Research by Marlene Newell
September 25, 2003
Being one of those pregnant women told hundreds of times to
eliminate caffeine from my diet during pregnancy, I was a bit amazed to hear so
many experts say caffeine does not pass through the placenta. Well, I
decided to check it out online and see if it simply is a case of the experts now
knowing something they told us before was wrong.
That's not what I found out. I didn't do an exhaustive search -- like hundreds of sites -- but the first 25 or so sites that came up on my search results (from medical research foundations, government sources, hospitals, etc.) yielded information in absolute contradiction to what the experts on the talk shows have been saying.
There is still much controversy over the amount of caffeine that is necessary to be harmful to the baby, but no disagreement over whether or not the caffeine passes through the placenta.
These are some of the more direct quotes:
Quote #1: The site for this 1st quote has links to the studies mentioned.
The March of Dimes (MOD 2002) notes that during pregnancy, OTIS (OTIS 2001) notes that, "…higher amounts of caffeine could affect babies in the same way as it does adults. Some reports have stated that children born to mothers who consumed >500mg/day were more likely to have faster heart rates, tremors, increased breathing rate, and spend more time awake in the days following birth." Source
A woman who wants to start a family should be aware that consuming over 300 milligrams of caffeine a day might increase the time it takes to get pregnant, as well as the risk of miscarriage or a low-birth-weight baby. The US Food and Drug Administration recommends that pregnant women avoid caffeine-containing foods and drugs or consume them only sparingly, because caffeine crosses the placenta and is a stimulant to the unborn baby. It is also transferred into breast milk, so women who breastfeed should avoid caffeine. Source
During pregnancy the rate at which caffeine is broken down and removed from the body is slower. This can lead to a build up of caffeine in the blood. Caffeine can have a stronger effect during pregnancy and can cross the placenta so that blood levels of caffeine are similar for both mother and unborn baby. Studies have shown that where the daily intake of caffeine is more than 300 mg a day, abortion and low birth weight are more likely. Source
Again, after visiting 25 or so sites, I did not find a single argument that caffeine DOES NOT cross the placenta -- only arguments about what levels of caffeine are necessary to have a detrimental affect on the unborn baby.
Finally, this information on the half-life of caffeine:
Pharmacokinetics of caffeine.
Significant blood levels of caffeine are reached in 30 to 45 minutes and complete absorption within the nest 90 minutes, with levels in plasma peaking in about 2 hours.
The half-life of caffeine is about 3.5 to 5 hours in most adults; it is longer in infants, pregnant women, and the elderly and shorter in smokers.
Like all psychoactive drugs, caffeine freely crosses the placenta to the fetus.
Caffeine has a longer half-life in the human fetus than in the adult because the fetus does not have the liver enzymes for detoxifying caffeine. The half-life of caffeine in the pregnant woman increases from 3 to 10 hours by the latter part of pregnancy. Source