The relation of maternal caffeine intake with birth outcomes is still inconclusive and has not been examined in Japan, where the sources of caffeine intake are different from those in Western countries. We hypothesized that maternal consumption of total caffeine and culture-specific major sources of caffeine would be associated with birth outcomes among Japanese pregnant. The study subjects were 858 Japanese women who delivered singleton infants. Maternal diet during pregnancy was assessed using a validated, self-administered diet history questionnaire. Birth outcomes considered were low birth weight (LBW; <2500 g), preterm birth (PTB; <37 weeks of gestation), and small for gestational age (SGA; <10th percentile). The main caffeine sources were Japanese and Chinese tea (73.5%), coffee (14.3%), black tea (6.6%), and soft drinks (3.5%). After controlling for confounders, maternal total caffeine intake during pregnancy was significantly associated with an increased risk of PTB (odds ratio per 100 mg/d caffeine increase, 1.28; 95% confidence interval, 1.03-1.58; P for trend = .03). However, no evident relationships were observed between total caffeine intake and risk of LBW or SGA. As for caffeine sources, higher Japanese and Chinese tea consumption was associated with an increased risk of PTB (odds ratio per 1 cup/d increase, 1.14; 95% confidence interval, 1.00-1.30; P for trend = .04), but not LBW or SGA. There were no associations between consumption of the other beverages examined and birth outcomes. In conclusion, this prospective birth cohort in Japan suggests that higher maternal total caffeine intake, mainly in the form of Japanese and Chinese tea, during pregnancy is associated with a greater risk of PTB.
Keywords: Caffeine; Japanese and Chinese tea; Pregnancy; Preterm birth; Prospective birth cohort.
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