Maternal coffee intake and the risk of bleeding in early pregnancy: a cross-sectional analysis

Background Caffeine can easily cross the placenta, and maternal caffeine intake, thus, has an effect on fetal growth. However, it is still unclear whether coffee consumption is an independent risk factor for bleeding in early pregnancy. The objective of this study was to examine the association between pre-pregnancy coffee consumption patterns and the risk of bleeding in early pregnancy. Methods A cross-sectional analysis was conducted among 3510 pregnant women from the Korean Pregnancy Outcome Study who underwent baseline examination and for whom the results of the pregnancy were available. Coffee consumption patterns before pregnancy were examined using a questionnaire. The participants were classified according to the frequency of coffee consumption into seldom (< 1 cup/week), light (< 1 cup/day), moderate (1 cup/day), and heavy coffee drinker (>= 2 cups/day) groups. Bleeding in early pregnancy was defined as the occurrence of vaginal bleeding in the first 20 weeks of pregnancy. Multiple logistic regression models were applied to examine the association between pre-pregnancy coffee consumption and the risk of bleeding in early pregnancy, after adjusting for age, body mass index (BMI), systolic blood pressure, cigarette smoking and alcohol consumption behavior, previous and current physical activity levels, stress levels, history of depression, antenatal depressive symptoms during the first trimester, type of emesis, parity, and the number of livebirths, stillbirths, miscarriages, and abortions. Results Women who were light, moderate, and heavy coffee drinkers before pregnancy had adjusted ORs of 1.086, 1.225, and 1.358, respectively, for bleeding in early pregnancy. In a fully adjusted model, heavy coffee drinkers showed a significantly higher risk of bleeding in early pregnancy, even in women aged 35 years and younger (OR 1.680) and in those with a normal body mass index (OR 1.389), who were at relatively low risk for pregnancy-related complications. Conclusions Our results showed that heavy coffee drinking was independently associated with a higher risk of bleeding in early pregnancy among pregnant Korean women, suggesting that caffeine intake before conception and during pregnancy should be reduced. Our study highlights the need for nutritional interventions for healthy coffee drinking among pregnant women in Korea.