Recurrence of preterm birth in singleton and twin pregnancies

OBJECTIVE: To assess recurrence of preterm birth and its impact on an obstetric population. METHODS: Women with consecutive births at our hospital beginning with their first pregnancy were identified (n = 15,945). The first pregnancy was categorized as delivered between 24 and 34 weeks' gestation or 35 weeks or beyond, singleton or twin, and spontaneous or induced. The risk of preterm delivery in these same women during subsequent pregnancies was then analyzed. RESULTS: Compared with women who delivered a singleton at or beyond 35 weeks' gestation in their first pregnancy, those who delivered a singleton before 35 weeks were at a significant increased risk for recurrence (odds ratio [OR] 5.6, 95% confidence interval [CI] 4.5, 7.0), whereas those who delivered twins were not (OR 1.9, 95% CI 0.46, 8.14). The OR for recurrent spontaneous preterm birth presenting with intact membranes was 7.9 (95% CI 5.6, 11.3) compared with 5.5 (95% CI 3.2, 9.4) with ruptured membranes. Of those women with a recurrent preterm birth, 49% delivered within 1 week of the gestational age of their first delivery and 70% delivered within 2 weeks. Among 15,863 nulliparous women with singleton births at their first delivery, a history of preterm birth in that pregnancy could predict only 10% of the preterm births that ultimately occurred in the entire obstetric population. CONCLUSION: In a population-based study at our hospital, women who initially delivered preterm and thus were identified to be at risk for recurrence ultimately accounted for only 10% of the prematurity problem in the cohort.     

Primiparity: an 'intermediate' risk group for spontaneous and medically indicated preterm birth.

OBJECTIVE: Most women in their first pregnancy are at 'unknown' risk for preterm birth. We hypothesized that such women may be at an increased risk for preterm birth in comparison to those with a prior term birth. METHODS: We used Missouri's maternally-linked data (1989-97), comprised of women delivering their first singleton live birth (N = 259 431) and women delivering their first two consecutive singleton live births (N = 154 810). We compared preterm birth (<37 weeks) rates among women with a previous term birth, women with no reproductive history (primiparous women), and in those with a previous preterm birth. Risks of spontaneous and medically indicated preterm birth were also examined after adjustments for confounders through multivariate log-binomial regression models. RESULTS: Preterm birth rates were 8.1%, 9.6%, and 23.3% among women with a previous term birth, among primiparous women, and among those with a previous preterm birth, respectively. In comparison to women with a prior term birth, risks of spontaneous preterm birth among primiparous women and among women with a prior preterm birth were 1.1-fold (95% confidence interval (CI) 1.0, 1.2) and 2.5-fold (95% CI 2.4, 2.6) higher, respectively. These risks were higher for medically indicated preterm birth among both primiparous women (RR 1.3, 95% CI 1.2, 1.4) and those with a prior preterm birth (RR 3.2, 95% CI 3.0, 3.5) than for spontaneous preterm births. CONCLUSIONS: Primiparous women are at increased risk of both medically indicated and spontaneous preterm birth. The findings suggest that studies on preterm birth should consider a risk assignment to include three groups: low-risk (prior term birth), intermediate risk (primiparity), and high-risk (prior preterm birth). This strategy will be informative for the identification of women with impending risk of delivering preterm, and complications associated with prematurity.     

