Even low levels of maternal coffee consumption impact birth weight

Pregnant women who drank about a half a cup of caffeinated coffee daily — fewer than the recommended two cups — had slightly smaller babies than pregnant women who did not consume caffeinated beverages, data show.

The American College of Obstetricians and Gynecologists recommends that pregnant women limit their caffeine consumption to less than 200 mg — about two cups of coffee — daily; however, previous systematic reviews and meta-analyses suggest “there may be no safe amount of caffeine during pregnancy,” Jessica Gleason, PhD, MPH, a postdoctoral fellow at the National Institute of Child Health and Human Development (NICHD), and colleagues wrote in JAMA Network Open.

There is evidence to suggest that caffeine may narrow the blood vessels in the uterus and placenta, which could decrease the blood supply to the fetus and inhibit growth, the researchers said in a press release. Caffeine may also fragment fetal stress hormones, putting infants at risk for rapid weight gain after birth and obesity, CVD and diabetes later in life.

Jessica Gleason

“Most of the research on caffeine and neonatal size at birth focuses on birth weight and length and relies on self‐reported measures of caffeine consumption,” Gleason told Healio Primary Care. “In the NICHD Fetal Growth Studies, we have rich data on multiple measures of neonatal anthropometry to more specifically characterize neonatal size, as well as objective measures of plasma concentrations of caffeine and its primary metabolite, paraxanthine. We were also able to characterize different components of anthropometry that make up birthweight.”

The NICHD Fetal Growth Studies included 2,055 women — 28.2% Hispanic, 27.4% white, 25.2% Black and 19.2% Asian/Pacific Islander — with a mean age of 28.3 years, mean BMI of 23.6 kg/m² and mean gestational age of 39.2 weeks at the time of delivery.

Compared with women who had no or minimal caffeine levels in plasma ( 28 ng/mL), Gleason and colleagues reported that those who had the highest caffeine levels (> 659 ng/mL) delivered infants who, on average, weighed 84.3 g lighter (95% CI, –145.9 to –22.6), were 0.44 cm shorter (95% CI, –0.78 to –0.12), and had a lower head circumference ( = –0.28 cm; 95% CI, –0.47 to –0.09), arm circumference ( = –0.25 cm; 95% CI, –0.41 to –0.09) and thigh circumference ( = –0.29 cm; 95% CI, –0.58 to –0.04).

“Similar reductions were observed for paraxanthine quartiles, and for continuous measures of caffeine and paraxanthine concentrations,” Gleason and colleagues wrote.

In addition, compared with women who reported no caffeinated beverage consumption, women who consumed about 50 mg (about one-half cup of coffee) daily had infants who weighed 66 g less (95% CI, –121 to –10) at birth. They also had a lower arm circumference ( = –0.17 cm; 95% CI, –0.31 to –0.02), thigh circumference ( = –0.32 cm; 95% CI, –0.55 to –0.09) and anterior flank skin fold ( = –0.24 mm; 95% CI, –0.47 to –0.01). The rate of caffeine metabolism had no impact on the results, according to the researchers.

“The clinical implications of our findings are unknown when considering that we found only small reductions in some neonatal anthropometric measures,” Gleason said. “Our results could indicate some disruption in normal fetal growth patterns but will require more research to confirm. Until we know more, it may be prudent to advise caution or possibly forego caffeine consumption.”

References

Gleason JL, et al. JAMA Netw Open. 2021;doi:10.1001/jamanetworkopen.2021.3238.

NIH. Moderate daily caffeine intake during pregnancy may lead to smaller birth size. https://www.nih.gov/news-events/news-releases/moderate-daily-caffeine-intake-during-pregnancy-may-lead-smaller-birth-size. Accessed April 28, 2021.