Results of best-quality study prove clinically trivial
The best-quality prospective cohort study in the review described above was also the largest, comprising two-thirds of the total patients. It found a statistically significant, but clinically trivial, association between caffeine intake and birth weight.4
Investigators from Norway’s Institute of Public Health mailed surveys to 106,707 pregnant Norwegian women and recruited 59,123 with uncomplicated singleton pregnancies. The survey assessed diet and lifestyle at several stages of pregnancy and correlated caffeine intake with birth weight, gestational length, and SGA deliveries. Investigators calculated caffeine intake from coffee and other dietary sources (tea and chocolate).
Higher caffeine intake was associated with a small reduction in birth weight (8 g/100 mg/d of additional caffeine intake; 95% CI, −10 to −6 g/100 mg/d). Higher intake was also associated with increasing likelihood of SGA birth, a finding of borderline significance (odds ratio [OR]=1.18; 95% CI, 1.00-1.38, comparing intake <50 mg/d with 51-200 mg/d; OR=1.62; 95% CI, 1.26-2.29, comparing <50 mg/d with 201-300 mg/d; and OR=1.62; 95% CI, 1.15-2.29, comparing <50 mg/d with >300 mg/d).