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.     

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.     

Evaluation of risk factors can help to predict preterm delivery within 7 days in women hospitalized for threatened preterm labour

Objective: The ability to predict birth within 7 days of enrolment in women hospitalized for threatened preterm labour is essential for a proper decision to introduce corticosteroids for the treatment.

Method: The study included 622 women hospitalized due threatened preterm labour. Eighteen risk factors were analysed. The predictive value for accumulation of studied risk factors was assessed using receiver operating characteristic (ROC) curve analysis and dimension-based models of assessment methods: (i) forward stepwise selection (conditional), (ii) forward stepwise selection (Wald) and (iii) backward stepwise elimination (conditional).

Results: The accumulation of five and above risk factors gives specificity and positive predictive value (PPV) of diagnosis preterm delivery within 7 days of enrolment approaching 100% (99 and 98, respectively). The predictive value for studied risk factors enabled establishing the following order for risk factors significance: (i) cigarette smoking before pregnancy; (ii) low socioeconomic status; (iii) frequent contractions during pregnancy; (iv) bleeding during pregnancy; (v) urinary tract infections.

Conclusion: In women hospitalized for threatened preterm labour, the accumulation of five risk factors of preterm delivery predicts preterm delivery within 7 days of enrolment. That makes easier decision to introduce corticosteroids for the treatment.     

Adenomyosis and risk of preterm delivery

OBJECTIVE: To evaluate the risk of preterm delivery in patients with adenomyosis. DESIGN: A 1:2 nested case-control study. SETTING: Tertiary-care institution. POPULATION: A base cohort population of 2138 pregnant women who attended routine prenatal check-up between July 1999 and June 2005. METHODS: From this base cohort population, gravid women with singleton pregnancy who delivered prior to the completion of 37 weeks of gestation were identified and formed the study group. Singleton gravid women who had term delivery and who matched with age, body mass index, smoking, and status of previous preterm delivery were recruited concurrently and served as control group. Preterm delivery cases were further divided into spontaneous preterm delivery and preterm premature rupture of membranes (PPROM) cases. MAIN OUTCOME MEASURES: Risk analysis of preterm delivery between gravid women with and without adenomyosis. RESULTS: One-hundred and four preterm delivery case subjects and 208 control subjects were assessed. Overall, gravid women with adenomyosis were associated with significantly increased risk of preterm delivery (adjusted odds ratio 1.96, 95% CI 1.23-4.47, P=0.022). For subgroup analysis, gravid women with adenomyosis had an adjusted 1.84-fold risk of spontaneous preterm delivery (95% CI 1.32-4.31, P=0.012) and an adjusted 1.98-fold risk of PPROM (95% CI 1.39-3.15, P=0.017). CONCLUSIONS: Gravid women with adenomyosis were associated with increased risk of both spontaneous preterm delivery and PPROM. A common pathophysiological pathway may exist in these two disorders. Further in-depth biochemical and molecular studies are necessary to explore this phenomenon.     

The impact of inter-pregnancy interval on subsequent risk of preterm birth

Objective: The aim of the study was to assess optimal time to conceive after previous delivery associated with smallest risk of preterm birth.

Methods: We selected all women (n?=?2723) with their first and second singleton delivery between the years 2004 and 2012. Inter-pregnancy interval was defined as that between live birth and subsequent conception. We performed logistic regression analyses to assess the risk of preterm birth adjusted for maternal age and body mass index.

Results: Association between inter-pregnancy interval and the natural logarithm of the adjusted relative risk of preterm birth had a J-shaped curve with lowest risk at 15?months after last birth.

Conclusion: The optimal time to conceive after a previous delivery is 15?months, as longer or shorter interval are associated with increased risk of preterm birth. Women with short or long inter-pregnancy intervals were 1.6 times more likely to experience preterm birth.     

