Dexamethasone, or DEX as it is called, is a powerful steroid that has been administered to pregnant women who have previously given birth to a child with congenital adrenal hyperplasia (CAH). The aim is to minimize (or altogether prevent) the virilization of the female fetus’s genitals that happens in utero. It’s a practice that has been going on for over two decades.
Genital development occurs early in pregnancy, so DEX is typically given as soon as the woman knows she is pregnant, which is often before anyone knows the sex of the child. When what is known as CVS testing is possible at about 11-12 weeks gestation, DEX will be discontinued if it is found the fetus is either male or an unaffected girl. Because of the gap between when genital development occurs and when fetal sex is typically known, there is a great deal of overtreatment. Some estimates are that as many as 7 out of 8 women given DEX have healthy fetuses. New methods that enable sex determination earlier in gestation will help to reduce this overtreatment, but these methods may not be widely used and this still doesn’t address a larger problem: we have very little information about the long term safety of DEX on the fetus and mother.
DEX, which has been used for years in adults and has not been approved for use in pregnant women, has a bunch of nasty side effects for pregnant women. Most of these, it is believed, disappear after discontinuation. A recent article, however, reviews worrying evidence from animal and human studies that suggests possible effects on cognition (such as working memory) as well as future health of the child (e.g., type II diabetes and high blood pressure). Based on the evidence, the authors conclude there is an "urgent need for in-depth studies of long term outcome of prenatal treatment of CAH regarding both maternal side effects and possible negative metabolic as well as cognitive and behavioral effects in the growing fetus and the child in her development into adulthood."
