Background
Excessive gestational weight gain (GWG) is associated with several pregnancy and foetal complications such as gestational diabetes mellitus (GDM), caesarean section, preterm delivery and high birth weight [
1‐
6]. Moreover, excessive GWG may influence maternal and infant long-term health. Research suggests that GWG is not only a determinant of maternal postpartum weight retention, but also increases the risk of obesity in both mother and child [
7‐
13]. The U.S. Institute of Medicine (IOM) proposed guidelines to define excessive GWG according to a woman’s pre-pregnancy Body-Mass-Index (BMI) [
14]. In Western countries, there is a trend towards an increase in the rate of excessive GWG [
15]. In Germany, more than 40% of pregnant women exceed the recommended IOM thresholds [
16]. Next to dietary behaviour, prenatal physical activity (PA) seems to be a major determinant of GWG. Apart from associations with GWG, prenatal PA was shown to beneficially influence several physiological functions for instance in the cardiovascular and pulmonary systems [
17,
18], and to lower the risk for pregnancy-induced complications such as GDM, preeclampsia and caesarean section [
19‐
22]. Moreover, PA improves a woman’s psychological well-being and quality of life in general as well as during pregnancy and decreases the risk for anxiety and depressive symptoms including postpartum depression [
23‐
27]. The evidence outlined above clearly demonstrates that PA plays a fundamental role with respect to a woman’s health status during pregnancy and in the postpartum period. However, only a minor proportion of pregnant women meets current PA recommendations [
18,
28,
29]. Moreover, PA often declines over the course of pregnancy [
30,
31]. This emphasises the need to develop interventions that address the prenatal lifestyle and include strategies to improve PA behaviour in order to reduce both excessive GWG and pregnancy-induced complications.
In the last decade, various lifestyle interventions focusing on dietary and PA behaviour have been initiated to prevent excessive GWG and to minimise resulting health complications for mothers and their infants. Most randomised-controlled trials (RCTs) showed rather modest effects in the prevention of excessive GWG [
32‐
35] and a recent meta-analysis suggested a decrease of GWG by − 0.70 kg in women receiving lifestyle advice [
36]. However, RCTs differed in their design, outcomes measures, procedures, study population, sample size as well as mode and intensity of the intervention. Only a small number of RCTs were conducted outside academic settings and implemented in routine prenatal care [
37‐
39]. With respect to the overall increasing rates of excessive GWG in all BMI categories and concomitant adverse health outcomes, it remains a challenge to establish effective and efficient interventions in “real-life” settings.
In this context, the FeLIPO trial (“Feasibility of a Lifestyle-Intervention in Pregnancy to Optimize maternal weight development”) was conducted in a routine care setting with the aim of reducing the number of pregnant women exceeding the IOM recommendations. The intervention consisted of two prenatal counselling sessions focusing on diet and PA and led to beneficial effects on the proportion of women with excessive GWG and on some lifestyle factors [
40].
The FeLIPO trial encouraged us to offer a lifestyle intervention programme within the framework of the well-established German prenatal care system, the “Gesund leben in der Schwangerschaft”/“healthy living in pregnancy” (GeliS) trial [
41]. By implementing an intervention under real-life conditions, the primary aim of the GeliS trial was to reduce the proportion of women with excessive GWG. The effect of the GeliS intervention on excessive GWG has been published recently [
42]. Furthermore, the trial endeavoured to improve women’s prenatal lifestyle and to maintain or even increase their PA in accordance with national and international PA recommendations [
43,
44]. This secondary analysis aims to investigate the PA behaviour of women enrolled in the GeliS trial and its influence on GWG.
Discussion
The purpose of this secondary analysis was to investigate the impact of a lifestyle intervention programme with basic PA advice in a routine care setting on prenatal PA behaviour. Although the intervention observed no effect on excessive GWG, which was the main outcome of the GeliS trial [
42], secondary analyses showed some positive effects of the intervention on intensity and type of reported PA. Significant between-group differences were found in the level of total PA, in TALIA, in moderate-, and vigorous-intensity activities as well as in the level of sport activities. The national and international PA recommendations for pregnant women were more often met in the IV. This highlights the success of the GeliS intervention in improving antenatal PA behaviour. As expected, PA declined over the course of pregnancy, which was equally observed by others [
30,
53,
54] and might be explained by an expected increasing discomfort in engaging in PA as pregnancy progressed [
55].
Previous antenatal lifestyle interventions differed in their study design, setting, participant characteristics and PA data collection. Therefore, it is difficult to compare findings. However, using the International Physical Activity Questionnaire to estimate antenatal PA behaviour, our pilot trial FeLIPO found no between-group differences, but observed a significant reduction of total PA in the course of pregnancy only in the control [
40]. In contrast to findings from the FeLIPO trial, we observed in this study that both groups decreased their total PA level over time. Nevertheless, the IV showed a higher level of vigorous-intensity activities and was even able to increase the level of sport activities, while the latter remained unchanged in the C. Two other large-scaled antenatal RCTs included women with overweight and/or obesity only and used different questionnaires to assess PA [
35,
56]. In line with our observations, both trials detected significant between-group differences in the level of total PA in late pregnancy. In LIMIT, these results were mainly explained by significant differences in household activities [
56]. However, data on PA intensities are not published. The authors of the UPBEAT trial attributed their observed difference to the fact that participants of the IV spent more time walking compared to the standard care group [
35]. In contrast to GeliS, the authors found no differences in moderate- and vigorous-intensity activities [
35]. Thus, the between-group differences in the level of moderate- and vigorous-intensity activities in GeliS may be explained in particular by different PA patterns in women with normal weight. This is in line with the observation of significant between-group differences in the level of TALIA at T1 only in the subgroup of women with normal weight.