The preterm prediction study: A clinical risk assessment system

OBJECTIVE: Our aims were to develop a risk assessment system for the prediction of spontaneous preterm delivery using clinical information available at 23 to 24 weeks' gestation and to determine the predictive value of such a system. STUDY DESIGN: A total of 2929 women were evaluated between 23 and 24 weeks' gestation at 10 centers. Demographic factors, socioeconomic status, home and work environment, drug and alcohol use, and medical history were evaluated. Information regarding symptoms, cultures, and treatments in the current pregnancy were ascertained. Anthropomorphic and cervical examinations were performed. Univariate analysis and multivariate logistic regression were performed in a random selection, constituting 85% of the study population. The derived risk assessment system was applied to the remaining 15% of the population to evaluate its validity. RESULTS: A total of 10.4% of women were delivered of preterm infants. The multivariate models for spontaneous preterm delivery were highly associated with spontaneous preterm delivery (p < 0.0001). A low body mass index (<19.8) and increasing Bishop scores were significantly associated with spontaneous preterm delivery in nulliparous and multiparous women. Black race, poor social environment, and work during pregnancy were associated with increased risk for nulliparous women. Prior obstetric outcome overshadowed socioeconomic risk factors in multiparous women with a twofold increase in the odds of spontaneous preterm delivery for each prior spontaneous preterm delivery. Current pregnancy symptoms, including vaginal bleeding, symptomatic contractions within 2 weeks, and acute or chronic lung disease were variably associated with spontaneous preterm delivery in nulliparous and multiparous women. When the system was applied to the remainder of the population, women defined to be at high risk for spontaneous preterm delivery (≥20% risk) carried a 3.8-fold (nulliparous women) and 3.3-fold (multiparous women) higher risk of spontaneous preterm delivery than those predicted to be at low risk. However, the risk assessment system identified a minority of women who had spontaneous preterm deliveries. The sensitivities were 24.2% and 18.2% and positive predictive values were 28.6% and 33.3%, respectively, for nulliparous and multiparous women. CONCLUSIONS: Although it is possible to develop a graded risk assessment system that includes factors that are highly associated with spontaneous preterm delivery in nulliparous and multiparous women, such a system does not identify most women who subsequently have a spontaneous preterm delivery. This system has investigational value as the basis for evaluating new technologies designed to identify at-risk subpopulations. (Am J Obstet Gynecol 1996;174:1885-95.)     

Risk factors for very preterm delivery and delivery of very-small-for-gestational-age infants among HIV-exposed and HIV-unexposed infants in Botswana

Objective

To evaluate risk factors for very preterm delivery (VPTD) and very-small-for-gestational-age (VSGA) births in a country with a high HIV prevalence.

Methods

Obstetric records at 6 hospitals across Botswana were reviewed at delivery; VPTD was defined as birth before 32 weeks of pregnancy and VSGA as birth weight below the 3rd percentile for Botswana-specific norms.

Results

Of 16 219 live births born after 26 weeks of pregnancy, 701 (4.3%) were delivered very preterm and 607 (3.7%) were VSGA; 4347 (28.4%) were documented as HIV-exposed. In a multivariable analysis, HIV infection and hypertension during pregnancy were associated with a VPTD (adjusted odds ratio [AOR]: HIV 1.65, hypertension 1.75) and a VSGA birth (AOR: HIV infection 1.90, hypertension 3.44). Among HIV-infected women, the continuation of highly active antiretroviral therapy (HAART) from before conception was associated with a VSGA birth (AOR 1.75) but not with a VPTD (AOR 0.78). In a secondary analysis, HAART continuation was associated with hypertension during pregnancy (AOR 1.34).

Conclusion

Hypertension and HIV infection were risk factors for a VPTD and a VSGA birth. Continuation of HAART from before conception was associated with a VSGA birth but not with a VPTD.     

Placenta previa and the risk of preterm delivery

Objectives. We aimed to quantify the risk of preterm delivery and maternal and neonatal morbidities associated with placenta previa.

Study design. We conducted a retrospective cohort study of singleton births that occurred between 1976 and 2001, examining outcomes including preterm delivery and perinatal complications. Multivariate logistic regression was used to control for potential confounders. Kaplan–Meier survival curves were constructed to compare preterm delivery in pregnancies complicated by previa vs. no previa.

