Endocrinology of parturition

Published on December 1, 2007 Reviewed on December 4, 2019   44 min

A selection of talks on Gynaecology & Obstetrics

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My name is Errol Norwitz. I am associate professor of obstetrics and gynecology at Yale University School of Medicine. Co-director of the division of Maternal Fetal Medicine and Director of the Maternal Fetal Medicine Fellowship Program in the Department of Obstetrics, Gynecology and Reproductive Sciences at Yale, New Haven Medical Center. The topic for our discussion today is the endocrinology of parturition.
Objectives over the next 40 to 50 minutes are to understand in detail the molecular and cellular mechanisms responsible for the onset of labor at term. To appreciate how and why these mechanisms occasionally fail, leading to pre-term birth or post-term pregnancy. And to discuss the rationale behind interventions designed to prevent and/or treat abnormalities of labor.
Labor is the physiological process by which the products of conception are passed from the uterus to the outside world, and is common to all viviparous species labor even in this day and age remains a clinical diagnosis characterised by regular painful uterine contractions increasing in frequency and intensity associated with progressive cervical effacement and dilatation leading ultimately to the expulsion of the products of conception in normal labor there appears to be a time dependent relationship between these factors. The biochemical connective tissue changes in the cervix usually precedes uterine contractions and cervical dilatation, which in turn occurs before spontaneous rupture of the fetal membranes. Similarly, pro-contractile biochemical changes in the uterus precede active and effective uterine contractions. Cervical dilatation in the absence of uterine contractions is seen most commonly in the second trimester and is suggestive of cervical insufficiency or cervical incompetence. Similarly, the presence of uterine contractions in the absence of cervical change does not meet criteria for the diagnosis of labor and should be referred to as preterm contractions. Of note, a diagnosis of labor can be made in nulliparous patient in the setting of regular painful uterine contractions if the initial cervical examination is greater than or equal to 80% effacement or greater than or equal to two centimeters dilatation.