Uterine electromyography characteristics for early diagnosis of mifepristone-induced preterm labor.
OBJECTIVE
Differentiating uterine contractions leading to preterm birth from ineffective uterine activity is difficult with current tools. Uterine electromyographic activity is recordable and consists of bursts (group of action potentials) characterized by characteristics that are different during pregnancy and labor. Our aim was to identify the chronology of the changes in uterine pressure and electromyographic characteristics during mifepristone-induced preterm labor in pregnant rats and to determine the earliest characteristic to change.


METHODS
On day 17 of gestation, intrauterine catheter and electromyography electrodes were implanted in the uterus. On day 18, rats were allocated for treatment with mifepristone or placebo. Intrauterine pressure and electromyography integral activities and electromyography mean were calculated before treatment and 6, 12, 18, 20, 22, and 24 hours after treatment. After mathematical transformation, burst analysis was performed by using power density spectrum energy, peak amplitude, and frequency.


RESULTS
As expected, delivery rate within 24 hours was higher in the mifepristone-treated group. Changes in electromyography integral activity and mean, power density spectrum energy, and intrauterine pressure integral activity occurred late during preterm labor, in a range of 2-4 hours before delivery. Electromyography peak frequency of the power density spectrum exhibited early changes, with a shift from low to high frequencies starting at 12 hours before delivery.


CONCLUSIONS
Electromyography peak frequency of the power density spectrum from individual bursts was the first characteristic to change after antiprogestin treatment, preceding any change in intrauterine pressure, making it a potentially useful marker for the early diagnosis of preterm labor.
Doret
Muriel
M
Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, Texas, USA. muriel.doret@chu-lyon.fr
Bukowski
Radek
R
Longo
Monica
M
Maul
Holger
H
Maner
William L
WL
Garfield
Robert E
RE
Saade
George R
GR
D000021:Abortifacient Agents, Steroidal; D000818:Animals; D004576:Electromyography; D005260:Female; D015735:Mifepristone; D007752:Obstetric Labor, Premature / Q000139:chemically induced / Q000175:diagnosis* / Q000503:physiopathology; D011247:Pregnancy; D011296:Prenatal Diagnosis; D051381:Rats; D017207:Rats, Sprague-Dawley; D014590:Uterine Contraction / Q000502:physiology*
D000021:Abortifacient Agents, Steroidal; D015735:Mifepristone