Funding agencies: This research was supported by National Institute of Child Health and Human Development (RO1HD058061) (Clinicaltrials.gov # NCT00950235).
Efficacy of a group-based dietary intervention for limiting gestational weight gain among obese women: A randomized trial
Version of Record online: 28 AUG 2014
© 2014 The Obesity Society
Volume 22, Issue 9, pages 1989–1996, September 2014
How to Cite
Vesco, K. K., Karanja, N., King, J. C., Gillman, M. W., Leo, M. C., Perrin, N., McEvoy, C. T., Eckhardt, C. L., Smith, K. S. and Stevens, V. J. (2014), Efficacy of a group-based dietary intervention for limiting gestational weight gain among obese women: A randomized trial. Obesity, 22: 1989–1996. doi: 10.1002/oby.20831
Relevant conflicts of interest/financial disclosures: The authors have no conflicts of interest to report.
Authors' Contributions: Kimberly K. Vesco: Involvement in the conception and design of the study, overall lead of activities, review and interpretation of data, primary author of manuscript. Njeri Karanja: Involvement in the conception and design of the study, led the dietary component of the intervention and infant feeding survey development, review and interpretation of data, critical revision, and approval of the final manuscript. Janet C. King: Involvement in the conception and design of the study, assisted with the dietary component of the intervention, review and interpretation of data, and critical revision and approval of the final manuscript. Matthew W. Gillman: Involvement in the conception and design of the study and selection of outcome measures, review and interpretation of data, and critical revision and approval of the final manuscript. Michael C. Leo: Assisted with data management, led completion of statistical analyses, assisted with interpretation of data, and with preparation, critical revision and approval of the final manuscript. Nancy Perrin: Involvement in the conception and design of the study, assisted with statistical analyses, approval of the final submitted manuscript. Cindy T. McEvoy: Involvement in the conception and design of the study, assisted with newborn outcome measurement training, review and interpretation of data, and approval of the final manuscript. Cara L. Eckhardt: Involvement in the conception and design of the study, infant feeding survey development, review and interpretation of data, and critical revision and approval of the final manuscript. K. Sabina Smith: Involvement in the conception and design of the study, review and interpretation of data, and assisted with preparation, critical revision, and approval of the final manuscript. Victor J. Stevens: Involvement in the conception and design of the study, led the intervention team, review and interpretation of data, and assisted with preparation, critical revision, and approval of the final manuscript.
Prior presentation of data: Dr. Vesco presented preliminary data from this study as oral abstracts at the Obesity Society Annual Meeting, San Antonio, Texas, September 20-24, 2012, and the Society for Maternal Fetal Medicine Annual Meeting, San Francisco, California, February 14-16, 2013, and as a poster presentation at The Obesity Society Annual Meeting, Atlanta, Georgia, November 11-16, 2013.
- Issue online: 28 AUG 2014
- Version of Record online: 28 AUG 2014
- Manuscript Accepted: 14 JUN 2014
- Manuscript Revised: 12 JUN 2014
- Manuscript Received: 12 MAR 2014
Observational studies suggest that minimal gestational weight gain (GWG) may optimize pregnancy outcomes for obese women. This trial tested the efficacy of a group-based weight management intervention for limiting GWG among obese women.
One hundred and fourteen obese women (BMI [mean ± SD] 36.7 ± 4.9 kg/m2) were randomized between 7 and 21 weeks' (14.9 ± 2.6) gestation to intervention (n = 56) or usual care control conditions (n = 58). The intervention included individualized calorie goals, advice to maintain weight within 3% of randomization and follow the Dietary Approaches to Stop Hypertension dietary pattern without sodium restriction, and attendance at weekly group meetings until delivery. Control participants received one-time dietary advice. Our three main outcomes were maternal weight change from randomization to 2 weeks postpartum and from randomization to 34 weeks gestation, and newborn large-for-gestational age (birth weight >90th percentile, LGA).
