Objective
The objective of the study was to assess physical activity intervention assessed by a pedometer with or without dietary intervention on gestational weight gain (GWG) in obese pregnant women by comparing with a control group.
Study Design
This study was a randomized controlled trial of 425 obese pregnant women comparing 3 groups: (1) PA plus D, physical activity and dietary intervention (n = 142); (2) PA, physical activity intervention (n = 142); and (3) C, a control group receiving standard care (n = 141). All participants routinely in gestational weeks 11-14 had an initial dietary counseling session and were advised to limit GWG to less than 5 kg. Physical activity intervention included encouragement to increase physical activity, aiming at a daily step count of 11,000, monitored by pedometer assessment on 7 consecutive days every 4 weeks. Dietary intervention included follow-up on a hypocaloric Mediterranean-style diet. Instruction was given by a dietician every 2 weeks. The primary outcome measure was GWG, and the secondary outcome measures were complications of pregnancy and delivery and neonatal outcome.
Results
The study was completed by 389 patients (92%). Median values of GWG (ranges) were lower in each of the intervention groups (PA plus D, 8.6 [–9.6 to 34.1] kg, and group PA, 9.4 [–3.4 to 28.2] kg) compared with the control group (10.9 [–4.4 to 28.7] kg [PA+D vs C]; P = .01; PA vs C; P = .042). No significant difference was found between the 2 intervention groups. In a multivariate analysis, physical activity intervention decreased GWG by a mean of 1.38 kg ( P = .040). The Institute of Medicine’s recommendations for GWG were more frequently followed in the intervention groups.
Conclusion
Physical activity intervention assessed by pedometer with or without dietary follow-up reduced GWG compared with controls in obese pregnant women.
Over the past 3 decades, the incidence of obesity among children and adolescents has increased dramatically. In Europe the incidence of overweight (body mass index [BMI] 25-29.9 kg/m 2 ) or obesity (BMI >30 kg/m 2 ) among pregnant women ranges between 33% and 50%. Obesity is a high-risk factor for several pregnancy and delivery complications such as gestational diabetes, gestational hypertension, and preeclampsia. The risk of giving birth to a macrosomic neonate increases proportionally with increasing BMI. Birth traumas, severe asphyxia, and neonatal hypoglycemia are all related to fetal macrosomia.
The risk of macrosomia as well as the risk of pregnancy complications are independently related to gestational weight gain (GWG), and high GWG is a predictor of obesity in infancy and adulthood. The 2009 Institute of Medicine (IOM) recommendations advise obese women to limit their GWG to 5-9 kg. Additional weight gain is associated with a risk of 2- to 3-fold excess weight retention after birth. Some observational studies indicate that these limits for gestational weight gain are optimal for the outcome of mother and child, and even a GWG of 5 kg or less may reduce the number of complications without increasing the number of adverse outcomes.
There are good opportunities to introduce lifestyle interventions during the antenatal period. A recent metaanalysis concluded that lifestyle interventions in pregnancy can reduce GWG. Physical activity during pregnancy reduces the risk of macrosomia and gestational diabetes but may be difficult to achieve. An economic evaluation of nonpharmacological interventions for weight management in nonpregnant women, undertaken by the National Institute for Health and Clinical Excellence, found that diet-based interventions were less costly than interventions based on physical activity.
Only a few studies have measured the isolated effect of a physical activity intervention based on a pedometer. Few studies have shown a beneficial effect on type 2 diabetes, and some have resulted in a modest weight loss in nonpregnant obese participants. A randomized controlled study has shown that a pedometer-based intervention could reduce weight retention after birth, but no studies have investigated the isolated effect of a pedometer intervention on weight gain during pregnancy.
The present study of obese pregnant women was designed to measure the effect on maternal GWG of an inexpensive physical activity intervention assessed by a pedometer with or without dietary intervention by comparing with a control group.
Furthermore, we assessed whether lifestyle intervention reduced incidences of pregnancy and delivery complications.
Materials and Methods
A prospective, randomized controlled trial was conducted from March 2009 to March 2012 at Hvidovre Hospital, University of Copenhagen, with 7000 deliveries annually. All pregnant women with a prepregnancy BMI of 30 kg/m 2 or greater were identified when booking for the initial ultrasound nuchal translucency scan. They were offered one consultation with a dietician as soon as possible after the ultrasound examination in gestational weeks 11-14, which is routine practice in the department.
The consultation consisted of an individual recommendation of a hypocaloric low-fat diet with 1200-1675 kcal (5000-7000 KJ), corresponding to a Mediterranean-style diet which covers preference of polyunsaturated fat by intake of fish and oils. The diet was based on the Danish national recommendations for a healthy diet. Only oral advice was given, and no meal plan was offered. After the dietary advice, eligible women were asked to participate in the study. To reduce GWG as much as possible by the intervention, all participants were advised by the dietitian to aim for a GWG less than 5 kg, which in other studies seems to be safe.
