An intervention aimed at the prevention of excessive weight gain during pregnancy

An assistant will perform the anthropometrical measurements and collect the blood samples at 15, 25 and 35 weeks of pregnancy and at 7, 25 and 51 weeks after delivery in the midwife practice to measure the following outcome measures:
1. Weight and body mass index (BMI) change
2. Height, measured in bare feet with a portable height scale with a wide measuring slide and a heel plate

Both weight and height will be measured twice, and the mean value of the two measurements will be computed. Calibrated scales are used to determine weight while participants are only wearing light clothing (e.g. underwear) and no shoes.

1. Percentage body fat (sum of four skinfolds): a Harpenden calliper is used to assess percentage body fat. Percentage body fat is determined by measuring the sum of the thickness of four skinfolds: biceps, triceps, subscapular and suprailiac according to the method described by Weiner and Lourie. During pregnancy the suprailliac skinfold measurement won't be executed. Therefore, the thigh skinfold is also measured on all occasions. All skinfolds will be assessed twice. A mean value of the two will be computed. In case the two measurements of a skinfold differ more than 10%, the skinfold will be measured a third time. Also the circumference of arm and thigh will be measured.
2. Change in physical activity and dietary intake: physical activity will be assessed with the Short Questionnaire to Assess Health enhancing physical activity (SQUASH). At 15 and 35 weeks of pregnancy and 26 weeks after delivery all participants will wear an (blinded) accelerometer for three consecutive days to gather additional data on the levels of physical activity. The focus of dietary intake will be on fat, fruit and vegetable intake. These questionnaires have been validated.
3. Blood samples: in order to study the influence of lifestyle factors on energy homeostasis and weight gain, blood samples will be taken from the participants. Women will be asked for blood samples at 15, 25 and 35 weeks of pregnancy and at seven, 25 and 51 weeks after delivery. If women refuse, they can still join the study. The midwives will take a blood sample from the umbilical cord. Collecting blood for routine test and the study will be combined as much as possible in order to limit the number of venapunctures for the participants. Blood levels of leptin, ghrelin, fasting insulin/glucose, insulin growth factor one, insulin growth factor binding protein one and three, and cortisol will be measured. Analyses will take place at the laboratory of the VU University Medical Centre.
4. Data (questionnaires) will also be collected on: perceived health, stage of change (for weight management, physical activity and diet according to the model of Prochaska), self efficacy (concerning weight management, physical activity and eating habits), the duration and complications of labour, and complications during pregnancy such as gestational diabetes, pre-eclampsia, pregnancy related hypertension, pelvic pain. Possible confounders that will also be assessed by questionnaires include smoking behaviour, certain demographics (age [at menarche], education, family income, ethnicity, marital status, etc) and health conditions.