Risk factors for spontaneous preterm delivery after arrested episode of preterm labor

Introduction: We aimed to identify specific risk factors for spontaneous preterm delivery (PTD) among women with arrested preterm labor (PTL).

Method: A retrospective study of women admitted due to imminent PTL and intact membranes, which did not progress to PTD within 24?h from admission. Eligibility was limited to singleton gestations at 24?+?0/7–33?+?6/7 weeks of gestations with no known chromosomal or structural anomalies. All women were treated with corticosteroids and tocolysis. Comparison was made between those who delivered at <37?+?0/7 weeks of gestation (study group) to women who delivered at ≥37?+?0/7 weeks of gestation (controls).

Results: Overall, 301 women were recruited, of which 85 (28.2%) delivered before 37?+?0/7 weeks and 216 (71.8%) delivered at term. Advanced cervical dilatation was found to be an independent risk factor for PTD [for women with no past PTD: adjusted odds ratio (aOR) 1.66, 95% CI: 1.06–2.61 for each 1?cm dilatation; for women with past PTD: aOR 2.81, 95% CI: 1.02–7.73 for each 1?cm dilatation]. Among women without past PTD, additional independent risk factors for PTD were earlier gestational week at admission (OR: 1.20, 95% CI: 1.09–1.32 for each earlier week) and short cervical length (OR: 1.04, 95% CI: 1.01–1.08 for each decrease of 1?mm in cervical length).

Conclusion: Advanced cervical dilatation, earlier gestational age at the episode of arrested PTL, and short cervical length are specific risk factors for PTD in women with arrested PTL. These findings may assist in counseling women and direct further investigation.     

Late preterm gestation: physiology of labor and implications for delivery

The late preterm infant represents a significant portion of preterm deliveries. Historically, this cohort has been referred to as near-term, which may not address adequately the increased perinatal morbidity these neonates experience. The changing demographics of pregnant women also are increasing the number of inductions in this gestational age group. More women with chronic hypertension, diabetes, and other chronic medical problems are getting pregnant, and often these pregnancies may require induction during this gestational age. The increasing numbers of multi-fetal gestations also have an average gestational age at delivery in this range of 34 to 36.6 weeks. Preeclampsia is another factor that can lead to delivery and induction during this gestational age. This article discusses some of the physiologic causes behind late preterm deliveries.     

The preterm labor index and fetal fibronectin for prediction of preterm delivery with intact membranes

OBJECTIVE: To compare the preterm labor index with the biochemical marker fetal fibronectin in predicting preterm delivery. METHODS: In 185 women with preterm labor and intact membranes, the preterm labor index was determined based on clinical findings of uterine contractions, bleeding, and cervical dilatation. An immunosorbent assay was used to measure oncofetal fibronectin. RESULTS: A significant negative correlation was noted between the preterm labor index and the interval from hospitalization to delivery. Based on a receiver operating characteristic curve, a preterm labor index 4 or higher was defined as positive. Rates of preterm delivery overall and of delivery within 1 week in the preterm labor index-negative group were 55.2% and 13.8%, respectively. Those in the preterm labor index-positive group were significantly higher (88.4% and 56.5%). With respect to predicting when a delivery would occur during the first week of hospitalization, the preterm labor index and fetal fibronectin did not differ in sensitivity (77.7% and 73.8%, respectively), specificity (79.5% and 74.2%), positive predictive value (66.7% and 60.8%), or negative predictive value (84.5% and 83.9%). However, within the preterm labor index-negative group, the rates of preterm delivery (68.4%), delivery within 1 week (28.9%), and neonatal treatment in an intensive care unit (36.8%) were significantly higher in fetal fibronectin-positive than in fibronectin-negative cases (46.2%, 9.0%, and 10.3%, respectively). CONCLUSION: The preterm labor index was similar to the fetal fibronectin assay in its ability to predict preterm delivery.     