Early preterm delivery due to placenta previa is an independent risk factor for a subsequent spontaneous preterm birth

ABSTRACT: BACKGROUND: To determine whether patients with placenta previa who delivered preterm have an increased risk for recurrent spontaneous preterm birth. METHODS: This retrospective population based cohort study included patients who delivered after a primary cesarean section (n = 9983). The rate of placenta previa, its recurrence, and the risk for recurrent preterm birth were determined. RESULTS: Patients who had a placenta previa at the primary CS pregnancy had an increased risk for its recurrence [crude OR of 2.65 (95 % CI 1.3-5.5)]. The rate of preterm birth in patients with placenta previa in the primary CS pregnancy was 55.9 %; and these patients had a higher rate of recurrent preterm delivery than the rest of the study population (p < .001). Among patients with placenta previa in the primary CS pregnancy, those who delivered preterm had a higher rate of recurrent spontaneous preterm birth regardless of the location of their placenta in the subsequent delivery [OR 3.09 (95 % CI 2.1-4.6)]. In comparison to all patients with who had a primary cesarean section, patients who had placenta previa and delivered preterm had an independent increased risk for recurrent preterm birth [OR of 3.6 (95 % CI 1.52-8.51)]. CONCLUSIONS: Women with placenta previa, who deliver preterm, especially before 34 weeks of gestation, are at increased risk for recurrent spontaneous preterm birth regardless to the site of placental implantation in the subsequent pregnancy. Thus, strict follow up by high risk pregnancies specialist is recommended.     

Risk of preterm birth that is associated with vaginal douching

OBJECTIVE: The purpose of this study was to examine the association between vaginal douching and preterm birth. STUDY DESIGN: We enrolled hospitalized women after delivery in a case-control study. Women who were delivered of a live preterm singleton infant were assigned as cases. Women who were delivered at term were randomly selected as control subjects. We surveyed women about their douching habits and risk factors for preterm birth and abstracted data from the records. RESULTS: After adjustment, vaginal douching within 6 months of pregnancy was not significantly associated with preterm birth (odds ratio, 1.1; 95% CI, 0.8-1.6). However, in secondary analyses, douching more than once per week (odds ratio, 4.0; 95% CI, 1.0-15.5) or longer than 10 years (odds ratio, 1.9; 95% CI, 1.1-3.2) was associated with preterm birth. CONCLUSION: Vaginal douching does not appear to be a strong risk factor for preterm birth. Further study is needed to confirm the risk that is associated with frequent or long-term douching.     

Second trimester folate status and preterm birth

OBJECTIVE: The purpose of this study was to show that maternal folate status during pregnancy may be related to preterm birth. STUDY DESIGN: Women were recruited at 24 to 29 weeks' gestation from 1995 to 2000 into the Pregnancy, Infection, and Nutrition Study. Those who completed an interview and a food frequency questionnaire, or provided a blood sample for radioassay of serum (n = 2026) and red blood cell (n = 1034) folate were included. RESULTS: Mean daily dietary folate intake was 463 microg (SD +/- 248). Intake 相似文献   

Risk of preterm delivery in relation to maternal low birth weight

OBJECTIVE: We examined the relationship between maternal low birth weight and preterm delivery risk. METHODS: Information concerning maternal birth weight was collected during in-person interviews. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI). Preterm delivery cases were studied in aggregate, 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 early preterm delivery [gestational age at delivery<34 weeks]). RESULTS: After adjusting for confounders, women weighing<2,500 g at birth had a 1.54-fold increased risk of preterm delivery versus women weighing=2,500 g (95% CI 0.97-2.44). Maternal low birth weight was associated with a 2-fold increased risk of spontaneous preterm delivery (95% CI 1.03-3.89), but weakly associated with preterm premature rupture of membranes (OR=1.44; 95% CI 0.67-3.09) and medically induced preterm delivery (OR=1.10; 95% CI 0.43-2.82). Maternal low birth weight was more strongly associated with early preterm delivery (OR=1.94) than with moderate preterm delivery (OR=1.46). Women weighing<2,500 g at birth and who became obese (pre-pregnancy body mass index, =30 kg/m2) before pregnancy had a 3.65-fold increased risk of preterm delivery (95% CI 1.33-10.02) versus women weighing=2,500 g at birth and who were not obese prior to pregnancy (<30 kg/m2). CONCLUSIONS: Results confirm earlier findings linking maternal low birth weight with future risk of preterm delivery.     

