Pediatric Highlight

International Journal of Obesity (2007) 31, 608–614. doi:10.1038/sj.ijo.0803582

Maternal weigh gain during pregnancy and overweight in Portuguese children

P Moreira1,2, C Padez3, I Mourão-Carvalhal4 and V Rosado5

  1. 1Faculty of Nutrition, University of Porto, Porto, Portugal
  2. 2Research Centre in Physical Activity Health and Leisure, University of Porto, Portugal
  3. 3Department of Anthropology, University of Coimbra, Coimbra, Portugal
  4. 4Department of Sports, University of Trás-os-Montes Alto Douro, Vila Real, Portugal
  5. 5Center of Anthropobiology, Instituto Investigação Cientifica Tropical, Lisboa, Portugal

Correspondence: Professor P Moreira, Faculty of Nutrition, University of Porto, Porto, Portugal. E-mail:

Received 4 September 2006; Revised 11 December 2006; Accepted 31 January 2007.





The objective of our study was to assess the association between maternal weight gain during pregnancy and childhood overweight.



This study was a cross-sectional analysis.



The data were derived from a community-based survey of children from primary schools of Portugal.



The study was performed in a sample of 6-12-year-old Portuguese school children (2445 girls and 2400 boys; age was 8.5plusminus0.91 years).



Height and weight were measured according to international standards, and body mass index (BMI) was calculated. The definition of overweight was based on average centiles according to the International Obesity Task Force cutoffs. Children's parents completed a self-administered questionnaire, which provided information on general family background characteristics, maternal weight gain during pregnancy and children's physical activity. The response rate was 70.6%. Children's dietary intake was measured using a 24-h dietary recall. Logistic regression models were fitted to estimate the magnitude of the association between maternal weight gain during pregnancy and overweight in their children, adjusting for confounders (gender, age, birthweight, order of birth, breastfeeding, smoking during pregnancy, physical activity, parental BMI, parental education, calcium to protein ratio and energy intake).



The prevalence of overweight (including obesity) was 29% in boys and 33% in girls. The odds favouring overweight (including obesity) increased significantly for those women who gained greater than or equal to16 kg during pregnancy, compared to those with <9 kg , even after adjustment for confounders (crude odds ratio (OR)=1.53, confidence interval (CI) 95% 1.27–1.84, P-trend <0.001; Adjusted OR=1.27, CI 95% 1.01–1.61, P-trend=0.038).



Large maternal weight gain during pregnancy (greater than or equal to16 kg) was significantly associated with higher risk of overweight in Portuguese children.


pregnancy, weight gain, overweight, children



Adult obesity has reached epidemic proportions in the world,1 and prevalence rates have increased sharply among children2 in the last decades. The health implications of childhood obesity are considerable because it is associated with co-morbidity and includes other chronic conditions such as insulin resistance, type 2 diabetes mellitus, orthopaedic disorders, hypertension, dyslipidemia, skin problems and psychological problems.3 Treatment of obesity at any age is very difficult which should be reinforced the need to trace obesity as early in life as possible to prevent children from becoming overweight, before school age.

Because early nutrition may modulate the regulation of food intake, influence adipose tissue cellularity and predispose to obesity,4 the origins of childhood obesity may well be at pregnancy, during embryonic and fetal development. However, much of the literature regarding weight gain during pregnancy has focused the mother, primarily from the perspective of post-partum weight retention,5, 6, 7, 8, 9 and to our best knowledge there are no published studies that specifically address the association between the weight gained during pregnancy and future risk of overweight/obesity in children. The aim of our study was to identify early life influences on the development of obesity, namely maternal weight gain during pregnancy and childhood overweight and obesity risk.




The study was carried out from October 2002 to June 2003, and was performed in a random sample of 6-12-year-old children. This age range was chosen for practical and physiological reasons. By age 6 years the adiposity rebound occurs, following the nadir of the body mass index (BMI) curve.10 This age range is also probably a favorable period for prevention strategies, which means that this is a period of particular interest.

The schools were randomly selected in districts of the country, and from each of them the participating children were selected using stratified randomization for age, with the aid of a random numbers table. A total of 4845 were included, comprising 2445 girls and 2400 boys. Children not included in our analysis (n=336),were those born in Asian countries, (n=16), in African countries (n=114), in other European countries (n=4), in South America (n=10); three had Down's syndrome, one had diabetes and one had nanism and were excluded. The response rate was 70.6%.

The number of children included was determined according to the equation:11 n=Nz2pq/d2(N-1)+z2pq, where, n is the sample, N the population size, Z=1.96 for an error of 0.05, p=the prevalence estimated, q=1 – p,and d represents the precision.

The study protocol was approved by the Ministry of Education (Direcção Regional de Educação), and informed consent was obtained previously from all the children's parents.


