October 31, 2022

expert reaction to study looking at caffeine in pregnancy and child height

A study published in JAMA Network Open looks at maternal caffeine consumption during pregnancy with child growth.

Helena Gibson-Moore, Nutrition Scientist, British Nutrition Foundation, said:

“We already know from previous research that there is a link between high caffeine consumption (>300mg a day) and lower birthweight and preterm birth, and intakes of more than 350mg a day are associated with pregnancy loss (miscarriage and stillbirth).

“The researchers in this study are looking at whether greater caffeine consumption in pregnancy is associated with childhood growth, both weight and height.  The study looked at two independent cohorts from the US to evaluate associations.  One was a more recent cohort with the aim to reflect modern caffeine consumption trends and the second was a historical cohort with high consumption.  The researchers measured concentrations of caffeine and its primary metabolite, paraxanthine, from plasma (ECHO-FGS) and serum (CPP) collected in the first trimester.  The researchers found that intrauterine exposure to increasing levels of caffeine and paraxanthine, even in low amounts, was associated with shorter stature in early childhood, but did not find strong associations between increasing maternal caffeine consumption and higher childhood BMI.  The researchers highlight that the association between maternal caffeine consumption and decreased child height, is biologically plausible given that caffeine and paraxanthine cross the placenta.

“But in the limitations of the study they also recognise that it’s unclear how well caffeine and paraxanthine measurements reflect habitual caffeine consumption, and that it is challenging to translate biomarker concentrations of caffeine back to milligrams.

“Other limitations included a lack of information on some potential confounding factors, such as maternal diet, nausea or vomiting during pregnancy, or paternal height.

“The study was also based in US so results can’t necessarily be extrapolated to other population groups in different countries.

“Although the results of the study are interesting, further research is needed to support the findings and as the researchers conclude, the clinical implication of this height difference is unclear and warrants future investigation.

“The Royal College of Obstetricians and Gynaecologists advice to limit caffeine intake to 200 milligrams (mg) per day, the equivalent to two cups of instant coffee, still remains.  This paper should not alarm pregnant women as the wealth of research on caffeine in pregnancy shows that pregnant women do not need to cut caffeine out entirely because any risks are small, and a limited intake of caffeine is safe for the majority of pregnant women.”

Prof Louise Kenny, Executive Pro Vice Chancellor of the Faculty of Health and Life Sciences, University of Liverpool, said:

“This is an interesting study which offers evidence that caffeine consumption in pregnancy, even at relatively low doses, is associated with slightly short stature (a reduction in height) in early childhood – though the clinical significance of this is unclear.

“The researchers used two large American cohorts: one of 788 children born between 2017 and 2019 and an older cohort of children born between 1959 and 1965.  The investigators measured caffeine and its metabolite in stored blood samples taken in pregnancy.  The finding of an association with caffeine consumption and a reduction in height up to 8 years of age was consistent across both cohorts.  It’s a strong association – in two cohorts that are temporally very distinct, and agrees with previous observational studies, separated by over 4 decades – but this study doesn’t prove causality.

“These findings add to those of other researchers who have previously reported an association between caffeine consumption in pregnancy and low birth weight and childhood obesity.  This study is of interest because it includes women with relatively low levels of caffeine intake, and demonstrates that the negative association between caffeine and childhood height persists even at low levels of caffeine consumption.  The long-term clinical significance of the slight reduction in height is unclear but it is concerning as previous work has shown that other parameters of abnormal growth in childhood is linked with a risk of cardiometabolic disease in adulthood.  Caffeine is a potent drug and caffeine and its metabolites have multiple physiological effects.  It is likely that caffeine crosses the placenta but the effect of this has been inadequately studied in pregnancy.  Further work is needed to understand the precise mechanism by which caffeine might exert any potential effect on child growth.

“The take home message is that these observational studies need to be backed up with robust research into causality.”

‘Association of Maternal Caffeine Consumption During Pregnancy With Child Growth’ by Jessica L. Gleason et al. was published in JAMA Network Open at 15:00 UK time on Monday 31 October 2022.

DOI: 10.1001/jamanetworkopen.2022.39609

https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2797983

Declared interests

Helena Gibson-Moore: “Funding to support the British Nutrition Foundation’s charitable aims and objectives comes from a range of sources including membership, donations and project grants from food producers and manufacturers, retailers and food service companies, contracts with government departments; conferences, publications and training; overseas projects; funding from grant providing bodies, trusts and other charities.  Further information about the British Nutrition Foundation’s activities and funding can be found at http://www.nutrition.org.uk/aboutbnf/.”

Prof Louise Kenny: “I’ve no conflicts of interest to declare.”