Weight gain and spontaneous preterm birth: the role of race or ethnicity and previous preterm birth

OBJECTIVE: To study how the relationship between gestational weight gain and spontaneous preterm birth interacts with maternal race or ethnicity and previous preterm birth status. METHODS: This was a retrospective cohort study of singleton births to women of normal or low prepregnancy body mass index. Gestational weight gain was measured as total weight gain divided by weeks of gestation at delivery, and weight gain was categorized as low (less than 0.27 kg/wk,), normal (0.27-0.52 kg/wk), or high (more than 0.52 kg/wk). Univariable and multivariable analyses were performed on the relationship between weight gain categories and spontaneous preterm birth, stratified by maternal race or ethnicity and history of previous preterm birth. RESULTS: Overall, low weight gain was associated with spontaneous preterm birth (adjusted odds ratio [AOR] 2.5, 95% confidence interval [CI] 2.0-3.1). Although low gain was consistently associated with increased spontaneous preterm birth, some differences were found in subgroup analysis. Among African Americans with a previous preterm birth, both low and high weight gain were associated with increased odds of spontaneous preterm birth (AOR for low weight gain 4.3, 95% CI 1.2-15.5; AOR for high weight gain 6.1, 95% CI 1.8-20.2). For all other groups, high weight gain was not associated with spontaneous preterm birth. Among Asians with a previous preterm birth, low weight gain was not statistically significantly associated with spontaneous preterm birth (AOR 1.9, 95% CI 0.5-7.7). Among Asians there was also a non-statistically significant inverse relationship between high weight gain and spontaneous preterm birth (AOR 0.5, 95% CI 0.3-1.1). CONCLUSION: These results confirm an association between low maternal weight gain and spontaneous preterm birth. The effect modification of maternal race or ethnicity and history of previous preterm birth on this association deserves further study. LEVEL OF EVIDENCE: II-2.     

Precancerous changes in the cervix and risk of subsequent preterm birth

OBJECTIVE: The aims of this study were (i) to examine whether women referred for assessment of precancerous changes in the cervix had higher rates of preterm birth compared with those in the general population and (ii) to compare preterm birth rates for treated and untreated women adjusting for possible confounding factors. DESIGN: Retrospective cohort design. SETTING: Teaching hospital. POPULATION: All women referred to the Royal Women's Hospital, Melbourne (1982-2000), who subsequently had a birth recorded on the Victorian Perinatal Data Collection system (n = 5548). METHODS: Record linkage of hospital dysplasia clinic records and population-based birth records. MAIN OUTCOME MEASURES: Total preterm delivery (<37 weeks of gestation) and subtypes. RESULTS: Both treated and untreated women were at a significantly increased risk for preterm birth compared with those in the general population: treated--standardised prevalence ratio (SPR) 2.0, 95% CI 1.8-2.3 and untreated--SPR 1.5, 95% CI 1.4-1.7. Within the cohort, the treated women were significantly more likely to give birth preterm (adjusted OR 1.23, 95% CI 1.01-1.51). An increased risk of preterm birth was also associated with a history of induced or spontaneous abortions, illicit drug use during pregnancy or a major maternal medical condition. Cone biopsy, loop electrosurgical excision procedure and diathermy were associated with preterm birth. After adjusting for possible confounding factors, only diathermy remained significant (adjusted OR 1.72, 95% CI 1.36-2.17). Women treated using laser ablation were not at an increased risk for preterm birth (adjusted OR 1.1, 95% CI 0.8-1.4). CONCLUSIONS: Diagnosis of precancerous changes in the cervix (regardless of the treatment) was associated with an increased risk of preterm birth. Consideration should be given to the preferential use of ablative treatments.     

