Council on Environmental Health
Article Review

Prepared by: Dana Best, MD, MPH
December 2007

TITLE
Tobacco smoke exposure of pregnant mothers and blood pressure in their newborns: results from the wheezing illnesses study Leidsche Rijn birth cohort.

AUTHORS
Geerts CC, Grobbee DE, van der Ent CK, et al.

REFERENCE
Hypertension. 2007;50(3):572-578.

STUDY TYPE
Prospective unselected birth cohort.

METHODS
Residents of a suburb of Utrecht, the Netherlands, completed a health profile used to develop a primary care electronic medical chart. When the health profile was requested, residents were invited to enroll in the Utrecht Health Project (UHP). The UHP is a study of health, disease, and healthcare determinants. A subset of the UHP, the Wheezing Illnesses Study Leidsche Rijn, is a birth cohort study (the "Whistler" birth cohort). The focus of the Whistler study is early determinants of respiratory disease in childhood. Parents and newborn infants were invited to enroll in the study at age 2-4 weeks. Exclusion criteria were gestational age <36 weeks, major congenital abnormalities, and neonatal respiratory disease. Information on the pregnancy, including tobacco use and secondhand smoke (SHS) exposure, was collected via parental questionnaire. Infant blood pressure (BP) was measured during sleep using a Dynamap. Three separate measurements were made; the average was used for analysis. Potential confounders included in the analysis were birth weight, infant gender, infant feeding (breastfeeding or formula), and maternal age. After adjustment for these confounders, general linear regression models were used to assess the relation between maternal smoking in pregnancy and BP.

MAIN FINDINGS
Of 1014 infants enrolled in the Whistler study, complete data sets were collected for 456. Maternal smoking status for the cohort was 363 (80%) not smoker/not SHS-exposed, 63 (14%) not smoker/SHS-exposed, and 30 (7%) smokers. Infants of mothers who smoked had 5.4 mm Hg (95% CI: 1.2 to 9.7; P = 0.01) higher systolic BP than infants of mother who did not smoke and were not SHS-exposed. No associations between maternal smoking status and diastolic BP were found. No associations between SHS-exposure and BP were found.

BACKGROUND
Higher BP has been reported in several studies of infants and children whose mothers smoked during pregnancy. Whether the higher BP was due to changes in utero, postnatal environmental effects (such as SHS exposure), or the child's weight (overweight/obesity during childhood has been associated with maternal smoking during pregnancy), has not been determined.

SIGNIFICANCE
This study provides more evidence about the dangers of SHS to infants and specifically contributes to our understanding of the timing of childhood BP changes associated with maternal smoking during pregnancy. The increase in BP seems to occur either during pregnancy or very soon thereafter. These results indicate that at least some of the BP changes precede long term SHS exposure or development of overweight/obesity. Maternal smoking during pregnancy may lead to a lifetime of elevated systolic BP.

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