A new study suggests that drinking just half a cup of coffee a day during pregnancy can shave nearly an inch off a child's height.
According to the research, children born to women who consumed 50 mg of caffeine a day were 2 cm (0.8 inches) shorter than their peers at the age of eight.
The finding held even after adjusting for other factors that affect a child's height, including maternal age, smoking status and income.
These results were based on an analysis of 2,500 children in the US, showing that mothers-to-be should abstain from coffee altogether.
The American Association of Pregnant Women (APA) recommends that pregnant women limit their daily intake to about 200mg , primarily because the average 8oz coffee contains about 100mg of caffeine.
Research claims that caffeine constricts blood vessels in the uterus and placenta, which could reduce the blood supply to the fetus and slow growth.
Other factors can influence growth
Mother-child pairs recruited for the study published in the journal Jama Network Open were divided into four groups based on the amount of caffeine the mother consumed during pregnancy.
Plasma samples were collected from each mother during the first and third trimesters to measure how much caffeine the mother was drinking.
Those with 25.4 nanograms per milliliter (ng/mL) or less of caffeine detected in plasma samples were placed in quartile one.
Mothers in the highest quartile had levels of 575.3 ng/mL or higher.
The researchers note that it would only take about 50 mg of caffeine per day to bring a person from the first to the fourth quartile.
After following the children for more than eight years, researchers at the National Institute of Child Health and Human Development in Maryland followed children born between 2009 and 2013 until they were eight years old.
The difference became apparent when the child was around 20 months old and only widened as he grew older.
At age seven, the difference in height between those who consumed the least caffeine and those who drank the most was 1.5 cm on average.
At eight years, there was a difference of 2.3.
All of this was after controlling for race and maternal education, factors that could also influence a child's height at a young age.