Uterine Electrical Activity Before and After Progesterone Treatment for Preterm Labor

This study will examine the effects of various formulations of progesterone on uterine electromyographic (EMG) activity in pregnant patients in premature labor to determine if progesterone will suppress uterine electrical activity and which formulation may be best for inhibition of uterine activity. Patients will be monitored prior to treatment and following treatment (every 2 to 4 hours) with one of three different formulations of progesterone for up to two days. Patients will continue to be observed until they deliver. Comparisons will be for uterine EMG activity from before treatment to that following treatments at 2, 4, 8, 12 24 and 48 hours and times of delivery after treatments (hours or days following treatments). Comparisons between mean values for EMG activity between the various treatments at the various times will also be made.

In this study the investigators will compare the effects of vaginal progesterone, intramuscular applied progesterone and topical progesterone on uterine electromyographic activity (EMG)in patients in preterm labor. Electrodes will be placed on the abdominal surface of pregnant patients in preterm labor and the EMG activity recorded for 30 minutes before and following treatments for up to 48 hours. In addition data on delivery times will be recorded when patients delivery vaginally or by Cesarian section. Eligibility criteria: Healthy patients without infection or rupture of membranes with gestational ages between 24 to 34 weeks. Outcome measures: Comparisons of uterine EMG activity (EMG amplitude, frequency, and specific information on EMG bursts) from measurements before treatment to following treatments with progesterone preparations at various times (at 2,4,8, 12,24 and to 48 hours following treatment) and delivery times of patients on various treatments (hours or days following treatments, average delivery times in patients treated by various formulations). Comparisons of mean values in uterine EMG activity (EMG amplitude, burst frequency and frequency of signals in a burst, power spectrum analysis of the bursts and peak power density spectrum of bursts) from before treatment to following treatments at 2 to 24 hours will be compared. Also the time of delivery following treatments will be obtained and the average time of delivery following the various treatments compared.

Eligibility Criteria:
Inclusion Criteria:

* Healthy patients in preterm labor between 24 to 34 weeks of gestation presenting to St. Joseph's Hospital and Medical Center.
* Preterm labor is defined as at least 6 contractions in 60 minutes with a cervix either dilated to 2 centimeters or effaced to 80% and a cervical length measured by ultrasound of less than 3 centimeters, and a positive fetal fibronectin.
* Maternal ages will be within 17 to 40 year-old range.

Exclusion Criteria:

* Patients with preterm premature rupture of membranes (PPROM) will be excluded from the study, due to possibility of ascending infection, as will those patients with suspected chorioamnionitis.
* Patients with medical conditions that contraindicate tocolysis, such as non-reassuring fetal heart tracings, will also be excluded.