Doxycycline antibiotic linked to higher pregnancy loss risk in new study

Study findings on drug safety

Researchers analyzed data from two U.S. insurance databases covering 224,870 pregnancies between ages 12 and 55. About 4,385 women took doxycycline during the first trimester while others received alternative antibiotics like amoxicillin or clindamycin. Those prescribed doxycycline for respiratory infections faced a 40 to 54 percent higher risk of pregnancy loss compared to those on amoxicillin. For acne treatment, users showed a 49 percent higher risk in one database though the second database found no statistical difference.

Researchers explain potential causes

The study was observational so it cannot prove the drug directly caused the losses which included miscarriages before 20 weeks and stillbirths after week 20. Animal studies suggest doxycycline might interfere with early placental development making it harder for the placenta to support the fetus properly. Doctors generally avoid this broad-spectrum antibiotic in later trimesters because it binds to calcium in developing bones potentially disrupting fetal bone growth.

Experts advise caution on use

Study first author Almut Winterstein from the University of Florida told Live Science that physicians must carefully consider the benefit-risk balance when prescribing doxycycline. The researchers reported seven to 11 additional pregnancy losses per 100 pregnancies for doxycycline users compared with other antibiotic options assessed in their analysis.