Prenatal Caffeine Assessment: Fetal and Maternal Biomarkers or Self-Reported Intake?

Purpose We sought to examine associations among measures of caffeine exposure, including maternal urine, umbilical cord blood, and maternal self report. Methods Pregnant women were recruited from 56 obstetric practices and 15 clinics associated with six hospitals in Connecticut and Massachusetts between September 1996 and January 2000; 3633 women were enrolled. Maternal urine throughout pregnancy and umbilical cord blood samples were analyzed for caffeine, paraxanthine, theophylline, and theobromine. Maternal caffeine intake was assessed throughout pregnancy. Results Urinary and cord blood biomarkers were correlated with reported intake throughout pregnancy (range r = 0.35–0.66; p < 0.0001). Infants of smokers had greater cord blood concentrations of paraxanthine, reflecting faster caffeine metabolism in smokers, and cord blood paraxanthine levels were more strongly correlated with intake in smokers. Conclusion Maternal self reported intake may still be the optimal and most valid measure of antenatal caffeine exposure, since biomarkers do not reflect exposure over pregnancy.