A C TA Obstetricia et Gynecologica
AOGS M A I N R E SE A RC H A R TI C LE
Postpartum weight retention and breastfeeding among obese women from the randomized controlled Lifestyle in Pregnancy (LiP) trial CHRISTINA ANNE VINTER1,2, DORTE MØLLER JENSEN2,3, PER OVESEN4, HENNING BECK-NIELSEN2,3, METTE TANVIG1,2, RONALD F. LAMONT1,2,5 & JAN STENER JØRGENSEN1,2 1
Department of Gynecology and Obstetrics, Odense University Hospital, Odense, Denmark, 2University of Southern Denmark, Odense, Denmark, 3Department of Endocrinology, Odense University Hospital, Odense, Denmark, 4Department of Gynecology and Obstetrics, Aarhus University Hospital, Skejby, Aarhus, Denmark, and 5Division of Surgery, University College London, Northwick Park Institute for Medical Research Campus, London, UK
Key words Breastfeeding, gestational weight gain, intervention, lifestyle, obesity, postpartum weight retention, pregnancy Correspondence Christina Anne Vinter, Department of Gynecology and Obstetrics, Odense University Hospital, Kløvervænget 10, 5000 Odense C, Denmark. E-mail: [email protected] Conflict of interest The authors have stated explicitly that there are no conflicts of interest in connection with this article. Please cite this article as: Vinter CA, Jensen DM, Ovesen P, Beck-Nielsen H, Tanvig M, Lamont RF, et al. Postpartum weight retention and breastfeeding among obese women from the randomized controlled Lifestyle in Pregnancy (LiP) trial. Acta Obstet Gynecol Scand 2014; 93:794–801. Received: 28 January 2014 Accepted: 12 May 2014 DOI: 10.1111/aogs.12429
Abstract Objectives. To study the effects of lifestyle intervention in pregnancy on weight retention 6 months postpartum among obese women from the “Lifestyle in Pregnancy” (LiP) study, and to determine associations between breastfeeding with postpartum maternal weight. Design. Six months postpartum follow up after a randomized controlled intervention trial. Setting. Two university hospitals in Denmark. Population. A total of 360 women with pregestational body mass index ≥30 kg/m2. Methods. The intervention involved lifestyle changes (diet and exercise) during pregnancy. The control group received routine pregnancy care. Both groups received standard postnatal care. Main outcome measures. Gestational weight gain, postpartum weight retention and breastfeeding. Results. Follow up was completed in 238 women of whom 46% in the intervention group and 57% in the control group had retained weight 6 months postpartum (p = 0.088). Women with gestational weight gain ≤9 kg, (recommended by the Institute of Medicine), retained less postpartum weight compared with those who exceeded 9 kg (median 0.7 vs. 1.5, p < 0.001). Ninety-two percent in both weight gain groups initiated breastfeeding. The number of breastfeeding mothers was higher among women with postpartum weight retention ≤5 kg compared with those with weight retention > 5 kg (94% vs. 85%, p = 0.034). Conclusions. We could not detect sustained weight control at 6 months postpartum despite a lower gestational weight gain for obese women during pregnancy who received a lifestyle intervention rather than standard care. Women who adhered to gestational weight gain recommendations had significantly lower postpartum weight retention. Breastfeeding for 6 months was negatively associated with postpartum weight retention. BMI, body mass index; GWG, gestational weight gain; IOM, Institute of Medicine; LiP, Lifestyle in Pregnancy (study); PPWR, postpartum weight retention.
Abbreviations:
Introduction Postpartum weight retention (PPWR) may contribute to the development or aggravation of obesity and has
794
important implications for the short-term and long-term health of women (1). Globally, obesity among women, including those of childbearing age, is increasing (2). High pregestational body mass index (BMI) and high gestational weight gain (GWG) are risk factors for weight
ª 2014 Nordic Federation of Societies of Obstetrics and Gynecology, Acta Obstetricia et Gynecologica Scandinavica 93 (2014) 794–801
C.A. Vinter et al.
