Relative Risk Of Preterm Birth Research Articles

Neighborhood deprivation and preterm birth in Plymouth, UK

Objective. To assess the relationship between neighborhood deprivation and the preterm birth rate in Plymouth, UK, using routinely collected data from a clinical information system.Methods. We used a clinic-based prospective case register study of all births in Plymouth UK between 1 January 1996 and 31 December 1997 combined with indices of neighborhood deprivation to assess the relationship between neighborhood deprivation and the preterm birth rate. Areas (n = 43) were classified according to the Townsend index, measuring material deprivation. Preterm births were compared with term births.Results. The incidence of singleton preterm birth was 5.3% (95% confidence interval (CI) 4.6, 6.0). The singleton preterm birth rate increased with Townsend material deprivation score. Crude rates increased by 31% (relative risk (RR) (95% CI) 1.31 (0.94, 1.84), p = 0.056) among those living in the most deprived areas compared to those living in the least deprived areas. A stepwise binary logistic regression model showed an increase in the relative risk of preterm birth of 7% for every unit increase in the Townsend material deprivation score (RR (95% CI) 1.07 (1.03, 1.11)).Conclusion. Neighborhood deprivation is related to preterm birth. Examining individual and neighborhood factors together may increase understanding of the complex causes of preterm birth.

Increased risk of preterm birth in singleton pregnancies resulting from in vitro fertilization–embryo transfer or gamete intrafallopian transfer: A meta-analysis

To perform a systematic review of the literature to determine whether singleton pregnancies resulting from IVF-ET/GIFT are at higher risk for preterm birth (<37 weeks). Literature search and systematic review. Medical school. A MEDLINE search (1965-2000) was performed using the terms "premature labor," "infertility," "pregnancy complications," "gonadotropins," "pregnancy outcome," "preterm delivery," and "in vitro fertilization." Criteria for inclusion were English language, original research article, study patients conceived using IVF-ET (with or without intracytoplasmic sperm injection) or GIFT, pregnancy outcome reported compared with a control group (e.g., naturally conceived singletons at their hospital or a national reference), and prematurity clearly defined. Incomplete articles (e.g., abstracts), reports of other studies, and studies that failed to separate multiple from singleton gestations were excluded. Summary of relative risks of preterm birth. Twenty-seven articles met all inclusion/exclusion criteria and were analyzed by meta-analysis. The random-effects summary relative risk of preterm birth in singleton pregnancies resulting from IVF-ET/GIFT was 1.98 (95% confidence interval, 1.77-2.22). The risk of preterm birth in singleton pregnancies resulting from IVF-ET/GIFT is twice that of natural conceived pregnancies.

The risk of recurrent preterm birth is significantly higher in patients with a previous history of very early premature delivery

540 541 THE RISK OF RECURRENT PRETERM BIRTH IS SIGNIFICANTLY HIGHER IN PATIENTS WITH A PREVIOUS HISTORY OF VERY EARLY PREMATURE DELIVERY ERIN CLARK, MICHAEL S. ESPLIN, ALISON FRASER, ELIZABETH O’BRIEN, GERI MINEAU, MICHAEL W. VARNER, University of Utah, Obstetrics and Gynecology, Salt Lake City, UT; University of Utah-Huntsman Cancer Institute, Population Sciences, Salt Lake City, UT University of Utah-Huntsman Cancer Institute, Population Sciences, Salt Lake City, UT University of Utah-Huntsman Cancer Institute, Oncological Sciences, Salt Lake City, UT OBJECTIVE: We hypothesized that the risk of recurrent PTB would be significantly higher in women with a history of very premature PTB. Our objective was to quantify the risk of recurrent PTB in patients with a previous history of very early PTB. STUDY DESIGN: The Utah Population Database was used to identify all women who had two or more deliveries in the state of Utah with the first birth occurring between 1989 and 2001. The final database included 99,499 patients who had 224,849 consecutive births. The relative risks for preterm birth were calculated based on the gestational age of the previous delivery. RESULTS: The Table depicts the rate of recurrent PTB for the 2nd birth based on the GA of the 1st delivery. Although the rate of recurrent PTB < 32 weeks was 15.9% in the next birth, the rate of recurrence fell to 7.1% in the third birth and 2.8% in the fourth birth. The relative risk of PTB < 32 weeks’ gestation in the second pregnancy was significantly higher among women with a history of PTB at < 32 weeks (RR = 27.2) as compared with women with a previous PTB at 32-33 weeks (RR = 5.95). CONCLUSION: Patients have recurrent PTB at approximately the sameGA as their previous PTB, suggesting that the etiologies for PTB differ at early vs later gestations. Although patients with prior PTB have a substantial recurrence risk, they can be reassured by the fact that a majority subsequently deliver at or near term. Individuals with subsequent term deliveries have an even better prognosis.

