It’s a cruel twist that while headaches are so common during pregnancy, there are more stringent restrictions on what medications are considered safe for expectant mamas. The one main exception that most doctors suggest to women in need of relief is acetaminophen—but a new study demonstrates that still is not without risks.

According to the study published this week in the journal European Psychiatry, the use of acetaminophen during pregnancy is correlated to language delays among girl children at the ages of 30 months.

The findings pose a complication for women who often turn to Tylenol or the generic acetaminophen as one of the few low-risk medications during pregnancy.

For the study, researchers from the Icahn School of Medicine at Mount Sinai analyzed outcomes from 754 women who participated in the Swedish Environmental Longitudinal, Mother and Child, Asthma and Allergy (SELMA) study at the end of their first trimesters of pregnancy. Of the women, 59% reported taking acetaminophen during pregnancy with levels that were verifiable through urine tests.

During a follow-up when the participants’ children were 30 months, the female children of mothers who took more than six doses of acetaminophen during the early days of pregnancy were six times more likely to have language delays—defined as a vocabulary of 50 or fewer words. The same correlation was not found with male children.

Although the overall scope was still relatively small with just 4.1% of the girls having language delays compared to 12.6% of the boys, the researchers say in their finding this should “suggest that pregnant women should limit their use of this analgesic during pregnancy.”

According to the journal American Family Physician, Tylenol or acetaminophen is classified as the “pain reliever of choice” during pregnancy due to its Class B categorization. This means that while animal studies haven’t shown fetal risk to its use, there are no controlled studies among pregnant women.

In contrast, other common pain relievers such as asprin, ibuprofren and naproxen are Category D, meaning there “is positive evidence of human fetal risk.”

For pregnant women who experience fevers, headaches of pain, that leaves acetaminophen as the best OTC medication option. However, as this study shows, the best option of all is avoiding medication when possible.

“I think women should be aware that acetaminophen use in pregnancy might not be as ‘harmless’ as once thought,” Joshua Klein, chief medical officer and reproductive endocrinologist at Extend Fertility in New York, tells Parents. “But I would not yet conclude that it is unsafe for pregnancy altogether.”

Expectant parents should speak with their health care professionals about the pros and cons of medications such as acetaminophen and to discuss alternative courses of treatment.