Caffeine and early pregnancy
A critical aspect of caffeine exposure includes the importance of measuring exposure to caffeine during the relevant time window and the need to capture changing patterns of pregnancy caffeine intake. Caffeine consumption tends to decrease during the early weeks of pregnancy, coinciding with increasing pregnancy symptoms and aversions1.
Pregnancy symptoms, including aversions to tastes and smells, nausea and vomiting are common in healthy pregnancies that result in live births, and occur less frequently among women whose pregnancies end in miscarriages. This relationship is attributed to a stronger pregnancy signal linked to higher concentrations of pregnancy hormones in viable pregnancies3.
Caffeine consumption has been shown to decrease with increasing pregnancy symptoms during the early weeks of pregnancy1.
It may be that women experiencing healthy pregnancies are more likely to reduce their caffeine intake in response to pregnancy symptoms than women who will have a miscarriage. As a result, reduced caffeine consumption may be a consequence of pregnancy viability as opposed to increased consumption causing any reproductive complication (“reverse causation”).
A study reviewing maternal self-reported consumption of beverages (caffeinated coffee,tea, and soda) and chocolate the year before pregnancy was used to estimate caffeine intake2. About 97% of mothers reported caffeine consumption (average intake of 129.9 mg/day the year before pregnancy); soda was the primary source of caffeine. The proportion of mothers reporting dietary caffeine intake of more than 300mg/day was significantly higher among those who smoked cigarettes or drank alcohol. Most mothers stopped or decreased their caffeinated beverage consumption during pregnancy. A high level of caffeine intake was associated with risk factors for adverse reproductive outcomes. The authors recommended further studies which may improve the maternal caffeine exposure assessment.
Coffee and Gestational Diabetes Mellitus
Gestational diabetes (or gestational diabetes mellitus, GDM) is a condition in which women without previously diagnosed diabetes exhibit high blood glucose levels during pregnancy (especially during their third trimester).
A population-based cohort of 71,239 women taking part in the Danish National Birth Cohort examined the relationship between first trimester coffee and tea consumption and gestational diabetes mellitus (GDM) risk and suggested that moderate first trimester coffee and tea intake is not associated with GDM increased risk; it may even have a protective effect19. The Kuopio Birth Cohort also concluded that moderate coffee intake had a minor protective association with the risk of GDM20.
A further 2025 review suggested that moderate maternal caffeine intakeis not significantly associated with increased risks of gestational diabetes mellitus5.
Caffeine and miscarriage
The epidemiological studies evaluating the risk of miscarriage, also known as spontaneous abortion, from caffeine exposure have been inconsistent1,18,21,22. However, many of these studies failed to evaluate the pregnancy signal.
A 2015 dose-response meta-analysis of 130,456 individuals suggested that higher maternal caffeine intake was associated with a higher risk of pregnancy loss, although adjustment for smoking and pregnancy symptoms may have been incomplete15.
However, a prospective cohort study of 5,921 women suggested that pre-conceptional caffeine consumption was not associated with an increased risk of spontaneous abortion, although the authors did note that consumption during early pregnancy was associated with a small increased risk16.
A 2017 systematic review and meta-analysis suggested that coffee and caffeine consumption was associated with an increased risk of spontaneous abortion at intakes of 300mg and 600mg a day23. The authors expressed their support for advice to limit caffeine intakes during pregnancy in line with the EFSA recommendations of a maximum of 200mg of caffeine per day4.
Data from the Nurses’ Health Study of 15,590 pregnancies concluded that pre-pregnancy coffee consumption at levels above 4 cups of coffee per day was associated with an increased risk of spontaneous abortion, particularly at weeks 8-1924.
A 2022 meta-analysis suggested that caffeine intake during pregnancy was associated with a higher relative risk of pregnancy loss in cohort andcase-control studies in a non-linear association22. The dose-response analysis suggested that an increase of one cup of coffee per day during pregnancy was associated with 3% increased risk of pregnancy loss. Likewise, increased intake of 100mg of caffeine per day during pregnancy increased the risk of pregnancy loss by 14% and 26% based on cohort and case-control studies, respectively22. The authors suggested that more research was required to understand the mechanisms that maybe involved.
The 2010 Committee Opinion of 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 miscarriage; … a final conclusion cannot be made as to whether there is a correlation between high caffeine intake and miscarriage”. This view was reaffirmed in 202325.
Caffeine and pre-term birth
The 2010 Committee Opinion of the American College of Obstetricians and Gynecologists (reaffirmed in 2020) stated that “Moderate caffeine consumption (less than 200mg per day) does not appear to be a major contributing factor in preterm birth”25.
A Polish study published in 2012 concluded that caffeine intake of no more than 300mg per day during pregnancy does not affect pregnancy duration and the condition of the newborn. Black tea was the major source of caffeine, whereas 26% of women gave up coffee during pregnancy. An underestimation of maternal caffeine intake during pregnancy could not be excluded, since the questionnaire was carried out on the last day before delivery9.
A 2014 Brazilian study suggested that caffeine consumption was independently associated with low birth weight, but not with preterm birth, however the frequency of high caffeine consumption was low10.
A 2024 review suggested no association with prematurity has been demonstrated, although one study reported a small reduction in gestational age with increasing reported caffeine intake6.