In each school, two trained persons performed anthropometric measurements using a standardized procedure.12 Anthropometric measurements were performed in light indoor clothing without shoes. Height was measured using a stadiometer, with the head in the Frankfort plane, and weight was measured using an electronic scale with a precision of 100 g.

BMI was calculated as weight/height (kg/m2). The definitions of overweight and obesity were based on average centiles published by Cole et al.13 These cutoff points are linked to the widely accepted adult cutoff points of a BMI of 25 kg/m2 (overweight) and 30 kg/m2 (obesity). As in other studies,14, 15 the cutoff for the adult BMI value of 25 kg/m2 was used exclusively in the analysis, considering simultaneously overweight and obese children in the same group, and other children in other group, which allowed for statistical analysis considering binary outcomes (logistic regression). Throughout the paper, unless stated otherwise, it can be assumed that overweight group includes also the obese children.

The childrens' parents completed a self-administered general questionnaire that provided information on general family background characteristics, including parental education, parental BMI, children's birthweight, extent and duration of breastfeeding, number of siblings, order of birth, smoking during pregnancy and weight gain during pregnancy.

Physical activity was also assessed, and parents were asked to report the number of days per week in which their children participated in light physical activity (walking) as well as the number of days in which they participated in vigorous physical activity (organized and unorganized sports). In addition, parents were asked to report their children's weekly frequency of physical inactivity or sedentary activity, including hours of television watched, hours of time spent on the computer, and hours spent playing video games.

In-person, 24-h dietary recalls were obtained from the children by nutritionists and trained interviewers. The training protocol included practice using photos and food models to quantify portion sizes, and experience in probing information from children without suggesting responses. The 24-h recall is the most commonly used dietary assessment method because it is easy to administer, can be done in large-scale studies,16, 17 and can be used to quantify and assess adequacy of energy and macronutrient intakes. During the 24-h recall, each child was asked to recall all food and beverages consumed during the previous 24 h. Daily routines were used as prompts (waking up, going to bed, time between classes and before or after school) to enhance recall. Portion sizes of foods and beverages consumed were also estimated, using food models and photos, and other props (cups, glasses, food wrappers or containers) as an aid in determining serving sizes. When the recall was complete, the child was asked how typical the 24-h recall is of his or her usual eating habits.

On the basis of previous research from our group on the inverse relationship between calcium and BMI,18 we assessed calcium intake, which was expressed as the calcium to protein ratio, both because this variable explicitly factors in the countervailing effects of the two nutrients and eliminates most of the portion size estimation error.19, 20

Statistical analysis

Student's t-tests, analysis of variance (ANOVA), and chi2 tests were used to compare several variables between genders, and to determine the degree to which variables correlated with maternal weight gain during pregnancy. A P-value of less than 0.05 was considered statistically significant.

Logistic regression models were fitted to estimate the magnitude of the association between maternal weight gain during pregnancy and overweight in their children. Gender, age, birthweight, order of birth, breastfeeding, smoking during pregnancy, physical activity, parental BMI, parental education, calcium to protein ratio intake and energy intake, were entered in the regression models in secondary analysis to control for the effects of these variables. The adjustment considered variables that presented a statistically significant effect in univariate analysis18, 21, 22 and were considered to sustain a plausible biological and temporal relationship with the outcome.

Statistics analysis were performed using SPSS 14.0 Inc Chicago, IL, USA.



Subjects included in the study were 2445 girls and 2400 boys, with an average age of 8.5 (plusminus0.92) in both.(P=0.962).

Average BMI was 18.1plusminus3.21 in girls and 17.9plusminus3.05 in boys (P=0.062), and prevalences of overweight and obesity were, respectively, 20.9 and 11.9% in girls and 18.5 and 10.3% in boys (P< 0.001).

Energy intake and nutritional pattern by overweight status in each gender are presented in Table 1. The diet was high in fat, particularly saturated fat, sugars and protein, and low in total carbohydrates and dietary fibre, but no statistically significant differences were found according to overweight status.

The nutritional pattern was combined with a sedentary lifestyle. In our study, overweight children were not significantly less involved in sport activities than other children although they showed higher use (<2 h/day) of television/videos during the week, and electronic games on Sunday (Table 2).

In relation to parental education, the level of more than 12 years was less frequent in overweight/obese children. Parental overweight and obesity was also more prevalent among overweight/obese children (Table 2).

There was a lower percentage of overweight and obese children in large families, and in those children higher in the order of birth. Breastfeeding duration and smoking during pregnancy were not associated with overweight in children (Table 3). However, there was a significant association between both birthweight and weight gain during pregnancy, and childhood overweight. In overweight children, there was a lower percentage of children with birthweight <2500 g, and a higher percentage of children with birthweight >3500 g. The occurrence of pregnancy weight gain greater than or equal to16.0 kg was also more frequent in overweight children (Table 3).