The impact of prenatal care on preterm births among twin gestations in the United States, 1989-2000

Objective The purpose of this study was to determine the association between prenatal care and preterm births among twin gestations in the presence and absence of high-risk pregnancy conditions. Study design Twin birth data in the United States were used to determine the association between preterm birth and prenatal care with the use of logistic regression. Results Of the 779,387 twin births, 54.7% twin births were delivered preterm. The rate was higher among black women than among white women in the presence (57.0% vs 51.2%, respectively) and absence (70.3% vs 61.6%, respectively) of prenatal care. The absence of prenatal care increased the relative risk for preterm birth by 1.24-fold among black women and by 1.22-fold among white women. Lack of prenatal care was associated with increased preterm birth rates in the presence of most high-risk conditions. Conclusion Prenatal care is associated with fewer twin preterm births in the presence and absence of high-risk conditions. Increased prenatal care participation may help decrease preterm birth rates and also narrow the black-white twin preterm birth disparity.

The impact of prenatal care in the United States on preterm births in the presence and absence of antenatal high-risk conditions

Objective: This study was undertaken to determine the association between prenatal care in the United States and preterm birth rate in the presence, as well as absence, of high-risk pregnancy conditions for African American and white women. Study Design: Data were derived from the natality data set for the years 1995 to 1998 provided by the National Center for Health Statistics. Analyses were restricted to singleton live births that occurred at ≥20 weeks' gestation. Multiple births, fetal deaths, congenital malformations, chromosomal abnormalities, missing data on gestational age, and birth weight less than 500 g were excluded. Multivariable logistic regression analyses were used to adjust for the presence or absence of various antenatal high-risk conditions, maternal age, gravidity, marital status, smoking, alcohol, and education. Prenatal care was considered present if there was one or more prenatal visits. Preterm delivery was defined as delivery at less than 37 completed weeks of gestation. Results: For 14,071,757 births analyzed, 1,348,643 (9.6%) resulted in preterm birth. Preterm birth rates were higher for African American women than white women in the presence (15.1% vs 8.3%) and absence (34.9% vs 21.9%) of prenatal care. The absence of prenatal care increased the relative risk for preterm birth 2.8-fold in both African American and white women. There was an inverse dose-response relationship between the number of prenatal visits and the gestational age at delivery both among African American and white women. Lack of prenatal care was associated with increased preterm birth rates to a similar degree in the presence of pregnancy complications for both African American and white women, ranging from 1.6-fold to 5.5-fold for the various antenatal high-risk conditions. Conclusion: In the United States, prenatal care is associated with fewer preterm births in the presence, as well as absence of high-risk conditions for both African American and white women. Strategies to increase prenatal care participation may decrease preterm birth rates. (Am J Obstet Gynecol 2002;187:1254-7.)

The contribution of maternal smoking to preterm birth, small for gestational age and low birthweight among Aboriginal and non-Aboriginal births in South Australia.