Intervention participants gained less weight from randomization to 34 weeks gestation (5.0 vs. 8.4 kg, mean difference = −3.4 kg, 95% CI [-5.1-1.8]), and from randomization to 2 weeks postpartum (−2.6 vs. +1.2 kg, mean difference = −3.8 kg, 95% CI [-5.9-1.7]). They also had a lower proportion of LGA babies (9 vs. 26%, odds ratio = 0.28, 95% CI [0.09-0.84]).
The intervention resulted in lower GWG and lower prevalence of LGA newborns.
In the United States, about 30% of women of reproductive age are obese [1, 2] and over 50% of obese women gain more weight during pregnancy than recommended by the Institute of Medicine (IOM) . Excessive gestational weight gain (GWG) increases the risk of macrosomia (birth weight >4000 g) [3, 4], large for gestational age (birth weight >90th percentile) , higher child BMI z-scores , and increased body fat and elevated systolic blood pressure in children at age 3 years . Excessive GWG is also associated with both short- and long-term maternal weight retention [6, 7].
How to reduce weight gain among obese pregnant women has been unclear. In nonpregnant adults, the most effective weight loss and weight maintenance interventions have employed dietary counseling and weekly participant contact . Of weight management trials conducted among obese, nondiabetic, pregnant women [9-14], most have used interventions with less frequent direct participant contact [10-13], and few have been successful [9, 10, 14] in limiting GWG. The goal of our study was to determine whether the weight management model often used in nonpregnant adults, that is, a weekly, group-based weight management intervention focused on diet and behavior change, would be effective among obese women for limiting GWG and reducing the proportion of large-for-gestational age (LGA) infants.
We conducted a randomized controlled trial (parallel groups design with a 1:1 allocation ratio) among English-speaking, obese (BMI ≥30 kg/m2) women aged 18 years or older who were receiving prenatal care at Kaiser Permanente, Northwest (KPNW). Women were excluded if they had diabetes mellitus or other medical conditions requiring specialized nutritional care (e.g., a history of bariatric surgery), or had plans to leave the area during the expected follow up period (through 1 year postpartum). We aimed to randomize participants as early as possible in pregnancy, and included women up to 21 weeks gestational age. There was no lower limit of gestational age for inclusion; however, our outreach started after the first prenatal visit, which typically occurs in KPNW at 8 weeks gestation.
KPNW is a federally qualified, nonprofit HMO that serves more than 470,000 members in Northwest Oregon and Southwest Washington. KPNW's membership is similar to the local insured community in terms of age, sex, race, and ethnicity. From October 2009 to June 2011, we used KPNW's electronic medical record and referrals (self or physician) to identify potentially eligible participants (n = 2279). We sent invitations to participate by mail and followed up by telephone (Figure 1). Interested women first attended an explanatory session, and those who wished to proceed returned in a week with completed baseline questionnaires and a five-day food record. Those who completed the questionnaires, food record, and provided informed consent, were informed of their randomization assignment by the study dietician, who used a computerized algorithm for random assignments stratified by age (<30 years, 30 years and older) and BMI (30-34.9 kg/m2, 35-39.9 kg/m2, and 40 or greater kg/m2), in blocks of four. All randomizations were completed by July 2011. Of the 118 women randomized, two miscarried and two formally withdrew from the study within a week after randomization, leaving a final sample size of 114.
KPNW's Institutional Review Board and an independent data safety and monitoring board approved the study protocol and consent procedures. All participants provided written informed consent. Data collectors were unaware of treatment group assignment.
