Hi Aimee,

There are a couple of cites I’ve seen that talks about the "crossing the placenta" issue, with the different glucocorticoids.  Here are two.  I don’t think it is merely an issue of dexamethasone being more potent than hydrocortisone, though I assumed, as anonymous did, that that was also a factor. 

From what I gather, the ability of dex to cross the placenta has something to do with it having no salt-retaining properties, while hydrocortisone does.  It is what is alluded to in the first article, when they mention the enzyme 11ß-hydroxysteroid dehydrogenase

The second article is the one that specifically talks about those adults taking dexamethasone---in this case, a woman with CAH, trying to conceive---being switched to a different glucocorticoid during pregnancy, in order to avoid potential side effects on the baby.  It sounds like the baby’s father was probably not a carrier, in this case, and that the parents were not concerned with having a child with CAH and the issue of reducing potential virilization.

 

Endocrine Reviews 21 (3): 245-291
Copyright © 2000 by The Endocrine Society

Congenital Adrenal Hyperplasia due to 21-Hydroxylase Deficiency¹

Perrin C. White and Phyllis W. Speiser

Division of Pediatric Endocrinology (P.C.W.), University of Texas Southwestern Medical Center, Dallas, Texas 75390-9063; and Division of Pediatric Endocrinology (P.W.S.), North Shore University Hospital and New York University School of Medicine, Manhasset, New York 11030

G. Prenatal therapy

1. Overview. In pregnancies at risk for a child affected with virilizing adrenal hyperplasia, suppression of fetal adrenal androgen production and decreased genital ambiguity in females have been achieved by administering dexamethasone to the mother (303, 304, 305, 306, 307, 308, 309, 310, 311). As compared with hydrocortisone, dexamethasone has no salt retaining activity and it is able to cross the placenta because it is not metabolized significantly by placental 11ß-hydroxysteroid dehydrogenase (269)....

 

1: Ned Tijdschr Geneeskd 2002 Feb 9;146(6):268-70

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[Article in Dutch]

van den Akker ES, Stikkelbroeck MM, Menheere PP, Roumen FJ, Otten BJ.

Atrium Medisch Centrum, afd. Verloskunde en Gynaecologie, Postbus 4446, 6401 CX Heerlen. evdakker@scarlet.nl

In an 18-year-old woman non-classic 21-hydroxylase deficiency was diagnosed and dexamethasone treatment was instituted. Ten years later, she became pregnant for the first time; at 37 weeks unexpected intrauterine foetal death was found to have occurred. A second pregnancy ended with a spontaneous abortion following a 12-week period of amenorrhoea. At the third pregnancy, the medication was replaced with hydrocortisone as it was suspected that the use of dexamethasone may have played a role in the intrauterine foetal death and the spontaneous abortion. The patient gave birth to a healthy, but dysmature, daughter. Female patients with non-classic congenital adrenal hyperplasia present with signs of androgen excess. Treatment with glucocorticoids reduces the symptoms and restores the menstrual cycle and fertility. Preconceptional advice by a clinical geneticist is recommended, because of the risk of an affected child. If there is no risk of having a child with congenital adrenal hyperplasia, hydrocortisone or prednisone is the treatment of choice during pregnancy as neither cross the placenta.

PMID: 11865658 [PubMed - in process]