retention within the first year postpartum (3). In addition, the long-term risk of obesity up to 21 years after delivery is influenced by GWG (4). Furthermore, the importance of restricting weight gain postpartum has been emphasized in a large population-based study in which inter-pregnancy weight gain, calculated as the difference in pregestational BMI between the first and second pregnancy, was linearly and significantly associated with an increased risk of adverse outcomes in the subsequent pregnancy (5). Breastfeeding has beneficial shortterm and long-term effects on maternal and infant health (6,7) and large epidemiological studies have demonstrated that breastfeeding reduces PPWR (8) whereas smaller studies found little or no effect (9). Several studies have shown that pregestational obesity is negatively associated both with the initiation and duration of breastfeeding (10,11). The Lifestyle in Pregnancy (LiP) study was designed to investigate whether lifestyle intervention in pregnancy could improve maternal and neonatal clinical outcomes (12). The present study is a postpartum follow up with the following objectives: 1 To determine the effects of lifestyle intervention in pregnancy on PPWR at 6 months postpartum among obese women from the LiP-study and to determine the association between breastfeeding and postpartum maternal weight. 2 To study the effect of GWG on PPWR 6 months postpartum in relation to Institute of Medicine (IOM) recommendations among obese pregnant women.
Material and methods The LiP-study was a randomized controlled trial conducted between October 2007 and October 2010 comprising Danish-speaking women with a pregestational BMI of 30–45 kg/m2. All women were booked for obstetric care at one of two university hospitals in Denmark, and detailed inclusion and exclusion criteria have been described previously (12). The project was approved by the local ethics committee of the Region of Southern Denmark (S-20070058) and the trial was registered at clinicaltrials.gov as NCT00530439. Randomization was in a ratio of 1:1 and blinding was not possible for pragmatic reasons. The 360 participants were randomized before 14 weeks of gestation to either the intervention or the control group. The control group received routine prenatal care. Both intervention and control groups were monitored by a project physician or midwife throughout the pregnancy by sequential measurement of maternal weight and blood pressure (at 10–14 weeks (baseline), 28–30 weeks and 34–36 weeks of gestation). Sonar fetal biometry was undertaken on two more
Postpartum follow-up from the LiP-Study
occasions during pregnancy than was routine. At a followup visit 6 months after delivery, information about the postpartum period with respect to lifestyle, breastfeeding and smoking status was collected. Information on daily physical activities during work or leisure time was based on the Saltin–Grimby Physical Activity Level Scale (13), which has been validated as a useful assessment tool (14). A short fitness test (the Danish step test) was performed at baseline, at 35 weeks of gestation, and at 6 months postpartum (15). The intervention in pregnancy consisted of different efforts to improve diet and physical activities. Individualized dietetic counseling was performed by trained dieticians on four separate occasions during pregnancy. This assessment was based on evaluation of each participant’s weight, dietary recollection, and level of activity. At the last visit before delivery, the dietetic counseling also considered the postpartum period and information on nutritional requirements during breastfeeding as well as weight loss was provided. The physical activities initiated consisted of aerobic classes with a physiotherapist (1 h weekly), free fitness membership during pregnancy, motivation using coaching-inspired methods and pedometers to improve physical activity. The intervention was not continued into the postpartum period.
Outcomes At study inclusion in early pregnancy, demographic information about previous pregnancies, smoking status, dietary habits, and physical activity was obtained. All weight measurements were recorded using the same scales (model 704; Seca, Hamburg, Germany) under standardized conditions. GWG was defined as the weight measured at 35 weeks of gestation minus the weight at study inclusion in early pregnancy. According to IOM recommendations, a GWG of 5–9 kg in pregestational obese women (16) was characterized as appropriate, low if ≤5 kg, and high if >9 kg. PPWR was measured as the weight at the postpartum visit 6 months after delivery,
Key Message Obesity in pregnancy is associated with an increased risk of excessive gestational weight gain and postpartum weight retention. Lifestyle intervention in obese pregnant women restricted gestational weight gain significantly in a large randomized controlled trial but no effect was seen 6 months postpartum. Restricting gestational weight gain according to Institute of Medicine recommendations helps women to return to a lower postpartum weight.
