Maternal steroid enhancement of fetal rabbit gastrointestinal motility

The purpose of the present study was to determine the potential maturational effects of maternal dexamethasone administration on fetal upper gastrointestinal motility.

Nineteen pregnant rabbits were randomized into two groups (DEX and CONT) and studied on either day 24, 27 or 30 of pregnancy (term 31 days). The DEX group received intramuscular dexamethasone (DEX) 2 days before study and the controls received saline. Under ultrasound guidance, a needle was percutaneously inserted into each fetal stomach and fluorescein, labeled with color-coded microspheres, was injected. Two hours later, the length of fluorescein travel throughout the small intestine was measured. The percent motility was calculated by dividing the length of fluorescein travel by the total fetal small intestinal length x 100%.

All maternal and fetal rabbits survived. On day 24 the length of fluorescein travel and the percent motility of the DEX group were significantly longer than controls. There were no differences on either day 27 or 30. Fetal growth was significantly suppressed by a single course of DEX at all gestational ages.

Fetal rabbit gastrointestinal motility is significantly increased after prenatal steroids are given early in the last trimester (day 24 of a 31-day gestation). Although beneficial in end-organ maturation, the timing of prenatal steroid administration is crucial to minimize its potential detrimental effects on fetal somatic growth.