1. Introduction
Obesity prevalence is increasing worldwide and represents one of the major public health concerns [
1,
2,
3]. In particular, increasing obesity rates are observed in women of childbearing age [
4,
5]. Moreover, a high pre-pregnancy body mass index (BMI) as well as excessive weight gain during pregnancy are strong contributors to the overall risk of obesity later in life [
6,
7,
8]. Accordingly, excessive gestational weight gain (GWG) is discussed to be an independent risk factor for both short- and long-term postpartum weight retention (PPWR) [
9,
10,
11,
12]. Breastfeeding may decrease PPWR, and the duration of breastfeeding has been found to be inversely associated with the woman’s risk of overweight [
13,
14,
15]. Despite this evidence, women with obesity are more likely to fail in breastfeeding and are more susceptible to long-term PPWR and inter-pregnancy weight gain, which contributes to a vicious cycle of obesity progression [
16,
17].
Ultimately, both the prevention of PPWR and the initiation of breastfeeding seem to be key determinants in the prevention of obesity in the postpartum (pp) period. Therefore, various randomized controlled trials (RCTs) offering antenatal and pp lifestyle interventions were conducted to tackle excessive GWG and persistent PPWR as well as to promote breastfeeding. Meta-analyses confirm that antenatal lifestyle interventions are effective in limiting GWG and in reducing long-term maternal PPWR until the 12th month pp [
18,
19]. However, the RCTs included small to moderate numbers of participants, and interventions were usually conducted in community settings and academic facilities [
13,
20,
21,
22,
23]. Approaches embedded in the real-life setting of routine antenatal care are urgently needed to not only assess their effect on excessive GWG but also on long-term PPWR in order to realistically estimate their potential to interfere with the cycle of obesity progression.
The large-scale, cluster-randomized “Gesund leben in der Schwangerschaft” (“healthy living in pregnancy”, GeliS) trial was designed as a public health approach embedded in the German antenatal routine care system. The primary aim of the GeliS study was to reduce the proportion of women with excessive GWG according to the weight gain recommendations of the Institute of Medicine (IOM) [
24] by offering a comprehensive lifestyle intervention alongside antenatal routine visits [
25]. Although the intervention was not effective in limiting excessive GWG [
26], it yielded some improvements in dietary (manuscript under revision) and physical activity behavior (manuscript under revision) [
27,
28]. The long-term influence on maternal health remains to be investigated. Herein, our aim was to investigate the effect of the GeliS intervention on short- and long-term maternal PPWR and on the women’s breastfeeding behavior assessed in a 12 month follow-up. Moreover, we sought to identify factors influencing long-term PPWR and maternal breastfeeding behavior.
4. Discussion
To our knowledge, this was the first large-scale trial to evaluate the effect of a lifestyle intervention conducted alongside routine care on short- and long-term PPWR and maternal breastfeeding behavior. The GeliS intervention did not improve maternal pp weight development until delivery [
26] but yielded some minor improvements in maternal pp weight development and in the proportion of women who exclusively breastfed compared to standard care, although the clinical meaning of these findings is unclear. While the intervention did not seem to influence short-term PPWR and weight loss from delivery until 6–8 weeks pp, mean PPWR at the 12th month pp tended to be lower in the intervention group. Accordingly, weight loss since delivery until the 12th month pp was found to be more pronounced in women who previously obtained counseling. Although a higher proportion of women reached pre-pregnancy weight 6–8 weeks after birth in the control group, this group difference disappeared at the 12th month pp weight measurement. Findings on the influence of pre- and postnatal lifestyle interventions on maternal PPWR are often inconclusive and depend on the definition of PPWR, participant characteristics, and follow-up period, which complicates a comparison of study outcomes. While some studies reported a positive influence of lifestyle interventions on PPWR [
20,
43], others found no effect [
44,
45,
46]. A recent meta-analysis suggested a favorable effect of the intervention with an overall weighted mean difference of −0.73 kg (95% CI −1.32 to −0.14;
p = 0.015) between groups and a weighted mean difference of −0.68 kg (95% CI −1.28 to −0.09;
p = 0.023) in PPWR 12 months after birth [
19]. Although we reported a comparable effect size for long-term PPWR, we found no significant evidence of a between-group difference. This might be explained by the specific study setting of the GeliS trial and the general problem of scaling-up interventions [
47]. Unlike GeliS, none of the in the meta-analysis included trials were performed under real-life conditions in the setting of routine antenatal care.
