Pregnancy
Caffeine intake and pregnancy
Healthy pregnancies may lead to reduction in caffeine intake
Caffeine consumption tends to decrease during the early weeks of pregnancy, coinciding with increasing pregnancy symptoms such as nausea, vomiting and aversions to smells and tastes2. These symptoms were responsible for a 59% reduction in caffeine intake from coffee observed between weeks 5 and 6 in a group of pregnant women5.
The reduced caffeine consumption observed is, therefore, likely to be a response to a healthier pregnancy with higher concentrations of pregnancy hormones, rather than a higher caffeine intake being related to any reproductive complication.
Moderate caffeine consumption and miscarriages
The current evidence for any effect of caffeine on miscarriage is difficult to assess due to a lack of well-designed studies accounting for all confounding factors.
One such study by Weng et al6, which reported an increase in miscarriage with caffeine intake over 200mg, is the basis upon which several professional associations have revised their upper safe limit for caffeine intake during pregnancy. However, Weng’s study was only stratified for caffeine intakes below or above 200mg, with no further qualification above 200mg. In addition, it did not control for cigarette smoking or duration of nausea and vomiting.
Another study in a small number of subjects found an association between caffeine intake and late miscarriage and stillbirth7. However, other more recent studies have failed to find any association between caffeine consumption and the risk of miscarriage8,9.
Further evidence for a lack of causal effect is provided by a study on miscarriage and nausea, where an increased risk of miscarriage was seen only in those consuming caffeine after the onset of nausea, but not in those who consumed caffeine before the onset of nausea, or those without nausea10.
No evidence for a link between caffeine and pre-term labour
There is no evidence for a link between caffeine intake and increased risk of delivery before 37 weeks2. In addition, in 2010, the American College of Obstetricians and Gynecologists stated that “Moderate caffeine consumption (less than 200mg per day) does not appear to be a major contributing factor in pre-term birth”11.
