Study finds many pregnant women exceed caffeine limits; even moderate intake linked to smaller babies

By: Nina Garlo

A new study from Finland sheds light on a habit that often goes unnoticed during pregnancy: daily caffeine consumption. According to the research, a significant share of pregnant women take in more caffeine than current recommendations allow.

Even moderate intake in early pregnancy was associated with babies being born smaller than expected for their gestational age, the study revealed.

The findings come from the Kuopio Birth Cohort (KuBiCo) study and form the basis of a doctoral dissertation by registered dietitian, Anni Kukkonen, whose work will be examined at the University of Eastern Finland. Her research shows that caffeine intake often exceeds the recommended limit of 200 milligrams per day, especially among coffee drinkers. In Finland, where coffee is firmly embedded in everyday life, this is hardly surprising, but the effects on fetal growth are becoming increasingly clear.

Kukkonen’s analysis showed that roughly one-third of all pregnant participants exceeded the recommended caffeine limit, and among those who drank coffee, the proportion was even higher. What makes the findings even more striking is that the elevated risk associated with smaller birth size was not limited to heavy caffeine users.

Even women who consumed what would typically be considered a moderate amount — between 51 and 200 milligrams per day — had a higher likelihood of giving birth to a baby small for gestational age. Early pregnancy appears to be a particularly sensitive window, and Kukkonen emphasises that people planning a pregnancy may benefit from clearer, more practical information about the caffeine content of everyday foods and drinks.

“It is important to follow the caffeine recommendations during pregnancy. Early pregnancy is a particularly sensitive time for fetal development, so even those planning to become pregnant need practical information and guidance on moderate caffeine intake,” says TtM, certified nutritionist Anni Kukkonen.

The study also uncovered an unexpected link between cola drinks and gestational diabetes. Although cola consumption was generally low, women who drank even small amounts — more than about a third of a decilitre per day — had a higher risk of developing gestational diabetes. This association appeared in both sugary and sugar‑free cola drinks. Interestingly, neither total caffeine intake nor coffee consumption showed a similar connection to gestational diabetes in this dataset.

Energy drinks, which are not recommended during pregnancy, were used by only a small minority of participants. This, despite researchers noting that their popularity among young adults is rising and may become a growing concern in future pregnancies.

One of the most innovative aspects of the KuBiCo study was its method of measuring fetal exposure to caffeine. Pregnancy alters caffeine metabolism, and the fetus is exposed to the caffeine the mother consumes. To better understand this exposure, researchers analysed newborn hair samples using high-resolution mass spectrometry. They found that caffeine consumed by the mother in late pregnancy accumulates in the baby’s hair, giving a direct way to assess fetal exposure, something that has been difficult to measure reliably until now.

The study drew on data from women giving birth at Kuopio University Hospital and their newborns. Dietary habits and caffeine intake were assessed through questionnaires, while the hair‑sample analysis provided a biochemical snapshot of exposure during late pregnancy.

The dissertation, titled Coffee and caffeine intake during pregnancy – associations with maternal and neonatal health, will be publicly examined in the Faculty of Health Sciences at the University of Eastern Finland.

Taken together, the findings add to a growing body of evidence suggesting that caffeine intake during pregnancy deserves careful attention. Many pregnant women unintentionally exceed recommended levels, and even moderate intake may play a role in fetal growth outcomes. The association between cola drinks and gestational diabetes raises additional questions that justify additional research. And the ability to measure caffeine directly from newborn hair opens new possibilities to understand how common dietary habits shape early development.

While the study does not offer individual medical guidance, it stresses the importance of clear, accessible information for anyone who is pregnant or planning a pregnancy. As Kukkonen notes, early pregnancy is a particularly vulnerable period for fetal development, and awareness of caffeine sources from coffee to cola to chocolate may help expectant parents make knowledgeable choices.

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