MATERNAL THEOPHYLLINE ADMINISTRATION AND BREATHING MOVEMENTS IN LATE-GESTATION HUMAN FETUSES

Objective: To investigate the relation between maternal administration of theophylline and breathing movements during late gestation in huma n fetuses. Methods: After a 1-hour control period, 17 women with norma lly grown fetuses at 33-38 weeks' gestation were given 400 mg of susta ined-release theophylline orally. Maternal plasma theophylline and glu cose concentrations were measured every hour, and the incidence of fet al breathing movements and breathing rates were measured continuously during the next 8 hours. Results were compared with those of a similar control group that did not receive theophylline. Results: The materna l plasma theophylline concentration increased to detectable levels aft er I hour, reached therapeutic levels of 6.9 +/- 0.4 mu g/mL (standard error of the mean) after 6 hours, and thereafter averaged 8.3 +/- 0.3 mu g/mL, significantly higher than initial control values (P < .05). The mean glucose concentration was unchanged during the first 6 hours (79.2 +/- 1.1 mg/dL) and then decreased somewhat, averaging 75.8 +/- 1 .1 mg/dL in the 7-8-hour period. The incidence of fetal breathing incr eased 26.4 +/- 1.9% after 5 hours and remained elevated during the nex t 3 hours at levels significantly higher than in the initial control p eriod (P < .05) and higher than in the control group that did not rece ive theophylline. The mean hourly breathing rate averaged 40.9 +/- 1.3 breaths per minute during the control period and 40.2 +/- 1.2 breaths per minute after ingestion of theophylline, a nonsignificant change. Conclusions: Ingestion of theophylline by pregnant women in late gesta tion is associated with an increase in fetal breathing movements. Theo phylline has been used widely in the management of asthma in pregnancy , and the assessment of fetal breathing movements is used routinely fo r evaluation of fetal status. Therefore, account must be taken of chan ges in breathing movements caused by maternal theophylline administrat ion. Copyright (C) 1996 by The American College of Obstetricians and G ynecologists.