Rats which were subjected to ovariectomy on day 18 of pregnancy and were treated with 17 beta-estradiol underwent delivery prematurely at 0900 +/- 1.9 hours on the morning of day 18. All animals had in plasma and uterine tissue a precipitate and highly significant progesterone withdrawal and a corresponding significant increase in prostaglandin F and prostaglandin F metabolite. Progesterone replacement therapy given to a second group of castrated animals prevented progesterone withdrawal and premature labor, because the hormonal profile in plasma and uterine tissue of these animals was identical with that of the intact pregnant vehicle controls. Electron microscopy of longitudinal and circular myometrial layers showed a precipitate and highly significant increase in the number, size, and area of gap junctions in the uteri of the group undergoing premature delivery. In the uteri of the progesterone-treated and vehicle control groups (both intact pregnant), gap junctions were conspicuously scarce. Thus the extensive regulatory imbalance, provoked by progesterone withdrawal, induced a significant increase in myometrial gap junctions. This structural change established contacts between individual myometrial cell which could transform the multibillion cell community of the uterus into a syncytium, to generate low-resistance pathways to the flow of current and thus promote the propagation of trains of electrical discharge in support of labor.
progesterone withdrawal premature labor rat model, myometrial gap junctions preterm delivery, Garfield Csapo uterine gap junctions pregnancy, progesterone replacement therapy prevention premature labor, prostaglandin F progesterone withdrawal preterm birth, ovariectomy estradiol premature delivery rat, uterine myometrial cell syncytium labor mechanism, gap junction formation electrical propagation uterus labor, progesterone withdrawal prostaglandin increase preterm mechanism, electron microscopy myometrial gap junctions pregnancy
PMID 7055167 7055167 DOI 10.1016/s0002-9378(16)32279-7 10.1016/s0002-9378(16)32279-7 Garfield et al. 1982, Garfield 1982
Cite this article
Garfield, R. E., Puri, C. P., & Csapo, A. I. (1982). Endocrine, structural, and functional changes in the uterus during premature labor. American journal of obstetrics and gynecology, 142(1), 21-27. https://doi.org/10.1016/s0002-9378(16)32279-7
Garfield RE, Puri CP, Csapo AI. Endocrine, structural, and functional changes in the uterus during premature labor. Am J Obstet Gynecol. 1982;142(1):21-27. doi:10.1016/s0002-9378(16)32279-7
Garfield, R. E., et al. "Endocrine, structural, and functional changes in the uterus during premature labor." American journal of obstetrics and gynecology, vol. 142, no. 1, 1982, pp. 21-27.
Progesterone support in pregnancy has been in use for over 60 years, having received its start in the 1940s. Its initial use was in patients who had habitual spontaneous abortion caused by luteal phase deficiency. More recently, the administration of progesterone later in pregnancy has been considered to be justified because of an observed decrease in circulating progesterone with the onset of labor, an association of premature labor with decreased progesterone concentrations, and the observation that progesterone has a tocolytic effect. A considerable boost to the use of progestational agents to reduce preterm delivery was received with the publication of two papers which showed a significant reduction in preterm delivery rates with the prophylactic administration of either progesterone or 17-a hydroxyprogesterone caproate. Recently it has been shown, however, that its use is not universal. This may be related to the significant late sequelae that were documented following the in utero exposure of the fetus to the potent steroid diethylstilbestrol (DES) and that this bad experience cast “a long shadow,” In spite of this, the use of progesterone, at least in early pregnancy, is widespread in the various artificial reproductive programs and is growing in its use as an agent to reduce prematurity. Over the years, there has been an extraordinary amount of confusion related to the use of progesterone support in pregnancy. The Food & Drug Administration (FDA) created some of this confusion. In various labeling of progesterone products by the FDA, one of the contraindications to the use of oral progesterone is listed as “known or suspected pregnancy.” And, yet, no such contraindication is identified for the use of progesterone gel. In fact, progesterone gel is indicated for progesterone supplementation or replacement as a part of an assisted reproductive technology (ART) treatment program for infertile women with a progesterone deficiency. To make this even more confusing, oral progesterone, while it was contraindicated in “known or suspected pregnancy,” its official labeling stated that it “should be used during pregnancy only if indicated (see contraindications).” Also, up until very recently, there was a dire “warning” contained in the labeling for USP progesterone injection in sesame seed oil regarding an increased possibility of birth defects. An analysis of the fetal safety of isomolecular progesterone (Pregn-4-ene-3,20-dione) administration during the course of 1,310 pregnancies over a 35-year period of time (1979-2014) was undertaken to address this confusion.
