The main finding of our study was that lifestyle counseling during pregnancy did not significantly slow weight gain among the offspring. A greater number of study participants and a longer follow-up period are needed in future studies. Based on the current differences between the groups, at least 300 children per group are needed in similar experimental studies.
Childhood obesity leads to substantially increased risk for type 2 diabetes and cardiovascular diseases [22, 38]. There is growing evidence for the important role of early preventive efforts since the unfavorable health consequences of obesity begin already during childhood and the treatment of childhood obesity tends not to lead to permanent results [4, 39]. The higher prepregnancy BMI, gestational weight gain and GDM of the mother,have been shown to increase the risk for childhood obesity [7, 8, 20, 21, 40]. Mother’s impaired glucose tolerance during pregnancy has been shown to increase offspring’s risk for obesity and adverse metabolic changes in several studies [13, 19]. The mother’s glucose tolerance is influenced by diet and physical activity, as well as genetic factors and BMI. Our study was a controlled trial conducted in six maternity health clinics in primary care. The participants were first-time mothers without especially sought risk determinants for having overweight offspring. There were no statistically significant differences in factors known to affect offspring’s risk of obesity between the two groups: mother’s age before pregnancy, prepregnancy BMI, gestational weight gain, education, smoking during pregnancy and duration of breastfeeding. In the intervention clinics the mothers received intensified individual counseling on physical activity and diet, as well as an option to attend sessions of supervised group exercise once a week during pregnancy. The control group received conventional health care counseling. The intervention did not increase mother’s physical activity or prevent excess weight gain during pregnancy, but the intensified counseling increased pregnant mothers’ intake of fiber, vegetable and fruit (primary outcomes reported earlier) [29–32, 41]. Thus this intervention could have an impact on the intrauterine environment via mother’s healthier diet. Gestational lifestyle intervention can also potentially influence offspring’s diet and time spent physically active via the healthier lifestyle adopted by their mothers. The role of parents is crucial in influencing lifestyle behavior among their offspring, and preschool age is an important period in the acquisition of food preferences and physical activity habits [23, 42]. Previously published results from our data have shown a smaller proportion of macrosomic newborns in the intervention group than in control group . Lawlor et al. (2011) showed in their recent study that the BMI of the offspring correlated with gestational weight gain if the mother was overweight or obese, but if the mother was of normal weight, the gestational weight gain had no correlation with offspring BMI, suggesting the role of intrauterine programming more clearly when the mother has high BMI . In our study the majority of participating mothers were of normal weight, which may have influenced the results. In the study by Fraser et al. (2010) they found that any weight gain during the first 14 weeks of gestation was associated with increased offspring adiposity, but later in pregnancy only > 500 g/week weight gain increased offspring adiposity . According to their result, the intervention targeting weight gain during pregnancy should start prior to conception rather than during the first trimester of pregnancy as in our study. The follow-up of the offspring of the HAPO study showed that maternal glucose at 28 weeks of gestation was not associated with offspring obesity at two years of age . Crume et al. (2011) showed that intrauterine exposure to maternal gestational diabetes mellitus resulted in higher average BMI among the offspring only after 27 months of age and higher BMI growth starting at age 10 years and thus no differences in weight gain was seen in infancy or early childhood . The follow-up period in our study probably should have been longer than four years to see the effect of intrauterine influences on offspring weight gain.
One weakness of our study was that the participants did not belong to risk groups such as mothers at risk for gestational diabetes or exclusively overweight/obese mothers. Another weakness was the relatively small number of participants in this pilot study. Moreover, the effect of lifestyle intervention would probably show more marked results in the reduction of offspring weight gain if the follow-up period of offspring growth had been longer than four years. One weakness of the study is lack of randomized design, since the clinics volunteered as intervention clinics due to the magnitude of the problems in their clients. Thus the intervention clinic mothers presumably had more adverse weight gain than the control mothers, which may have confounded the results in their offspring weight development as well.
The strengths of our study include a feasible counseling method, a controlled trial setting and reliable growth data based on repeated measurements by nurses in primary health care. We also utilized the recently updated growth data on Finnish children by using z-scores of weight-for-length/height and BMI-for-age described in that growth data. Our sample included healthy first-time mothers, thereby constituting a more homogeneous group than mothers with earlier deliveries. We were also able to take into account confounding factors on childhood growth, such as smoking and mothers’ prepregnancy BMI. A successful lifestyle intervention should create adequate motivation to change the lifestyle. Pregnancy is a suitable period to induce changes in lifestyle towards healthier, because pregnant mothers generally have good motivation to have a positive pregnancy outcome. Pregnant mothers have also regular contacts with health care nurses, and thus this kind of intervention is feasible. Our study was also integrated with primary health care follow-up of pregnancy. The intensified counseling helped pregnant mothers to increase the proportion of vegetables, fruit and fiber in their diet, as we have previously reported [25, 28, 41]. This change towards a lower glycemic index diet could improve mother’s glucose tolerance below gestational diabetes level as well as lower mother’s insulin levels. These metabolic changes may have beneficial sequelae in offspring weight gain by altering the intrauterine environment affecting the programming of offspring energy intake and metabolism.