Forty-eight uterine strips were excised from 24 New Zealand white rabbits and studied in vitro. Sixteen strips were examined when eight animals were 25 days pregnant, 24 strips when 12 animals were about 12 hours postpartum, and eight strips about 12 hours after four animals received a single dose of 5 mg. progesterone (P) at spontaneous delivery. When after repeated exposures to electric fields (60 cycles per second, alternating current, of optimum strength, four seconds' duration at intervals of 30 seconds) the approximately 0.5 Gm. strips developed approximately 40-50g wall tension (WT) in steady state, the field strength was reduced in graded steps from 12 v per 5 cm. to 10, 8, 6, 4 and 3 v per 5 cm. and WT recorded. By measuring the effect on WT of "decreasing electric field stimulation" (DEFS), myometrical excitably and threshold were characterized and quantitated. The technique is based on the relationship between the fraction of myometrial cells activated in the total cell population and WT. As the stimulus is decreased in graded steps from optimal to increasingly suboptimal, DEFS activates fewer and fewer cells reflected by the decrease in WT. Threshold is defined by the strength of the minimum electric field which provokes WT and subthreshold by the field strength which fails to excite. Thus fractional WT averages the excitability of cells in the tissue and thus DEFS characterizes this important parameter of uterine function and quantitates threshold under a variety of regulatory conditions. The comparative study of excised uteri in three different endocrine states showed that the regulatory conditions of normal pregnancy (P levels 9 ng. per milliliter) suppressed excitability and increased threshold (to 6 v per 5 cm.). Post partum (P levels 1 ng. per milliliter) excitability increased and threshold decreased (to 4 v per 5 cm.), unless P treatment prevented this characteristic change by suppressing excitability and increasing threshold (to 6 v per 5 cm.). Both regulatory agents, prostaglandin F2alpha (PGF2alpha) and its analogue ICI 81008, increased excitability and decreased threshold significantly in picogram per milliliter concentrations. However, this effect was observed only when the P levels were low. These compounds had little effect, even in manogram per milliliter concentrations, when the P levels were high. The studies also revealed a close relationship between threshold and spontaneous uterine activity. Low threshold promoted while high threshold suppressed spontaneous activity. In similar concentrations the oxytocic actions of PGF2alpha and ICI 81008 were similar but the effect of ICI 81008 was prolonged through strong binding at myometrical sites.
PMID 943144 943144 DOI 10.1016/0002-9378(76)90095-8 10.1016/0002-9378(76)90095-8
Cite this article
Csapo, A. I. (1976). Effects of progesterone, prostaglandin F2alpha and its analogue ICI 81008 on the excitability and threshold of the uterus. American journal of obstetrics and gynecology, 124(4), 367-378. https://doi.org/10.1016/0002-9378(76)90095-8
Csapo AI. Effects of progesterone, prostaglandin F2alpha and its analogue ICI 81008 on the excitability and threshold of the uterus. Am J Obstet Gynecol. 1976;124(4):367-378. doi:10.1016/0002-9378(76)90095-8
Csapo, A. I. "Effects of progesterone, prostaglandin F2alpha and its analogue ICI 81008 on the excitability and threshold of the uterus." American journal of obstetrics and gynecology, vol. 124, no. 4, 1976, pp. 367-378.
Intrauterine pressure was monitored in vivo in oestrogen-treated ovariectomized ewes before, during and after treatment with progesterone (50 mg s.c./day for 3 days). Progesterone reversibly reduced the frequency and amplitude of myometrial activity and abolished uterine reactivity to oxytocin (i.v.) and PGF-2alpha (intrauterine infusion). The rate of rise of intrauterine pressure during active pressure cycles was significantly reduced. These results confirm that the action of progesterone on the ovine myometrium is comparable to the classic progesterone 'block'. The intrauterine infusion of PGF-2alpha (10 microgram/min), which elicited a marked mechanical response in the control animals, failed to stimulate the progesterone-'blocked' uterus, suggesting that the inhibition produced by progesterone is due to a direct action of the hormone on the uterine muscle and not to an indirect mechanism operating through endometrial prostaglandin output.
PROSTAGLANDINS (PGs) are being used increasingly as abortifacients although their precise mechanism of action is uncertain. One of the compounds frequently used is PGF2α, which has been shown to stimulate the myometrium in vitro1 and in vivo2. Whether or not the direct action of this agent on the uterine muscle alone is responsible for the interruption of pregnancy is not clear, but the long interval between infusion and abortion3 suggests that other mechanisms might be involved; for example, a luteolytic effect4–6. The prompt increase in uterine activity after treatment with prostaglandin, however, argues that the direct effect plays some part in the abortifacient action. Little is known of the influence of other myometrial regulatory agents such as the ovarian steroids on the uterine response to PGs. Accordingly we examined the influence of progesterone on myometrial responses to prostaglandin F2α in the rabbit, a species in which progesterone is known to have a blocking action on the uterine muscle7.
