Lifestyle during pregnancy: neurodevelopmental effects at 5 years of age. The design and implementation of a prospective follow-up study.

BACKGROUND: It has been suggested that even mild exposure to alcohol, caffeine, smoking, and poor diet may have adverse long-term neurodevelopmental effects. In addition, there is evidence that timing of high exposures (e.g. binge drinking) can have particularly negative effects. This paper describes the design and implementation of The Lifestyle During Pregnancy Study addressing major methodological challenges for studies in this field. The study examines the effects of lifestyle during pregnancy on offspring neurodevelopment. METHODS: In 2003, we initiated a prospective follow-up of 1750 mother-child pairs, sampled on the basis of maternal alcohol drinking patterns from The Danish National Birth Cohort (DNBC), a study of 101,042 pregnancies enrolled 1997-2003. Data collection in the DNBC involved four prenatal and postnatal maternal interviews, providing detailed information on maternal alcohol drinking patterns before and during pregnancy, caffeine intake, smoking, diet, and other lifestyle, medical, and sociodemographic factors. RESULTS: At the age of 5 years, the children and their mothers participated in a comprehensive assessment of neurobehavioural development focusing on global cognition, specific cognitive functions, and behaviour. Two new tests assessing attention and speed of information processing among children were developed, and data on important potential confounders such as maternal intelligence quotient, vision, and hearing abilities were collected. Efforts were made to standardise procedures and obtain high inter-rater reliability. CONCLUSIONS: We expect that the study will illuminate the significance or lack of significance of maternal lifestyle during pregnancy and contribute to better understanding the effects of alcohol drinking during pregnancy at low to moderate consumption levels.

Predictors of intelligence at the age of 5: family, pregnancy and birth characteristics, postnatal influences, and postnatal growth.

Parental education and maternal intelligence are well-known predictors of child IQ. However, the literature regarding other factors that may contribute to individual differences in IQ is inconclusive. The aim of this study was to examine the contribution of a number of variables whose predictive status remain unclarified, in a sample of basically healthy children with a low rate of pre- and postnatal complications. 1,782 5-year-old children sampled from the Danish National Birth Cohort (2003-2007) were assessed with a short form of the Wechsler Preschool and Primary Scale of Intelligence - Revised. Information on parental characteristics, pregnancy and birth factors, postnatal influences, and postnatal growth was collected during pregnancy and at follow-up. A model including study design variables and child's sex explained 7% of the variance in IQ, while parental education and maternal IQ increased the explained variance to 24%. Other predictors were parity, maternal BMI, birth weight, breastfeeding, and the child's head circumference and height at follow-up. These variables, however, only increased the explained variance to 29%. The results suggest that parental education and maternal IQ are major predictors of IQ and should be included routinely in studies of cognitive development. Obstetrical and postnatal factors also predict IQ, but their contribution may be of comparatively limited magnitude.

Effects of tobacco smoking in pregnancy on offspring intelligence at the age of 5.

The aim of the study was to examine the effects of tobacco smoking in pregnancy on children's IQ at the age of 5. A prospective follow-up study was conducted on 1,782 women, and their offspring were sampled from the Danish National Birth Cohort. At 5 years of age, the children were tested with the Wechsler Preschool and Primary Scale of Intelligence-Revised. Parental education, maternal IQ, maternal alcohol consumption in pregnancy, the sex and age of the child, and tester were considered core confounders, but the full model also controlled for prenatal paternal smoking, maternal age and Bodymass Mass Index, parity, family/home environment, postnatal parental smoking, breast feeding, the child's health status, and indicators for hearing and vision impairments. Unadjusted analyses showed a statistically significant decrement of 4 points on full-scale IQ (FSIQ) associated with smoking 10+ cigarettes per day compared to nonsmoking. After adjustment for potential confounders, no significant effects of prenatal exposure to tobacco smoking were found. Considering the indisputable teratogenic effects of tobacco smoking, these findings should be interpreted with caution. Still, the results may indicate that previous studies that failed to control for important confounders, particularly maternal intelligence, may be subject to substantial residual confounding.