Risk Of Spontaneous Preterm Labor Research Articles

Maternal Asthma and Risk of Preterm Delivery

We studied the relation between maternal history of asthma and preterm delivery. The 312 preterm delivery cases, studied in aggregate, and in subgroups (spontaneous preterm labor, preterm premature rupture of membranes, medically induced preterm delivery), were compared with 424 randomly selected women who delivered at term. Maternal medical records provided information on maternal lifetime asthma status, pregnancy outcome, and sociodemographic characteristics. Using multivariate logistic regression, we derived maximum likelihood estimates of adjusted odds ratios (OR) and 95% confidence intervals (CI). Maternal history of asthma was associated with an increased risk of preterm delivery overall (OR = 2.37; 95% CI 1.15-4.88). Analyses of preterm delivery sub-groups indicated that maternal history of asthma was associated with at least a doubling in risk of spontaneous preterm labor (OR = 2.35; 95% CI 0.84-6.58) and medically induced preterm delivery (OR = 2.69; 95% CI 1.11-6.53), though only the latter approached statistical significance. There was some evidence of a modest association between maternal asthma and risk of preterm premature rupture of membranes (OR = 1.63; 95% CI 0.50-5.33). These results support the hypothesis that maternal asthma is associated with an increased risk of preterm labor and delivery.

Looking to the future

Since the 7th and 13th Study Groups of the Royal College of Obstetricians and Gynaecologists met in 1977 and 1985, respectively, no meeting of this magnitude has convened to discuss the problems of spontaneous preterm labour and delivery and the associated fetomaternal mortality and morbidity. In the 17 years or so since that time, advances have been made in our understanding of the mechanisms of labour, the role of infection, the benefit of antepartum corticosteroids and the development of safer more specific tocolytics. In the future, an understanding of the genetic risk of spontaneous preterm labour and preterm birth is essential, particularly with respect to the predisposition to produce potentially damaging pro‐inflammatory cytokines. The examination of the tissue damage will require pathologists specifically trained in perinatal pathology if the aetiology is to be ascertained and future management tailored to the risks. A greater understanding of fetomaternal immunology and response to antigen exposure in pregnancy may help us to understand which fetomaternal pairs are at greatest risk of responding by delivering preterm, with greater or lesser tissue damage than others with similar risk. Specifically, the relation between spontaneous preterm labour and proteinuric pre‐eclampsia with their common immunology, inflammatory response and tissue damage leading to either spontaneous preterm labour or iatrogenic preterm birth will need to be addressed. This meeting has been very clinically and obstetrically orientated, in future we will need to involve epidemiologists, neonatologists, microbiologists, genito‐urinary medicine physicians, immunologists, geneticists, biochemists, physiologists and endocrinologists. Although spontaneous preterm labour and preterm birth are the major causes of perinatal mortality and morbidity in the developed world, the definition and management protocols for spontaneous preterm labour varies from unit to unit and country to country. A process has already begun, hopefully fuelled by this meeting and those attending, to develop an international consensus on definitions and evidence‐based practical guidelines on the management of spontaneous preterm labour. Perhaps in the longer term it may be possible to influence standards of care, outcome measures and training across international boundaries.

Looking to the future

Since the 7th and 13th Study Groups of the Royal College of Obstetricians and Gynaecologists met in 1977 and 1985, respectively, no meeting of this magnitude has convened to discuss the problems of spontaneous preterm labour and delivery and the associated fetomaternal mortality and morbidity. In the 17 years or so since that time, advances have been made in our understanding of the mechanisms of labour, the role of infection, the benefit of antepartum corticosteroids and the development of safer more specific tocolytics. In the future, an understanding of the genetic risk of spontaneous preterm labour and preterm birth is essential, particularly with respect to the predisposition to produce potentially damaging pro-inflammatory cytokines. The examination of the tissue damage will require pathologists specifically trained in perinatal pathology if the aetiology is to be ascertained and future management tailored to the risks. A greater understanding of fetomaternal immunology and response to antigen exposure in pregnancy may help us to understand which fetomaternal pairs are at greatest risk of responding by delivering preterm, with greater or lesser tissue damage than others with similar risk. Specifically, the relation between spontaneous preterm labour and proteinuric pre-eclampsia with their common immunology, inflammatory response and tissue damage leading to either spontaneous preterm labour or iatrogenic preterm birth will need to be addressed. This meeting has been very clinically and obstetrically orientated, in future we will need to involve epidemiologists, neonatologists, microbiologists, genito-urinary medicine physicians, immunologists, geneticists, biochemists, physiologists and endocrinologists. Although spontaneous preterm labour and preterm birth are the major causes of perinatal mortality and morbidity in the developed world, the definition and management protocols for spontaneous preterm labour varies from unit to unit and country to country. A process has already begun, hopefully fuelled by this meeting and those attending, to develop an international consensus on definitions and evidence-based practical guidelines on the management of spontaneous preterm labour. Perhaps in the longer term it may be possible to influence standards of care, outcome measures and training across international boundaries.

History of fetal loss and other adverse pregnancy outcomes in relation to subsequent risk of preterm delivery.