ª 2014 Nordic Federation of Societies of Obstetrics and Gynecology, Acta Obstetricia et Gynecologica Scandinavica 93 (2014) 794–801
795
Postpartum follow-up from the LiP-Study
minus the weight at study inclusion. PPWR was considered as substantial if ≥5 kg and insubstantial if < 5 kg. Blood pressure was measured electronically (model Boso-medicus control, CMA Medico, Espergaerde, Denmark) under standardized conditions with a large cuff when appropriate. To measure physical fitness, a short fitness test (the Danish Step-test) was performed. The Step-test is simple to conduct and requires minimal equipment (a 20–35 cm high bench/platform and an online computer program). A fitness score was calculated using time to exhaustion (in minutes), which also incorporated body weight and the height of the bench (17). At the 6 months postpartum visit women were asked how they had fed their infants from delivery, including duration of breastfeeding, use of infant formula and complementary feeding (solid or semi-formed). Information about breastfeeding was reported as never initiated, stopped within 1 week, 1–4 weeks, 1–4 months, >4 months, or still breastfeeding at 6 months postpartum. The infant’s age at the time of introduction of solid food was reported in months as well as the age at which formula feeding started. Full breastfeeding was defined as breastfeeding at 6 months postpartum without the introduction of formula feeding or solid food. For breastfeeding women, outcome data used for statistical analysis were presented as either any or full breastfeeding at 6 months. Finally, women were asked about their reasons for stopping or failing to initiate breastfeeding.
Statistical analysis The original study was powered for a combined endpoint of five maternal and neonatal outcomes. This 6-month postpartum follow up was a secondary analysis. The chisquared test was used for categorical variables to analyze weight changes between intervention and control groups as well as the comparison of women gaining weight according to IOM recommendations. The Student’s t-test was used for continuous variables that were normally distributed, whereas the Mann–Whitney U-test was applied to other continuous data. A significance level of 0.05 (two-sided) was chosen. A simple linear regression model was used to estimate the effect of breastfeeding (full or any breastfeeding) on PPWR. Adjustments for possible confounding factors (parity, smoking, pregestational BMI) were made with a multiple logistic regression model. All analyses were performed with the statistical program STATA 10.0 software (StataCorp, College Station, TX, USA).
Results Of 360 women included in the study 304 were followed up until delivery (84%). Of these, 238 women (78%)
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attended the follow-up visit 6 months postpartum, 123 from the intervention group and 115 from the control group (Figure 1). Sixty-six women did not attend and were excluded. These 66 women were characterized by having a higher mean pregestational BMI, higher GWG and more obstetric or neonatal complications, but the differences were not significant compared with those who did attend. Fifty-nine percent of the dropouts were from the control group. Among the total dropouts during pregnancy and postpartum (122 women) the maternal baseline characteristics were not statistically significantly different from those women who completed the study. The results of postpartum weight and weight retention, physical fitness and blood pressure are shown in Table 1. There was no significant difference in PPWR between the intervention and control groups. The results shown are unadjusted. When adjusting for confounding variables (smoking, parity and BMI) the results with respect to the PPWR were unchanged. However, adjusting for smoking significantly influenced the VO2max negatively (regression coefficient 4.44, p < 0.001). The 6 months postpartum results were also compared in women with a GWG within or above the IOM recommendations, regardless of the randomization groups (Table 2). We found a significantly lower PPWR in women with a GWG within the IOM recommendations. The low weight gain group had lost weight postpartum (mean 0.9 kg) compared with the high weight gain group that had retained a mean of 2.5 kg postpartum, giving a mean weight difference of 3.4 kg (p = 0.001). The physical fitness score was higher in the low weight gain group, but these results were not significant. Data on initiation and duration of any or full breastfeeding and time of introducing formula feeding and solid food are demonstrated in Table 3 and compared between intervention and control groups and between substantial and insubstantial PPWR groups (>5 kg vs. ≤5 kg). The percentage of women initiating breastfeeding was 92%, which was comparable between the intervention and control groups. Among women with insubstantial PPWR, the rate of initiating breastfeeding was significantly higher than among women with PPWR >5 kg (94% vs. 85%, p = 0.034). Similarly, more women from the insubstantial PPWR group were still fully breastfeeding at 6 months postpartum (27% vs. 15%), but this difference was not statistically significant (p = 0.079). In the simple linear regression analysis full breastfeeding significantly negatively influenced PPWR (regression coefficient 2,64, p = 0.002). In contrast, initiating breastfeeding or breastfeeding for less than 6 months was not associated with significantly less weight retention 6 months postpartum. Among women who never breastfed or who stopped breastfeeding within 4 weeks, 66 (68%) reported inappropriate milk production as their reason for stopping.
ª 2014 Nordic Federation of Societies of Obstetrics and Gynecology, Acta Obstetricia et Gynecologica Scandinavica 93 (2014) 794–801
C.A. Vinter et al.
