Original ArticlesEffect of corticosteroids on brain growth in fetal sheep☆
Section snippets
Materials and methods
The effects of corticosteroids on organ weights were reported on animals in this study.16 Ewes were date-mated, then singleton pregnancy was confirmed in each case by ultrasound examination at 85 days’ gestation. All ewes were injected intramuscularly at 100 days’ gestation with 150 mg medroxyprogesterone acetate (Depo Provera; Upjohn, Rydalmere, Australia) to minimize risks of preterm births.
Pregnant ewes were ear-tagged at mating; then, a random number sequence was used to assign them to one
Results
Table 1 provides the data of maternal body weights, lamb birth weights, and gestational ages. As we reported, lamb weights were significantly reduced.16 There were no significant differences in baseline variables of maternal weight or gestational age. Table 2, Table 3 summarize brain growth data for the preterm and term animals in the control and single - and repeated-corticosteroid groups, respectively.
In the single corticosteroid group, after delivery at 125 days’ preterm gestation,
Discussion
Single and repeated doses of corticosteroids retarded brain growth in fetal sheep; repeated doses had more profound effects, particularly at term.
The clinical dose of betamethasone (Table 4) 17, 18, 19, 20, 21 results in a 75% occupancy of corticosteroid receptors in the lung; higher or more frequent doses have little additional benefit.5 The dosage for the current study was similar to that used clinically (Table 4) and conformed to previous studies in sheep in which fetal lung maturation was
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Supported by Women and Infants Research Foundation, Western Australia, Australian Government Overseas Postgraduate Research Scholarship (to WLH); and National Health and Medical Research Council (NH and MRC) of Australia Program Grant (952304) and Project Grant (980578).