Caffeine intake in pregnancy is linked to lower birth weight but not to preterm delivery, according to findings from the Norwegian Mother and Child Cohort Study. Caffeine from coffee, but not from other sources, is associated with slightly longer pregnancies.
A research group from the Sahlgrenska Academy in Sweden and the Norwegian Institute of Public Health studied data about maternal health and birth details collected from almost 60,000 women in the Norwegian Mother and Child Cohort Study. Pregnant women with medical and pregnancy-related conditions were not included in the study. Various sources of caffeine were studied, including coffee, tea, carbonated drinks and cocoa-based food such as cakes, desserts and chocolate.
Together with oxygen and necessary nutrients, caffeine crosses the placenta but embryos are unable to process it. Pregnant women in many countries are currently recommended to consume less than 200 mg caffeine per day, equivalent to one or two regular cups of coffee.
Increased risk of low birth weight babies
Caffeine intake from different sources was linked to lower birth weight and a higher number of babies who were small for gestational age. For a child with an expected average birth weight (3.6kg) this is equivalent to 21-28 g lost per 100 mg caffeine per day. An intake of 200-300 mg caffeine per day is associated with an increase in the risk of giving birth to a small for gestational age baby by almost a third. Babies who are small for gestational age are at higher risk of both short-term and lifelong health problems.
"Caffeine consumption is strongly correlated with smoking which is known to increase the risk for both preterm delivery and the baby being small for gestational age. In this study we found no association between caffeine intake and preterm delivery but we did find an association between caffeine and babies who were small for gestational age. This association remained even when we corrected for maternal smoking habits and when we only looked at non-smoking mothers, which implies that caffeine itself also is associated with birth weight" explains Dr. Verena Sengpiel from the Sahlgrenska Academy in Sweden, who led the project.
No effect on preterm delivery
The source of caffeine was significant for pregnancy length. Caffeinated coffee was associated with an extra eight hours of pregnancy per 100mg caffeine consumed per day. However, caffeine intake from all other sources in the group of non-coffee drinkers was associated with a decreased pregnancy length. This association implies that it is either other substances present in coffee or behaviour solely associated with coffee drinking that increases pregnancy length, not the caffeine itself.
About the study
Babies that are born preterm (before 37 weeks of gestation) or small for gestational age (according to a defined standard) account for most health problems and deaths among new-born babies.
The association between maternal caffeine intake from different sources and these adverse pregnancy outcomes was studied in 59,123 pregnancies included in the Norwegian Mother and Child Cohort Study. While there was no statistical association between caffeine consumption and pregnancy length, there was a strong association between caffeine intake from different sources and decreased birth weight. Even the mothers who followed the official recommendations had a higher incidence of delivering a baby born small for gestational age. The study took into account a range of potential confounding variables including maternal age, pre-pregnancy body mass index, number of children, smoking habits, passive smoking, nicotine intake from other sources, alcohol consumption during pregnancy, energy intake, maternal education, marital status and household income.
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