No safe level of caffeine consumption for pregnant women

By Dr. Ananya Mandal, MDAug 26 2020

A new study shows that caffeine consumption by pregnant mothers could harm the fetus and baby. The new study titled, "Maternal caffeine consumption and pregnancy outcomes: a narrative review with implications for advice to mothers and mothers-to-be," was published in the latest issue of the journal British Medical Journal Evidence Based Medicine.

Study: Maternal caffeine consumption and pregnancy outcomes: a narrative review with implications for advice to mothers and mothers-to-be. Image Credit: Dejan Dundjerski / Shutterstock

What was the study about?

The researchers wrote that despite being one of the commonly consumed beverages, caffeine present in coffee is known to be habit-forming. They added that it is routinely consumed by the majority of pregnant women daily (ranging from 82 percent in the United States to 91 percent in France). The authors wrote, "Pharmacological actions of caffeine suggest potential threats to fetal development from maternal caffeine consumption." This study was an attempt to look at the available evidence regarding the potential harm that could be caused by caffeine when consumed during pregnancy.

What was done?

For this study, the team searched the available databases for studies that looked at the association between caffeine and caffeinated beverages and outcomes from pregnancies. From online databases, they found a total of 1,261 peer-reviewed studies on this topic in English. Of these, there were 48 original observational studies and meta-analyses that studies consumption of caffeine by pregnant mothers over the past twenty years. The negative outcomes of pregnancy studied were;

• Miscarriage
• Stillbirth
• Low birth weight and/or small for gestational age
• Preterm birth
• Childhood acute leukemia
• Childhood overweight and obesity

What was found?

From the 32 observational studies included in the analysis, there were 42 different findings. Some of the highlights of the results were;

• A total of 32 findings showed that there was a raised risk associated with caffeine
• Only 10 findings showed that there was an inconclusive association between maternal caffeine consumption and poor pregnancy outcomes
• There were 17 meta-analyses that included several studies. Of these, 14 meta-analyses showed that maternal caffeine consumption could raise the risk of four adverse pregnancy outcomes "stillbirth, low birth weight and/or small for gestational age, and childhood acute leukemia."
• Three meta-analyses did not find any conclusive evidence of harm caused by caffeine.
• None of the meta-analyses showed an association between maternal caffeine consumption and childhood overweight and obesity. Some individual studies showed an association between maternal caffeine consumption and childhood overweight and obesity, however.

Implications

The authors wrote, "the American College of Obstetricians and Gynecologists (ACOG) advises that pregnant women may safely consume up to 200 mg caffeine (the approximate equivalent of two cups of moderate-strength coffee) per day, and the same advice is contained in the (currently under review) Dietary Guidelines for Americans (DGAC)... the European Food Safety Authority (EFSA) states that maternal consumption of caffeine up to 200 mg per day does 'not give rise to safety concerns for the fetus' (p. 75), and the UK National Health Service (NHS) advises pregnant women to 'limit' daily intake to 200 mg."

This study compiles available data on maternal caffeine consumption and harm to the fetus and child and finds, "maternal caffeine consumption is reliably associated with major negative pregnancy outcomes." The study accounts for confounding factors and goes on to show that there is a "dose response relationship." This means that an increasing amount of maternal caffeine consumption is tied to more harm to the baby. There are no reports that show a safe threshold amount of caffeine below which no harm would occur to the child. Authors conclude, "current evidence does not support health advice that assumes 'moderate' caffeine consumption during pregnancy is safe. On the contrary, the cumulative scientific evidence supports pregnant women and women contemplating pregnancy being advised to avoid caffeine."

They wrote, "current advice such as that issued by ACOG, the DGAC, EFSA, and the NHS is not consistent with the level of threat indicated by biological plausibility of harm and extensive empirical evidence of actual harm. Accordingly, current health recommendations concerning caffeine consumption during pregnancy are in need of radical revision."

Expert speak

The British Coffee Association in response to the study said, "The current evidence given by the NHS is based on a comprehensive review of all the scientific evidence available on coffee and health, which shows that pregnant women should limit caffeine intake to 200mg per day or less, and at these levels does not increase the risk of reproductive complications... This new study was observational, so importantly does not show any direct cause-and-effect link and also is subject to confounding factors such as cigarette smoking and wider dietary issues, which may limit its ability to draw clear conclusions." Study author Prof Jack James of Reykjavik University called this study robust because a lot of effort has been made to remove the possible confounders which could affect the results.

The Food Standards Agency said in a statement, "Based on current scientific opinion, the FSA advises pregnant and breastfeeding women not to have more than 200mg of caffeine over the course of a day, which is roughly two mugs of instant coffee or one mug of filter coffee."

Commenting on the new study Dr. Mary Ross-Davie, the Royal College of Midwives, Director for Scotland, said, "Current NHS guidance on caffeine in pregnancy says that women should limit their intake to no more than 200mg of caffeine a day, equivalent to around two cups of instant coffee.  There is a need to ensure that women can make informed choices about what they eat and drink during pregnancy, and midwives will support women to do that, taking into account this latest research... It is important that all available evidence is considered to shape UK recommendations, and we hope the current guidance will now be reviewed in light of these findings."

Obstetrician Dr. Daghni Rajasingam, a spokesperson for the Royal College of Obstetricians and Gynaecologists, said, "(The) advice to limit caffeine intake to 200 milligrams (mg) per day -- the equivalent to two cups of instant coffee -- still stands... This paper does not supersede all the other evidence that has found that a limited intake of caffeine is safe for the majority of pregnant women."

James JE, Maternal caffeine consumption and pregnancy outcomes: a narrative review with implications for advice to mothers and mothers-to-be