A detailed description of the intervention rationale, procedures and dietary recommendations has been published ; a brief outline is provided here. The intervention program included a combination of dietary and exercise recommendations, as well as the use of behavioral self-management techniques to help participants initiate and maintain behavior changes. This combination approach has been shown to be effective in adult weight management interventions, and has become the standard for high quality programs . The intervention goal was to help participants maintain their weight during pregnancy to within 3% of their weight at randomization . We chose this goal based on observational studies suggesting that limited weight gain or weight maintenance may result in better pregnancy outcomes for obese women [17, 18], and believed a 3% change was large enough to allow for fluctuations in weight due to edema
The study dietician advised intervention participants to follow an energy reduced eating plan, based on Dietary Approaches to Stop Hypertension (DASH) dietary pattern  without sodium restriction. Energy-reduced versions of the DASH pattern have been used extensively for both initial weight loss interventions and also for long-term weight loss maintenance interventions [20, 21]. The DASH dietary pattern was selected because it is also consistent with the dietary recommendations for pregnant women [22, 23]. The study dietician used this formula for personalizing daily calorie goals: Initial caloric needs = [(Prepregnant weight in kg) (30 Kcal/kg/day) (0.70)] + [(10 Kcal) (gestational age in weeks)]. The formula first calculates energy needs based on 30 kcal/kg/day of prepregnancy weight for nonobese women, then reduces calorie consumption by 30% . The equation then adds 10 Kcal per week of gestation to accommodate rising basal metabolic rate during gestation. A woman with a pre-pregnancy weight of 91 kg who is 10 weeks pregnant, for example, would be assigned an initial caloric intake of 2011 Kcal/day, gradually rising to 2311 by the time she delivers. A detailed rationale for this formula has been published .
The intervention leaders encouraged participants to accumulate at least 30 min of moderate physical activity per day in the absence of medical or obstetrical complications, a goal consistent with the recommendations of the American College of Obstetricians and Gynecologists (ACOG) . They gave each intervention participant a pedometer, and encouraged them to record their physical activity in their daily food and activity records. The intervention did not involve an exercise component that was directly observed by the study team.
Intervention format and content
Intervention participants started by attending two individual counseling sessions, the first immediately after randomization and the second 1 week later. The study's dietician used the individual sessions to tailor the diet and physical activity guidelines to the participant's specific needs. Participants began attending weekly group sessions after their second individual session, and continued to attend group sessions throughout their pregnancy. We had rolling entry and exit from the group sessions, such that new participants would enter after randomization and leave after they delivered. There was one group session per week with seven to eight women in attendance per session (mean 7.4, standard deviation 3.3, maximum 15). The 16-session core curriculum was presented in a cyclical manner, so each woman would have the opportunity to experience the full curriculum. Interventionists used behavioral self-management principles  during the group intervention sessions to help participants set reasonable short-term goals, formulate action plans, and develop sources of reinforcement and social support to support behavior change.
Each 90-min group session included a nutrition and/or exercise topic, a behavior change topic, and a goal-setting activity for the next week . The meetings began with the check-in when participants reported on their experiences during the preceding week. The intervention team encouraged participants to discuss the behavior change challenges and encouraged questions, group discussions, and group problem solving focused on potential barriers and facilitators for behavior change. They asked women to keep food and physical activity diaries and to monitor their progress weekly by charting their weight. Special attention was focused on identifying antecedents for both positive behaviors such as physical activity and healthful eating, and triggers for problematic behaviors such as eating inappropriate foods or eating large portions. Individual behavior change plans often included using this information to guide environmental changes (situational control techniques) designed to support behavior change.
Usual care control
Control participants received a one-time advice session from the study dietician that included general information about eating a healthy diet during pregnancy, without specific focus on the DASH dietary pattern or weight management. The session included feedback about their food diaries and a recommendation to follow their obstetrical care providers' advice. Our study did not provide any aspect of routine prenatal care for control or intervention participants. The information our participants received through the study was in addition to their routine medical care.
We asked participants in both conditions to return to the research clinic at 34 weeks gestation and at 2 weeks postpartum with their babies. The primary outcome measure for this study was total GWG, defined as weight measured at 2 weeks postpartum minus the weight measured at randomization (baseline). We chose weight at 2 weeks postpartum rather than the end of pregnancy to avoid including the weight of the products of conception, maternal edema, and increased maternal blood volume. In practice, the 34 week visit occurred at a mean ± standard deviation (SD) of 33.7 ± 1.7 weeks and the 2 week postpartum visit occurred at a mean of 3.2 ± 1.0 weeks. For consistency, we will continue to call these visits 34 weeks gestation and 2 weeks (rather than 3 weeks) postpartum.