The impact of interpregnancy interval and previous preterm birth on the subsequent risk of preterm birth

OBJECTIVE: To examine the impact of the interpregnancy interval and a previous preterm birth on the subsequent risk of a preterm birth. METHODS: A retrospective analysis was conducted on a group of 4072 women who had at least two consecutive births, excluding multiple gestation, fetal anomalies, cervical incompetence, and stillbirth. Multivariate logistic regression was used to investigate the association between interpregnancy interval, preterm birth of the first child in the pair (index pregnancy), and the risk of a preterm birth of the second child in the pair (outcome pregnancy). RESULTS: Women with interpregnancy intervals of less than 12 months (odds ratio [OR] 1.3; 95% confidence interval [CI] 1.0-1.7) were at increased risks of preterm birth with the outcome pregnancy. Furthermore, there was an increased risk for a subsequent preterm birth in women who had a preterm birth in the index pregnancy (OR 4.2; 95% CI 3.0-6.0). The risk decreased as the interpregnancy interval increased, with a relatively low risk at 18 to 48 months; subsequently, it increased sharply. In contrast, women who had delivered their previous infants at term carried an increased risk of preterm birth with the outcome pregnancy only if the interval was less than 6 months. CONCLUSION: A difference was found in the impact of the interpregnancy interval on the subsequent risk of preterm birth between women with a prior preterm birth and those who previously delivered an infant at term.     

Recurrence risk of preterm birth due to preeclampsia.

There may be an increased risk of preterm birth due to preeclampsia among women whose previous pregnancies ended in preterm birth due to preeclampsia. We studied 1,130 women who delivered 2 successive singleton infants in our hospital, excluding women who delivered an abnormally formed infant during the study period. We reviewed the gestational week at delivery in these 2,260 pregnancies and found a total of 182 preterm deliveries (8.1%) by 156 women. The causes of preterm birth were reviewed. Failed tocolysis, including premature rupture of membranes and clinical chorioamnionitis, and preeclampsia accounted for 135 (74.2%) and 30 (16.5%) of the 182 preterm deliveries, respectively. Women whose 1st delivery was preterm had a 3.26 times (95% CI 2.21-4.79) higher risk of a subsequent preterm delivery than women whose 1st delivery was term (26/96 vs. 60/1,034). The risk of preeclampsia-related preterm delivery was 54.4 times (17.2 to 172.5) higher in women with a previous preeclampsia-related preterm delivery than in women with a previous term delivery (5/19 vs. 5/1034). Women who had a history of preeclampsia-related preterm birth had a greater risk of preeclampsia-related preterm birth in a subsequent pregnancy as compared with women with a previous term birth.     

The impact of fetal gender on preterm birth in a southern Chinese population

Objective: This study was conducted to determine whether carrying a singleton male fetus increases the risk of preterm birth (PTB) in Chinese women. Methods: A retrospective cohort study was conducted on women with singleton pregnancies and delivered in our hospital. Maternal characteristics, pregnancy outcome, and incidence of PTB, were compared between women carrying a male versus a female fetus. The independent effect of a male fetus on PTB was examined with multiple logistic regression analysis adjusting for the other confounding factors identified. Results: There were significant differences in maternal and infant characteristics between women with a male versus a female fetus. Despite similar or lower incidences of complications and labor induction, women with a male fetus had increased birth <37 weeks (7.0% versus 6.2%, p?<?0.001) and birth at 34–36 weeks (5.15% versus 4.4%, p?<?0.001), but not for birth <34 weeks (2.0% versus 1.8%, p?=?0.163). Regression analysis confirmed the association between male fetus with birth at 34–36 weeks (aOR 1.11, 95% CI 1.10–1.33) and spontaneous preterm labor (aOR 1.09, 95% CI 1.00–1.19). Conclusions: The results confirmed that carrying a male fetus is an independent risk factor for spontaneous preterm labor and PTB at 34–36 weeks gestation in southern Chinese women.     

