Current obstetric practice is to administer corticosteroids e.g. 2 doses of betamethasone or dexamethasone 12 or 24 h apart to promote fetal lung maturity in situations of threatened pre-term labour or where a decision is made to deliver the fetus prematurely for maternal or fetal reasons. The effects on the maternal immune system from a single course of corticosteroids are unclear but the evidence does not suggest that it results in sufficient immuno-suppression to cause maternal harm or exacerbation of infection.