BETHESDA, Md. — Drinking just half-a-cup of coffee during pregnancy can knock nearly an inch off of a child’s height by the time they are eight, a new study reveals.
The discovery is based on an analysis of almost 2,500 boys and girls from around the United States. Researchers say their results add to evidence that mothers-to-be should abstain from drinking caffeine.
“Though the clinical implications of an approximately 2-cm height difference are unclear, our findings for height are similar in magnitude to those of children whose mothers smoked during pregnancy,” corresponding author Dr. Katherine Grantz and the team write in the journal JAMA Network Open.
Some public guidelines recommend that pregnant women should have less than 200mg of caffeine a day — about two cups of instant coffee. However, Dr. Grantz, from the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Maryland, says the team identified this phenomenon at caffeine levels far below this mark.
“We consistently observed shorter height, which has been associated with increased risk of multiple cardiometabolic diseases in both pregnant and nonpregnant individuals,” the researchers report.
These diseases include obesity and diabetes. Modest coffee consumption during pregnancy has also displayed a link to lower birth weight.
“Higher maternal caffeine and paraxanthine concentrations were associated with shorter stature persisting up to age 8 years in 2 pregnancy cohorts with longitudinal follow-up and distinct patterns of low and high caffeine consumption,” the team writes. “Our findings indicate that maternal caffeine consumption is associated with long-term decreases in child height.”
What’s causing coffee to stunt growth?
In the first study of its kind, Dr. Grantz and the team analyzed data from two separate groups, tracking participants into grade school.
“Children of women with low measured caffeine and paraxanthine during pregnancy were shorter than the children of women who consumed no caffeine during pregnancy, with increasing gaps in height in a historical cohort through age 8 years,” the team continues. “These findings suggest that small amounts of daily maternal caffeine consumption are associated with shorter stature in their offspring that persist into childhood.”
The potential mechanism for causing shorter height is unclear, but the team notes that caffeine is a neural stimulant not metabolized by the fetus that accumulates in its tissue. Coffee is the world’s most popular beverage, with up to eight in 10 people enjoying a daily cup.
“It is important to determine whether in utero caffeine exposure has long-term growth implications in offspring,” the researchers conclude.
Previous studies looking at caffeine’s effects on pregnancy relied on women to self-report how much they consumed daily. The new study used blood samples taken during pregnancy to determine participants’ exact levels of caffeine and its metabolite, paraxanthine.
South West News Service writer Mark Waghorn contributed to this report.