Whitley J et al., 2025·American journal of obstetrics and gynecology·
Open Access
Our objective was to determine if oxytocin discontinuation in the active phase of labor impacts the rate of cesarean delivery compared to continuation of oxytocin. This study was a systematic review and meta-analysis of randomized controlled trials. A research librarian performed a database search using a combination of standardized terms and keywords related to oxytocin discontinuation and stages of labor from database inception until February 2024. This protocol was registered in The International Prospective Register of Systematic Reviews (PROSPERO). Randomized controlled trials of pregnant patients who received oxytocin for induction or augmentation of labor, whose outcomes compared discontinuation and continuation of oxytocin in active labor, were included. We defined "active phase of labor" as defined by each trial. Nonrandomized trials, quasi-randomized trials, and animal models were excluded. The primary outcome was the rate of cesarean delivery. Secondary maternal outcomes included postpartum hemorrhage, total blood loss, and infectious outcomes. Secondary neonatal outcomes included Apgar score at 5 minutes <7, umbilical arterial pH <7.10, neonatal therapeutic hypothermia, neonatal intensive care unit admission, neonatal resuscitation at birth, and neonatal death. STUDY APPRAISAL The risk of bias in each study was assessed using the guidelines outlined in the Cochrane Handbook for Systematic Reviews of Interventions. Heterogeneity was measured using Higgins I2. Meta-analysis was performed in Review Manager 5.4.1 and StataSE 16 to determine summary treatment effects in terms of relative risk or mean difference with 95% confidence intervals. The adherence of each included trial to the trustworthiness criteria outlined by the OBGYN Editors' Integrity Group was assessed, and a leave-1-out analysis was performed to evaluate the effect of studies with concerns regarding trustworthiness. Fifteen randomized controlled trials, including 5734 patients, were ultimately included in the meta-analysis. The rate of cesarean delivery, reported in 13 studies, was lower with discontinuation of oxytocin in the active phase of labor (relative risk=0.80; 95% confidence interval, 0.66-0.97; 95% prediction interval, 0.38-1.22). Discontinuation of oxytocin was also associated with a lower risk of uterine tachysystole (relative risk=0.45; 95% confidence interval, 0.34-0.60; I2, 26%), and nonreassuring fetal heart rate tracing (relative risk=0.64; 95% confidence interval, 0.49-0.82; I2, 41%). Discontinuation of oxytocin increased the duration of active labor by an average of 30 minutes and second stage of labor by an average of 6 minutes. Although associated with an extension of labor by half an hour, discontinuation of oxytocin in the active phase of labor was associated with a 20% decreased risk of cesarean delivery and a lower risk of uterine tachysystole and nonreassuring fetal heart rate tracing. While the pooled analysis suggests a beneficial effect, this finding is dependent on the inclusion of studies with concerns regarding trustworthiness.
Coomarasamy A et al., 2020·Am J Obstet Gynecol·
Open Access
Progesterone is essential for the maintenance of pregnancy. Several small trials have suggested that progesterone supplementation may reduce the risk of miscarriage in women with recurrent or threatened miscarriage. Cochrane Reviews summarized the evidence and found that the trials were small with substantial methodologic weaknesses. Since then, the effects of first-trimester use of vaginal micronized progesterone have been evaluated in 2 large, high-quality, multicenter placebo-controlled trials, one targeting women with unexplained recurrent miscarriages (the PROMISE [PROgesterone in recurrent MIScarriagE] trial) and the other targeting women with early pregnancy bleeding (the PRISM [PRogesterone In Spontaneous Miscarriage] trial). The PROMISE trial studied 836 women from 45 hospitals in the United Kingdom and the Netherlands and found a 3% greater live birth rate with progesterone but with substantial statistical uncertainty. The PRISM trial studied 4153 women from 48 hospitals in the United Kingdom and found a 3% greater live birth rate with progesterone, but with a P value of .08. A key finding, first observed in the PROMISE trial, and then replicated in the PRISM trial, was that treatment with vaginal micronized progesterone 400 mg twice daily was associated with increasing live birth rates according to the number of previous miscarriages. Prespecified PRISM trial subgroup analysis in women with the dual risk factors of previous miscarriage(s) and current pregnancy bleeding fulfilled all 11 conditions for credible subgroup analysis. For the subgroup of women with a history of 1 or more miscarriage(s) and current pregnancy bleeding, the live birth rate was 75% (689/914) with progesterone vs 70% (619/886) with placebo (rate difference 5%; risk ratio, 1.09, 95% confidence interval, 1.03-1.15; P=.003). The benefit was greater for the subgroup of women with 3 or more previous miscarriages and current pregnancy bleeding; live birth rate was 72% (98/137) with progesterone vs 57% (85/148) with placebo (rate difference 15%; risk ratio, 1.28, 95% confidence interval, 1.08-1.51; P=.004). No short-term safety concerns were identified from the PROMISE and PRISM trials. Therefore, women with a history of miscarriage who present with bleeding in early pregnancy may benefit from the use of vaginal micronized progesterone 400 mg twice daily. Women and their care providers should use the findings for shared decision-making.
The purpose of this study was to evaluate the effect of prophylactic vaginal progesterone in decreasing preterm birth rate in a high-risk population. A randomized, double-blind, placebo-controlled study included 142 high-risk singleton pregnancies. Progesterone (100 mg) or placebo was administered daily by vaginal suppository and all patients underwent uterine contraction monitoring with an external tocodynamometer once a week for 60 minutes, between 24 and 34 weeks of gestation. Progesterone (n = 72) and placebo (n = 70) groups were compared for epidemiologic characteristics, uterine contraction frequency, and incidence of preterm birth. Data were compared by chi(2) analysis and Fisher exact test. The preterm birth rate was 21.1% (30/142). Differences in uterine activity were found between the progesterone and placebo groups (23.6% vs 54.3%, respectively; P <.05) and in preterm birth between progesterone and placebo (13.8% vs 28.5%, respectively; P <.05). More women were delivered before 34 weeks in the placebo group (18.5%) than in the progesterone group (2.7%) (P <.05). Prophylactic vaginal progesterone reduced the frequency of uterine contractions and the rate of preterm delivery in women at high risk for prematurity.