Antenatal treatment of a mother bearing a fetus with congenital adrenal hyperplasia
- London Centre for Paediatric Endocrinology, Great Ormond Street Hospital for Children and The Middlesex Hospital, London, UK
- Professor Brook, The Middlesex Hospital, Mortimer Street, London W1N 8AA, UK email: c.brook{at}ucl.ac.uk
- Accepted 26 October 1999
The virilisation of a female fetus by overproduction of adrenal androgens secreted by an adrenal gland with 21-hydroxylase deficiency is well known. Although reconstructive genital surgery can greatly improve matters, the long term outlook for reproduction is extremely poor for many reasons, including anatomy.1 2 The idea of prenatal treatment of 21-hydroxylase deficiency by administering glucocorticoids to the mother to prevent virilisation was superficially extremely attractive.3 Where do we stand 15 years later?
Treatment protocol and rationale
The aim of treatment is to suppress the secretion of androgens from the adrenal gland of the affected female fetus because they will masculinise her external genitalia and probably, through conversion to oestrogen by aromatase, defeminise her brain and subsequent behaviour. In principle, the management protocol for a mother suspected of carrying a fetus affected with 21-hydroxylase deficiency, usually because she and her partner have had a previously affected child, is logical and straightforward.
Dexamethasone is started as soon as the pregnancy is confirmed and before virilisation can start. It is important to recognise that male sexual differentiation starts at about six weeks of gestation, and formation of the penis is complete at 14 weeks, so there is no time to lose.
It is necessary before conception to perform molecular studies on the proband and on both parents and also to confirm biochemically the heterozygote state of both parents to determine whether a molecular diagnosis will be possible. If it is, DNA can be isolated from a chorionic villous sample taken at between 10 and 12 weeks of gestation or from an amniotic fluid sample at 15–16 weeks. It should be possible to determine quickly whether the fetus has the same molecular defect as the proband and what is its karyotype.
In the one in eight eventuality that the mother is carrying an affected female …
