Effects of oophorectomy, sympathetic denervation and sex steroids on uterine norepinephrine content and myometrial contractile response to norepinephrine in the guinea pig

Studies were performed in guinea pigs to elucidate alterations in endogenous uterine norepinephrine (NE) levels and changes in the contractile response to exogenous NE following local sympathetic denervation, oophorectomy, or treatment with sex steroids. Both in intact and oophorectomized animals the myometrial NE concentration was reduced after sex steroid treatment (0.5 microgram 17-beta-estradiol, or 0.1 microgram estradiol plus 2 mg progesterone, during 2 weeks), mainly as a result of increased uterine weight. After surgical removal of the hypogastric nerves and section of the suspensory ligaments, a similar response to sex steroids was seen if the animals had previously been oophorectomized. The myometrial contractile activity induced by exogenous NE was measured in vitro. The EC50 values (NE concentration giving 50% of the maximal response) showed a similar pattern of variations after hormonal treatment and oophorectomy as did the concentration of endogenous NE. Thus, exposure to the steroids leading to a reduction of neuronal NE also caused an increased sensitivity of the myometrial smooth musculature to exogenous NE, and in the various experimental groups the two parameters showed a close and significant relationship. The underlying mechanism may induce a denervation supersensitivity to NE induced by exposure to estrogen and progesterone

Modified Ritgen's maneuver for anal sphincter injury at delivery: a randomized controlled trial.

OBJECTIVE: To investigate whether Ritgen's maneuver decreases the risk of third- to fourth-degree perineal tears compared with simple perineal support. METHODS: A total of 1,623 nulliparous women in term labor, singleton pregnancy, and cephalic presentation were randomly assigned to Ritgen's maneuver or standard care. Ritgen's maneuver denotes extracting the fetal head, using one hand to pull the fetal chin from between the maternal anus and the coccyx, and the other on the fetal occiput to control speed of delivery. Ritgen's maneuver was performed during a uterine contraction, rather than, as originally recommended, between contractions. Our standard care entailed perineal support with one hand and control of the speed of crowning with the other, and use of Ritgen's maneuver only on specific indications. Women delivered by cesarean delivery (n=10) or instrumentally (n=142) were excluded, as well as 39 erroneously included women (parous or in preterm labor), six inaccurately assigned participants, one with missing data, and two participants who withdrew consent. For the remaining 1,423 women, the result was analyzed according to intention to treat. RESULTS: Ritgen's maneuver was performed in 554 (79.6%) of 696 women randomly assigned to this procedure and in 31 (4.3%) of 727 women randomly assigned to simple perineal support. The rate of third- to fourth-degree tears was 5.5% (n=38) in women assigned to Ritgen's maneuver and 4.4% (n=32) in those assigned to simple perineal support (relative risk 1.24; 95% confidence interval 0.78-1.96). CONCLUSION: Ritgen's maneuver does not decrease the risk of anal sphincter injury at delivery, at least not when performed during a contraction