Cervical dimensions and risk of preterm birth: a prospective cohort study

OBJECTIVE: To examine the relation between cervical dilatation and length and the risk of spontaneous preterm birth, including its subtypes preterm labor and preterm premature rupture of membranes (PROM). METHODS: Cervical dimensions assessed by clinical examination were recorded prospectively at 24-29 weeks' gestation in 871 subjects with singleton pregnancies who were followed to delivery. Relative risks (RRs) of preterm birth, preterm labor, and preterm PROM were calculated for clinically distinguishable categories of cervical dilatation and length and for cervical score (length minus dilatation). Regression analysis was used to adjust for confounding. Time to delivery from baseline examination was summarized using survival analysis. RESULTS: There were 73 spontaneous preterm births (8.3%), 46 preterm labors and 27 cases of preterm PROM. All cervical measurements were associated with increased risks of preterm birth, with increasing abnormality more strongly predictive of risk. The adjusted RR for preterm birth with dilatation of at least 0.5 cm was 2.9 (95% confidence interval [CI] 1.2, 7.3); for length of 1.5 cm or less, the RR was 2.1 (95% CI 1.0, 4.5), and for cervical score less than 2.0, the RR was 2.8 (95% CI 1.4, 5.6). The association with cervical measurements was stronger for preterm PROM than for preterm labor, although precision was limited. These measurements had high specificity (93-99%) and low sensitivity (8-20%) for predicting preterm birth. CONCLUSION: In asymptomatic women at 24-29 weeks' gestation, greater cervical dilatation and shorter length were associated with increased risk of spontaneous preterm delivery, particularly preterm PROM.     

Effects of domestic violence on preterm birth and low birth weight

BACKGROUND: Domestic violence is increasingly recognized as a potentially modifiable risk factor for adverse pregnancy outcomes. This study was conducted to evaluate the relationship between abuse during pregnancy or within the last year and low birth weight and preterm birth. METHODS: From 1997 to 2001, 3149 low income, relatively low-risk pregnant women (82% African-American) participated in this prospective study. The Abuse Assessment Screen, a validated screening tool, which assesses emotional, physical or sexual abuse, injuries due to physical abuse and physical abuse in the index pregnancy, was filled out by 3103 women. RESULTS: Of the women screened, 26.6% reported emotional abuse, 18.7% reported physical abuse in the past year and 10.3% women reported being beaten, bruised, threatened with a weapon or being permanently injured. Abuse during pregnancy was reported by 5.9% of the women. Low birth weight and preterm birth occurred in 10.9% and 10.2% of the pregnant women, respectively. Logistic regression analyzes indicated that injury due to physical abuse within the past year was significantly associated with both preterm birth [adjusted odds ratio (AOR) = 1.6, 95% confidence interval (CI) = 1.1-2.3] and low birth weight (AOR = 1.8, 95% CI = 1.3-2.5) after adjusting for other covariates. The mean birth weight of infants born to women who were injured due to physical abuse was significantly lower (-75.2 g, p = 0.04) than the mean birth weight of infants of women who were not injured. CONCLUSION: These results indicate that in our population, injuries resulting from physical abuse are associated with both low birth weight and preterm birth.     

Transvaginal ultrasonography in the prediction of preterm birth after treatment for cervical intraepithelial neoplasia

