Caffeine, Fertility and Fetus
Our Drug of Choice
While we don't necessarily think of caffeine as a drug, it really is. And, it's the drug of choice for most people in the world. As a matter of fact, research indicates this psychoactive drug is consumed by 90 percent of adults on a daily basis through the mediums of coffee, tea and soda. The March of Dimes says that Americans consume a daily average of about 280mg with nearly a third consuming more than 600mg a day. That's a lot of jittery people. For those who are not trying to conceive, or who are not pregnant, you'll be healthier if you lower your intake - but if you're trying to conceive, you're better off leaving it alone.
Fertility Affected Negatively
Some studies indicate that moderate amounts of caffeine (maximum two cups of coffee per day or less than 300mg) probably won't reduce a woman's chances of becoming pregnant. However, there are also studies that clearly show consumption in excess of 500mg or greater decreases fertility in women.
Recent research conducted by Sean Ward, a scientist at the University Of Nevada School Of Medicine, in his study that was published in the British Journal of Pharmacology, found that muscle activity in the fallopian tubes, the carriers of eggs from the ovaries to the uterus, is reduced with caffeine ingestion. When investigating the fallopian tubes of mice, he discovered that caffeine stops the function of specialized pacemaker cells in the wall of the tubes. Since these cells coordinate contractions in the tubes, the cessation of function means the egg can't move down the tube.
"This provides an intriguing explanation as to why women with high caffeine consumption often take longer to conceive than women who do not consume caffeine," said Ward.
There are older studies confirming this as well. In the 1980s a Yale University School of Medicine study of 1,900 women found that the risk of infertility in women who drank only one cup of coffee per day was 55 percent higher than those who did not drink coffee. Additionally, it was 100 percent higher for those who drank 1.5 to three cups per day and 176 percent higher for women who drank more than three cups.
Caffeine Induced Miscarriage and Stillbirth
The effect on fertility isn't the only issue, of course. Once a woman becomes pregnant, caffeine can have a very adverse effect upon the pregnancy and the fetus. Some of the results of research have been confusing. For instance, two studies done in 2008 showed different results. One indicated that women who consume 200mg or more of caffeine in a day are twice as likely to miscarry as women who don't drink caffeine (25 percent vs. 12.5 percent). The second study found there was no increased risk for women who drank modest amounts (200mg to 350mg/day) of coffee daily. Earlier studies showed that women who consume more than 500mg of caffeine in a day are more likely to miscarry. The bottom line - err on the side of safety and cut consumption way back.
A study completed in Denmark in 2003 covering the connection between caffeine consumption and stillbirth found that women who drank between four and seven cups of coffee a day may be at a slightly higher risk for stillbirth. However, women who drank eight cups or more per day had twice the risk of having a stillbirth than women who did not drink coffee.
One study found a connection between caffeine consumption equal to three cups of coffee in a day increased the risk of having a baby boy born with undescended testes - a situation where the testicles do not drop down from the pelvis into the scrotum as they should in late pregnancy.
Caffeine causes dehydration, which is harmful to both mother and baby. As pregnancy develops and progresses, the mother's body is slower to process caffeine and it stays in the system longer. It crosses into the placenta and, since the fetus has an immature metabolism, the breakdown of caffeine takes exponentially longer. The more caffeine that is consumed, the more it builds up in the baby's body sometimes resulting in a shortened gestation period and lower birth weight. The buildup creates a risk of fetal growth restriction which occurs when the baby is smaller than expected with weight below the 10th percentile for their gestational age.
For more details on the effects of caffeine on pregnancy, see our article here.