Effects of repeated administration of cocaine to the fetal sheep in the last days of pregnancy

Abstract

There are no reports on the direct effects of repeated cocaine administration to the fetus in late pregnancy. The aim of our study was therefore to examine the effects of repeated fetal exposure to cocaine on fetal development. Ten fetal sheep were instrumented at 123 +/- 1 days' gestation. Five fetuses received a single daily intravenous injection of cocaine (2 mg/kg) commencing at 130 to 131 days of gestation until delivery at 132 to 144 days of gestation; those fetuses were compared with fetuses that did not receive cocaine (n = 5). Basal fetal arterial blood gas values, blood pressure, heart rate, and nuchal and diaphragmatic activities did not change in the days preceding labor. Fetal arterial PO2 fell after cocaine administration, but this was significant only on the first day. Cocaine induced consistent significant alterations in fetal pH and PCO2, blood pressure, and heart rate. During labor cocaine stimulated diaphragmatic and nuchal muscle activity when compared with the other days. There was no increase in diaphragmatic and nuchal muscle activity in the controls. Our studies indicate that in fetal sheep the cardiovascular and blood gas response to cocaine in late pregnancy is not altered by repeated exposure to cocaine and that cocaine stimulates fetal breathing during labor.