The odds favouring overweight, increased with increasing weight gained during pregnancy (P-value for trend was <0.001). The odds ratio (OR) for those children whose mothers gained >16 kg during their pregnancy was 1.53 (1.27–1.84), compared with those who gained less than 9 kg (Table 4). After adjusting for gender, age, birthweight, order of birth, breastfeeding, smoking during pregnancy, physical activity, parental BMI, parental education, calcium to protein ratio and energy intake, the odds favouring overweight remained significantly higher in the group of children whose mothers gained >16 kg during their pregnancy (OR=1.27 (1.01–1.61)).



We have explored different weight gain patterns during pregnancy and the risk in overweight during childhood. The main finding of this study was that the odds favouring overweight increased significantly for those women who gained 16 kg or more during pregnancy, compared with those who gained less than 9 kg, even after adjustment for confounders. As reported by other authors,23 we also used self-reported pregnancy weight gain. We have found 9.8% missing information on reported pregnancy weight gain, but missing subjects did not show significant statistical differences on studied variables compared with other subjects. Guidelines for prenatal weight gain recommend that women with a normal prenatal BMI should not gain more than 16 kg during pregnancy.24, 25, 26

Although we cannot infer causality from our study, and several limitations exist, it is reasonable to propose that high pregnancy weight gain during pregnancy, may have contributed to subsequent development of overweight and obesity during childhood.

Maternal weight gain during gestation is positively correlated with birthweight27 and neonatal body composition,28 but evidence relating this condition to overweight or obesity during childhood is lacking. The observations in the present study may be a latter sign of prenatal programming of adipogenesis, and weight gain during pregnancy may be an early 'window' during which variations in nutrition, energy balance29 or weight gain may programme subsequent growth and development, rendering the offspring more likely to overweight and obesity during childhood. Furthermore, high weight gain during pregnancy may change the total energy costs of pregnancy30 and influence hormones that modulate adjustments in maternal energy metabolism,31 which in turn may regulate fetal growth rates by several pathways such as the expression of insulin-like growth factors and their binding proteins.32 However, whereas the mechanisms that link pregnancy weight gain to childhood obesity remain speculative, adequate patterns of maternal weight gain may be advantageous to prevent excessive weight gain during childhood.

Limitations to our study include the fact that we did not have retrospective data about the rate of children's growth during the first years of life, which may be a predictor of obesity during childhood.33, 34 Nevertheless, ORs were adjusted to birthweight, infant breastfeeding, smoking during pregnancy, and mothers' parity recognizing these variables as factors that may influence early postnatal weight gain, subsequent fat distribution and long-term risk for obesity.33, 35, 36, 37 When we combined potential confounders (gender, age, birthweight, order of birth, breastfeeding, smoking during pregnancy, physical activity, parental BMI, parental education, calcium to protein ratio, and energy intake) in the regression model, OR were still statistically significant for mothers who gained more than 16 kg during pregnancy, than mothers in the reference weight gain category.

Other potential factors that were not available in our study and may influence postnatal growth rates and overweight risk during childhood included infant feeding practices (extra breastfeeding), mothers' birthweight, and maternal prepregnant BMI.31, 33, 34, 36, 37, 38, 39, 40 Although we did not have data regarding maternal obesity during pregnancy, the odds favouring overweight in children with increasing weight gained during pregnancy was adjusted for the current maternal BMI. As in other studies,41, 42, 43, 44 we used self-reported height and weight in order to categorize parental BMI, although this measures might not be extremely reliable, because of the low sensitivity of this method to evaluate the prevalence of overweight and obesity.45

Although several lifestyle measures have been useful in the treatment of obesity, they often fail; prevention rather than treatment has gained newfound interest from a public health perspective. Existing recommendations to prevent childhood obesity advise obese women to lose weight and achieve a normal BMI before conception, and promote adequate weight gain during pregnancy.46, 47 On the basis of our study results, avoiding high weight gain during pregnancy could be an additional opportunity to prevent childhood obesity. Furthermore, these results favour future guidelines for prenatal weight gain, which recommend women not to gain more than 16 kg during pregnancy, to prevent higher risk of overweight in their children. The final aim is to implement a healthy life style, to promote an adequate energy balance resulting in positive and adequate weight changes.

Future studies should also assess the relative contribution of maternal energy balance and genetic factors to maternal weight gain, birthweight, and rate of weight gain during the first years of life, which may be a crude measure of the intrauterine environment of metabolic programming and the pattern of fat mass increase.



We found that high weight gain during pregnancy (greater than or equal to16 kg) was significantly associated with higher risk of overweight in Portuguese children. Primary prevention strategies of obesity in children should encourage adequate weight gain during pregnancy.



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