2.1. Effect of Prenatal Lifestyle Interventions on Gestational Weight Gain
2.1.1. Successful Interventions at Reducing Mean Gestational Weight Gain
Asbee at al. [55
] () examined the effect of a prenatal intervention on GWG in women of various pre-pregnancy BMI categories (normal weight, overweight, and obese women). This randomised controlled trial (RCT) included detailed recommendations regarding dietary intake, physical activity, and appropriate GWG based on the women's pre-pregnancy BMI. The authors found lower GWG in the intervention group (16.2 ± 7.0
kg) compared to the control group (13.0 ± 5.7, P
= 0.01), regardless of BMI status. Although the participants received specific recommendations about dietary intake and physical activity, compliance to these recommendations was not reported. In addition, no information was given regarding physical activity levels and eating habits of the control group. Two other successful interventions included only women who were overweight and/or obese prior to pregnancy. Shirazian et al. [57
] () conducted a prenatal intervention that included six seminars and one-on-one counseling sessions (n
≥ 5) aimed at promoting healthy eating and encouraging walking (food diaries and pedometers were provided to the participants) and educating the women on obesity during pregnancy. The intervention group gained less weight than the control group (8.1 ± 7.4
kg versus 15.4 ± 7.5
kg, resp.; P
= 0.003). Unfortunately, eating and physical activity habits of the women during the intervention were not reported, although the participants received tools (diaries and pedometers) to monitor their daily dietary intake and physical activity levels. Further, physical activity levels and eating habits of the control group were not reported. Finally, the study of Nascimento et al. [68
] () included weekly supervised aerobic dance classes of moderate-intensity, combined with recommendations about weekly physical activity level and healthy GWG. The authors reported lower mean GWG in the intervention group (10.0 ± 1.7
kg) compared with the control group (16.4 ± 3.9
= 0.001) but only in overweight women (17.5% of the sample) [68
]. Sixty-three percent of the women were compliant with the exercise intervention and accumulated a mean of 80 ± 49 minutes of walking every week and 57 ± 22 minutes of exercise from the study protocol. However, no information was provided regarding physical activity levels in overweight and obese women separately. Moreover, the authors did not report physical activity levels for the control group.
Taken together, although these 3 studies were successful at reducing mean GWG, none of them produced statistically significant differences in adherence to IOM recommendations, based on the 1990 [55
] or 2009 [57
2.1.5. Summary and Points to Discuss
Based on the studies presented above, it appears that prenatal lifestyle interventions promoting healthy eating and physical activity habits were more successful at decreasing mean GWG and/or preventing excessive GWG compared to those including an exercise component alone (69% versus 33%). This suggests that the same principle may apply to the prevention of excessive GWG as in weight loss: the major component is in dietary changes and the role of physical activity is to support and maintain these achievements [73
However, there are still a large number of prenatal lifestyle interventions that were unsuccessful and it is important to discuss the factors that may explain their ineffectiveness in order to design future successful prenatal lifestyle interventions. These factors may be numerous and include characteristics of the women (parity, socioeconomic status, maternal pre-pregnancy BMI, pre-pregnancy physical fitness levels, pre-pregnancy lifestyle habits), the design of the intervention, the gestational age at which the intervention was initiated, the components of the intervention (nutrition, physical activity, behavioral change), the frequency and intensity of physical activity, the type of intervention (i.e., phone-based, mail-based, or supervised intervention), the frequency of the interaction with the women, the contexts or providers of counseling, and, of course, compliance with the intervention.
