Coffee consumption and pregnancy Part 2

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This blog continues from the last post focusing on the topic of coffee consumption and pregnancy, with key areas of focus including miscarriage, pre-term labour and fetal health. Further information on this topic can also be found on Coffee and Health, in addition to a wide range of coffee-related topics.

Moderate caffeine consumption and miscarriages

The current evidence for any effect of caffeine on miscarriage is difficult to assess due to a lack of well-designed studies accounting for all confounding factors.

One such study by Weng et al, reported an increase in miscarriage with caffeine intake over 200mg. This is the basis upon which several professional associations have revised their upper safe limit for caffeine intake during pregnancy. However, Weng’s study was only stratified for caffeine intakes below or above 200mg, with no further qualification above 200mg. In addition, it did not control for smoking or duration of nausea and vomiting.

Another study in a small number of subjects found an association between caffeine intake and late miscarriage and stillbirth. A further study in Italy also concluded that caffeine may increase the risk of sine causa recurrent miscarriage, however the authors did indicate that a potential recall bias cannot be ruled out, cautioning the requirement for further clinical studies. However, other more recent studies have failed to find any association between caffeine intake and the risk of miscarriage.

Additional evidence for a lack of causal effect is provided by a study on miscarriage and nausea, where an increased risk of miscarriage was seen only in those consuming caffeine after the onset of nausea, but not in those who consumed caffeine before the onset of nausea, or those without nausea.

No evidence for a link between caffeine and pre-term labour

There is no evidence for a link between caffeine intake and increased risk of delivery before 37 weeks, confirmed by a 2010 meta-analysis of 15 cohort and 7 case control studies. In addition, in 2010, the American College of Obstetricians and Gynecologists stated that “Moderate caffeine consumption (less than 200mg per day) does not appear to be a major contributing factor in pre-term birth”.

Caffeine intake and fetal health

Effect of caffeine on fetal growth undetermined

Effects of caffeine on fetal growth have been observed in some studies.

In a Dutch study of 7,346 pregnant women, consistent observations were seen between caffeine intake and fetal head circumference or approximate fetal weight, with intakes of caffeine over 540mg/day related to shorter birth length. However, this has not been observed elsewhere and further studies are needed.

In addition, the American College of Obstetricians and Gynecologists states that the association between caffeine and growth restriction remains uncertain.

No clear link between caffeine intake and congenital malformations

There is limited published research into the effects of caffeine on congenital malformations.

Modest associations between total caffeine intake neural tube defects (spina bifida) have been observed, though there is potential for bias in the concerning study. In 2010 it was also hypothesised by Schmidt that persons may run different risks based on whether they are slow or fast metabolisers of caffeine.

Data from the National Birth Defects Prevention Study however did not find any convincing evidence of an association between maternal caffeine intake and the birth defects. Additionally it was shown that coffee and tea consumption were not associated with any limb deficiency subtype.

Brent et al summarised in their risk analyses that it is very unlikely that usual or even high exposures to dietary caffeine increase the risk of birth defects for pregnant mothers exposed to caffeine. Accounting for a few exceptions, recent studies have not recorded an increased risk of malformations with greater caffeine consumption.

Caffeine and fetal death

Studies have consistently reported modest associations between caffeine intake and fetal death. However, the understanding of the science on caffeine and fetal death needs to consider that these studies contain frequent sources of bias, which may explain the observed relationship with caffeine use. Good quality research is required before any conclusions can be reached.

In conclusion, the scientific evidence does not support a positive relationship between moderate (200-300mg/day) caffeine consumption and adverse reproductive or perinatal outcomes. Although associations with infertility, pre-term delivery and congenital malformations are not regularly observed, reports of any adverse effects of caffeine use tend to produce great interest and coverage. However, a majority of these studies have serious methodological weaknesses which bring into question the reliability of their conclusions. Further well-designed studies are therefore required to fully explain any effects of caffeine on pregnancy and its outcomes.

For more information on coffee and pregnancy, and to view information sources, click here.

 

Please also note that the Pregnancy topic has recently been updated on the Coffee and Health website to include the most recent published research. To view the updated content please click here.

This information is intended for Healthcare professional audiences.
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