excessive gestational weight gain. Am J Obstet Gynecol 2004;191:530–6.
© 2009 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.
8. Polley BA, Wing RR, Sims CJ. Randomized controlled trial to prevent excessive weight gain in pregnant women. Int J Obes Relat Metab Disord 2002;26:1494–502.