Why is doxycycline contraindicated in pregnancy?

Doxycycline is contraindicated in pregnancy primarily because it can cause discoloration of teeth in children. This antibiotic belongs to the tetracycline class of medications, which are known to bind to calcium ions. When administered during pregnancy, particularly in the second and third trimesters, doxycycline can cross the placenta and deposit in the developing fetal teeth, leading to permanent discoloration and enamel hypoplasia once the child is born. This effect is particularly significant when considering the long-term implications for dental health in the child.

Though other potential risks of doxycycline in relation to pregnancy, such as increased risk of miscarriage or potential effects on fetal brain development, exist, they are not as directly linked to the use of this medication as the dental staining concern. Thus, the possibility of causing permanent discoloration of teeth is a critical reason why doxycycline is avoided during pregnancy.