Postpartum follow-up from the LiP-Study
Assessed for eligibility n = 1224 Excluded n = 864: Meeting exclusion criteria n = 493 Declined participation n = 317 Other reasons n = 54 (miscarriage, malformations, multiple pregnancies)
Randomized n = 360
Allocated to Intervention n = 180
Dropout in pregnancy n = 30: GDM (inclusion) n = 9 Withdraw n = 18 Missed abortion n = 1 Misclassification n = 2
Allocated to Control n = 180
Dropout in pregnancy n = 26: GDM (inclusion ) n = 3 Withdraw n = 14 Twin pregnancy n = 2 Missed abortion n = 4 Abortion n = 3
Analyzed at birth n = 150
Analyzed at birth n = 154
Dropout postpartum n = 27
Dropout postpartum n = 39
Analyzed postpartum n = 123
Analyzed postpartum n = 115
Figure 1. Flowchart for participation. GDM, gestational diabetes mellitus.
The results of self-reported lifestyle at baseline (beginning of pregnancy), late pregnancy and 6 months postpartum are shown in Table 4. The self-reported physical activity level and eating habits improved in the intervention group during pregnancy though postpartum, no significant differences were seen between the groups.
When self-reported responses on physical activity and eating habits were analyzed between substantial and insubstantial PPWR groups, the only statistically significant difference was that women with an insubstantial PPWR described their dietary habits as significantly more healthy compared with women with substantial weight retention.
ª 2014 Nordic Federation of Societies of Obstetrics and Gynecology, Acta Obstetricia et Gynecologica Scandinavica 93 (2014) 794–801
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Postpartum follow-up from the LiP-Study
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Table 1. Maternal outcomes 6 months postpartum in intervention and control group. Intervention (n = 123) Prepregnancy weight Primiparous Gestational weight gain Smoking during postpartum period Maternal weight 6MPP PPWR >0 kg (weight retention) PPWR >5 kg Systolic blood pressure Diastolic blood pressure VO2max (mL/kg/min)
Control (n = 115)
p-value
94.5 (87.3–103.7)
0.625
63 (51) 7.0 (4.5–10.1)
61 (53) 9.1 (5.7–11.6)
0.778 0.006
10 (8)
16 (14)
0.153
95 (87.9–105.0)
95 (87.3–106.6) 57 (46)
94.4 (87–107.3) 66 (57)
21 (17) 122 (116–129)
26 (23) 122 (115–128)
0.878 0.088
0.284 0.770
83.5 (78–88)
82 (78–88)
0.733
27 (23–32)
27 (23–30)
0.119
Data are given as median (interquartile range) or number (%). Differences between groups were analyzed with chi-squared test for categorical variables. Student’s t-test was used for continuous variables with normal distribution; otherwise, the Mann–Whitney U-test was used. 6MPP, 6 months postpartum; PPWR, postpartum weight retention (weight 6MPP – weight at inclusion in pregnancy).
Forty-eight percent of the participants were multiparous and at baseline we had self-reported information about GWG in the most recent pregnancy before their participation in the LiP-study (Table 2). Women in the low GWG group from the LiP-study also had a significantly lower GWG in their previous pregnancy compared with women who exceeded the IOM recommendations [median (interquartile range; IQR)]: 12 kg (8–16 kg) vs. 20 kg (15–27 kg), (p < 0.001). When comparing PPWR between nulliparous and multiparous women, there was a statistically significant difference between nulliparous women who had a median PPWR of 0.95 kg (IQR 1.75 to 4.2) and multiparous women who had a median PPWR of 0.40 kg (IQR 3.2 to 2.9), (p = 0.019).
