Maternal caffeine intake during pregnancy and the risk of delivering a small for gestational age baby: Kuopio Birth Cohort

Abstract Purpose High caffeine intake during pregnancy is associated with restricted fetal growth. We aimed to evaluate the association between maternal caffeine intake during early and late pregnancy and the risk of delivering a small for gestational age (SGA) baby. Methods Kuopio Birth Cohort (KuBiCo) is a prospective cohort study including women whose pregnancies and deliveries were treated at the prenatal clinics in outpatient healthcare centers and in Kuopio University Hospital, Finland. Maternal diet and caffeine intake during the first (n = 2007) and third (n = 4362) trimester of pregnancy were assessed using a 160-item food frequency questionnaire (2013–2022). SGA was defined as birth weight corrected for gestational age below  − 2 standard deviations from the mean, according to the sex-specific Finnish fetal growth curves. Results Altogether in 32 and 38% (1st and 3rd trimester) of all women and in 44 and 52% of coffee drinkers, caffeine intake exceeded the recommendation for caffeine intake ($$\le $$ ≤ 200 mg/day) during pregnancy. The women with moderate (51–200 mg/day) (aOR 1.87; 95% CI: 1.16–3.02) and high (> 200 mg/day) (aOR 1.51; 95% CI: 1.08–2.10) caffeine intake during the first trimester were in the highest risk of having an SGA newborn. Caffeine intake in the third trimester of pregnancy was not associated with SGA. Conclusions Moderate and high caffeine intake during early pregnancy is associated with SGA. As the results suggest that even moderate caffeine intake during the first trimester may increase the risk of SGA, the intake within recommendation limits does not necessarily appear to be safe for pregnant women and their newborns.