Cambridge Study Finds Coffee During Pregnancy Does Not Raise Premature Birth Risk
Researchers at the University of Cambridge examined whether coffee consumption during pregnancy affects outcomes, and they found no link to an increased risk of premature birth. In contrast, smoking during pregnancy was associated with a notably higher risk, specifically about 2.6 times greater than for non-smokers. The observations were reported in the International Journal of Epidemiology.
From 2008 to 2012, the study enrolled more than 4,200 pregnant women in the United Kingdom. Blood samples were collected at four points across gestation, enabling detailed analysis of exposure and outcomes. These serial samples helped provide a clearer picture of how lifestyle choices might influence pregnancy results.
To quantify tobacco exposure, researchers measured cotinine, a metabolite of nicotine. Within the analyzed group of 914 women, roughly 79 percent were nonsmokers during pregnancy, around 12 percent were occasional smokers, and about 10 percent smoked regularly. Notably, only two of the three women with high cotinine levels reported smoking. This pattern suggests that a portion of high cotinine readings could reflect secondhand smoke exposure rather than direct smoking.
Compared with women who did not smoke, those who smoked throughout pregnancy faced a 2.6-fold increase in the likelihood of delivering prematurely. They were also about four times more likely to experience fetal growth restriction, a condition that can lead to complications such as breathing difficulties and higher infection risk for newborns. Babies born to smokers weighed, on average, 387 grams less than babies born to nonsmokers, equating to roughly a 10 percent reduction in birth weight on average.
On caffeine intake, the study used paraxanthine as a biomarker to gauge exposure. Higher caffeine consumption from coffee or other beverages did not appear to raise the risk of preterm birth or other adverse outcomes. This finding challenges some earlier work that linked caffeine to lower birth weight or slower fetal growth.
In addition to smoking and caffeine, the analysis considered the broader picture of how maternal behaviors interact with pregnancy health. The results emphasize that tobacco use during pregnancy has clear, measurable risks for both preterm birth and fetal growth. The study’s design, with repeated biological measurements and a large, well-defined cohort, strengthens the reliability of these conclusions and offers practical guidance for expectant families, clinicians, and public health programs. Researchers and health professionals may use these insights to tailor conversations about fetal development, smoking cessation, and nutrition during pregnancy. Attribution for these findings is provided to the International Journal of Epidemiology, with the Cambridge team contributing significant observational data and interpretation.