Discussion In this large randomized controlled trial of obese women who had participated in a lifestyle intervention study during their pregnancy, we found at the 6-month postpartum follow up that the difference in weight between the intervention and control groups was no longer significant and their self-reported lifestyles were comparable. Partici-
798
Table 2. Maternal outcomes 6 months postpartum in gestational weight gain groups according to the Institute of Medicine recommendations. GWG ≤9 kg (n = 138) Maternal weight 6MPP PPWR PPWR >0 kg (weight retention) PPWR ≥5 kg (5-kg weight retention) VO2maxa (mL/kg/min) GWG before pregnancyb (kg)
93.6 (89–104)
GWG >9 kg (n = 100) 96 (89–110)
p-value 0.038
0.7 ( 3.3 to 2.3) 56 (41)
1.5 ( 0.6 to 5.9) 68 (67)
AOGS M A I N R E SE A RC H A R TI C LE
Postpartum weight retention and breastfeeding among obese women from the randomized controlled Lifestyle in Pregnancy (LiP) trial CHRISTINA ANNE VINTER1,2, DORTE MØLLER JENSEN2,3, PER OVESEN4, HENNING BECK-NIELSEN2,3, METTE TANVIG1,2, RONALD F. LAMONT1,2,5 & JAN STENER JØRGENSEN1,2 1
Department of Gynecology and Obstetrics, Odense University Hospital, Odense, Denmark, 2University of Southern Denmark, Odense, Denmark, 3Department of Endocrinology, Odense University Hospital, Odense, Denmark, 4Department of Gynecology and Obstetrics, Aarhus University Hospital, Skejby, Aarhus, Denmark, and 5Division of Surgery, University College London, Northwick Park Institute for Medical Research Campus, London, UK
Key words Breastfeeding, gestational weight gain, intervention, lifestyle, obesity, postpartum weight retention, pregnancy Correspondence Christina Anne Vinter, Department of Gynecology and Obstetrics, Odense University Hospital, Kløvervænget 10, 5000 Odense C, Denmark. E-mail: [email protected] Conflict of interest The authors have stated explicitly that there are no conflicts of interest in connection with this article. Please cite this article as: Vinter CA, Jensen DM, Ovesen P, Beck-Nielsen H, Tanvig M, Lamont RF, et al. Postpartum weight retention and breastfeeding among obese women from the randomized controlled Lifestyle in Pregnancy (LiP) trial. Acta Obstet Gynecol Scand 2014; 93:794–801. Received: 28 January 2014 Accepted: 12 May 2014 DOI: 10.1111/aogs.12429
Abstract Objectives. To study the effects of lifestyle intervention in pregnancy on weight retention 6 months postpartum among obese women from the “Lifestyle in Pregnancy” (LiP) study, and to determine associations between breastfeeding with postpartum maternal weight. Design. Six months postpartum follow up after a randomized controlled intervention trial. Setting. Two university hospitals in Denmark. Population. A total of 360 women with pregestational body mass index ≥30 kg/m2. Methods. The intervention involved lifestyle changes (diet and exercise) during pregnancy. The control group received routine pregnancy care. Both groups received standard postnatal care. Main outcome measures. Gestational weight gain, postpartum weight retention and breastfeeding. Results. Follow up was completed in 238 women of whom 46% in the intervention group and 57% in the control group had retained weight 6 months postpartum (p = 0.088). Women with gestational weight gain ≤9 kg, (recommended by the Institute of Medicine), retained less postpartum weight compared with those who exceeded 9 kg (median 0.7 vs. 1.5, p < 0.001). Ninety-two percent in both weight gain groups initiated breastfeeding. The number of breastfeeding mothers was higher among women with postpartum weight retention ≤5 kg compared with those with weight retention > 5 kg (94% vs. 85%, p = 0.034). Conclusions. We could not detect sustained weight control at 6 months postpartum despite a lower gestational weight gain for obese women during pregnancy who received a lifestyle intervention rather than standard care. Women who adhered to gestational weight gain recommendations had significantly lower postpartum weight retention. Breastfeeding for 6 months was negatively associated with postpartum weight retention. BMI, body mass index; GWG, gestational weight gain; IOM, Institute of Medicine; LiP, Lifestyle in Pregnancy (study); PPWR, postpartum weight retention.
Abbreviations:
Introduction Postpartum weight retention (PPWR) may contribute to the development or aggravation of obesity and has
794
important implications for the short-term and long-term health of women (1). Globally, obesity among women, including those of childbearing age, is increasing (2). High pregestational body mass index (BMI) and high gestational weight gain (GWG) are risk factors for weight
ª 2014 Nordic Federation of Societies of Obstetrics and Gynecology, Acta Obstetricia et Gynecologica Scandinavica 93 (2014) 794–801
C.A. Vinter et al.