OBJECTIVE: To estimate whether cervical length measured by transvaginal ultrasonography in women having had loop electrosurgical excision procedure (LEEP), cold knife conization, or cryotherapy predicts spontaneous preterm birth. METHODS: Women with a history of LEEP, cold knife conization, or cryotherapy and who were subsequently pregnant with singleton gestations were prospectively compared with both a low-risk control group and women with previous spontaneous preterm birth. A transvaginal ultrasonogram measuring cervical length was performed at 24 to 30 weeks of gestation. Primary outcomes included cervical length and spontaneous preterm birth less than 37 weeks. Secondary outcomes were spontaneous preterm birth less than 34 weeks, low birth weight, and maternal and neonatal outcomes. RESULTS: Women with previous LEEP (N = 75), cold knife conization (N = 21), and cryotherapy (N = 36) had shorter cervical lengths (3.54, 3.69, and 3.75 cm respectively) than the low-risk control group (N = 81, 4.21 cm) (P < .001, P = .03, P = .02 respectively) and similar lengths to women with a previous spontaneous preterm birth (N = 63, 3.78 cm). Loop electrosurgical excision procedure and cold knife conization, but not cryotherapy, were associated with spontaneous preterm birth less than 37 weeks (odds ratio 3.45, 95% confidence interval 1.28-10.00, P = .02; and odds ratio 2.63, 95% confidence interval 1.28-5.56, P = .009, respectively). Using a cutoff of 3.0 cm, transvaginal ultrasonography had a positive predictive value of 53.8% and negative predictive value of 95.2% for spontaneous preterm birth less than 37 weeks in women with LEEP. CONCLUSION: Women with a history of LEEP, cold knife conization, and cryotherapy all independently have shorter cervical lengths than low-risk controls and similar lengths to women with previous spontaneous preterm birth. Loop electrosurgical excision procedure and cold knife conization are associated with spontaneous preterm birth less than 37 weeks, and transvaginal ultrasonography predicts preterm birth in women who have had LEEP. LEVEL OF EVIDENCE: II-2.     

Effect of coitus on recurrent preterm birth

OBJECTIVE: To estimate the impact of sexual behavior on the risk of recurrent spontaneous preterm birth at less than 37 weeks of gestation. METHODS: This is a secondary analysis of a multicenter, blinded observational study of endovaginal sonographic examinations performed at 16-18 weeks of gestation on 187 women with singleton gestations who were at high risk for recurrent spontaneous preterm birth (prior spontaneous preterm birth at < 32 weeks of gestation). At the time of enrollment, each woman was interviewed by a research nurse with regard to her sexual history. The patient was asked about the number of sexual partners in her lifetime, the number of sexual partners since the start of her pregnancy, and, on average, the frequency of intercourse per week in the preceding month. RESULTS: A total of 165 pregnancies were available for this analysis. The population incidence of spontaneous preterm birth at less than 37 weeks of gestation in the study pregnancy was 36%. An increasing number of sexual partners in a woman's lifetime was associated with an increased risk of spontaneous preterm delivery (one partner 19%, 2-3 partners 29%, >or= 4 partners 44%, P = .007), whereas the number of sexual partners since the start of pregnancy was not (P = .42). Women who reported infrequent sexual intercourse during early pregnancy had an incidence of recurrent spontaneous preterm birth of 28% compared with 38% in those women who reported some intercourse (P = .35). CONCLUSION: Self-reported coitus during early pregnancy was not associated with an increased risk of recurrent preterm delivery. There was an association between increasing number of sexual partners in a woman's lifetime and recurrent preterm delivery. LEVEL OF EVIDENCE: II-2.     

The preterm prediction study: maternal serum relaxin, sonographic cervical length, and spontaneous preterm birth in twins

OBJECTIVE: The risk of spontaneous preterm birth has been related to decreased cervical length and to increased serum relaxin. To explore a relationship between these findings, we used data collected from two prior studies to correlate relaxin levels with cervical length and risk of spontaneous preterm birth in women with twin pregnancies. METHODS: In a secondary analysis of data collected in two previous observational studies of risk factors for preterm birth, relaxin levels in maternal serum and cervical length were measured at 24 (n= 188) and 28 (n= 145) weeks in women with spontaneous twin pregnancies. Relaxin, as a continuous variable, was related by logistic regression analysis to risk of spontaneous preterm birth before 37, 35, and 32 weeks' gestation, and by Spearman correlation coefficients to cervical length at 24 and 28 weeks. Cervical length at 24 weeks was known to be correlated with spontaneous preterm birth before 37, 35, and 32 weeks (P =.03,.01, and.002, respectively) in this study population. RESULTS: Cervical length did not correlate with relaxin levels at 24 (P=.601) or 28 (P=.304) weeks. Relationships between relaxin and spontaneous preterm birth were observed at 24 weeks for births before 37 weeks (odds ratio [OR] 1.56, 95% confidence interval [CI] 1.00, 2.44; P=.05), and at 28 weeks for births before 35 weeks (OR 1.97, 95% CI 1.05, 3.70; P=.034) and 32 weeks (OR 2.43, 95% CI 1.01, 5.83; P=.048). CONCLUSION: The absence of an association between relaxin and cervical length suggests that increased relaxin does not explain the inverse correlation between cervical length and spontaneous preterm birth in women with spontaneous twin pregnancies.     