Circadian incidence of labor onset hour in preterm birth and chorioamnionitis

Normal labor begins most frequently between midnight and 2 AM, presumably because of an unidentified circadian labor-activating mechanism. We used records of the Collaborative Perinatal Project to determine whether such a circadian mechanism is present with intrauterine growth retardation (IUGR) or preterm birth, and whether chorioamnionitis is associated with alternative patterns. In the absence of chorioamnionitis, both preterm births and term births with IUGR demonstrated nocturnal labor onset distributions like those of control term deliveries, which had a peak incidence at 1:45 AM and an amplitude of 35%. With chorioamnionitis, in contrast, there was a different circadian distribution of term labor onset hour, with a peak at 7:45 PM and a 32% amplitude. A similar trend was found among preterm births. These data suggest the presence of the normal nocturnal labor-activating mechanism in both growth-retarded term deliveries and a defined subset of preterm deliveries. Chorioamnionitis appears to be associated with a prominent, unidentified alternative labor-activating mechanism that is maximal in the evening.     

Presentation to delivery interval in women with early preterm delivery presenting with preterm labor: the effect of gestational age

Background: To evaluate the association between gestational age at presentation and interval to delivery in women with early spontaneous preterm delivery (PTD).

Methods: A retrospective cohort study of women who presented with threatened preterm labor (tPTL) and intact membranes and had a spontaneous PTD <34 weeks in a university-affiliated hospital (2009–2015). The interval from presentation to delivery was compared between different gestational age subgroups.

Results: Of 67 550 deliveries during the study period, 252 met inclusion criteria. This cohort was divided to three gestational age subgroups at presentation: 24–28^6/7 weeks (n?=?83), 29–31^6/7 weeks (n?=?61) and 32–33^6/7 weeks (n?=?108). Median time from presentation to delivery was 24.5?h. An inverse relation was observed between gestational age at presentation and admission–delivery interval (group A: 74.7?h, group B: 21.0?h, group C: 14.0?h, p?Conclusion: Gestational age at presentation is inversely related to admission–delivery interval in women with tPTL and intact membranes.     

Preterm delivery in patients admitted with preterm labor: a prediction study

OBJECTIVE: To develop a model for prediction of preterm delivery in patients treated with parenteral tocolysis using combinations of maternal demographic and clinical factors. METHODS: We performed a retrospective cohort study using a perinatal database to identify women admitted with preterm labor and treated with parenteral tocolysis from 1980 to 1994. We developed an explanatory model using multiple logistic regression to determine the effect of four variables (prior preterm delivery, substance abuse, maternal complications and third-trimester care) on the likelihood of preterm delivery. For the prediction model, we initially included these four variables and then removed them in a stepwise fashion to determine the combination of the variables that offered the greatest model sensitivity and specificity. RESULTS: A total of 900 women were identified for the study and 247 (27%) had a preterm delivery. In the explanatory model, prior preterm delivery (OR 2.4; 95% CI 1.5-3.6), substance abuse (OR 2.2; 95% CI 1.2-5.1), initiation of care in the third trimester (OR 2.0; 95% CI 1.3-2.8) and medical complications of pregnancy (OR 1.8; 95% CI 1.2-2.6) increased the likelihood of preterm delivery. For the prediction tool, a three-variable model (prior preterm delivery, substance abuse and initiation of care in the third trimester) had high specificity (98%) and modest negative predictive value (73%). CONCLUSIONS: A simple three-variable model can correctly identify 98% of women with preterm labor treated with parenteral tocolysis who will not deliver preterm. Patients with no prior history of preterm delivery, no substance abuse and initiation of prenatal care before the third trimester have a 73% probability of not delivering preterm.     

Preterm delivery in patients admitted with preterm labor: a prediction study

Objective : To develop a model for prediction of preterm delivery in patients treated with parenteral tocolysis using combinations of maternal demographic and clinical factors. Methods : We performed a retrospective cohort study using a perinatal database to identify women admitted with preterm labor and treated with parenteral tocolysis from 1980 to 1994. We developed an explanatory model using multiple logistic regression to determine the effect of four variables (prior preterm delivery, substance abuse, maternal complications and third-trimester care) on the likelihood of preterm delivery. For the prediction model, we initially included these four variables and then removed them in a stepwise fashion to determine the combination of the variables that offered the greatest model sensitivity and specificity. Results : A total of 900 women were identified for the study and 247 (27%) had a preterm delivery. In the explanatory model, prior preterm delivery (OR 2.4; 95% CI 1.5-3.6), substance abuse (OR 2.2; 95% CI 1.2-5.1), initiation of care in the third trimester (OR 2.0; 95% CI 1.3-2.8) and medical complications of pregnancy (OR 1.8; 95% CI 1.2-2.6) increased the likelihood of preterm delivery. For the prediction tool, a three-variable model (prior preterm delivery, substance abuse and initiation of care in the third trimester) had high specificity (98%) and modest negative predictive value (73%). Conclusions : A simple three-variable model can correctly identify 98% of women with preterm labor treated with parenteral tocolysis who will not deliver preterm. Patients with no prior history of preterm delivery, no substance abuse and initiation of prenatal care before the third trimester have a 73% probability of not delivering preterm.     

