Background: little is known of the consequences of tobacco smoking in pregnancy for cardiovascular risk in offspring.

Objectives: To estimate the association between foetal tobacco smoke exposure and vascular damage in young adulthood.

Participants: A birth cohort of 732 young adults born between 1970–1973.

Measures: Registered pregnancy and birth data, anthropometry and cardiovascular risk profiles in young adulthood, including ultrasound measurement of common carotid artery intima-media thickness (CIMT). Pregnancy and current smoking habits data of parents were obtained by standardized questionnaires.

Results: Twenty nine percent of the mothers reported to have smoked during their pregnancy. Adult offspring of mothers who smoked had 13.4 μm thicker CIMT (95% CI: 5.5, 21.3; p=0.001) than offspring of mothers who did not smoke in pregnancy. Adjustment for known CIMT risk factors (participant’s age, gender, BMI, pulse pressure, and LDL-cholesterol) did not abolish this estimate (9,4 μm, 95% CI: 1.9, 16.3; p=0.01). Similarly, adjustment for current smoking of parents did not change the association (10.6 μm, 95% CI: 0.4, 20.8; p=0.04) nor did adjustment for participants’ current smoking (yes/no) and pack-years (11.5 μm, 95% CI: 3.5, 19.4; p=0.004). Offspring of parents who both smoked in pregnancy had thicker CIMT than offspring with one or no smoking parent (p _{linear trend} <0.0001), and offspring of particularly mothers who smoked an above median number of cigarettes in pregnancy had thicker CIMT than those smoking less than median or no cigarettes (p _{linear trend} <0.0001).

Conclusion: Permanent vascular damage due to tobacco smoke exposure is initiated in gestation.