- The American College of Obstetricians and Gynecologists (ACOG) has long suggested that moderate caffeine consumption (fewer than 200 milligrams per day) does not cause serious problems during pregnancy.
- Now a new study finds that pregnant people who ingest a moderate amount of caffeine tend to give birth to slightly smaller infants.
- Experts say more research is needed to fully understand the risks.
One of the most difficult adjustments for people who are newly pregnant is the dietary changes.
Experts recommend that if you're pregnant, you should avoid a variety of foods and drinks, including alcohol, sushi, soft cheeses, and caffeine.
The American College of Obstetricians and Gynecologists (ACOG) has long suggested that moderate caffeine consumption — fewer than 200 milligrams (mg) per day, about one 12-ounce cup of coffee — does not cause serious problems during pregnancy.
But now new research published this month is suggesting that pregnant people who consume even as little as half a cup of coffee a day had, on average, slightly smaller babies than those who did not consume caffeinated beverages.
What the study found
The study, which was conducted at the National Institutes of Health, looked at data from more than 2,000 racially and ethnically diverse participants. They were all nonsmokers and did not have any health problems before pregnancy.
The study participants who consumed moderate amounts of caffeine, or under 200 mg, were more likely to have children that weighed slightly less than those born to people who consumed no caffeine.
Infants born to mothers with the highest blood levels of caffeine were an average of 3 ounces lighter and 0.17 inches shorter at birth compared with infants born to mothers with no or minimal blood levels of caffeine.
Why birth weight matters
Dr. Tracy Grossman, maternal-fetal medicine specialist in the department of obstetrics and gynecology at NYU Langone Health, explains that low birth weight can be associated with a variety of increased health risks.
“The technical definition is growth restriction,” Grossman said of low birth weight. “That means a weight less than the 10th percentile for age. Those babies have a longer stay in the hospital, more problems with breathing, higher risk of infection, trouble with feeding, etc.”
March of Dimes defines low birth weight as a baby being born weighing less than 5 pounds, 8 ounces.
However, just because a baby is born at a certain weight does not mean they will have health problems or need medical treatment.
The most typical cause of low birth weight is premature birth (before 37 weeks of pregnancy) as well as fetal growth restriction.
What is the link between caffeine and low birth weight?
According to Grossman, the jury has been out on answering this question.
“Birth weight has a lot of different influencers, from underlying medical disorders to simply because the baby might have a lower birth weight because that's the family history,” Grossman said.
“There have been studies that look at preterm birth and miscarriages associated with caffeine, but the birth weight is still something debated,” she added.
As per the ACOG guidelines, pregnant people are advised not to have more than 200 mg of caffeine per day.
This doesn't mean 200 mg of coffee.
Caffeine is just one aspect of coffee. It can be found in other beverages as well as food.
For example, a shot of espresso contains 75 mg of caffeine, while an 8-oz. cup of decaf contains about 15 mg of caffeine. Chocolate has caffeine. So does tea.
“Caffeine is a known neural stimulant, and it is believed that it can negatively affect the developing fetal brain, altering the appetite-regulating centers and the feedback systems involving the brain, pituitary gland, and the adrenal gland, which can lead to abnormal neuroendocrine changes, impacting the release and balance of critical hormones and neurotransmitters involved in metabolic health,” said Dr. Felice Gersh, OB-GYN, and founder and director of the Integrative Medical Group of Irvine in California. She is also co-author of “PCOS SOS Fertility Fast Track.”
“Studies have shown that there is an association between caffeine and the development of low birth weight, though the exact amount of caffeine that causes harm remains unclear and somewhat controversial,” she said.
Moderate caffeine and low birth weight
If you're currently pregnant and enjoying a moderate amount of caffeine (under 200 mg daily), experts say don't panic or immediately give up all caffeine.
This new study shows that babies born to mothers who consumed moderate caffeine were only lighter by a few ounces and shorter by just a fraction of an inch.
And this doesn't necessarily mean they were in less than the 10th percentile, or that they were categorically unhealthier than their counterparts.
“The study talks about birth weight being off by 2 or 3 percent,” Grossman said. “We worry about extremely low weight babies, like those that weigh in less than the 10th percentile at delivery,” she said.
“If a patient had a 6-pound, 6-ounce baby at 37 weeks, and if she didn't have caffeine the baby would be 6 pounds, 9 ounces, there is no clinical difference in outcome,” Grossman said.
Alternatives to caffeine?
There's no other natural alternative to caffeine that provides the same “jolt” that makes it so popular.
There are alternatives to coffee, but for the most part they all still contain a decent amount of caffeine.
Gersh recommends opting for ginger tea, chamomile, tea, purified water with lemon or lime juice, or natural sparkling water with a dash of fruit juice.
These won't deliver the same effects as caffeine, but they can be a replacement.
For people who are concerned, they may try switching to decaf, which has significantly less caffeine, if they don't wish to give up coffee entirely. They can also speak with their OB-GYN about the risk.
“The safest approach is to avoid all caffeine,” Gersh said. “Different studies have published different amounts that are ‘threshold' amounts that place babies at risk. Newer studies suggest the threshold of 300 mg per day is safe, while others say there is no minimum safe intake.”
Still, experts like Grossman believe that studies such as this one should be taken with caution, especially since the results don't suggest that the babies born were in an unhealthy weight range.