To compare with the 2009 IOM guidelines , the rate of weight gain between baseline and 34 weeks gestation was stratified into three categories: above (>0.6 pounds [0.27 kg] per week), within (0.4-0.6 pounds [0.18-0.27 kg] per week), and below (<0.4 pounds [0.18 kg] per week) the guidelines.
Newborn weight outcomes included large-for-gestational-age (LGA, gender-specific birth weight greater than the 90th percentile), small-for-gestational-age (SGA, birth weight less than the 10th percentile), and weight-for-gestational-age z-score, which were calculated based on the 2000 US Natality data set , and macrosomia (birth weight ≥4000 g).
We used the study participants' medical records (ICD-9 codes, laboratory, and blood pressure measures) to identify additional key maternal and infant secondary outcomes: hypertensive disorders of pregnancy (gestational hypertension/pre-eclampsia); gestational diabetes; mode of delivery (cesarean section versus vaginal); preterm birth (<37 weeks, <34 weeks), neonatal hypoglycemia requiring treatment with IV glucose or supplemental feeds; hyperbilirubinemia requiring treatment within the first 8 days of life with phototherapy; respiratory morbidities requiring use of supplemental oxygen for ≥6 h total within first 72 h of life, or any CPAP or ventilator use in first 72 h of life; admissions to the special care nursery or neonatal intensive care unit; and perinatal mortality. Data about breastfeeding were obtained by maternal survey supplemented with medical record review.
There were 93 women who attended the 34 week and 93 women who attended the 2 week postpartum visit (81.6% attendance at each visit). In determining how to handle missing weight data, we discussed methods such as multiple imputation and direct maximum likelihood. However, because we had access to participant electronic medical record (EMR) weights measured during routine maternal care, we considered using EMR weights as a direct replacement for missing and out-of-window research visit weights. To determine whether the substitution of maternal EMR weights for research visit weights is valid (i.e., exchangeable), we obtained pairs of research and clinic weights collected within ±14 days of each other for 102 participants and examined the agreement between the weights. We found that the absolute agreement between the research and EMR weights was extremely high (Intraclass correlation coefficient [2,1] = 0.999), providing strong support for exchangeability. Therefore, we chose to use EMR data to augment missing weight data for participants who did not attend the 34 week or 2 week postpartum research clinic visit or who did not attend the clinic visit within the specified collection windows (32-36 weeks gestation, and 10-42 days postpartum, respectively) (Figure 1). In these cases, we selected the medical record weight closest to the center of the window. Using this methodology we had complete weight data for 98% (N = 112) of participants at 34 weeks' gestation and 98% (N = 112) at 2 weeks' postpartum.
Prior to analysis, we examined the central tendency, variability, and distribution for all variables to ensure the assumptions for the analysis were met. We analyzed data from all participants as originally randomized (i.e., intent to treat). The primary endpoint was weight change from baseline to 2 weeks postpartum. To determine whether the intervention was efficacious, we used a 2 × 2 mixed-design ANOVA in which time was the within-subjects factor (baseline vs. 2 weeks postpartum), and arm was the between-subjects factor (intervention vs. control). We assessed weight change from baseline to 34 weeks with a similar analysis. We used t-tests to compare the intervention and control groups on rate of weight gain and birth weight (raw and z-score). We also repeated the analysis on birth weight controlling for gestational age with an ANCOVA. We assessed the categorical outcomes using chi-square or Fisher's exact test, depending on the distribution of the variable. Effect size measures for continuous outcomes are expressed as the standardized mean difference between groups (Cohen's d) and for categorical outcomes as Cramer's V. Because of the lack of published results of similar interventions, it is difficult to provide context regarding the magnitude of effects with standardized effect sizes. However, we provide the conventions for small, medium, and large effect sizes defined by Cohen for situations in which no other data is available. For Cohen's d, this corresponds to 0.20, 0.50, and 0.80 and for Cramer's V, this corresponds to 0.10, 0.30, and 0.50, respectively [28, 29].
