Preterm labor: emerging role of genital tract infections

Maternal and perinatal outcomes associated with a trial of labor after prior cesarean delivery

Landon MB et al., 2004 · New England Journal of Medicine

The proportion of women who attempt vaginal delivery after prior cesarean delivery has decreased largely because of concern about safety. The absolute and relative risks associated with a trial of labor in women with a history of cesarean delivery, as compared with elective repeated cesarean delivery without labor, are uncertain. We conducted a prospective four-year observational study of all women with a singleton gestation and a prior cesarean delivery at 19 academic medical centers. Maternal and perinatal outcomes were compared between women who underwent a trial of labor and women who had an elective repeated cesarean delivery without labor. Vaginal delivery was attempted by 17,898 women, and 15,801 women underwent elective repeated cesarean delivery without labor. Symptomatic uterine rupture occurred in 124 women who underwent a trial of labor (0.7 percent). Hypoxic-ischemic encephalopathy occurred in no infants whose mothers underwent elective repeated cesarean delivery and in 12 infants born at term whose mothers underwent a trial of labor (P<0.001). Seven of these cases of hypoxic-ischemic encephalopathy followed uterine rupture (absolute risk, 0.46 per 1000 women at term undergoing a trial of labor), including two neonatal deaths. The rate of endometritis was higher in women undergoing a trial of labor than in women undergoing repeated elective cesarean delivery (2.9 percent vs. 1.8 percent), as was the rate of blood transfusion (1.7 percent vs. 1.0 percent). The frequency of hysterectomy and of maternal death did not differ significantly between groups (0.2 percent vs. 0.3 percent, and 0.02 percent vs. 0.04 percent, respectively). A trial of labor after prior cesarean delivery is associated with a greater perinatal risk than is elective repeated cesarean delivery without labor, although absolute risks are low. This information is relevant for counseling women about their choices after a cesarean section. Copyright 2004 Massachusetts Medical Society.

Prevention of recurrent preterm delivery by 17 alpha-hydroxyprogesterone caproate

Meis PJ et al., 2003 · N Engl J Med

Women who have had a spontaneous preterm delivery are at greatly increased risk for preterm delivery in subsequent pregnancies. The results of several small trials have suggested that 17 alpha-hydroxyprogesterone caproate (17P) may reduce the risk of preterm delivery. We conducted a double-blind, placebo-controlled trial involving pregnant women with a documented history of spontaneous preterm delivery. Women were enrolled at 19 clinical centers at 16 to 20 weeks of gestation and randomly assigned by a central data center, in a 2:1 ratio, to receive either weekly injections of 250 mg of 17P or weekly injections of an inert oil placebo; injections were continued until delivery or to 36 weeks of gestation. The primary outcome was preterm delivery before 37 weeks of gestation. Analysis was performed according to the intention-to-treat principle. Base-line characteristics of the 310 women in the progesterone group and the 153 women in the placebo group were similar. Treatment with 17P significantly reduced the risk of delivery at less than 37 weeks of gestation (incidence, 36.3 percent in the progesterone group vs. 54.9 percent in the placebo group; relative risk, 0.66 [95 percent confidence interval, 0.54 to 0.81]), delivery at less than 35 weeks of gestation (incidence, 20.6 percent vs. 30.7 percent; relative risk, 0.67 [95 percent confidence interval, 0.48 to 0.93]), and delivery at less than 32 weeks of gestation (11.4 percent vs. 19.6 percent; relative risk, 0.58 [95 percent confidence interval, 0.37 to 0.91]). Infants of women treated with 17P had significantly lower rates of necrotizing enterocolitis, intraventricular hemorrhage, and need for supplemental oxygen. Weekly injections of 17P resulted in a substantial reduction in the rate of recurrent preterm delivery among women who were at particularly high risk for preterm delivery and reduced the likelihood of several complications in their infants.

