How Safe Is Betamethasone in Pregnancy?

Use of betamethasone in pregnancy is not commonly advised by doctors, as evidence in animal tests have showed that the drug can cause damage to the baby. Betamethasone crosses the placental barrier and may produce developmental problems in the growing fetus. These effects have been observed in humans, especially in the first few months of pregnancy. Sometimes, though, betamethasone in pregnancy has useful effects on babies in the later stages of pregnancy, and so may be beneficial rather than detrimental to the child.

Part of a group of medications called corticosteroids, betamethasone is a drug that acts on the immune system. It can be useful to dampen down an overactive immune response, which produces allergic reactions. It has benefits, therefore in conditions like psoriasis and other skin problems due to allergies. As the drug treats problems that tend to occur over months and years, a long term course of betamethasone is common.

When a woman becomes pregnant, she may have been using corticosteroid treatment for her chronic condition over the longterm. Ceasing the use of the drug during pregnancy may allow symptoms of the condition to return, which can be uncomfortable, unsightly and interfere with lifestyle. For some women, who experience severe attacks of allergy, a doctor may approve the use of betamethasone despite the risk to the fetus.

Commonly, drugs are tested in groups of people and the results collated and examined. Drug studies in pregnancy, however, are uncommon, due to the potential for damage to the baby, and so the closest information on drug safety during this time is from animal studies. Betamethasone in pregnancy studies on rabbits show that the drug can cause teratogenic effects on developing rabbits in the womb. Teratogenic is a term that describes a substance that can affect normal development of a fetus, producing developmental abnormalities. Some evidence from previous cases is available to show that facial cleft palates are more likely in women who take betamethasone in pregnancy.

A subgroup of pregnant women may, conversely, benefit from betamethasone treatment. Babies who may be born prematurely can have underdeveloped lungs, which can be made more efficient through betamethasone injections for the mother before birth. Thus the drug may help the baby's chance of survival if he or she is born in the range of about the 24th to 34th week of pregnancy.

As well as pregnancy, betamethasone is not considered suitable for use while breastfeeding. This is because the drug may be able to get into the milk of the mother, and then into the baby during feeding. The way betamethasone works in the body is to mimic the effects of natural immune molecules, and this interference with normal immune system development in babies may be dangerous. All forms of betamethasone, from skin creams to injections, carry the same risks.