The effect of nicotine on fetal breathing movements in conscious pregnant ewes.
Nicotine (0.14--0.25 mg/kg), injected intravenously or intraarterially into conscious pregnant ewes, caused a decrease in fetal PaO2 within 5 minutes, persisting for up to 30 minutes. There was a significant fall in the incidence of fetal breathing movements. These changes did not occur if the ewe was treated with an alpha-blocking agent (phentolamine) or if the nicotine was infused for 30 minutes at 0.27 to 0.85 mg/minute. Nicotine crossed the placenta; fetal concentrations equaled those in the ewe 5 minutes after the injection and remained at or above maternal levels for 1 hour. Nicotine given directly to the fetus (0.005--0.03 mg/kg estimated fetal weight) stimulated fetal breathing movements in a dose-related manner. We suggest that the maternal injection of nicotine results in a fall of uterine blood flow by a sympathomimetic action, leading to transient fetal hypoxemia and a reduction of fetal breathing movements and that a similar phenomenon may occur when a pregnant woman smokes cigarettes.
D000818:Animals; D001769:Blood; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000097:blood; D004305:Dose-Response Relationship, Drug; D005260:Female; D005318:Fetal Heart / Q000187:drug effects; D005333:Fetus / Q000187:drug effects* / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008431:Maternal-Fetal Exchange; D009068:Movement / Q000187:drug effects; D009538:Nicotine / Q000378:metabolism / Q000494:pharmacology*; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D010646:Phentolamine / Q000494:pharmacology; D011247:Pregnancy; D012119:Respiration / Q000187:drug effects*; D012756:Sheep
D002245:Carbon Dioxide; D009538:Nicotine; D010100:Oxygen; D010646:Phentolamine