Williams Obstetrics, 21st Edition

Cunningham FG et al., 2001

Prevention of premature birth

Goldenberg RL et al., 1998 · N Engl J Med

Preterm birth, which occurs in 11 percent of all pregnancies, is responsible for the majority of neonatal deaths and nearly one half of all cases of congenital neurologic disability, including cerebral palsy.1Although all births before 37 weeks of gestation are considered premature, births before 32 weeks' gestation (2 percent of all births) account for most neonatal deaths and disorders.2 State and national vital statistics indicate that the incidence of preterm birth has risen over the past 15 years (Figure 1), and it remains twice as high among black women as among white women.35 Preterm birth is commonly categorized . . .

Causes of preterm delivery

Gravett MG, 1984 · Semin Perinatol

Although major advances have been made in both obstetric care of the high-risk patient and in neonatal care, prematurity and its consequences remain the major contributor to perinatal mortality. The identification of maternal or obstetric risk factors associated with preterm delivery has enhanced our ability to provide special obstetric care to gravidas at increased risk. The selective management of patients at increased risk for preterm delivery may ultimately reduce the incidence of preterm births. Maternal genital infections are also associated with preterm delivery. Further research is needed to explore the pathogenesis of preterm delivery associated with genital infections, since infections may represent a potentially preventable cause of prematurity.

A review of premature birth and subclinical infection

Gibbs RS et al., 1992 · Am J Obstet Gynecol

Premature birth causes high rates of neonatal morbidity and mortality. There are multiple causes of preterm birth. This article reviews the evidence linking subclinical infection and premature birth. Although maternal genital tract colonization with specific organisms has been inconsistently associated with preterm birth and/or premature rupture of membranes, some infections have been consistently associated with preterm delivery. The association of histologic chorioamnionitis with prematurity is a consistent finding, but the mechanisms require further study. The relationship between histologic chorioamnionitis infection and the chorioamnionitis of prematurity requires additional research. A varying number of patients in "idiopathic" preterm labor have positive amniotic fluid cultures (0% to 30%), but it is not clear whether infection preceded labor or occurred as a result of labor. Evidence of subclinical infection as a cause of preterm labor is raised by finding elevated maternal serum C-reactive protein and abnormal amniotic fluid organic acid levels in some patients in preterm labor. Biochemical mechanisms for preterm labor in the setting of infection are suggested by both in vitro and in vivo studies of prostaglandins and their metabolites, endotoxin and cytokines. Some, but by no means all, antibiotic trials conducted to date have reported decreases in prematurity. These results support the hypothesis that premature birth results in part from infection caused by genital tract bacteria. In the next few years, research efforts must be prioritized to determine the role of infection and the appropriate prevention of this cause of prematurity.

The association of subclinical infection with preterm labor: the role of C-reactive protein

Potkul RK et al., 1985 · Am J Obstet Gynecol

The role of subclinical intrauterine infection in preterm labor was evaluated prospectively in 40 patients and appropriate control subjects. The 24 preterm labor patients (60%) with a negative C-reactive protein value responded to tocolysis 95.8% of the time, with a mean delay of delivery of 35.5 days and a mean gestational age of 36.9 weeks. The 16 patients (40%) with a positive C-reactive protein value responded to tocolysis only 37.5% of the time, with a mean delay of delivery of 14.4 days and a mean gestational age of 33.2 weeks. Pathologic evidence of chorioamnionitis was present in 32.9% of 310 preterm deliveries as compared to only 22.3% of 1631 term deliveries. The presence of subclinical infection must be considered in cases of preterm labor, especially among patients for whom tocolytic therapy is unsuccessful.

The role of placental insufficiency in spontaneous preterm birth: A literature review

Preston M et al., 2024 · European journal of obstetrics, gynecology, and reproductive biology · Free to read

Preterm Birth (delivery before 37 weeks of gestation) is the leading cause of childhood mortality and is also associated with significant morbidity both in the neonatal period and beyond. The aetiology of spontaneous preterm birth is unclear and likely multifactorial incorporating factors such as infection/inflammation and cervical injury. Placental insufficiency is emerging as an additional contributor to spontaneous preterm delivery; however, the mechanisms by which this occurs are not fully understood. Serum biomarkers and imaging techniques have been investigated as potential predictors of placental insufficiency, however none have yet been found to have a sufficient predictive value. This review examines the evidence for the role of the placenta in preterm birth, preterm prelabour rupture of the membranes and abruption as well as highlighting areas where further research is required.