The LIMIT and the UPBEAT trials placed a stronger emphasis on antenatal PA behaviour by including supervised walking sessions, exercise videos and PA monitoring tools, whereas the GeliS study only provided basic PA advice and distributed leaflets to participants. The question remains whether PA modification should be considered as a critical component of antenatal interventions and whether it has the potential to mitigate several maternal health outcomes. In this context, Simmons et al. (2017) compared the effectiveness of three lifestyle interventions (diet, PA, diet and PA combined) for women with a BMI ≥ 29.0 kg/m
2 with usual care [
57]. The joint intervention, including both diet and PA coaching, had the greatest effect and resulted in substantially lower GWG (− 2.02 kg; 95% CI − 3.58 to − 0.46 kg) and a lower risk for excessive GWG (OR: 2.13; 95% CI 1.05 to 4.33) compared to the usual care group. Despite improvements in the PA and dietary behaviour of participants [
47], we found no evidence that the GeliS intervention succeeded in reducing the proportion of women with excessive GWG, although we likewise focused on both lifestyle factors [
42]. Nevertheless, we detected significant differences in the level of vigorous-intensity activities between women with and without excessive GWG and trends for differences in TALIA and moderate-intensity activities (data not shown). Furthermore, total GWG was inversely associated with TALIA, light- and vigorous-intensity activities in late pregnancy. This overall effect of PA on GWG is supported by current research. A meta-analysis including RCTs which only implemented a PA intervention reported beneficial effects on overall GWG (
p < 0.001) in women of all BMI categories [
58]. Correspondingly, a recently published meta-analysis, including studies with normal weight women only, concluded that exercise during pregnancy can reduce GWG (mean difference = − 1.61 kg, 95% CI − 1.99 to − 1.22 kg) [
20] and highlights the need for large-scale interventions and for including normal weight women. Both demands were met within the GeliS trial. Aside from decreasing the risk for excessive GWG, research found that prenatal PA influences a woman’s overall health status due to beneficial effects on physiological and psychological well-being and decreases the risk for pregnancy-induced complications [
18]. Drawing from the evidence presented herein, we suggest that pregnant women should be encouraged to engage in an active lifestyle according to the ACOG recommendations.
In the GeliS study, women in the IV (63.6%) were more likely to meet the national and international PA recommendations [
43,
44] in late pregnancy than women in the C (49.2%). However, compared to other observations, the adherence of both groups to PA recommendations is relatively high. The percentage of pregnant women meeting the PA recommendations of the ACOG [
44], depending on different thresholds, was estimated to range between 12.7 and 45.0% [
28]. On the one hand, the discrepancy with GeliS observations might be explained by self- and over-reporting, leading to a higher percentage of women that were found to meet the recommendations. On the other hand, estimating whether or not women adhere to the PA recommendations by means of the PPAQ is prone to error, although it was similarly done by others [
51] and recommended by the developer of the questionnaire (personal communication).
There are further limitations of this secondary analysis. First, we observed differences in the baseline PA level between women in the IV and C groups. In order to overcome this limitation and to more accurately assess the intervention effect on PA behaviour, we included baseline PA level (T0) as a covariate. This most likely explains why we found significant evidence for between-group differences in adjusted but not in unadjusted models in late pregnancy. We reported PA behaviour at two different time points in pregnancy, before the end of the 12th week and after the 29th week of gestation. Assessing PA behaviour shortly before delivery, would have given further insights into the PA decline over the entire course of pregnancy. We assessed PA by means of a frequency questionnaire, which could lead to inaccuracies as physical activity questionnaires in general are known to have limited reliability and validity [
59]. Nevertheless, the questionnaire we administered was extensively validated [
48] and recommended for PA assessments in pregnancy [
60]. We slightly adapted it to German habits and are not aware of its implication on the overall validity, although we do not anticipate differences in PA levels compared to using the original PPAQ. It is important to consider, that the self-administration of the PPAQ might have introduced selective bias and might have influenced observed results. The GeliS study was performed outside an academic setting. Interviewer-administered PPAQs or any other type of PA assessment were not feasible. Thus, a comparison between PA data of GeliS and studies who applied interviewer-administered PPAQs [
51,
61] is more challenging. As with any self-reported activity questionnaire, we face the problem that self-reports rely on the subjective estimation of participants and on their ability to remember their physical activity level and type of performed sports for the past 4 weeks. Moreover, self-reports are susceptible to over- and under-reporting [
62], which cannot completely be excluded within the presented data. For instance, we found higher levels of TALIA and more outliers in the subgroup of women with overweight, and in particular in women with obesity in the C group (data not shown). However, we intended to minimise this influence by clearly defining over-reporting, a priori, as described in the Methods part. To this end, reported unrealistic activity levels were not included in the analyses. The overall prevalence of normal weight, overweight and obesity in the GeliS cohort differs from the general population of women of childbearing age in Germany, which makes our findings difficult to generalise [
63]. Furthermore, educational level was found to significantly influence TALIA in late pregnancy but was not controlled for in our adjusted model. However, we observed neither group differences in educational level nor an interaction with group allocation. Therefore, we can conclude that educational level influences prenatal PA behaviour without distorting between-group observations. Finally, we did not include dietary intake and in particular dietary modification as covariate and are aware that this shortcoming might lead to a slightly biased estimation of the effect of prenatal PA on overall GWG [
47]. We acknowledge that a more detailed PA intervention, such as counselling given by PA experts, integrating behavioural change strategies, supervised PA classes or digital activity trackers and smartphone applications might have strengthened the effect of the intervention on PA and could lead to an impact on GWG. An evaluation of incorporated behaviour change techniques, by applying behaviour change taxonomies from the beginning on, would provide valuable details about the quality of the intervention.
