The issue
A large proportion of women gain more weight than is recommended during pregnancy. Excessive weight gain in pregnancy is associated with complications such as diabetes, high blood pressure, caesarean section, and large babies. This review aimed to determine whether diet or exercise measures,or both, could prevent excessive gestational weight gain (GWG), and if they were safe.
How we conducted the review
This is an update of a review first published in 2012 and is current to November 2014 and included randomised controlled trials (RCTs) only in the updated review. We grouped studies according to the types of interventions, and according to the types of participants, i.e. normal weight women (the low-risk group), all pregnant women (the mixed-risk group), and overweight or obese women, or women with or at risk of gestational diabetes (the high-risk group).
Findings
We included 65 randomised controlled trials, of which 49 trials involving 11,444 women contributed data. Twenty studies were at a moderate-to high-risk of bias. The diets tested were low sugar (low glycaemic load), diabetic, low-calorie or low-fat diets, with or without food diaries and regular weighing. The exercise interventions were most often of moderate intensity and involving regular walking, dance or aerobic classes. The comparison or control group generally received standard care. Overall, weight management interventions led to a reduction in the number of women gaining excess weight by a fifth (20%; range 13% to 27%) over the pregnancy. We considered this evidence to be high-quality.
Overall, we found no clear benefits of all diet or exercise interventions, or both, on other outcomes including pre-eclampsia, caesarean section, preterm birth, and having a baby weighing more than 4 kg (macrosomia), although we could not rule out a small effect on caesarean section (5% reduction) and macrosomia (7% reduction), particularly for women receiving combined diet and exercise counselling interventions. There was a tendency for supervised exercise-only interventions to reduce macrosomia too. Maternal hypertension (high blood pressure) was also reduced with the interventions. We found no clear differences between study groups with regard to most infant complications, except that for high-risk women the babies born to the women in the intervention group were less likely to experience breathing difficulties (respiratory distress syndrome) than babies in the control group. This evidence was mostly of a moderate quality.
The studies had differences in the types of interventions, types of participants (for example in terms of body mass index (BMI), number of previous pregnancies and age), delivery of the intervention (whether the intervention was incorporated into antenatal visits or delivered separately by a dietician), timing of the measurements, timing of commencement of the intervention (first, second or third trimester), the intensity of the intervention, and how it was monitored or supervised. Most included studies were carried out in developed countries and it is not clear whether these results are widely applicable to lower income settings.
Conclusions
We found high-quality evidence that diet or exercise interventions, or both, help to reduce excessive weight gain in pregnancy. They may also reduce caesarean deliveries, especially with combined diet and exercise interventions, and maternal hypertension. In addition, the chances of having a baby over 4 kg and the chances of the newborn having breathing difficulties after birth may be reduced, especially in overweight and obese women. Moderate-intensity exercise appears to be an important part of weight-control strategies in pregnancy; however, more research is needed on side-effects to inform safe guidelines.
High-quality evidence indicates that diet or exercise, or both, during pregnancy can reduce the risk of excessive GWG. Other benefits may include a lower risk of caesarean delivery, macrosomia, and neonatal respiratory morbidity, particularly for high-risk women receiving combined diet and exercise interventions. Maternal hypertension may also be reduced. Exercise appears to be an important part of controlling weight gain in pregnancy and more research is needed to establish safe guidelines. Most included studies were carried out in developed countries and it is not clear whether these results are widely applicable to lower income settings.
This is an update of a Cochrane review first published in 2012, Issue 4. Excessive weight gain during pregnancy is associated with poor maternal and neonatal outcomes including gestational diabetes, hypertension, caesarean section, macrosomia, and stillbirth. Diet or exercise interventions, or both, may reduce excessive gestational weight gain (GWG) and associated poor outcomes; however, evidence from the original review was inconclusive.
To evaluate the effectiveness of diet or exercise, or both, interventions for preventing excessive weight gain during pregnancy and associated pregnancy complications.
We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (5 November 2014), contacted investigators of the previously identified ongoing studies and scanned reference lists of retrieved studies.
