As well as oxygen and nutrients, caffeine easily passes the placental barrier, however the developing embryo doesn’t have the enzymes needed to inactivate it effectively. The WHO now recommends a limit of 300mg daily while pregnant although many countries suggest a limit of 200mg, and this could be less than a single cup of coffee.
To examine the impact of caffeine intake while pregnant on babies, researchers made use of information regarding mother’s diet as well as birth details collected over 10 years. All sources of caffeine were observed: coffee, fizzy drinks, tea, as well as foods which include cocoa-containing cakes and chocolate.
The researchers explained that despite the fact that caffeine intake is strongly related to smoking and has been proven to increase risk of preterm delivery as well as the baby being small for gestational age at birth, in this study they found no link between either coffee caffeine or total caffeine and preterm delivery, however they did find a connection between caffeine and being small for gestational age. This link continued to be even when they only examined mothers who did not smoke which suggests the caffeine on its own is having an impact on birth weight.
The researchers discovered that caffeine coming from all sources lowered birth weight. It wasn’t just caffeine, but the source of caffeine that impacted pregnancy outcomes. Caffeine coming from all sources increased pregnancy duration by 5hr for every 100mg caffeine each day, and caffeine consumption coming from coffee was connected with an even longer gestational duration – 8hr extra for each 100mg of caffeine every day.
This connection suggests that it isn’t just the caffeine in coffee that increases gestational duration but there must either be a substance in coffee that’s the cause of the additional time or there’s a behavior connected with coffee drinking not present in women who don’t drink coffee. Small for gestational age babies are at greater risk of both short term as well as long term health issues and it appears from these results that given that even 200-300mg caffeine daily could increase the risk of small for gestational age by nearly one third these recommendations should be re-evaluated.