Inclusion criteria were age older than 18 years, a singleton pregnancy, and a normal scan in weeks 11-14, gestational age (GA) at inclusion of less than 16 weeks, and an ability to read and speak Danish. Subjects were excluded if they had a multiple pregnancy, pregestational diabetes, or other serious diseases limiting their level of physical activity, previous bariatric surgery, or alcohol or drug abuse.
After written informed consent was obtained, the women were randomized by the dietitian into 3 groups (1:1:1): (1) group PA plus D received mixed intervention with follow-up on dietary advice and encouragement to increase physical activity as assessed by pedometer; (2) group PA was encouraged to increase physical activity as assessed by pedometer; and group C served as the control group and received the usual hospital standard regimen for obese pregnant women.
The randomization was stratified according to parity to ensure equal distribution of primiparous in the 3 groups. Web allocation by an independent organization (Trial Partner, Public Health and Quality Improvement, Department of Data Management, Central Denmark Region) properly concealed the procedure.
The women allocated to physical activity intervention (groups PA plus D and PA) were immediately after randomization individually advised and encouraged by the dietitian to increase physical activity, aiming at a daily step count of 11,000, which corresponds to 150% of the average step count in healthy lean pregnant women. Physical activity was monitored by a validated pedometer: a Yamax Digiwalker CW-700/750 (Yamax Corporation, Tokyo, Japan) counting the daily number of steps was provided to each participant.
Daily step counts were registered on 7 consecutive days every 4 weeks. The women were contacted with a reminding text message when a recording period started, with encouragement to obtain the 11,000 daily steps. If this was not obtainable, they were asked to set their own target. The pregnant women themselves registered the actual weight and daily pedometer-assessed step counts on a chart and returned it to the department. They did not receive any feedback on their reporting of weight and step count.
The dietary intervention consisted of contact with an experienced dietitian every 2 weeks, alternating between outpatient visits and phone contacts (11-13, depending on length of gestation). Follow-up included measurement of weight, encouragement, and correcting advice on the diet if the weight gain was greater than aimed for or if the participant reported an incorrect diet.
Additional demographic data including smoking history, educational level, and data about prepregnancy physical activity were recorded at inclusion. The level of prepregnancy physical activity was self-evaluated in a simple validated questionnaire to detect whether there was any baseline difference between the 3 groups.
Several additional tests were performed. A test for gestational diabetes mellitus (GDM) was performed. The women were tested for GDM twice with a 75-g, 2-hour standard oral glucose tolerance test (OGTT) at gestational weeks 17-20 and 27-30. If gestational diabetes was diagnosed, care continued in the multidisciplinary diabetic clinic, but the patient was not excluded from the study.
Weight was measured on an electronic scale (Model Sv-Seca 769; Seca, Hamburg, Germany), with the woman wearing light indoor clothes and no shoes at inclusion and at gestational weeks 18-22 and 36-37.
GWG was calculated as the weight measured at a visit during gestational weeks 36-37 minus the self-reported prepregnancy weight.
Pregnancy complications and mode of delivery were extracted from hospital files and validated using the Danish national guidelines (DSOG guidelines). According to these, GDM was diagnosed if the 2-hour standard OGTT capillary blood glucose was 9 mmol/L or greater. Preeclampsia was defined as proteinuria (dipstick, greater than 1+) and persistently elevated blood pressure greater than 140/90 mm Hg on more than 1 occasion. Gestational hypertension was diagnosed using the same criteria but without proteinuria.
Neonatal outcome was measured. Gestational age, placenta weight, birthweight, birth length, Apgar score, and umbilical cord pH were recorded. The actual birthweight was transformed to a relative birthweight with a percentage deviation from the expected weight adjusted for gestational age and sex using the reference population and formula according to Marsal et al. This provides an SD of 12%. Accordingly, small for gestational age (SGA) was set to a relative birthweight less than 76% (–2 SD) of normal, whereas large for gestational age (LGA) refers to a relative birthweight ≥124% or greater (2 SD) of normal. Macrosomia was defined as birthweight of 4000 g or greater.
Dropouts were defined as participants dropping out of the study before delivery because of miscarriage, withdrawal of informed consent, or because they moved out of the region.
Attendance to the dietary intervention as well as compliance to the pedometer-assessed physical activity intervention was measured by filling in and returning the forms with step counts and weight.
Ethics
This study received approval from the Ethics Committee for the Capital Region of Denmark (January 2009) (identification number H-D-2008-119). The study is registered at ClinicalTrials.gov (identification number NCT01345149 ).