retention within the first year postpartum (3). In addition, the long-term risk of obesity up to 21 years after delivery is influenced by GWG (4). Furthermore, the importance of restricting weight gain postpartum has been emphasized in a large population-based study in which inter-pregnancy weight gain, calculated as the difference in pregestational BMI between the first and second pregnancy, was linearly and significantly associated with an increased risk of adverse outcomes in the subsequent pregnancy (5). Breastfeeding has beneficial shortterm and long-term effects on maternal and infant health (6,7) and large epidemiological studies have demonstrated that breastfeeding reduces PPWR (8) whereas smaller studies found little or no effect (9). Several studies have shown that pregestational obesity is negatively associated both with the initiation and duration of breastfeeding (10,11). The Lifestyle in Pregnancy (LiP) study was designed to investigate whether lifestyle intervention in pregnancy could improve maternal and neonatal clinical outcomes (12). The present study is a postpartum follow up with the following objectives: 1 To determine the effects of lifestyle intervention in pregnancy on PPWR at 6 months postpartum among obese women from the LiP-study and to determine the association between breastfeeding and postpartum maternal weight. 2 To study the effect of GWG on PPWR 6 months postpartum in relation to Institute of Medicine (IOM) recommendations among obese pregnant women.
Material and methods The LiP-study was a randomized controlled trial conducted between October 2007 and October 2010 comprising Danish-speaking women with a pregestational BMI of 30–45 kg/m2. All women were booked for obstetric care at one of two university hospitals in Denmark, and detailed inclusion and exclusion criteria have been described previously (12). The project was approved by the local ethics committee of the Region of Southern Denmark (S-20070058) and the trial was registered at clinicaltrials.gov as NCT00530439. Randomization was in a ratio of 1:1 and blinding was not possible for pragmatic reasons. The 360 participants were randomized before 14 weeks of gestation to either the intervention or the control group. The control group received routine prenatal care. Both intervention and control groups were monitored by a project physician or midwife throughout the pregnancy by sequential measurement of maternal weight and blood pressure (at 10–14 weeks (baseline), 28–30 weeks and 34–36 weeks of gestation). Sonar fetal biometry was undertaken on two more
Postpartum follow-up from the LiP-Study
occasions during pregnancy than was routine. At a followup visit 6 months after delivery, information about the postpartum period with respect to lifestyle, breastfeeding and smoking status was collected. Information on daily physical activities during work or leisure time was based on the Saltin–Grimby Physical Activity Level Scale (13), which has been validated as a useful assessment tool (14). A short fitness test (the Danish step test) was performed at baseline, at 35 weeks of gestation, and at 6 months postpartum (15). The intervention in pregnancy consisted of different efforts to improve diet and physical activities. Individualized dietetic counseling was performed by trained dieticians on four separate occasions during pregnancy. This assessment was based on evaluation of each participant’s weight, dietary recollection, and level of activity. At the last visit before delivery, the dietetic counseling also considered the postpartum period and information on nutritional requirements during breastfeeding as well as weight loss was provided. The physical activities initiated consisted of aerobic classes with a physiotherapist (1 h weekly), free fitness membership during pregnancy, motivation using coaching-inspired methods and pedometers to improve physical activity. The intervention was not continued into the postpartum period.
Outcomes At study inclusion in early pregnancy, demographic information about previous pregnancies, smoking status, dietary habits, and physical activity was obtained. All weight measurements were recorded using the same scales (model 704; Seca, Hamburg, Germany) under standardized conditions. GWG was defined as the weight measured at 35 weeks of gestation minus the weight at study inclusion in early pregnancy. According to IOM recommendations, a GWG of 5–9 kg in pregestational obese women (16) was characterized as appropriate, low if ≤5 kg, and high if >9 kg. PPWR was measured as the weight at the postpartum visit 6 months after delivery,
Key Message Obesity in pregnancy is associated with an increased risk of excessive gestational weight gain and postpartum weight retention. Lifestyle intervention in obese pregnant women restricted gestational weight gain significantly in a large randomized controlled trial but no effect was seen 6 months postpartum. Restricting gestational weight gain according to Institute of Medicine recommendations helps women to return to a lower postpartum weight.