The Preterm Prediction Study: association between maternal body mass index and spontaneous and indicated preterm birth

OBJECTIVE: The purpose of this study was to evaluate the relationship between prepregnancy maternal body mass index and spontaneous preterm birth and indicated preterm birth. STUDY DESIGN: This was a secondary analysis of the Maternal-Fetal Medicine Units Network, Preterm Prediction study. Patients were classified into categories that were based on their body mass index. Rates of indicated and spontaneous preterm birth were compared. RESULTS: Five hundred ninety-seven (20.5%) of 2910 women were obese. Obese women had fewer spontaneous preterm births at < 37 weeks of gestation (6.2% vs 11.2%; P < .001) and at < 34 weeks of gestation (1.5% vs 3.5%; P = .012). Women with a body mass index of < 19 kg/m2 had 16.6% spontaneous preterm birth, with a body mass index of 19 to 24.9 kg/m 2 had 11.3% spontaneous preterm birth, with a body mass index of 25 to 29.9 kg/m2 had 8.1% spontaneous preterm birth, with a body mass index of 30 to 34.9 kg/m2 had 7.1% spontaneous preterm birth, and with a body mass index of > or = 35 kg/m2 had 5.2% spontaneous preterm birth (P < .0001). Indicated delivery was responsible for an increasing proportion of preterm births with increasing body mass index (P = .001). Obese women had lower rates of cervical length < 25 mm (5% vs 8%; P = .012). Multivariable regression analysis confirmed a lower rate of spontaneous preterm birth in obese gravid women (odds ratio, 0.57; 95% CI, 0.39-0.83; P = .003). CONCLUSION: Obesity before pregnancy is associated with a lower rate of spontaneous preterm birth.     

Placental histology in spontaneous and indicated preterm birth: A case control study

IntroductionPlacental pathology is an important contributor in preterm birth, both spontaneous and indicated. The aim of this study was to describe and compare placental histological features of spontaneous preterm birth versus indicated preterm birth.MethodsA case control study was performed at the University Medical Center Utrecht. Women with spontaneous or indicated preterm birth (17–37 weeks of gestation) delivered in 2009 were included. Women with a pregnancy complicated by congenital and/or chromosomal abnormalities were excluded. Placentas were systematically examined by an expert pathologist blinded for pregnancy outcome, except for gestational age. Placental histological abnormalities were classified into infectious inflammatory lesions and maternal vascular malperfusion lesions and compared between spontaneous and indicated preterm birth. Analysis was stratified for immature (17–23⁺⁶ weeks), extremely (24–27⁺⁶ weeks), very (28–31⁺⁶ weeks) and moderate/late (32–36⁺⁶ weeks) preterm birth.ResultsWe included 233 women, 121 women with spontaneous preterm birth and 112 women with indicated preterm birth. Among women with spontaneous extremely preterm birth, higher rates of severe chorioamnionitis were found (56.0% vs. 0%). Furthermore, a shift from infectious-inflammatory lesions to maternal vascular malperfusion lesions was seen after 28 weeks; in women with spontaneous very and moderate/late preterm birth, maternal vascular malperfusion lesions were the main finding (46.8% and 47.7% respectively). In women with indicated preterm birth, maternal vascular malperfusion lesions were most often contributing through all gestational age categories.ConclusionMaternal vascular malperfusion lesions are most frequent in both spontaneous and indicated very and moderate/late preterm birth. In spontaneous extreme preterm birth chorioamnionitis is the main finding.     