Statistics
The power calculation relied on a pilot study of 70 obese pregnant women with a BMI ≥30 kg/m 2 and a GWG of 9.1 kg ± 8.5 kg. Thus, a total of 112 participants should be included in each group to detect a minimal difference of 3 kg in GWG (power, 80%; alpha, 5%, 2-sided test). Expecting up to 20% dropouts, we included 140 in each of the 3 groups (n = 420).
Data are presented in accordance with their distribution: as median and ranges or mean and SDs. Categorical data were tested with χ 2 statistics or Fisher exact test. Differences between all groups were tested by a Kruskal-Wallis test or an analysis of variance (ANOVA), whereas the Mann-Whitney U test analyzed differences between 2 groups.
The effect of diet or physical activity intervention on GWG was tested by multiple linear regression across the groups. Categorical predictor variables (0, 1) for diet and physical activity intervention were incorporated into the analysis together with maternal age, parity, BMI, smoking, and education.
Finally, we evaluated the relation between birthweight and GWG by grouping all participants according to recommendations of IOM.
All analyses were performed according to the intention-to-treat approach. The statistical package SPSS version 19 (IBM Corp, Armonk, NY) was used, and the level of significance was set to P = .05.
Results
In the inclusion period, 758 pregnant women were considered eligible for inclusion, and 425 (56%) participated. In total 389 women completed the study ( Figure 1 ).
Participants still included at delivery did not differ with respect to dropout rate or to sociodemographic characteristics within the 3 groups ( Table 1 ). The women who dropped out were more often nonwhite. Information on weight gain missed in 13 women because they delivered preterm. One woman allocated to group PA delivered in gestational week 35 and had an unexpected stillbirth caused by placental abruption.
| Characteristic | Group PA plus D (n = 130) | Group PA (n = 125) | Control group C (n = 134) | Dropouts (n = 36) | Significance |
|---|---|---|---|---|---|
| Parity | |||||
| Primiparous | 69 (53%) | 68 (54%) | 75 (56%) | 24 (67%) | NS a |
| Previous caesarean section: | 10 (7.8%) | 11 (8.8%) | 11 (8.2%) | 2 (10%) | NS a |
| Pre-pregnancy BMI, kg/m 2 | |||||
| Mean +/- 1 SD | 34.4 ± 4.2 | 34.1 ± 4.4 | 33.7 ± 3.5 | 34.2 ± 3.7 | NS b |
| Age, y | |||||
| Mean +/- 1 SD | 31.2 ± 4.4 | 30.9 ± 4.9 | 31.3 ± 4.2 | 30.4 ± 4.8 | NS b |
| Caucasian, n (%) | 128 (98) | 123 (98) | 130 (97) | 31 (86) a | .0011 a |
| Smoking, n (%) | 12 (9.3) | 7 (5.7) | 11 (8.2) | 5 (13.9) | NS a |
| Missing data | 1 | 3 | 0 | ||
| Quit smoking during pregnancy | 2 | 2 | 0 | ||
| Educational level, n (%) | |||||
| Grammar school 10 y or less | 11 (8.5) | 17 (13.6) | 16 (11.9) | 5 (13.9) | NS a |
| Secondary school 12 y | 16 (12.3) | 17 (13.6) | 13 (9.7) | 6 (16.7) | |
| Vocational training school or further education 1-2 y | 41 (31.5) | 37 (29.6) | 34 (25.4) | 11 (30.6) | |
| Tertiary education 3-4 y (bachelor level) | 47 (36.2) | 36 (28.8) | 49 (36.6) | 9 (25) | |
| Advanced education (postgraduate) | 13 (10.0) | 18 (14.4) | 18 (13.4) | 5 (13.9) | |
| Missing data | 2 (1.5) | 0 (0) | 4 (3.0) | 0 (0) |
Women in group PA plus D attending dietary consultations every 2 weeks could have 11-13 contacts with the dietitian, depending on the length of gestation. The median number of dietary consultations was 11 (range, 0–14) for the 130 participants who participated until delivery.
Intervention and GWG
GWG (medians [ranges]) was as follows: group PA plus D, 8.6 kg (–9.6 to 34.1) kg; group PA, 9.4 kg (–3.4 to 28.2) kg; and group C, 10.9 kg (–4.4 to 28.7) ( P = .024). GWG for participants in the intervention groups PA plus D and PA was significantly lower than that in the control group ( P = .008). Each intervention per se resulted in lower GWG compared with the control group GWG (PA plus D vs C, P = .01, and PA vs C, P = .042), but no significant difference was found between the 2 intervention groups: PA plus D and PA ( P = .57).
