Objective: To determine whether prednisone exposure in utero is associated with an increased risk of adverse effects in the infant- including teratogenicity, prematurity and low birthweight.

Methods: Three groups of women were prospectively enrolled: (i) Women who contacted the Motherisk program (a teratogen information service) for information about the safety of steroid use and who took prednisone for at least two consecutive weeks during pregnancy, (ii) Women with recurrent fetal loss who took prednisone as part of a research project, and (iii) Women who contacted Motherisk for information about drugs not associated with adverse fetal effects. All subjects were contacted after expected date of delivery to collect details of pregnancy outcomes. Information was confirmed by contacting the relevant physicians. Repeated measures ANOVA was used to compare continuous data, and contingency test analysis was used for categorical data.

Results: 188 women were enrolled in each of groups (i) and(iii); 127 in group (ii). Baseline characteristics (age, smoking/alcohol ingestion) were similar in all 3 groups. Most of the women in group (i) suffered from collagen-vascular diseases. Steroid dosage was highest in group(ii), as was duration of therapy. There were no differences in the rates of birth defects between the three groups. The percentage of live births was lowest in group (ii), prematurity rates were also highest in that group. Birthweights were significantly lower in groups (i) and (ii) than in group(iii): 3114g vs 2632g vs 3429g (p<0.01). The incidence of SGA infants was highest in group (i): 7% vs 4.1% in group (ii) and 2.4% in the unexposed group(p=0.05)

Conclusions: In utero exposure to corticosteroids does not appear to be associated with an increased rate of birth defects.Increased rates of prematurity in women with recurrent fetal losses, and low birthweights in infants of women with collagen- vascular diseases are likely secondary to underlying disease, and not steroid exposure