Estimated effect of 17 alpha-hydroxyprogesterone caproate on preterm birth in the United States

OBJECTIVE: A multicenter, randomized placebo-controlled trial among women with singleton pregnancies and a history of spontaneous preterm birth found that weekly injections of 17 alpha-hydroxyprogesterone caproate (17P), initiated between 16 and 20 weeks of gestation, reduced preterm birth by 33%. The current study estimated both preterm birth recurrence and the potential reduction in the national preterm birth rate. METHODS: Using 2002 national birth certificate data, augmented by vital statistics from 2 states, we estimated the number of singleton births delivered to women eligible for 17P through both a history of spontaneous preterm birth and prenatal care onset within the first 4 months of pregnancy. The number and rate of recurrent spontaneous preterm births were estimated. To predict effect, the reported 33% reduction in spontaneous preterm birth attributed to 17P therapy was applied to these estimates. RESULTS: In 2002, approximately 30,000 recurrent preterm births occurred to women eligible for 17P, having had a recurrent preterm birth rate of 22.5%. If 17P therapy were delivered to these women, nearly 10,000 spontaneous preterm births would have been prevented, thereby reducing the overall United States preterm birth rate by approximately 2%, from 12.1% to 11.8% (P < .001), with higher reductions in targeted groups of eligible pregnant women. CONCLUSION: Use of 17P could reduce preterm birth among eligible women, but would likely have a modest effect on the national preterm birth rate. Additional research is urgently needed to identify other populations who might benefit from 17P, evaluate new methods for early detection of women at risk, and develop additional prevention strategies. LEVEL OF EVIDENCE: III.     

Progesterone for the prevention of preterm birth: a systematic review

OBJECTIVE: We performed a systematic review to assess the benefits and harms of progesterone administration for the prevention of preterm birth in women and their infants. DATA SOURCES: The Cochrane Controlled Trials Register was searched, and reference lists of retrieved studies were searched by hand. No date or language restrictions were placed. METHODS OF STUDY SELECTION: Randomized trials comparing antenatal progesterone for women at risk of preterm birth were considered. Studies were evaluated for inclusion and methodological quality. Primary outcomes were perinatal death, preterm birth before 34 weeks, and neurodevelopmental handicap. TABULATION, INTEGRATION AND RESULTS: Eleven randomized controlled trials (2,425 women and 3,187 infants) were included. For women with a history of spontaneous preterm birth, progesterone was associated with a significant reduction in preterm birth before 34 weeks (one study, 142 women, RR 0.15, 95% CI 0.04-0.64, number needed to treat 7, 95% CI 4-17), but no statistically significant differences were identified for the outcome of perinatal death. For women with a short cervix identified on ultrasound, progesterone was not associated with a significant difference in perinatal death (one study, 274 participants, RR 0.38, 95% CI 0.10-1.40), but there was a significant reduction in preterm birth before 34 weeks (one study, 250 women, RR 0.58, 95% CI 0.38-0.87, number needed to treat 7, 95% CI 4-25). For women with a multiple pregnancy, progesterone was associated with no significant difference in perinatal death (one study, 154 participants, RR 1.95, 95% CI 0.37-10.33). For women presenting after threatened preterm labor, no primary outcomes were reported. For women with "other" risk factors for preterm birth, progesterone was not associated with a significant difference in perinatal death (two studies, 264 participants, RR 1.10, 95% CI 0.23-5.29). CONCLUSION: Progesterone is associated with some beneficial effects in pregnancy outcome for some women at increased risk of preterm birth.