Randomised controlled trials (RCTs) of diet or exercise, or both, interventions for preventing excessive weight gain in pregnancy.
Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We organised RCTs according to the type of interventions and pooled data using the random-effects model in the Review Manager software. We also performed subgroup analyses according to the initial risk of adverse effects related to poor weight control. We performed sensitivity analysis to assess the robustness of the findings.
We included 65 RCTs, out of which 49 RCTs involving 11,444 women contributed data to quantitative meta-analysis. Twenty studies were at moderate-to-high risk of bias. Study interventions involved mainly diet only, exercise only, and combined diet and exercise interventions, usually compared with standard care. Study methods varied widely; therefore, we estimated the average effect across studies and performed sensitivity analysis, where appropriate, by excluding outliers and studies at high risk of bias.
Diet or exercise, or both, interventions reduced the risk of excessive GWG on average by 20% overall (average risk ratio (RR) 0.80, 95% confidence interval (CI) 0.73 to 0.87; participants = 7096; studies = 24; I² = 52%). This estimate was robust to sensitivity analysis, which reduced heterogeneity, therefore we graded this evidence as high-quality. Interventions involving low glycaemic load diets, supervised or unsupervised exercise only, or diet and exercise combined all led to similar reductions in the number of women gaining excessive weight in pregnancy.
Women receiving diet or exercise, or both interventions were more likely to experience low GWG than those in control groups (average RR 1.14, 95% CI 1.02 to 1.27; participants = 4422; studies = 11; I² = 3%; moderate-quality evidence). We found no difference between intervention and control groups with regard to pre-eclampsia (RR 0.95, 95% CI 0.77 to 1.16; participants = 5330; studies = 15; I² = 0%; high-quality evidence); however, maternal hypertension (not a pre-specified outcome) was reduced in the intervention group compared with the control group overall (average RR 0.70, 95% CI 0.51 to 0.96; participants = 5162; studies = 11; I² = 43%; low-quality evidence).
There was no clear difference between groups with regard to caesarean delivery overall (RR 0.95, 95% CI 0.88 to 1.03; participants = 7534; studies = 28; I² = 9%; high-quality evidence); although the effect estimate suggested a small difference (5%) in favour of the interventions. In addition, for combined diet and exercise counselling interventions there was a 13% (-1% to 25%) reduction in this outcome (borderline statistical significance).
We found no difference between groups with regard to preterm birth overall (average RR 0.91, 95% CI 0.68 to 1.22; participants = 5923; studies = 16; I² = 16%; moderate-quality evidence); however limited evidence suggested that these effect estimates may differ according to the types of interventions, with a trend towards an increased risk for exercise-only interventions.
We found no clear difference between intervention and control groups with regard to infant macrosomia (average RR 0.93, 95% CI 0.86 to 1.02; participants = 8598; studies = 27; I² = 0%; high-quality evidence), although the effect estimate suggested a small difference (7% reduction) in favour of the intervention group. The largest effect size occurred in the supervised exercise-only intervention group (RR 0.81, 95% CI 0.64 to 1.02; participants = 2445; studies = 7; I² = 0%), which approached statistical significance (P = 0.07). Furthermore, in subgroup analysis by risk, high-risk women (overweight or obese women, or women with or at risk of gestational diabetes) receiving combined diet and exercise counselling interventions experienced a 15% reduced risk of infant macrosomia (average RR 0.85, 95% CI 0.73 to 1.00; participants = 3252; studies = nine; I² = 0; P = 0.05; moderate-quality evidence)
There were no differences in the risk of poor neonatal outcomes including shoulder dystocia, neonatal hypoglycaemia, hyperbilirubinaemia, or birth trauma (all moderate-quality evidence) between intervention and control groups; however, infants of high-risk women had a reduced risk of respiratory distress syndrome if their mothers were in the intervention group (RR 0.47, 95% CI 0.26 to 0.85; participants = 2256; studies = two; I² = 0%; moderate-quality evidence).