Prenatal Smoking Tied to Higher Blood Pressure in 13,120 Children Across 52 US Study Sites

Childhood hypertension is not simply a pediatric curiosity - elevated blood pressure during childhood tracks into adulthood and increases the lifetime risk of cardiovascular disease. Understanding what causes blood pressure to run higher in children is therefore a public health question with long-range implications. Maternal smoking during pregnancy has been a candidate risk factor, but prior studies produced inconsistent results, partly because they relied on self-reported smoking data and often examined only systolic blood pressure.

A new analysis from the NIH ECHO Cohort - the Environmental influences on Child Health Outcomes program - addressed those limitations directly. The study enrolled 13,120 children born between 1999 and 2020 across 52 study sites in the United States and Puerto Rico, measured blood pressure between ages 3 and 18, and assessed maternal smoking through three independent methods: self-report, medical records, and urine cotinine testing during pregnancy. Results were published in Circulation.

Self-reported versus biochemically confirmed smoking

The distinction between reported and confirmed smoking matters. Self-report systematically underestimates actual smoking rates due to social desirability bias - pregnant women who smoke are often reluctant to disclose it. Cotinine, a metabolite of nicotine excreted in urine, provides an objective marker of recent tobacco exposure. Using both measures allowed the researchers to compare associations under the stronger and weaker evidence conditions.

Both were associated with elevated childhood blood pressure, but the associations were stronger and broader when smoking was confirmed by urine testing. Active smoking during pregnancy was linked to higher systolic blood pressure - the pressure when the heart contracts - as well as higher diastolic blood pressure, the pressure when the heart rests between beats. Self-reported smoking was primarily associated with diastolic blood pressure and hypertension risk, with less consistent systolic findings.

Self-reported secondhand smoke exposure during pregnancy - exposure to others' cigarette smoke without direct smoking - was not associated with higher blood pressure in children in this dataset.

Key patterns in the data

The study's 13,120-child sample, drawn from 52 geographically diverse sites across the US and Puerto Rico, gives the findings statistical weight and geographic breadth that smaller studies lack. Blood pressure was measured across the age range of 3 to 18, allowing the researchers to observe how the association changed across childhood.

Two patterns stand out. First, associations were stronger among female children than male children. The biological mechanism for this sex difference is not established from this observational data, but the finding is consistent across both self-reported and cotinine-confirmed smoking. Second, the effect size tended to increase with age - suggesting the impact of prenatal exposure on blood pressure may accumulate or become more apparent over time rather than diminishing as children grow.

What the data can and cannot establish

The ECHO Cohort is an observational study. The associations between prenatal smoking and childhood blood pressure are consistent and supported by objective exposure measurement, but the design cannot rule out residual confounding from other factors that co-occur with maternal smoking - socioeconomic stress, diet, housing conditions, or other exposures. Smoking during pregnancy also correlates with a cluster of other risk factors, and fully disentangling the specific blood pressure contribution of tobacco itself from the broader environment in which prenatal smoking occurs is difficult in observational data.

The study does not examine the mechanism through which prenatal nicotine or tobacco constituents might affect fetal cardiovascular development. Animal studies have suggested that nicotine exposure during gestation affects the sympathetic nervous system and renin-angiotensin regulation in ways that could elevate blood pressure, but the human data here are associational.

"These findings suggest that reducing maternal smoking during pregnancy could lower hypertension rates in children and adults," said Christine Ladd-Acosta, PhD, of Johns Hopkins University, a co-lead author of the study.