We used a two-tailed alpha level of .05 for all analyses. The original sample size target for this study was 160, and was based on the ability to detect a standardized effect size difference of at least 0.39 in the weight change between the intervention and control groups from baseline to 2 weeks postpartum at a two-tailed alpha level of 0.05 with 80% power.
The majority of participants were non-Hispanic White (86%), just under half were nulliparous (47%), and 56% had Class 2 or 3 obesity (Table 1). Mean ± SD for maternal BMI at randomization was 36.7 ± 4.9 kg/m2 (range 30.2-51.6), weight was 99.7 ± 15.3 kg (range 73.6-146.0), age was 31.8 ± 4.9 years (range 19.1-45.2), and gestational age was 14.9 ± 2.6 weeks (range 6.9-21.1).
|Mean ± SD or N (%)|
|Control group||Intervention group||Overalla|
|N = 58||N = 56||N = 114|
|Maternal age (years)||31.2 ± 4.6||32.4±5.1||31.8±4.8|
|Gestational age at randomization (weeks)||15.1 ± 2.5||14.6±2.8||14.9±2.6|
|Weight (kg)||100.5 ± 15.6||98.8±15.1||99.7±15.3|
|BMI (kg/m2)||36.8 ± 4.7||36.7±5.2||36.7±4.9|
|BMI category (kg/m2)|
|30–34.9||25 (43%)||25 (45%)||50 (44%)|
|35–39.9||21 (36%)||19 (34%)||40 (35%)|
|40+||12 (21%)||12 (21%)||24 (21%)|
|Nulliparous||27 (47%)||26 (46%)||53 (47%)|
|White race||49 (85%)||49 (88%)||98 (86%)|
|Less_than_$14,999||3 (5%)||3 (5%)||6 (5%)|
|$15,000_to_$29,999||7 (12%)||3 (5%)||10 (9%)|
|$30,000_to_$44,999||5 (9%)||15 (27%)||20 (18%)|
|$45,000_to_$59,999||6 (10%)||13 (23%)||19 (17%)|
|$60,000_to_$74,999||12 (21%)||7 (13%)||19 (17%)|
|$75,000_to_$89,999||6 (10%)||5 (9%)||11 (10%)|
|90,000+||14 (24%)||10 (18%)||24 (21%)|
|Missing||5 (9%)||0 (0%)||5 (4%)|
|High school graduate||20 (34%)||10 (18%)||30 (26%)|
|Technical school||5 (9%)||8 (14%)||13 (11%)|
|College graduate||29 (50%)||37 (66%)||66 (58%)|
|Missing||4 (7%)||1 (2%)||5 (4%)|
|Single||5 (9%)||2 (4%)||7 (6%)|
|Married||47 (81%)||45 (80%)||92 (81%)|
|Living together||5 (9%)||8 (14%)||13 (11%)|
|Divorced/separated||1 (2%)||1 (2%)||2 (2%)|
|Prior to pregnancy||8 (14%)||7 (13%)||15 (13%)|
|At enrollment||0 (0%)||1 (2%)||1 (1%)|
Maternal weight change and pregnancy outcomes
Overall, mean weight decreased by 0.6 ± 5.8 kg (range −18.3 to +13.7) from baseline to 2 weeks postpartum and increased by 6.8 ± 4.7 kg (range −4.6 to +20.0) from baseline to 34 weeks gestation. The mean rate of weight gain during pregnancy was 0.36 ± 0.25 kg/wk (range −0.27 to +1.00).