To evaluate the association between maternal reproductive history and preterm delivery. The 312 preterm delivery cases, studied in aggregate, and in subgroups (spontaneous preterm labor, preterm premature rupture of membranes, medically induced preterm delivery, moderate preterm delivery [gestational age at delivery 34-36 weeks], and very preterm delivery [gestational age at delivery <34 weeks]), were compared with 424 randomly selected women who delivered at term. Maternal medical records provided information on maternal reproductive history, pregnancy outcome, as well as sociodemographic characteristics. Using multivariate logistic regression, we derived maximum likelihood estimates of adjusted odds ratios (OR) and 95% confidence intervals (CI). A history of 2+ miscarriages was (OR = 2.2; 95% CI 1.2-3.9), but a history of 2+ prior induced abortions (OR = 1.2; 95% CI 0.7-2.0) was not, associated with preterm delivery in the index pregnancy. Analyses of preterm delivery subgroups indicated that a history of 2+ miscarriages was associated with an increased risk of spontaneous preterm labor (OR = 2.6; 95% CI 1.2-2.8), preterm premature rupture of membrane (OR = 1.8; 95% 0.7-4.4), and medically induced preterm delivery (OR = 1.9; 95% CI 0.8-4.2), though only the former approached statistical significance. Excess risk of preterm delivery was associated with maternal prior history of delivering a stillborn infant (OR = 10.7), a prior history of delivering a newborn that later died during the neonatal period (OR = 3.2), and a prior history of having a pregnancy complicated by spontaneous preterm delivery (OR = 6.0). Generally these associations were evident for each subgroup of preterm delivery, though inferences were often hindered by our relatively small sample size. These results support the hypothesis that maternal adverse reproductive history is associated with an increased risk of preterm labor and delivery.

Serial salivary estriol to detect an increased risk of preterm birth

Objective: To evaluate serial measurements of salivary estriol (E3) to detect increased risk of spontaneous preterm labor and preterm birth. Methods: A masked, prospective, multicenter trial of 956 women with singleton pregnancies was completed at eight United States medical centers. Saliva was collected weekly, beginning at the 22nd week of gestation until birth, and tested for unconjugated E3 by enzyme-linked immunosorbent assay. Women were separated into high-risk and low-risk groups using the Creasy scoring system. Results: A single, positive (at or above 2.1 ng/mL) salivary E3 test predicted an increased risk of spontaneous preterm labor and delivery in the total population (relative risk [RR] 4.0, P < .005), in the low-risk population (RR 4.0, P ≤ .05), and in the high-risk population (RR 3.4, P = .05). Two consecutive positive tests significantly increased the RR in all study groups, with a dramatic improvement in test specificity and positive predictive value but only a modest decrease in sensitivity. In women who presented with symptomatic preterm labor, salivary E3 identified 61% of those who delivered within 2 weeks, using a threshold of 1.4 ng/mL. Conclusion: Elevated salivary E3 is associated with increased risk of preterm birth in asymptomatic women and symptomatic women who present for evaluation of preterm labor.

Antepartum hemorrhage of unknown origin ‐ what is its clinical significance?

Antepartum hemorrhage of unknown origin is a common antenatal complication, accounting for more than half of the cases of antepartum hemorrhage. Few investigators had reported the importance of this condition and the proper management. The present study reviewed retrospectively 718 cases with singleton pregnancies diagnosed as having antepartum hemorrhage of unknown origin after 24 weeks from 1991 to 1996 and compared their pregnancy outcomes with controls who delivered during the same period of time as the study cases. Clinical and ultrasound examinations were performed in all recruited cases to exclude accidental hemorrhage, placenta previa or lower genital tract bleeding. Patients with antepartum hemorrhage of unknown origin ran a higher risk of spontaneous preterm labor (p<0.001). The birthweight, when adjusted for gestation, did not differ between the two groups. Labor induction rate and cesarean section rates were significantly higher in the antepartum hemorrhage group. The incidences of major antepartum complications and neonatal complications did not differ between the two groups. There were more babies with congenital abnormalities in the antepartum hemorrhage group (p<0.001) and perinatal mortality rate was also higher, though this difference was not statistically significant. The main fetal risks associated with antepartum hemorrhage of unknown origin is preterm labor and its subsequent fetal complications. A small but significant proportion of these pregnancies might be associated with fetal congenital abnormalities. Routine induction at term for this group of patients is of questionable value as adverse fetal outcomes are mostly associated with those that delivered prematurely, or with babies with congenital malformations. When gross fetal abnormalities could be reasonably excluded, labor induction at term should only be contemplated in the presence of other obstetric indications.

Risk of pre-term delivery in patients with previous pre-term delivery and/or abortion.

Patients with a history of two or more pregnancies which ended spontaneously before 37 weeks gestation had an increased risk of spontaneous pre-term labour and delivery in future pregnancies. This increased risk related mainly to previous second trimester abortions and not to previous first trimester abortions. Patients with one previous spontaneous pre-term labour and delivery had a 37 per cent risk, and those with two or more pre-term deliveries a 70 per cent risk of again delivering pre-term. There appeared to be no beneficial effect of cervical suture on the incidence of pre-term delivery in these patients.