Currently, there is a debate about factors that influence maternal PPWR in the short and the long term and thus might predict the risk for sustained PPWR [
48]. We found strong evidence for an association between excessive GWG and long-term PPWR, which was consistently observed by others, confirming excessive GWG as a major risk factor for PPWR even beyond the first year after birth [
9,
10,
24,
44,
46,
49]. Moreover, our findings suggest that parity is associated with PPWR, with multiparous women showing a lower PPWR at the 12th month pp compared to primiparous women. Albeit our observations are consistent with reports of others [
48,
50], the overall opinion on the role of parity in PPWR is inconclusive [
51]. Similar to others, we reported pre-pregnancy BMI category and educational level to be consistent predictors of long-term PPWR [
20,
52] and found short-term PPWR > 5 kg to be strongly associated with PPWR at one year after birth, but not antenatal well-being and PPD. Furthermore, the only breastfeeding pattern we found to beneficially influence PPWR was exclusive breastfeeding, with no observed effect in mothers who practiced any breastfeeding. Some studies confirm a link between breastfeeding and PPWR [
13,
14,
46], while others fail to provide sufficient evidence [
20]. This discrepancy might be explained by the heterogeneity observed in methodological procedures and breastfeeding outcomes. Drawing evidence from our findings and relevant literature, the overall effect of breastfeeding on PPWR seems to depend on breastfeeding intensity and duration. We acknowledge that other determinants such as postnatal diet and physical activity behavior may have a fundamental influence on PPWR, and analyzing their contribution on maternal pp weight development might generate ideas for initiatives to prevent long-term PPWR and inter-pregnancy weight gain [
53].
Evaluating the success of lifestyle interventions on a woman’s risk for sustained weight retention, Sagedal et al. [
45] demonstrated a broader spectrum of pp weight characteristics beyond PPWR, addressing variables such as returning to pre-pregnancy weight and weight loss since delivery. Our results showed that weight loss since delivery until the first year after delivery was 14.3 kg in the IV and 13.4 kg in the C on average and corresponded to findings by Sagedal et al. (IV: 13.3 kg; C: 14.0 kg) [
45] and Phelan et al. (IV: 13.6 kg; C: 12.5 kg) [
20], who included participants from all BMI classes. However, only the GeliS trial showed that women in the IV achieved greater weight loss pp, suggesting the effectiveness of our lifestyle intervention for this outcome. Sagedal et al. reported significant between-group differences in women returning to pre-pregnancy weight (IV: 53.2%; C: 43.1%) [
45], which is in contrast to results of the “Fit for Delivery” [
20] and the GeliS study. Although studies describe effects of lifestyle interventions on pp weight development, its clinical relevance remains to be questioned. PPWRs above 4.55 kg or 5 kg are commonly used as markers to define relevant or sustained PPWR and consequently to assess the clinical relevance of PPWR, as weight retention above these thresholds is associated with obesity later in life [
24,
33,
34,
35,
36,
54]. Our data did not provide any evidence for an effect of the GeliS intervention on relevant PPWR. Unfortunately, relevant PPWR is only reported in a few other trials [
21,
43,
44,
46,
55]. Among them, only one study found that lifestyle interventions significantly impacted clinically relevant PPWR at the 12th month after birth [
44].
