(NaturalNews) Consuming caffeine while pregnant leads to low birth weights and longer pregnancies, according to a new study conducted by researchers from Norwegian Institute for Public Health and published in the journal BMC Medicine.
"As the risk for having a low birth weight baby was associated with caffeine consumption, pregnant women might be counseled to reduce their caffeine intake during pregnancy as much as possible," said lead researcher Verena Sengpiel, of Sahlgrenska University in Sweden.
Caffeine is able to cross the placental barrier, which is meant to supply nutrients to the developing child but keep out other chemicals. Because caffeine can be toxic and the human embryo cannot yet produce enyzmes to inactivate the substance, the World Health Organization recommends that pregnant women consume no more than 300 milligrams of caffeine per day. Some national governments recommend that intake be kept to 200 milligrams or fewer.
According to the Mayo Clinic, the average home-brewed, eight ounce cup of coffee contains between 95 and 200 milligrams of caffeine. Coffee purchased at coffee shops is typically much higher in caffeine, and often comes in much larger servings.
A cup of tea contains significantly less caffeine than coffee, while a piece of chocolate contains about 35 milligrams. Other common sources of caffeine are sodas and energy drinks.
Lower birth weight, longer gestation
The researchers examined diets and birth information collected over the course of 10 years from nearly 60,000 pregnant women who were free of any medical or pregnancy-related conditions. The researchers recorded all sources of dietary caffeine intake, including coffee, tea, soda and chocolate-containing foods.
They found that after adjusting for the effects of smoking (because people who consume more caffeine are also significantly more likely to smoke), caffeine intake had no effect on the risk of premature delivery. However, women who consumed more caffeine during pregnancy were significantly more likely to give birth to a child who was officially considered to have a low birth weights
"This association remained even when we looked only at non-smoking mothers," Sengpiel said, "which implies that the caffeine itself is also having an effect on birth weight."
Specifically, for every 100 mg of caffeine consumed each day from all sources, a child of average expected weight (3.6 kilograms, or 7.9 pounds), could be expected to lose 21-28 grams (0.74-0.99 ounces). This implies that for many women, even an intake of 200-300 milligrams per day may be problematic.
Surprisingly, the researchers found that higher caffeine intake was actually associated with a longer, rather than a shorter, length of pregnancy. Every 100 milligrams of caffeine per day increased pregnancy length by an average of five hours. When only caffeine from coffee was looked at, the effect was even more dramatic: every 100 mg of caffeine consumed from coffee each day increased pregnancy length by an average of eight hours.
The researchers said they were unsure whether some other chemical in coffee is causing the longer pregnancies, or whether the difference is due to some still unknown, third factor.