ª 2014 Nordic Federation of Societies of Obstetrics and Gynecology, Acta Obstetricia et Gynecologica Scandinavica 93 (2014) 794–801
795
Postpartum follow-up from the LiP-Study
minus the weight at study inclusion. PPWR was considered as substantial if ≥5 kg and insubstantial if < 5 kg. Blood pressure was measured electronically (model Boso-medicus control, CMA Medico, Espergaerde, Denmark) under standardized conditions with a large cuff when appropriate. To measure physical fitness, a short fitness test (the Danish Step-test) was performed. The Step-test is simple to conduct and requires minimal equipment (a 20–35 cm high bench/platform and an online computer program). A fitness score was calculated using time to exhaustion (in minutes), which also incorporated body weight and the height of the bench (17). At the 6 months postpartum visit women were asked how they had fed their infants from delivery, including duration of breastfeeding, use of infant formula and complementary feeding (solid or semi-formed). Information about breastfeeding was reported as never initiated, stopped within 1 week, 1–4 weeks, 1–4 months, >4 months, or still breastfeeding at 6 months postpartum. The infant’s age at the time of introduction of solid food was reported in months as well as the age at which formula feeding started. Full breastfeeding was defined as breastfeeding at 6 months postpartum without the introduction of formula feeding or solid food. For breastfeeding women, outcome data used for statistical analysis were presented as either any or full breastfeeding at 6 months. Finally, women were asked about their reasons for stopping or failing to initiate breastfeeding.
Statistical analysis The original study was powered for a combined endpoint of five maternal and neonatal outcomes. This 6-month postpartum follow up was a secondary analysis. The chisquared test was used for categorical variables to analyze weight changes between intervention and control groups as well as the comparison of women gaining weight according to IOM recommendations. The Student’s t-test was used for continuous variables that were normally distributed, whereas the Mann–Whitney U-test was applied to other continuous data. A significance level of 0.05 (two-sided) was chosen. A simple linear regression model was used to estimate the effect of breastfeeding (full or any breastfeeding) on PPWR. Adjustments for possible confounding factors (parity, smoking, pregestational BMI) were made with a multiple logistic regression model. All analyses were performed with the statistical program STATA 10.0 software (StataCorp, College Station, TX, USA).
Results Of 360 women included in the study 304 were followed up until delivery (84%). Of these, 238 women (78%)
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attended the follow-up visit 6 months postpartum, 123 from the intervention group and 115 from the control group (Figure 1). Sixty-six women did not attend and were excluded. These 66 women were characterized by having a higher mean pregestational BMI, higher GWG and more obstetric or neonatal complications, but the differences were not significant compared with those who did attend. Fifty-nine percent of the dropouts were from the control group. Among the total dropouts during pregnancy and postpartum (122 women) the maternal baseline characteristics were not statistically significantly different from those women who completed the study. The results of postpartum weight and weight retention, physical fitness and blood pressure are shown in Table 1. There was no significant difference in PPWR between the intervention and control groups. The results shown are unadjusted. When adjusting for confounding variables (smoking, parity and BMI) the results with respect to the PPWR were unchanged. However, adjusting for smoking significantly influenced the VO2max negatively (regression coefficient 4.44, p < 0.001). The 6 months postpartum results were also compared in women with a GWG within or above the IOM recommendations, regardless of the randomization groups (Table 2). We found a significantly lower PPWR in women with a GWG within the IOM recommendations. The low weight gain group had lost weight postpartum (mean 0.9 kg) compared with the high weight gain group that had retained a mean of 2.5 kg postpartum, giving a mean weight difference of 3.4 kg (p = 0.001). The physical fitness score was higher in the low weight gain group, but these results were not significant. Data on initiation and duration of any or full breastfeeding and time of introducing formula feeding and solid food are demonstrated in Table 3 and compared between intervention and control groups and between substantial and insubstantial PPWR groups (>5 kg vs. ≤5 kg). The percentage of women initiating breastfeeding was 92%, which was comparable between the intervention and control groups. Among women with insubstantial PPWR, the rate of initiating breastfeeding was significantly higher than among women with PPWR >5 kg (94% vs. 85%, p = 0.034). Similarly, more women from the insubstantial PPWR group were still fully breastfeeding at 6 months postpartum (27% vs. 15%), but this difference was not statistically significant (p = 0.079). In the simple linear regression analysis full breastfeeding significantly negatively influenced PPWR (regression coefficient 2,64, p = 0.002). In contrast, initiating breastfeeding or breastfeeding for less than 6 months was not associated with significantly less weight retention 6 months postpartum. Among women who never breastfed or who stopped breastfeeding within 4 weeks, 66 (68%) reported inappropriate milk production as their reason for stopping.
ª 2014 Nordic Federation of Societies of Obstetrics and Gynecology, Acta Obstetricia et Gynecologica Scandinavica 93 (2014) 794–801
C.A. Vinter et al.