From baseline to 2 weeks postpartum, the mean weight declined by 2.6 kg in the intervention group, and increased by 1.2 kg in the control group (mean difference of change = −3.8, 95% CI [−5.9 to −1.7], P < 0.001) (Table 2). Between baseline and 34 weeks gestation, intervention participants gained less weight (5.0 vs. 8.4 kg, respectively; mean difference = −3.4 kg, 95% CI [−5.1 to −1.8], P < 0.001), had a lower rate of weight gain (0.27 kg/wk vs. 0.44 kg/wk; mean difference = −0.18, 95% CI [−0.26 to −0.09]) and a lower prevalence of weight gain in excess of the 2009 IOM guidelines (44 vs. 82% exceeding 0.27 kg/wk, P < 0.001). Based on Cohen's conventions, the magnitude of these effects were large (Cohen's d = 0.69-0.77). We also performed a residualized change analysis (evaluation of change score adjusting for baseline weight), and the results are entirely consistent with the original analysis.
|Mean ± SD or N (%)||Mean ± SD or N (%)||Mean difference||95% CI of difference||Effect size|
|2 weeks postpartum—randomization (kg)||1.2 ± 5.6||−2.6 ± 5.5||−3.8a||[−5.9 to −1.7]||0.69b|
|34 weeks gestation—randomization (kg)||8.4 ± 4.7||5.0 ± 4.1||−3.4a||[−5.1 to −1.8]||0.77b|
|Rate of weight gain (kg/week)||0.4 ± 0.2||0.3 ± 0.2||−0.2a||[−0.3 to −0.1]||0.77b|
|Rate of weight gain according to 2009 IOM guidelines for obese women||N/Aa||N/A||0.40c|
|Below (<0.18 kg/week)||7 (12%)||21 (38%)|
|Within (0.18 to 0.27 kg/week)||3 (5%)||10 (18%)|
|Above (>0.27 kg/week)||47 (82%)||24 (44%)|
Breastfeeding was initiated by 109 participants. We did not detect differences between groups for gestational diabetes, hypertensive disorders of pregnancy, or cesarean delivery and the estimated effect sizes were small (Table 3).
|N (%)||Odds ratio||95% CI for Odds ratio||Effect sizea|
|Maternal||Control N = 58||Intervention N = 56|
|Gestational hypertension, preeclampsia||6 (10%)||5 (9%)||0.85||[0.24-2.96]||0.02|
|Gestational diabetes||7 (12%)||6 (11%)||0.87||[0.28-2.78]||0.02|
|Cesarean delivery||26 (45%)||21 (38%)||0.74||[0.35-1.56]||0.07|
|Primary cesarean delivery||12 (21%)||15 (27%)||1.40||[0.59-3.34]||0.07|
|LGA||15 (26%)||5 (9%)||0.28b||[0.09-0.84]||0.22|
|Macrosomia (>4000 g)||13 (22%)||6 (11%)||0.42||[0.15-1.18]||0.16|
|SGA||4 (7%)||3 (5%)||0.76||[0.11-4.76]||0.03|
|Preterm birth (<37 weeks)||1 (2%)||4 (7%)||4.38||[0.41-219.64]||0.13|
|Preterm birth (<34 weeks)||1 (2%)||0 (0%)||N/Ac||N/Ac||0.09|
|NICU admissiond||6 (11%)||2 (4%)||0.33||[0.03-2.00]||0.13|
|Hyperbilirubinemiad||7 (12%)||6 (11%)||0.91||[0.29-2.91]||0.02|
|Birth traumad||2 (4%)||2 (4%)||1.08||[0.08-15.38]||0.01|
|Hypoglycemiad||1 (2%)||1 (2%)||1.08||[0.01-86.03]||<0.01|
|Respiratory morbidityd||7 (12%)||3 (6%)||0.43||[0.07-2.03]||0.11|
|Birth weight (grams)||Mean (SD)||Mean difference||95% CI for difference||Effect sizee|
|Unadjusted||3678 ± 583||3484 ± 583||−194||[−411 to +22]||0.33|
|Adjusted for gestational age||3654 ± 498||3508 ± 498||−146||[−331 to +39]||0.29|
|z-score for gestational age||0.52 (1.0)||0.21 (1.0)||−0.31||[−0.67 to +0.01]||0.32|
