Adriëtte Oostvogels

using a Leicester portable height measure (Seca). Blood pressure was measured twice on the right arm in sitting position with the arm supported at heart level, with an Omron 705 IT (Omron Heathcare Inc, Bannockburn, IL, USA) with appropriate cuff size (arm circumference 17-22 cm) after a 10-min rest period to relax the child and mean SBP and DBP were calculated. Capillary blood was taken by finger prick collected in a validated kit developed for ambulatory purposes (LabAnywhere, Haarlem, the Netherlands). 21 Definitions We used standardized measures (z-scores) for the individual components of the metabolic profile (WHtR, SBP, DBP, fasting glucose, TG and HDL). 22 Since no formal definition for the diagnosis of the metabolic syndrome in children under 10 years exists, 23 we used our own continuous measure, the metabolic score; which was calculated by adding all z-scores of the individual components (HDL inverse) together. DBP was not included because this would result in a metabolic score unevenly influenced by childhood blood pressure. More important, SBP is known to be a better predictor of hypertension and an adverse metabolic profile in later life. 24 Covariates Maternal age (years; continuous), ethnicity, education level and smoking were available from the pregnancy questionnaire. Ethnicity (Dutch, Turkish, Moroccan, other Western and other non-Western) was defined by the country of birth of the mother of the pregnant woman. Years of education after primary school (continuous) were considered as proxy for socioeconomic status. Smoking during pregnancy was dichotomized (yes/no). Information on hypertension (no/pre-existent/pregnancy- induced, based on International Society for the Study of Hypertension in Pregnancy guidelines (www.isshp.com) ), was available by combining data from the pregnancy questionnaire and The Netherlands Perinatal Registry (PRN). Parity (primiparous/ multiparous), gestational age, birth weight and sex of the child were available from the PRN and YHC. Gestational age was based on ultrasound by the obstetric care provider or, when unavailable (<10%), on the first day of the last menstrual period. Duration of exclusive breastfeeding (no breastfeeding, <1 month, 1-3 months, >3 months) was available from the infancy questionnaire completed with YHC and 5-year questionnaire. Screen time (computer and television) hours per day (continuous) was obtained from the 5-year questionnaire and a validated food frequency questionnaire 25 was used to calculate child’s energy intake in kilocalories (kcal, continuous). Height of the child at age 5-6 years was measured during the health check and the exact age at that time was calculated. 180 Chapter 7