Postpartum follow-up from the LiP-Study
Assessed for eligibility n = 1224 Excluded n = 864: Meeting exclusion criteria n = 493 Declined participation n = 317 Other reasons n = 54 (miscarriage, malformations, multiple pregnancies)
Randomized n = 360
Allocated to Intervention n = 180
Dropout in pregnancy n = 30: GDM (inclusion) n = 9 Withdraw n = 18 Missed abortion n = 1 Misclassification n = 2
Allocated to Control n = 180
Dropout in pregnancy n = 26: GDM (inclusion ) n = 3 Withdraw n = 14 Twin pregnancy n = 2 Missed abortion n = 4 Abortion n = 3
Analyzed at birth n = 150
Analyzed at birth n = 154
Dropout postpartum n = 27
Dropout postpartum n = 39
Analyzed postpartum n = 123
Analyzed postpartum n = 115
Figure 1. Flowchart for participation. GDM, gestational diabetes mellitus.
The results of self-reported lifestyle at baseline (beginning of pregnancy), late pregnancy and 6 months postpartum are shown in Table 4. The self-reported physical activity level and eating habits improved in the intervention group during pregnancy though postpartum, no significant differences were seen between the groups.
When self-reported responses on physical activity and eating habits were analyzed between substantial and insubstantial PPWR groups, the only statistically significant difference was that women with an insubstantial PPWR described their dietary habits as significantly more healthy compared with women with substantial weight retention.
ª 2014 Nordic Federation of Societies of Obstetrics and Gynecology, Acta Obstetricia et Gynecologica Scandinavica 93 (2014) 794–801
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Postpartum follow-up from the LiP-Study
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Table 1. Maternal outcomes 6 months postpartum in intervention and control group. Intervention (n = 123) Prepregnancy weight Primiparous Gestational weight gain Smoking during postpartum period Maternal weight 6MPP PPWR >0 kg (weight retention) PPWR >5 kg Systolic blood pressure Diastolic blood pressure VO2max (mL/kg/min)
Control (n = 115)
p-value
94.5 (87.3–103.7)
0.625
63 (51) 7.0 (4.5–10.1)
61 (53) 9.1 (5.7–11.6)
0.778 0.006
10 (8)
16 (14)
0.153
95 (87.9–105.0)
95 (87.3–106.6) 57 (46)
94.4 (87–107.3) 66 (57)
21 (17) 122 (116–129)
26 (23) 122 (115–128)
0.878 0.088
0.284 0.770
83.5 (78–88)
82 (78–88)
0.733
27 (23–32)
27 (23–30)
0.119
Data are given as median (interquartile range) or number (%). Differences between groups were analyzed with chi-squared test for categorical variables. Student’s t-test was used for continuous variables with normal distribution; otherwise, the Mann–Whitney U-test was used. 6MPP, 6 months postpartum; PPWR, postpartum weight retention (weight 6MPP – weight at inclusion in pregnancy).
Forty-eight percent of the participants were multiparous and at baseline we had self-reported information about GWG in the most recent pregnancy before their participation in the LiP-study (Table 2). Women in the low GWG group from the LiP-study also had a significantly lower GWG in their previous pregnancy compared with women who exceeded the IOM recommendations [median (interquartile range; IQR)]: 12 kg (8–16 kg) vs. 20 kg (15–27 kg), (p < 0.001). When comparing PPWR between nulliparous and multiparous women, there was a statistically significant difference between nulliparous women who had a median PPWR of 0.95 kg (IQR 1.75 to 4.2) and multiparous women who had a median PPWR of 0.40 kg (IQR 3.2 to 2.9), (p = 0.019).
Discussion In this large randomized controlled trial of obese women who had participated in a lifestyle intervention study during their pregnancy, we found at the 6-month postpartum follow up that the difference in weight between the intervention and control groups was no longer significant and their self-reported lifestyles were comparable. Partici-
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Table 2. Maternal outcomes 6 months postpartum in gestational weight gain groups according to the Institute of Medicine recommendations. GWG ≤9 kg (n = 138) Maternal weight 6MPP PPWR PPWR >0 kg (weight retention) PPWR ≥5 kg (5-kg weight retention) VO2maxa (mL/kg/min) GWG before pregnancyb (kg)
93.6 (89–104)
GWG >9 kg (n = 100) 96 (89–110)
p-value 0.038
0.7 ( 3.3 to 2.3) 56 (41)
1.5 ( 0.6 to 5.9) 68 (67)