We did not detect differences between the intervention and control groups in mean birth weight (3484 vs. 3678 g, mean difference = −194; 95% CI for mean difference [−411 to +22]), birth weight adjusted for gestational age (3508 vs. 3654 g, mean difference = −146; 95% CI for mean difference [−331 to +39]), or weight for gestational age z-score (0.21 vs. 0.52, mean difference = −0.31; 95% CI for mean difference [−0.67 to +0.05]) and had small effect sizes (Cramer's V ranged from 0.02 and 0.07) (Table 3). However, there was a difference in the prevalence of LGA within the intervention group compared to the control group (9 vs. 26%; odds ratio = 0.28, 95% CI [0.09-0.84]; P = 0.02), a nonsignificant reduction in macrosomia (11 vs. 22%; odds ratio = 0.42, 95% CI [0.14-1.18]; P = 0.09), and no detectable difference in SGA (5 vs. 7%; odds ratio = 0.76, 95% CI [0.11-4.76]; Fisher's exact P = 1.00). The effect sizes for LGA and macrosomia were in between small and moderate (Cramer's V = 0.22 and 0.16, respectively), and the effect size was small for SGA (Cramer's V = 0.03). We did not find differences between groups in preterm birth (<37 weeks, <34 weeks), neonatal hypoglycemia or hyperbilirubinemia, respiratory morbidity, or NICU admission (Table 3). All nonsignificant findings had small effect sizes (Cramer's V ranged from <0.01 and 0.13).
The mean (±SD) interval between randomization and delivery was 24.7 ± 3.0 weeks (range 18.7-34.3). Intervention participants attended an average of 20 ± 7 (range 0-28) weekly sessions. When considering the number of intervention sessions participants attended normalized for number of the weekly sessions they could have attended, we found an average attendance of 79 ± 25% (range 0-100%). Of the 56 women in the intervention group, 18% maintained their weight during pregnancy to within 3% of weight measured at randomization and 9% lost weight (maximum loss 3.0 kg).
This intervention helped obese women minimize GWG and reduced prevalence of large for gestational age (LGA) newborns, with no apparent evidence for increasing the prevalence of small for gestational age (SGA) newborns. Given the low prevalence of SGA, larger studies with sufficient power to confirm the lack of impact of weight management on SGA are needed; as reducing the risk of LGA newborns through weight management during pregnancy without increasing the risk of SGA is of significant public health importance. LGA infants are at risk for neonatal hypoglycemia requiring medical intervention [30, 31] and in the long-term may be at increased risk for childhood obesity and metabolic syndrome . LGA is also associated with an increased risk of cesarean delivery, postpartum hemorrhage, and shoulder dystocia, which can result in newborn clavicular fracture and brachial plexus injury .
In nonpregnant adults, the most successful weight management interventions are comprehensive lifestyle modification programs that are (a) designed to modify eating and physical activity habits and (b) provided in weekly individual or group sessions . Frequent contacts and self-monitoring (keeping food and activity records, weekly weigh-ins, and plotting weight gain), provide accountability and are among the most important components of behavioral weight management . These components, which were included in our study, likely contributed to the intervention participants' success. The only prior randomized trials of dietary and lifestyle interventions conducted among obese, nondiabetic pregnant women that have been successful in limiting GWG are those that have included detailed dietary counseling and frequent participant contact [9, 10, 14]. Among these trials, ours was the first to use weekly group sessions, which may have the advantage of being less resource intensive than weekly individual contacts.