Neonatal outcome after indomethacin treatment for preterm labor

Forty-six infants exposed to indomethacin in utero for treatment for preterm labor were compared with infants from two control groups. In one control group the next consecutive patient treated with a tocolytic agent was used, and the other control group was formed by picking the next consecutive patient matched by gestational age who did not receive any tocolytic agent. There was no significant difference in Apgar scores, birth weight, or gestational age in the three groups. The incidence of neonatal complications including hypocalcemia, hypoglycemia, respiratory distress syndrome, patient ductus arteriosus, sepsis, and neonatal mortality were not significantly different in the three groups. No cases of premature closure of the ductus arteriosus or persistent fetal circulation were seen.     

Prevention and not merely prediction of preterm labor and delivery

Different methods have been proposed to screen for preterm labor and delivery; most of these aim to predict the risk that preterm delivery is going to take place. However, interesting though this knowledge might be, knowing the future is of no use when no changes can be made. Recent publications have suggested new and exciting modalities to actually diminish the frequency of preterm birth in patients selected by transvaginal cervical length measurement; these modalities include vaginal progesterone and vaginal pessaries. Although promising, many questions remain to be answered; not least about the long term outcome for both neonates and mothers, but also on the eventual introduction of such strategies to the general obstetric population. One of the main problems that urgently needs clarification is how we are going to offer this best of medicine to those needing it most: deprived and socially isolated women who have the highest risk for preterm labor and delivery, probably not due to any congenital cervical problems, but to a combination of environmental, microbiological and social factors, including transgenerational poverty and deprivation.     

Neonatal outcome after preterm delivery for preeclampsia

Objective: Our purpose was to determine whether maternal preeclampsia per se has a beneficial effect on neonatal outcome after delivery before 35 weeks.Study design: A matched cohort study design was used. Two hundred twenty-three infants of strictly defined preeclampsia women were matched for gestational age, race, gender, and mode of delivery with infants of normotensive women with preterm labor and delivery. Pregnancies with multiple gestation, premature rupture of membranes, known fetal anomalies, diabetes, or maternal medical disease were excluded. Information was obtained by review of maternal and neonatal charts. Paired categoric and continuous data were compared by McNemar's test and the Wilcoxon signed-rank test, respectively.Results: There was no difference in the incidence of neonatal death (4.5% vs 4.5%, p = 0.82), respiratory distress syndrome (22.0% vs 22.0%, p = 0.88), grades 3 and 4 intraventricular hemorrhage (2.2% vs 2.2%, p = 0.72), grades 2 and 3 necrotizing enterocolitis (5.8% vs 4.0%, p = 0.48), and culture-proved sepsis (9.0% vs 9.0%, p = 0.85). Results were similar when analysis was limited to infants born at ≤ 32 weeks, infants born to mothers with severe preeclampsia, and infants with intrauterine growth restriction.Conclusion: Maternal preeclampsia per se does not have a beneficial effect on the postnatal course] of infants born at 24 to 35 weeks' gestation.     

Contemporary management and conduct of preterm labor and delivery: a review.

Current concepts in the conduct of preterm labor and management of delivery of the premature infant are reviewed. Pharmacologic modalities available for inhibiting preterm labor are discussed as well as the efficacy, indications and contraindications for these agents. An analysis of the role of corticosteroids in achieving fetal pulmonary maturity in the preterm infant is reviewed, and based on the existent literature the intrapartum management of the small fetus is outlined. The mode of delivery, vaginal or via cesarean section, for these infants is likewise discussed.     

