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Control of parturition in man.
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The regulation of corticosteroids during late pregnancy and their role in parturition.
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Differential regulation of prostaglandin EP and FP receptors in pregnant sheep myometrium and endometrium during spontaneous term labor.
In the present study, we characterized the mRNA abundance of prostaglandin E(2) receptor subtypes (EP1 and EP3, which stimulate excitatory responses; EP2 and EP4, which stimulate inhibitory responses) and the FP receptor in pregnant sheep myometrium and endometrium in relation to parturition. Myometrial and endometrial poly(A) RNA was extracted from control ewes at 143-147 days gestational age (dGA, n = 6) and from ewes in spontaneous term labor at 145-147 dGA (n = 6), and was subjected to Northern blot analysis for FP, EP1, EP2, EP3, and EP4 mRNA. Myometrial EP3, EP4, and FP mRNA abundance increased during labor (P<0.05); EP2 mRNA did not change. EP1 mRNA was not detectable in the myometrium. Endometrial EP2 and EP4 mRNA remained unchanged during labor. EP3 mRNA was expressed at a very low level, and EP1 and FP mRNA were not detected in endometrium in any animals studied. In conclusion, there is differential expression in myometrium and endometrium of EP subtypes and FP receptor in relation to labor. Increases in EP3 and FP, together with increased prostaglandin production from intrauterine tissues, may lead to the switch in the myometrial contraction pattern that occurs during labor. These differences within and between myometrium and endometrium may result from different anatomical location, such as longitudinal or circular layers of myometrium, or vascular location.
The morphology of the human cervix.
The normal human cervix is a collagenous structure that undergoes a dramatic and probably unique metamorphosis in late pregnancy and labor, effacing and dilating without injury to permit the baby to pass through and, thereafter, returning in the course of a few weeks to its former state. In addition to collagen, the cervix contains small amounts of smooth muscle and elastic tissue, and it is unreasonable to presume they would be found here if they were not to have some function. Whatever this function may be, it appears to be secondary, and possibly supportive, to the role of the collagenous system. Coordinated uterine contractions are involved in the processes of effacement and dilatation of the cervix. However, they appear to be incidental rather than causative, being initiated by the same factors that are also responsible for the cervical changes. When these influences are withdrawn after delivery, remodeling processes begin and the cervix returns to its nonpregnant morphologic and functional state.
The ripening of the human uterine cervix in terms of connective tissue biochemistry.
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Physical characteristics of the cervix.
The cervix must remain closed during pregnancy to maintain the pregnancy yet open during parturition. It must perform at the right time and in the right sequence. The process that coordinates these activities is labor and it is an equal mixture of uterine contractions and cervical effacement/dilatation. Neither of these factors can be ignored if one is to understand parturition. Dilatation of the cervix depends upon the biochemical and physical processes that produce effacement. A better understanding of this active, ongoing process will enable one to manipulate them with new drugs that could produce effacement without uterine contractions. Conversely, the capacity to "stiffen" the cervix to ward off premature birth is another potential therapeutic approach that may be utilized. Research into the genesis and physical expression of the incompetent cervix is needed, as are studies of the cervix after forceable dilatation following a D and C. All of these possibilities and future advances are dependent upon our ability to quantitate the physical state of cervical tissue, both in situ and in vitro.
Methods of cervical priming.
It is now well recognized that a priming agent without untoward effects on mother or fetus is highly desirable when an indicated induction is required in the face of an unripe cervix. There appears to be a potential role for Laminaria, estrogens, relaxin, and various forms and routes of administration of prostaglandins because efficacy has been reported with all of these methods. With careful selection of patients and judicious fetal monitoring, there are multiple reasonable modes available, although an ideal priming agent has not yet emerged.
Initiation of spontaneous labor.
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Pharmacology of labor.
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Characteristics of oral prostaglandin E2-induced labor.