There is good evidence to suggest that pre-pregnancy BMI is an important factor influencing the success of an intervention and that it should be taken into consideration when designing a prenatal lifestyle intervention. For example, overweight and obese pregnant women likely had unhealthy eating habits and a sedentary lifestyle before becoming pregnant. Asking them to make behavioral changes while participating in a prenatal lifestyle intervention may be challenging. Moreover, they may have body weight issues and low self-esteem. Because of these factors, overweight and obese pregnant women may need more support and encouragement during an intervention to be able to overcome the barriers they may face in order to improve their lifestyle habits and be successful in limiting their weight gain. Accordingly, intervention studies that included overweight and obese women and were successful at reducing mean GWG and preventing excessive GWG were based on frequent individualized nutrition counseling sessions and discussions regarding healthy weight gain throughout pregnancy, combined with supervised exercise sessions [44
]. On the other hand, intervention studies based only on written or oral recommendations regarding healthy lifestyle habits during pregnancy and of less frequent interactions were unsuccessful at reducing mean GWG or preventing excessive GWG in overweight and obese women [59
]. The way of approaching behavioral change is also of paramount importance, especially in overweight and obese women. Only few prenatal lifestyle interventions included any theoretical background as a basis for behavioral change. However, we may speculate that interventions based on frequent interactions with the participants and discussions regarding healthy weight gain included behavioral change objectives, which may have contributed to the success of these interventions. The background of the providers of counseling may also have influenced the success of the intervention. Counseling provided by the same team of healthcare professionals throughout the intervention (nurse, midwife, dietician, kinesiologist, or psychologist) may have had a stronger impact on helping the women to improve their lifestyle habits and be successful in limiting their weight gain, emphasizing a team approach.
Another factor that may have contributed to the mixed results of prenatal lifestyle interventions may be the use of the 1990 versus 2009 IOM GWG guidelines, although we cannot draw conclusions as to whether studies using the 1990 or 2009 IOM guidelines were more likely to be successful at preventing excessive GWG. However, with the increased prevalence of maternal obesity and the new GWG guidelines that are more restrictive, especially for obese women, we may expected that upcoming studies will have to provide more interactive and frequent counseling sessions to be successful at preventing excessive GWG in obese women.
Finally, an important methodological issue that was identified in several prenatal lifestyle interventions presented above is that although they all included a physical activity component, combined or not with nutritional advice, they did not assess dietary intake and physical activity levels of the participants pre- and post-intervention. Similarly, some interventions provided food diaries and pedometers to the participants in order to encourage them to monitor their daily dietary intake and physical activity levels but the data collected using these tools were not reported by the authors. This is important missing information because researchers need to identify from previous successful interventions what contributed to their success in order to design future successful prenatal lifestyle interventions. Consequently, it is highly important that researchers document the important/effective aspects of their intervention by examining whether the participants were compliant with the recommendations given during the intervention and whether they had modified eating and/or physical activity habits. Further, it is important to examine eating and/or physical activity habits of the control group. The few authors who reported data regarding the impact of their intervention on changes in nutrition and physical activity habits of the participants have found that decreasing fat intake [58
], decreasing carbohydrate intake while increasing protein consumption [44
], and increasing physical activity levels to meet physical activity recommendations during pregnancy [44
] helped to achieve a healthy GWG.
However, compliance is always difficult to interpret and the authors should report as much information regarding compliance as possible. For example, if compliance with physical activity recommendations is defined as being active 3 times per week, the authors should not only report the mean number of weekly exercise sessions performed by the women but also the percentage of women having been active 3 times per week. In the case where there is few but exceptionally well-adhered women who were active 6 times per week, these women will pull the group average up. The reader will then consider that the intervention was effective because all women were compliant with physical activity recommendations. In fact, the few but exceptionally well-adhered women were mostly responsible for the positive results. However, compliance with the physical activity component of a prenatal lifestyle intervention was found to be a major problem. Factors such as concerns for the safety of the baby, physical limitations, and lack of energy, motivation, or resources may contribute to the low compliance with the physical activity program/recommendations. The inclusion of supervised exercise sessions may help to favor compliance with the physical activity component of the intervention and achievement of healthy weight gain. It would allow frequent interactions with the women during which physical activity-related behavior change objectives may be provided and emphasis put on the safety and health benefit of physical activity during pregnancy.
Taken together, differences in the characteristics of the women, the nutritional, physical activity, and behavioral change approaches used make the comparison of different interventions difficult and the identification of the most effective ways to prevent GWG challenging. Further research is needed to identify the effective aspects of prenatal lifestyle interventions, especially for overweight and obese women, in order to support the current evidence suggesting that prenatal lifestyle interventions may play an important role in the prevention of excessive GWG.