Besides improving maternal weight outcomes in the pp period, the GeliS intervention sought to support participants in the initiation of breastfeeding and showed significant between-group differences in the proportion of women who exclusively breastfed (IV: 87.4% vs. C: 84.4%; adjusted
p < 0.001). However, this difference was rather small, and therefore the clinical meaning of this finding remains unclear. No other breastfeeding outcome appeared to be affected by counseling, which suggests that our intervention was not effective in changing maternal breastfeeding behavior and therefore does not support adoption of our counseling methods in clinical practice. Unfortunately, a comparison with other studies in this field is limited, as few trials included breastfeeding advice or reported relevant data. In a pilot trial that we conducted prior to the GeliS study, we were not able to show between-group differences in the duration of either any breastfeeding or exclusive breastfeeding [
44]. Vinter et al. reported similar high numbers of women with obesity initiating breastfeeding in their Danish cohort but no effect of the intervention on breastfeeding outcomes [
13]. In the “Fit for Delivery” study, which included women from all BMI classes and did not target breastfeeding behavior, breastfeeding rates were low and did not differ between groups (IV: 10.4% and C: 8.3% at the 6th month pp and 3.4% and 4.6%, respectively, at the 12th month pp). Overall, our breastfeeding rates correspond to other German observations that report an increasing trend towards the initiation of any breastfeeding over the last decade [
37,
56]. Similar to our observations, German and US studies found educational level and age before or at birth to be predictive for any breastfeeding [
37,
57]. Moreover, US observational studies extend our findings, showing that BMI category not only influences breastfeeding initiation but also breastfeeding maintenance beyond both the first and the 6th month pp [
57]. We found that antenatal well-being and PPD were associated with any breastfeeding but not with exclusive breastfeeding. Others have observed that women with depressive symptoms exclusively breastfed less frequently [
58]. Current research expands our findings, reporting inverse associations between antenatal depressive symptoms and the initiation of breastfeeding as well as observations that both antenatal depression and PPD predict early cessation of breastfeeding [
57,
59,
60]. Drawing from evidence presented herein, we suggest future initiatives to offer tailored and personalized counseling according to the individual needs of the mother. This will help to elucidate whether antenatal interventions are effective in achieving improvements in maternal breastfeeding behavior.
The analyses presented herein have some limitations. Weight was partly self-reported, which is generally thought to provide valid estimates and is widely used in comparable trials [
61,
62], but remains subjective. We are aware that weight measurements may not be completely standardized, as data were collected in all participating practices by varying personnel. Moreover, we observed inconsistencies in the first measured weight between groups that we attributed to the timing of the first weight measurement and to between-group differences in participants that were lost to follow-up. To address this limitation, we included “time of the first weight measurement” as a covariate in our analyses on PPWR. Power calculation was conducted based on the primary study endpoint (GWG). The power to detect differences in the secondary outcomes, including PPWR and breastfeeding, was not considered in the study design. We found differences between baseline characteristics among women included in follow-up analyses and those who dropped out in the pp period. Although we adjusted for some of these parameters in our analyses (BMI category and parity), this might have introduced bias and could have influenced results. Counseling was not based on concepts of behavioral change theory, which we acknowledge as a shortcoming related to both the training of counselors and the content of the counseling sessions. Our cohort differed slightly from the average German women of childbearing age in terms of educational level and BMI classes and was therefore not completely representative of the general German population [
5]. In order to analyze the effect of GWG on PPWR, we combined women with underweight (
n = 38) and normal weight to one group. Moreover, we pooled women with inadequate and adequate GWG to one group defined as women with non-excessive GWG. We acknowledge that pooling might have biased the overall influence of the dichotomized outcome excessive GWG on PPWR. We are aware that the contribution of other relevant predictors of PPWR, such as smoking, diet, and physical activity, are not included in our analyses. Moreover, we acknowledge that data on breastfeeding behavior were collected retrospectively by a questionnaire, which may limit its validity.
Notwithstanding our limitations, there are several strengths that merit particular attention. Current research in this field is mainly conducted under controlled conditions in community and academic settings or includes only small to moderate numbers of participants [
19]. The GeliS trial was designed as a large-scale lifestyle intervention that was implemented under real-life conditions. Assessing whether a public health intervention is successful and ultimately effective largely depends on its scalability. Through our study, we were able to demonstrate that we could implement a lifestyle intervention in the setting of routine care reaching a wider population of our target group. Findings from this study on pp weight development are promising first steps towards reducing obesity risk of women in the pp period on a broader scale. Herein, we reported minor effects on long-term pp weight development and slight improvements in the rate of exclusive breastfeeding. We were able to assess PPWR in women from all BMI categories and to selectively describe the overall influence of BMI on PPWR and breastfeeding behavior on the cohort level. During the follow-up period, we lost only 10.8% of participants and in total—since group allocation until the 12th month pp—only 21.1%. This was a rather low drop-out rate for the pp period considering that other studies reported drop-out rates after birth between 15% and 25% [
13,
20,
45]. We attribute the pp drop-out rate of 10.8% to our effort of thoroughly informing participants about the importance of the long-term follow-up at study entry. Finally, we reported data on a 12 months follow-up, which was longer than in most other trials and contributed valuable information towards estimating the long-term effect of interventions on PPWR. By following participants until the 5th year after birth, we will be able to provide further data on maternal weight development.