GWG was analyzed across the study groups; potential predictors for low weight gain were incorporated in a multiple linear regression analysis. Pedometer-assessed physical activity intervention minimized GWG by a mean of 1.38 kg compared with women not assigned to the pedometer ( P = .040). Furthermore, GWG decreased significantly with increasing BMI (–0.38 kg per kilogram per square meter; P < .0001). However, neither dietary intervention nor other maternal factors influenced GWG significantly.
GWG less than 5 kg was obtained by 26% in group PA plus D, 22% in group PA, and 17% of the women in the control group ( P = .068). The difference was significant when comparing intervention groups (PA plus D) plus PA and group C ( P = .021) ( Figure 2 ).
A GWG of maximal 9 kg was obtained in 55% in group PA plus D, 49% in group PA, and 37% in the control group ( P = .013) ( Figure 2 ). The difference was statistically significantly different between intervention groups (PA plus D) plus PA and C ( P = .010).
Physical activity
In gestational week 13, 64% in group PA plus D and 55% in group PA returned the chart with step counts and weight, whereas the chart was returned by 53% and 56% in week 33. There was no difference in the compliance between the group PA and the group allocated to combined intervention PA plus D.
The daily pedometer-assessed step counts were similar in groups PA plus D and PA: in week 13, 8838 ± 2878 and 8828 ± 2798 steps/d (n= 91/78); in week 21, 8122 ± 3121 and 8829 ± 2980 steps/d (n = 98/94), and in week 37, 6219 ± 2198 and 5972 ± 2133 steps/d (n = 46/59).
Secondary outcomes
There was no significant difference in the birthweight among the 3 intervention groups, neither absolute nor after adjusting for gestational age and sex ( Table 2 ).
| Numbers at follow-up (n = 389) | Group PA+D n = 130 | Group PA n = 125 | Control group C n = 134 | Significance |
|---|---|---|---|---|
| Week 17-20 OGTT | (n = 118) | (n = 113) | (n = 109) | NS a |
| 2-h value, mmol/L | 7. 1 ± 1.4 | 6.8 ± 1.1 | 7.1 ± 1.4 | |
| Week 27-30 OGTT | (n = 111) | (n = 108) | (n = 109) | NS a |
| 2-h value, mmol/L | 6.7 ± 1.4 | 6.8 ± 1.2 | 6.9 ± 1.2 | |
| Development of GDM (%) | 6/103 (3.8) | 2/125 (1.6) | 7/134 (5.2) | NS b |
| Blood pressure, mm Hg week 18-22 | ||||
| Systolic | 123 ± 1 | 122 ± 1 | 124 ± 1 | NS a |
| Diastolic | 77 ± 1 | 75 ± 1 | 76 ± 1 | NS a |
| Blood pressure, mm Hg week 36-37 | ||||
| Systolic | 129 ± 1 | 127 ± 1 | 127 ± 1 | NS a |
| Diastolic | 80 ± 1 | 80 ± 1 | 80 ± 1 | NS a |
| Hypertensive disease, n (%) | 7 (5.4) | 9 (7.2) | 12 (9.0) | NS b |
| Hypertension | 5 | 4 | 9 | |
| Preeclampsia | 2 | 5 | 3 | |
| Induction of labor, n (%) | 47 (36.1) | 42 (33.6) | 46 (34.3) | NS b |
| Cesarean section all, n (%) a | 32 (25) c | 51 (41) | 50 (37) | .016 c |
| Emergency/unplanned CS, n (%) b | 14 (11) d | 27 (22) | 32 (24) | .015 d |
| Planned CS | 18 (14) | 24 (19) | 18 (14) | NS b |
| Gestational age, wks | 278 ± 11 | 278 ± 14 | 278 ± 12 | NS a |
| Preterm delivery, n (%) | NS b | |||
| Gestational age 28-34 wks | 1 (1) | 3 (2) | 1 (1) | |
| Gestational age 34-37 wks | 3 (2) | 5 (4) | 5 (4) | |
| Fetal weight, g | 3605 (1945–5450) | 3695 (805–4910) | 3641 (1223–5280) | NS a |
| Relative birthweight | Mean: 102.6 ± 14.7 Median: 103.0 (59–151) | Mean: 102.3 ± 13.4 Median: 101.0 (64–142) | 102.5 ± 13.3 Median: 101.0 (60–137) | NS a |
| SGA, n (%) | 7 (5.4) | 4 (3.2) | 2 (1.5) | NS b |
| LGA, n (%) | 9 (6.9) | 8 (6.4) | 9 (6.7) | NS b |
| Birthweight >4000 g, n (%) | 29 (22) | 37 (30) | 33 (25) | NS b |
| pH of umbilical cord blood | 7.24 ± 0.08 | 7.24 ± 0.09 | 7.23 ± 0.08 | NS a |
| Weight placenta, g | 684 ± 162 | 687 ± 173 | 670 ± 164 | NS a |
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