Apart from these limitations, the secondary findings presented herein have several strengths that are worth noting. By pooling both groups to form one cohort, it was possible to assess the influence of different PA intensities on overall GWG. To our knowledge, there is no other trial that addressed this effect in such detail. In addition, we were able to estimate the PA behaviour, including type and intensity of PA, of women in all BMI categories. Moreover, we could demonstrate PA behaviour patterns of women who had received basic PA advice given by trained counsellors in the routine care setting. To the best of our knowledge, there is no other trial to-date which was conducted on a large scale in a routine care setting that showed such comprehensive findings on the impact of a lifestyle intervention on prenatal PA behaviour.
Considering the public health approach of this study, providing only simple recommendations was a feasible and a realistic way of motivating pregnant women to engage in PA and to maintain an active lifestyle during the course of pregnancy. However, future approaches could implement some of the above strategies to examine if complementary methods of self-monitoring coupled with expert instruction may exert a more pronounced change on prenatal lifestyle, and ultimately, on GWG.
Acknowledgements
We gratefully acknowledge the valuable contribution from the Munich Study Centre at the Technical University of Munich and project managers at the expert centres for nutrition/community catering at the regional offices (AELF) of the Bavarian State Ministry of Food, Agriculture and Forestry (StMELF) which have been coordinating the study on the regional level. We gratefully acknowledge the work and contribution of our colleague Dr. Christina Holzapfel, Institute for Nutritional Medicine, Klinikum rechts der Isar, Technical University of Munich. The support from Prof. Kurt Ulm and Dr. Victoria Kehl, Institute of Medical Informatics, Statistics and Epidemiology, Klinikum rechts der Isar of the Technical University of Munich, the network Healthy Start - Young Family Network, Federal Center for Nutrition (BZfE), Federal Office for Agriculture and Food (BLE), belonging to the national IN FORM initiative (Maria Flothkötter, Katharina Krüger), Bonn, Dr. Uta Engels, Sports Centre, University of Regensburg, Prof. Karl-Heinz Ladwig, Head of Research Group Mental Health at the Institute of Epidemiology, Helmholtz Centre Munich, Prof. K.T.M. Schneider, Division of Obstetrics and Perinatal Medicine, Technical University of Munich, Prof. Rüdiger von Kries, Institute of Social Paediatrics and Adolescent Medicine, Ludwig-Maximilians-University Munich, Prof. Regina Ensenauer, Dr. von Hauner Children’s Hospital, Ludwig-Maximilians-University Munich and Heinrich Heine University Düsseldorf, Prof. Rolf Holle, Institute of Health Economics and Health Care Management, Institute of Epidemiology, Helmholtz Centre Munich, Gabi Pfeifer, Educational Center Nuremberg, and Eveline Rieg, Competence Centre for Nutrition, Freising/Kulmbach, are gratefully acknowledged. We are also indebted to the Board of Trustees: Maria Flothkötter, German Federal Ministry of Food and Agriculture (BZfE) in the Federal Office for Agriculture and Food (BLE), Bonn; Dr. Beatrix Heilig and Dr. Martina Enke, Bavarian State Ministry of Health and Care; Marion Kratzmair and Dr. Wolfram Schaecke, Bavarian State Ministry of Food, Agriculture and Forestry; Dr. Annette Scheder and Katharina Leopold, AOK Bayern. We would also like to acknowledge the support of the Bayerische Landesärztekammer, Bayerischer Hebammen Landesverband e.V. and the Company Beurer GmbH, Ulm. Finally, we would like to thank our colleague Annie Naujoks, Institute for Nutritional Medicine, Klinikum rechts der Isar, Technical University of Munich for her support and all participating practices, gynaecologists, medical personnel, midwives, participants and their families for their involvement.
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