To determine the contribution of maternal smoking to preterm birth (< 37 weeks' gestation), small for gestational age (SGA, birthweight < 10th percentile for gestational age) and low birthweight (< 2500 g) among Aboriginal and non-Aboriginal births in South Australia. Retrospective cohort analysis of population-based perinatal data. The State of South Australia, population 1.5 million. 36059 women (of whom 851 were Aboriginal women) who had singleton births in 1998-1999. Relative risks and population-attributable risks of preterm birth, SGA and low birthweight from smoking in the second half of pregnancy, by age and Aboriginality. Aboriginal women had a higher rate of smoking in pregnancy than non-Aboriginal women (57.8% v 24.0% at the first antenatal visit) and high rates for all age groups, while the rates decreased with age among non-Aboriginal women. Heavy smoking increased with age, and Aboriginal women were heavier smokers. Women who smoked had elevated relative risks of preterm birth (1.64), SGA (2.28) and low birthweight (2.52), and all these showed a dose-response relationship. Among Aboriginal (versus non-Aboriginal) births, population-attributable risks were significantly higher for SGA (48% v 21%, and 59% for births to Aboriginal teenagers), low birthweight (35% v 23%) and preterm birth (20% v 11%). Health promotion programs, with a focus on smoking cessation and reducing uptake of smoking, need to be implemented in an appropriate cultural context, especially among young Aboriginal women. Such a program is being developed in South Australia.

A meta-analysis of salivary estriol (sE 3) as a means to identify women at risk for preterm birth due to fetal-placental endocrine mechanisms

Objective: 1) Analyze overall performance of salivary estriol testing in two similarly conducted large multicenter prospective trials and 2) gain information regarding the highly integrated and regulated endocrine mechanisms controlling parturition. Methods: Meta-analysis of evaluable mother-perinate dyads from two large prospective trials was conducted. Overall, 993 pregnant women were followed prospectively with weekly saliva samples from 24 weeks to delivery. Results: 1) Occurrence of a single positive test (sE 3 ≥ 2.1 ng/mL) predicted delivery prior to 37 weeks gestation ( P < .0003; OR 3.4, 95% CI 1.7–6.8). If a rescreen test at one week was also ≥2.1 ng/mL (8.9% of all subjects) then relative risks of preterm birth increased to 6.86 CI (3.2–14.5) P < .0001. Having two consecutive positive tests was associated with a mean time to delivery of 2.3 weeks (negative predictive value of 97%). 2) Survival analysis of women delivering at term and preterm demonstrated that sE 3 ≥ 2.1 ng/mL predicted onset of labor and birth in approximately 3 weeks: Conclusion: Meta-analysis of these two large prospective trials confirms that 1) an sE 3 ≥ 2.1 ng/mL provides timely warning of a presumed endocrine signal for impending preterm and term parturition, 2) the 2–3 week mean time to delivery after a positive signal allows time for intervention, and 3) lack of a positive sE 3 signal allows a confident prediction (NPV) that delivery will not occur within 2–3 weeks.

Prognostic significance of prior preterm twin delivery on subsequent singleton pregnancy

OBJECTIVE: Our purpose was to determine whether preterm birth of twins is associated with an increased risk of preterm birth in a subsequent singleton pregnancy. STUDY DESIGN: The Medical University of South Carolina perinatal database was accessed to identify a cohort of patients who were delivered of twins followed by a singleton gestation (1981 to 1993). Maternal transports were excluded to minimize referral bias. Preterm birth was defined as <37 weeks' gestation. Relative risks with 95% confidence intervals were calculated. RESULTS: One hundred forty-four patients were identified who were delivered of twins followed by a singleton gestation. Preterm delivery occurred in 86 (59.7%) of the twins and 21 (14.6%) of the subsequent singletons. Preterm birth of twins was associated with a significantly increased risk of preterm delivery in a subsequent singleton pregnancy (relative risk 2.87, 95% confidence interval 1.02 to 8.09). In the subset of women who were delivered of twins at <30 weeks' gestation, 42% of the subsequent singletons were delivered preterm (relative risk 6.11, 95% confidence interval 2.07 to 18.02). The relative risk of preterm birth of a singleton after delivery of twins between 30 and 34 weeks' gestation was 3.63 (95% confidence interval 1.02 to 12.92). However, if the preceding twins delivered between 34 and 37 weeks' gestation, the relative risk of preterm birth of the subsequent singleton was not significantly increased (relative risk 1.42, 95% confidence interval 0.40 to 5.01). CONCLUSIONS: Preterm birth of twins before 34 weeks' gestation is associated with a significant risk for preterm delivery in a subsequent singleton pregnancy. The magnitude of risk increases with decreasing gestational age of the preceding twin delivery. (A M J O BSTET G YNECOL 1996;174:1429-32.)