Results. Among the 38 540 women, 230 women had previas (0.6%). Compared to controls, pregnancies with previa were significantly associated with preterm delivery prior to 28 weeks (3.5% vs. 1.3%; p = 0.003), 32 weeks (11.7% vs. 2.5%; p < 0.001), and 34 weeks (16.1% vs. 3.0%; p < 0.001) of gestation. Patients with previa were more likely to be diagnosed with postpartum hemorrhage (59.7% vs. 17.3%; p < 0.001) and to receive a blood transfusion (11.8% vs. 1.1%; p < 0.001). Survival curves demonstrate the risk of preterm delivery at each week and showed an overall higher rate of preterm delivery for patients with a placenta previa.

Conclusions. Placenta previa is associated with maternal and neonatal complications, including preterm delivery and postpartum hemorrhage. These specific outcomes can be used to counsel women with previa.     

Adipokinins in pregnancies at risk of preterm delivery

Objective: To compare adipokinins between women experiencing preterm labor (PTL) and prior preterm deliveries (PTD).

Study design: In this prospective observational cohort, 110 women with a singleton <35 weeks at increased risk of PTD were studied. Serum leptin, adiponectin, and resistin were obtained at three times (23–34 weeks, 35–36 weeks, at delivery) and analyzed via enzyme-linked immunosorbent assay. The adipokinins were compared across time and between PTL (n?=?59) and prior PTD (n?=?51) groups using generalized estimated equation models.

Results: There were no differences in leptin, adiponectin, or resistin levels over the three times between the PTL and PTD groups. There was a trend toward higher leptin levels (p?=?0.06 unadjusted analysis, p?=?0.09 adjusted analysis) at 23–34 weeks. When stratified by body mass index (BMI), there were differences in leptin (p?p?=?0.77 for BMI?≥?30) and adiponectin (p?=?0.04 for BMI?p?=?0.09 for BMI?≥?30), but not in resistin over the three times between the PTL and prior PTD groups.

Conclusion: There were no significant differences in adipokinins in women with PTL and a prior PTD. The trends toward higher leptin levels at 23–34 weeks in women with PTL may represent a compensatory response and require further evaluation in the study of treatments for PTL.     

Short interpregnancy interval and risk of spontaneous preterm delivery

OBJECTIVES: Short interpregnancy intervals are related to increased prevalence of adverse perinatal outcomes. However, the reported association with preterm birth might be due to confounding by factors such as previous pregnancy outcomes, socioeconomic level or lifestyles. The objective of this study was to evaluate the effect of short interpregnancy interval on the occurrence of spontaneous preterm delivery. STUDY DESIGN: The prevalence of a short interpregnancy interval, defined as six or less months between a preceding delivery or abortion and the last menstrual period before index pregnancy, was compared between 263 spontaneous preterm (<37 weeks) and 299 term (37-42 weeks) consecutive births. Separate analyses were performed for early (<34 weeks) and late (34-36 weeks) preterm deliveries. Crude and adjusted odds ratios (ORs) and 95% confidence intervals (CI) were calculated using unconditional logistic regression. RESULTS: There was a significant association between short interpregnancy interval and spontaneous early preterm delivery, both crude (OR=3.9; 95% CI: 1.91-8.10) and adjusted for maternal age, school education, previous birth outcomes, antenatal care, smoking habits, body mass index and gestational weight gain (adj(OR)=3.6; 95% CI: 1.41-8.98). No significant effect on spontaneous late preterm delivery was found (crude(OR)=0.8; 95% CI: 0.32-1.83). CONCLUSIONS: This study showed that short interpregnancy intervals significantly increased the risk of early spontaneous preterm birth but no such effect was evident for late preterm deliveries.     

The management of preterm labour

This article explores the complexities of diagnosing and managing preterm labour and highlights the importance of tailoring labour and delivery care to the individual, based on gestation and neonatal prognosis. Available diagnostic criteria and interventions to optimize the preterm infant are discussed, and the limitations of evidence to inform current practice described. The benefit of national improvement drives in the quality and consistency of preterm labour care is introduced to encourage local education and clinical training to combat the harmful sequelae of preterm birth.     