Oral prostaglandin E2 appears to play a dual role in human parturition. It induces normal uterine contractions and softens the cervix, thereby decreasing the resistance of the cervix to dilatation. Labor and delivery with oral PGE2 is achieved with less total uterine work when compared with spontaneous nonstimulated labor. This contention is supported by the fact that the rate of cervical dilatation in the active phase of labor is faster (2.73 cm/hr) than that reported by Hendricks et al. for ideal labor (2.12 cm/hour), yet uterine contractility is not increased. Analysis of the composite data of Friedman and Sachtleman in 1974 also shows a more rapid active phase dilatation in the PGE2-stimulated labors (3.3 cm/hour) as compared with spontaneous labor (2.98 cm/hour). Oral PGE2 offers a safe and efficacious alternative to oxytocin for the induction of labor in women. It appears to have a major advantage over oxytocin. The softening effect of PGE2 on the cervix would make this drug an ideal agent for use in patients with low Bishop scores who have medical indications for induction of labor. Regardless of route of administration, prostaglandin E2 is a potent uterine stimulant and must be used with the same precautions and safeguards as intravenous oxytocin.
Local application of prostaglandin E2 for cervical ripening or induction of term labor.
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Biomolecular processes in the initiation of parturition: decidual activation.
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Intrapartum management of vaginal birth after cesarean section.
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Complementary and alternative medicine in the labor and delivery suite.
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Failure of hypnotic relaxation in the treatment of postterm pregnancies.
An attempt to utilize hypnotic relaxation in the induction of labor with women with postterm pregnancies had no results. These negative findings contrast with previously shown success of hypnotic relaxation in inhibiting preterm labor.
Psychological characteristics of women with postterm pregnancies.
Sixty-one women with postterm pregnancies were compared with 72 term controls on scales of life-events, psychopathology, and attitudes towards pregnancy. Contrary to expectations, the postterm women scored lower in psychopathology than the controls. The slope of these scores declined from women with preterm, to those with term and postterm labor, paralleling the known slope for uterine reactivity to oxytocin. Results are interpreted as suggesting a low degree of autonomic and psychologic reactivity in the postterm women.
Comparison of two strategies for administering nevirapine to prevent perinatal HIV transmission in high-prevalence, resource-poor settings.
Universal nevirapine (NVP) therapy (provision of the drug without HIV testing) has been suggested as potentially superior to targeted NVP therapy (provision of the drug to seropositive patients identified through voluntary HIV counseling and testing [VCT]) for perinatal HIV prevention in low-resource, high-prevalence settings. The authors postulated that uptake (the proportion of women who accept the strategy when offered) may be higher for universal therapy, since it does not require a woman to learn her serostatus; they further postulated that adherence (the proportion of women who actually ingest the NVP tablet at labor onset) may be higher for targeted therapy, since knowledge of serostatus could motivate better adherence. Two clinics in Lusaka, Zambia were assigned to provide either the targeted or universal strategy. Halfway through the study period, the approach offered at each clinic was crossed over. Adherence was assessed by liquid chromatographic assay for NVP of cord blood. Regarding uptake, 1524 pregnant women were offered participation, and 1025 (67%) accepted. Of 694 women offered enrollment in the universal strategy, 496 (71%) accepted; of 830 women offered enrollment in the targeted strategy, 529 (64%) accepted (p <.01). Uptake was similar at both clinics for the universal strategy: 250 of 339 (74%) at clinic A and 246 of 355 (69%) at clinic B (p =.2), but differed significantly between clinics for the targeted strategy: 229 of 316 (72%) at clinic A and 300 of 514 (58%) at clinic B (RR, 1.51; 95% CI, 1.23, 1.86). Increased uptake correlated with having been offered the universal rather than the targeted strategy (AOR, 1.5; 95% CI, 1.1, 2.1), attendance at clinic A (AOR, 1.4; 95% CI, 1.01, 2.0), and maternal report of a prior fetal or infant death (AOR, 1.6; 95% CI, 1.1, 2.5). Regarding adherence, in the universal strategy, 40 of 103 women (39%) were nonadherent compared with 25 of 98 women (26%) in the targeted strategy (RR, 1.5; 95% CI, 1.004, 2.3). Failure to adhere correlated with participation in the universal strategy (AOR, 2.0; 95% CI, 1.04, 4.2) and illiteracy (AOR, 2.6; 95% CI, 1.2, 5.3). In high-prevalence settings with adequate VCT services, uptake of NVP using the universal or targeted approach appears comparable. However, the universal strategy may result in better uptake in clinics with less well-functioning VCT services (as with clinic B). Adherence to the single-dose NVP intervention was lower among women who did not learn their HIV status. Programs that seek to save the greatest possible number of infants from perinatal HIV acquisition should consider a combination approach, in which women who desire HIV testing can access NVP through a targeted strategy, and women who do not desire testing can access NVP through a universal strategy.