Taking doxycycline, a widely prescribed antibiotic, during the first trimester of pregnancy may be linked to a higher risk of miscarriage and stillbirth, a new study suggests, Live Science reported. Doxycycline is a broad-spectrum drug used for acne, respiratory infections, and sexually transmitted infections such as chlamydia and syphilis.
Doctors generally already avoid the drug in the second and third trimesters because it belongs to a class of antibiotics that can bind to calcium in developing bones. Animal studies have suggested that this may disrupt fetal bone development. Evidence on safety in early pregnancy has been thinner, which is why the new work is being treated as notable rather than as a settled rule-change on its own.
The study was published Tuesday, Nov. 10, in the Annals of Internal Medicine. Researchers analyzed 224,870 pregnancies in people ages 12 to 55, Live Science said. More than 218,230 of the patients were treated for respiratory tract infections and more than 6,630 for acne between conception and the end of the first trimester. About 4,385 women filled a doxycycline prescription. Compared with other options, those prescribed doxycycline had a 40 to 54 percent higher risk of pregnancy loss, the report said, and the drug was associated with seven to 11 additional losses per 100 pregnancies. Among people treated for acne, one analysis found a 49 percent higher risk. Miscarriage was defined as loss before 20 weeks, and stillbirth as loss after the 20th week. Those are relative risks from an observational study, not a statement that the drug caused each loss.
The study, as described by Live Science, is observational. It does not prove that doxycycline caused the losses, and women who are prescribed the drug may also have infections or other risks that affect pregnancy. Those caveats belong next to the finding. The practical point for clinicians and patients is narrower: a commonly used antibiotic that is already avoided later in pregnancy now has new evidence suggesting caution in the first trimester too, and any change in prescribing should be weighed against the danger of leaving an infection untreated.
People who are pregnant and already taking doxycycline should not stop a prescribed medicine on the basis of a news story. That decision belongs with a doctor who knows the infection being treated and the available alternatives. Live Science's report is about a study that found an association, not a regulator's ban. The verified takeaway is the association with pregnancy loss when the drug is used early, the existing later-pregnancy caution about bone development, and the need to treat the result as a signal for medical advice, not as a do-it-yourself stop order.
Doxycycline remains a standard treatment for several infections outside pregnancy. The new paper is about timing in early pregnancy, and it should be read that way: a possible added risk, reported from a study, that doctors and regulators will have to put next to the benefits of treating serious bacterial disease.