The impact of fetal gender and ethnicity on the risk of spontaneous preterm delivery in women with symptoms of preterm labor

Objective: The objective of this study is to evaluate the relation among fetal gender, ethnicity, and preterm labor (PTL) and preterm delivery (PTD).

Methods: A secondary analysis was performed of a prospective cohort study including women with symptoms of PTL between 24 and 34 weeks. The proportion of women carrying a male or female fetus at the onset of PTL was calculated. Gestational age at delivery and risk of PTD of both fetal genders was compared and interaction of fetal gender and maternal ethnicity on the risk of PTD was evaluated.

Results: Of the 594 included women, 327 (55%) carried a male fetus. Median gestational age at delivery in women pregnant with a male fetus was 37 5/7 (IQR 34 4/7–39 1/7) weeks compared with 38 1/7 (IQR 36 0/7–39 5/7) weeks in women pregnant with a female fetus (p?=?0.032). The risk of PTD did not differ significantly. In Caucasians, we did find an increased risk of PTD before 37 weeks in women pregnant with a male fetus (OR 1.9 (95% CI 1.2–3.0)).

Conclusions: The majority of women with PTL are pregnant with a male fetus and these women deliver slightly earlier. Race seems to affect this disparity.     

Prenatal care and the prevention of preterm delivery

This paper reports the methods and results of an innovative program of prenatal care, designed to prevent preterm delivery in Clamart, France, during 1976-1981. Rates of preterm delivery among women who entered the prenatal care program early in pregnancy (and, thus, could derive full benefit of the program) were compared with those among two comparison groups: (1) women who entered the same program later in pregnancy; and (2) women who delivered in Paris. In the first comparison, women who entered the program early had significantly lower rates of preterm delivery than did women who entered later, even when stratified by various risk factors, and when high-risk women were eliminated altogether. In the second comparison, the early care group in Clamart did not exhibit the usual inverse relationship between socioeconomic status and rates of preterm delivery. The usual significant inverse relationship was found in the Clamart population as a whole, and in the Paris series.     

Diabetes mellitus and the risk of preterm birth with regard to the risk of spontaneous preterm birth

Introduction.?It is internationally agreed that diabetes mellitus (DM) is associated with increased maternal and fetal morbidity and long-term complications. To avoid these complications, it is often necessary to induce birth before term. The impact of DM on spontaneous preterm birth (spontaneous labor, preterm premature rupture of membranes and/or cervical incompetence resulting in delivery before the completion of 37 gestation weeks) is still unexplained. Preterm birth accounts for the most neonatal deaths and infant morbidities, and therefore it still remains one of the biggest challenges in obstetrics.

Objective.?Our study determined if there is an increasing tendency towards spontaneous preterm birth in mothers with gestational and preexisting DM.

Methods.?In this retrospective cohort study, 187 pregnant women with gestational DM and preexisting DM were compared to a randomized control group consisting of 192 normoglycemic women concerning gestational age and perinatal outcome. Data were collected by the Medical University of Vienna. Multiple pregnancies and women with severe maternal diseases, such as preeclampsia, were excluded.

Results.?Women with DM tended significantly more often to preterm births (P?=?0.002). A significant difference in the incidence of spontaneous preterm birth was found (P?=?0.047).

Conclusion.?DM affects the length of gestation and incidence of spontaneous preterm birth.     

Heavy prenatal alcohol exposure and risk of stillbirth and preterm delivery

We prospectively identified 96 women consuming at least 4 drinks/day during pregnancy by screening 9628 pregnant women. In these women with heavy prenatal alcohol use, there were three stillbirths and one preterm delivery; 98 matched nondrinking women had no stillbirths and two preterm births. Preterm rates did not differ significantly. The stillbirth rate was higher in the exposed group (p?=?0.06). Additional investigation showed the stillbirth rate in the exposed population (3.1%) was significantly higher (p?=?0.019) than the reported Chilean population rate (0.45%). Our data suggest that heavy alcohol consumption may increase the risk for stillbirth but not preterm delivery.