Maternal plasma and amniotic fluid dehydroepiandrosterone-sulfate concentrations in preterm labor and delivery

The purpose of this study was to determine whether preterm parturition is associated with changes in maternal plasma and amniotic fluid dehydroepiandrosterone-sulfate concentrations. A cross sectional study was constructed according to the gestational age at admission and response to tocolysis. Group 1 consisted of women admitted with preterm labor and intact membranes between 28 and 31 weeks and 6 days gestational age (n=40). Group 2 included 40 patients with preterm labor between 32 and 36 weeks gestational age. Both groups were classified into two subgroups: preterm delivery within seven days of admission and term delivery. Commercially available immunoassay kits validated for amniotic fluid analysis of DHEA-S, were used to measure maternal plasma and amniotic fluid DHEA-S concentrations. Maternal plasma DHEA-S concentrations were significantly higher in women with preterm labor who delivered preterm than in those who delivered at term. (Group 1: median 800 ng/ml [range 100–1100] vs. median 200 ng/ml [70–800],P<0.001; Group 2: median 850 ng/ml [300–1700] vs. median 300 ng/ml [90–1100],P<0.001). In contrast, no significant differences were detected in amniotic fluid DHEA-S concentrations. Our data suggest that the rise in maternal plasma DHEA-S concentrations observed in patients with preterm labor may be related to the effects of stress during labor.     

Term induction of labor and risk of cesarean delivery by parity

Abstract

Objective: To evaluate the risk of cesarean delivery among both nulliparous and multiparous women undergoing a term induction of labor compared to women that present in spontaneous labor at term.

Methods: We performed a retrospective cohort study of term (≥37 weeks) singleton pregnancies between 2005 and 2010 comparing women that had an induction to those that presented in spontaneous labor. Multiparity was defined as a prior delivery after 20 weeks’ gestation. Chi-square was used to compare categorical variables. Multivariable logistic regression was used to control for confounders. Analyses were stratified by parity.

Results: 863 women were included in the analysis. There were 605 inductions (cesarean rate 23%) and 257 spontaneous labor (cesarean rate 7%), OR 3.4, 95% CI [2.1–5.4]. Stratified by parity, nulliparas undergoing induction had an increased cesarean rate compared to spontaneous labor (27% versus 11%, OR 3.13, 95% CI [1.76–5.57]) as did multiparas (13% versus 3%, OR 4.04, 95% CI [1.36–11.94]). This increased risk for cesarean after induction remained in both nulliparous and multiparous women even after controlling for confounders (aOR 2.90, 95% CI [1.60–5.25] and aOR 3.47, 95% CI [1.12–10.67], respectively). Neither starting cervical exam nor indication for induction altered this increased risk.

Conclusions: The increased risk of cesarean in women undergoing an induction is present regardless of parity and indication for induction. This should be taken into account when counseling women regarding risks of induction, regardless of parity. Future studies should focus on other clinical characteristics of induction that may mitigate this risk.     

Review: Eicosanoids in preterm labor and delivery: Potential roles of exosomes in eicosanoid functions

Preterm delivery is a major obstetric health problem contributing to poor neonatal outcome including low birth weight, respiratory distress syndrome, gastrointestinal, immunologic, central nervous system, hearing, and vision problems. Worldwide, approximately 15 million babies are born prematurely each year. The critical question which remains is how to identify women destined to deliver preterm from those who will achieve a term delivery. Prostaglandins, in all mammals, are important in the parturient process. Increased intrauterine prostaglandin production is associated with labor and in fact prostaglandin E₂ (PGE₂) or analogs are widely used clinically for cervical ripening and labor induction. Measurements of circulating eicosanoids have been problematic because of the rapid and major clearance by the lungs and then kidneys resulting in very low concentrations in plasma. Moreover, since eicosanoids are produced by all mammalian tissues, the sources of the measured eicosanoids are unknown. Our understanding of how cells communicate has undergone a paradigm shift with the recognition of the role of exosomes in intercellular signaling. Recent publications have identified enzymes and products of arachidonic acid metabolism (eicosanoids) within exosomes. This review will explore the potential roles of exosomes in eicosanoid functions that are critical in preterm labor and delivery.