EndometriosisAMH and Ovarian ReserveSurgical Staging and TypologyAnti-Müllerian Hormone
Endometriosis is a chronic, gynecologic condition in which tissue similar to the lining of the uterus implants throughout the body. Women with endometriosis have a higher prevalence of infertility and a greater risk of early natural menopause compared to those without endometriosis. This study aimed to evaluate preoperative serum AMH levels among women with and without incident endometriosis and to assess whether levels differ by surgical staging and typology. The ENDO (Endometriosis: Natural History, Diagnosis, and Outcomes) study was conducted between 2007 and 2009. The ENDO study consisted of an operative and population cohort (n=600). Only those in the ENDO operative cohort from the Utah site were used for this analysis, and included women aged 18 to 44 years who were scheduled for gynecologic surgery, irrespective of clinical indication (n=476). AMH levels were measured from stored serum collected before surgery using a quantitative enzyme-linked immunosorbent assay. After excluding participants with missing outcome data (n=51), unilateral oophorectomy (n=8), or those within the population cohort (n=69), 348 participants remained for the analysis. Surgically confirmed endometriosis diagnosis, staging (American Society for Reproductive Medicine I-IV), and typology (superficial, deep, ovarian) were ascertained by the operative report. Outliers for AMH (>14.0 ng/mL) were excluded from the analyses and AMH values were log-transformed. Multivariable linear regression models adjusted for age (squared and continuous), body mass index, serum cotinine levels, and exogenous hormonal contraceptive use were conducted. Percentage differences in AMH were calculated as (exp[β]-1)×100, and 95% confidence intervals were reported. Compared with no endometriosis, incident endometriosis diagnosis was associated with lower AMH levels (-19.8%; 95% confidence interval, -37.0 to 1.0); however, this association was not statistically significant. Stage III to IV disease was associated with 40.1% lower AMH levels (95% confidence interval, -58.9 to -12.7). Ovarian endometriomas were most strongly associated with lower AMH levels (-54.3%; 95% confidence interval, -69.4 to -31.8), with a more pronounced association among those with infertility (-72.6%; 95% confidence interval, -85.4 to -48.5). Deep (-24.1%; 95% confidence interval, -48.2 to 11.0) and superficial (-15.5%; 95% confidence interval, -34.6 to 9.3) endometriosis also showed a trend toward lower AMH levels, but these findings were not statistically significant. Compared with a postoperative diagnosis of a normal pelvis, incident endometriosis was associated with 26.8% lower AMH levels (95% confidence interval, -44.6 to -3.4). Stage III to IV disease was associated with 47.8% lower AMH levels (95% confidence interval, -65.8 to -23.2), and all subtypes of endometriosis were statistically significantly associated with lower levels of AMH compared with a postoperative diagnosis of a normal pelvis (ovarian: -60.8%; 95% confidence interval, -74.4 to -39.9; -34.3%; 95% confidence interval, -56.2 to -1.4; -24.8%; 95% confidence interval, -43.9 to -0.8). Ovarian and moderate to severe (stage III-IV) endometriosis were associated with markedly lower AMH levels compared with no endometriosis. Compared with a postoperative diagnosis of a normal pelvis, incident endometriosis and moderate to severe stages (stage III-IV) were associated with statistically significantly lower AMH levels. Additionally, typology (deep, ovarian, or superficial) was associated with statistically significantly lower AMH levels. However, this association was likely driven by the presence of ovarian endometriomas across all subtypes. These findings are consistent with previous studies and demonstrate that endometriosis lesions themselves, independent of surgical intervention, influence AMH levels.
General OB/GYNUterine Closure TechniqueHysterotomy RepairCesarean Scar Complications
Bujold E et al., 2026·American Journal of Obstetrics and Gynecology
Normal uterine function depends on cyclical regeneration and the capacity to sustain pregnancy. A cesarean incision represents an injury to this remarkable organ. Although the uterus possesses exceptional healing potential, cesarean delivery increases the risk of secondary infertility, pelvic pain, uterine rupture, and abnormal placentation in subsequent pregnancies. The two most important determinants of successful hysterotomy healing after cesarean delivery are the location of the incision and the surgical technique used for closure. The anatomic site of entry-whether the corpus, lower uterine segment, or cervix-defines the tissue composition, vascularity, and contractility at the wound margins, which in turn influence how the scar remodels and withstands subsequent pregnancies. Surgical technique is also important. A robust body of experimental and clinical evidence demonstrates that restoring anatomic integrity by reapproximating uterine layers while excluding the endometrium produces stronger scars and reduces late complications. The rationale for excluding the endometrium is to prevent displacement of endometrial tissue into the myometrium and to avoid mucosal tearing against a foreign body (i.e. suture material), both of which predispose to defective healing. When the endometrium is incorporated, healing is often impaired, leading to niches or isthmoceles, adenomyosis, and endometriosis at the scar site. Over time, these defects have been recognized as contributors to abnormal bleeding, pelvic pain, infertility, uterine rupture, and placenta accreta spectrum disorders. Despite this evidence, single-layer closures that incorporate endometrium became widely adopted because of their speed and simplicity, while their long-term sequels were initially underappreciated. This has prompted renewed scrutiny of closure techniques, including comparisons of single-layer vs double-layer closure, locking vs nonlocking sutures, type of sutures, and the direction of suture. Collectively, the data show that optimal closure respects uterine anatomy, restores the natural alignment of tissues, and achieves hemostasis without compromising perfusion or strangulating tissues. Building on these principles, we herein describe a refined 3-layer closure. The first layer approximates decidua and junctional myometrium while excluding surface endometrium to prevent tissue entrapment and bacterial contamination. The second layer restores anatomic wall integrity by reapproximating the bulk of the myometrium, thereby reinforcing strength and distributing tension across the scar. The third layer reapproximates superficial myometrium and serosa, smoothing the uterine surface and reducing adhesions. This technique is not simply a return to traditional double-layer methods or an extension of single-layer practice, but rather a refinement that integrates lessons from visceral surgery and contemporary obstetric data. Its rationale is to restore anatomy, secure hemostasis without ischemia, and preserve long-term uterine function. While short-term safety appears comparable across closure methods, evidence increasingly indicates that long-term reproductive outcomes depend on how closure respects tissue biology. We argue that appropriate repair is more meticulous restoration of uterine anatomy should take precedence over operative speed. The enduring success of a hysterotomy repair depends on the surgical technique employed, as it directly affects women's future reproductive health.