Prior observational studies suggest that for obese women, limited or no weight gain during pregnancy may lead to improved pregnancy outcomes such as reduced preterm birth and pre-eclampsia [5, 17, 18]. In this trial, we found that having women aim for weight maintenance actually resulted in an average weight gain within the IOM guidelines. Our study did not show an adverse effect of our intervention approach on pregnancy outcomes; however, our study was not adequately powered to assure there were no differences between groups. A much larger sample size of obese women who were able to maintain their weight through healthy lifestyle changes would be required to truly understand the effects of limited weight gain or weight loss on outcomes such as SGA, GDM, or pre-eclampsia. Our next step will be to determine the longer term impact of the intervention on maternal and infant weight measures at 1 year postpartum. New studies of pregnancy weight gain should also include long-term follow up and measures of maternal and child health that we were unable to obtain such as measures of maternal and infant metabolism and body composition and infant development. A new group of ongoing trials [Lifestyle Interventions For Expectant Moms (LIFE-Moms) clinical trial consortium, https://lifemoms.bsc.gwu.edu] may overcome some of the limitations of our study and add information about longer term maternal and child health outcomes.
Our study is limited by minimal racial and ethnic diversity and inclusion of only insured women with access to routine prenatal care. As would be expected in most obstetrics clinical trials, our participants were highly motivated to have successful pregnancies. One of our main barriers to recruitment was that we only had a single time, day, and night of the week when the intervention was offered. Another reason for study refusal was concern that the intervention required too much time or effort. KPNW serves a large geographic region covering 6000 square miles from Longview, Washington, to Salem, Oregon, thus geographically limiting weekly study participation for many women. Since our study and others show that frequent participant contact is necessary to achieve successful weight management during pregnancy among obese women, future studies among obese pregnant women should include interventions with a similar frequency of patient contact conducted on-line, by webinar, or by individual phone counseling to determine if these modalities are similarly effective as direct in-person contact. Another option, for health systems which utilize the group prenatal visit model or are considering its implementation, would be to incorporate weight management interventions into group prenatal visits. A recent retrospective study found that women in group prenatal care were less likely to have excessive GWG than those receiving individually delivered prenatal care .
In summary, our comprehensive lifestyle modification intervention produced lower GWG and reduced the likelihood of LGA infants among obese women. Whether this or similar interventions can improve long-term maternal and child health is yet to be determined.
- 1Institute of Medicine and National Research Council. Weight Gain During Pregnancy: Reexamining the Guidelines. Washington, DC: The National Academies Press; 2009.
- 6Excessive gestational weight gain and postpartum weight retention among obese women. Obstet Gynecol 2009;114:1069-1075., , , et al.
- 11Reducing excessive weight gain in pregnancy: a randomised controlled trial. Med J Aust 2009;191:429-433., , , , .
- 22ACOG Technical Bulletin. Nutrition during pregnancy. Int J Gynecol Obstet 2007;179:67-74.
- 23United States Department of Agriculture. Health and Nutrition Information for Pregnant and Breastfeeding Women: Making Healthy Choices in Each Food Group. Available at: http://www.choosemyplate gov/pregnancy-breastfeeding/making-healthy-food-choices html. Accessed on May 9, 2013.
- 24American Diabetes Association. Nutritional Management During Pregnancy in Preexisting Diabetes. Medical Management of Pregnancy Complicated by Diabetes. 3rd ed. Alexandria, Virginia: ADA; 2000. p 70-86.
- 25ACOG Committee Opinion. Exercise during pregnancy and the postpartum period. ACOG Tech Bull 2002:267:171-173.
- 26Behavior Modification: Principles and Procedures. 4th ed. Pacific Grove, CA: Homson/Wadsworth; 2008..
- 28Statistical Power Analysis for the Behavioral Sciences. 2nd ed. Hillsdale, NJ: Lawrence Erlbaum Associates; 1988..
- 30ACOG Practice Bulletin No. 22. Fetal macrosomia. Am Coll Obstetr Gynecol 2000;22:1-11.
- 33Comparative effectiveness of group and individual prenatal care on gestational weight gain. Matern Child Health J 2013;1-10., , .