Fetal Growth Retardation, Particularly within Lymphoid Organs, following Repeated Maternal Injections of Betamethasone in Sheep*

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Abstract
Objective: To examine the effect of single or repeated injections of maternally administered corticosteroids on fetal growth in sheep.Methods: Forty‐six date‐mated singleton gestation ewes were allocated at random to one of 3 groups: a single, or repeated injections of betamethasone, or a control group which received saline. On days 125 (preterm) or 145 (term) caesarean section delivery was performed. After lambs were killed, measures of size and weight were recorded. Data were analysed using Fishers Exact test and the Student's t‐test.Results: Significant betamethasone dose dependent reductions in body and organ weights and biometry were found at preterm and term gestational ages (p < 0.05). There was little catch up growth in those in whom delivery was delayed until term. Thymus, spleen and liver were particularly targeted.Conclusion: Repeated injections of betamethasone to the pregnant ewe cause significant reductions in fetal growth with little evidence of catch up by term. The effect of repeated maternal injections of corticosteroids in human pregnancy will await the results of randomized controlled trials.