Nicotine-induced changes in the cerebral circulation in ovine fetuses

Pulsed Doppler ultrasound was used to investigate fetal and maternal ovine circulation in 16 ewes. Resistance index (R) was measured at the following sites: umbilical, fetal cerebral, and uterine arteries. Measurements were performed at days 80, 100, and 130 of gestation, day 0 being the day of mating. Normal ranges of the Doppler indices were delimited on the six control ewes. Five ewes were treated by intramuscular injection of 10 mg of nicotine 5 days per week and five others received placebo injections. No difference was found on the Doppler indices between the control group and the placebo group. The cerebral indices did not differ in the three groups at days 80 and 100 but were significantly higher at day 130 in the nicotine group in comparison to the two others (p less than 0.01). The umbilical indices were slightly elevated at days 80 and 130 in the nicotine group. No significant difference was found on the uterine indices at any of the three stages of gestation whatever the treatment. In the control and placebo groups the ewes delivered in the normal ranges of gestation length. In these groups 2 of 20 lambs (10%) died at birth. In the nicotine group 2 ewes delivered prematurely and 8 of the 13 lambs (62%) were stillborn. In conclusion, repeated nicotine injections induce vasoconstriction on the umbilical and cerebral arteries of the fetus at the end of the gestation and are associated with poor perinatal outcome.