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.     

Recurrence of preterm birth in twin pregnancies in the presence of a prior singleton preterm birth

OBJECTIVE: We examined recurrence of preterm birth in twin pregnancy in the presence of a previous singleton preterm pregnancy, and assessed if these recurrence risks differed for medically indicated and spontaneous preterm birth. METHODS: A retrospective cohort study was designed using the maternally-linked data of women who delivered a first singleton live birth followed by a twin birth in the second pregnancy (n = 2329) in Missouri (1989--97). We examined preterm birth recurrence at <37 in the second twin pregnancy among women with a prior singleton preterm birth. Recurrence risks were based on hazard ratios (HR) and 95% confidence intervals (CI) estimated from Cox proportional hazards models after adjusting for potential confounders. RESULTS: Preterm birth rates in the second twin pregnancy were 69.0% and 49.9% among women who had a previous preterm and term singleton birth, respectively (HR 1.8, 95% CI 1.6-2.1). The preterm birth rate in the second pregnancy was about 95% when the first singleton pregnancy ended at <30 weeks. Women delivering preterm following a medical intervention in the first pregnancy had increased recurrence for both spontaneous (HR 1.4, 95% CI 1.1-2.0) and indicated (HR 2.4, 95% CI 1.8-3.2) preterm birth; similarly among women with a prior spontaneous preterm birth, hazard ratios were 1.8 (95% CI 1.5-2.1) and 1.6 (95% CI 1.3-1.9), for spontaneous and indicated preterm birth in the second twin pregnancy, respectively. CONCLUSIONS: Women with a singleton preterm birth carry increased risk of preterm birth in the subsequent twin pregnancy. A history of a singleton preterm birth has an independent and additive contribution to risk of preterm birth in the subsequent twin gestation.     

Second-trimester cervical ultrasound: associations with increased risk for recurrent early spontaneous delivery

OBJECTIVE: To determine whether short cervical length or internal os funneling before 20 weeks' gestation predicts early preterm birth or pregnancy loss in women with at least one prior spontaneous early preterm birth. METHODS: Transvaginal cervical ultrasound examinations were done every 2 weeks on 69 women with singleton gestations and histories of at least one prior spontaneous birth between 16 and 30 weeks' gestation. The results of those examinations were correlated with gestational age at delivery. RESULTS: Among 53 women who had ultrasound examinations before 20 weeks' gestation, those with cervical lengths at or below the tenth percentile for the study population (22 mm, n = 4) or funneling of the internal os (n = 5) were more likely than women without those factors to have spontaneous preterm births within 2 weeks (33% versus 0%, P = .01) or 4 weeks from the ultrasound examination (67% versus 0%, P < .001) or before 35 weeks' gestation (100% versus 19%, P < .001). Short cervical length or funneling between 20-24 and 25-29 weeks was also associated with increased risk of spontaneous preterm birth before 35 weeks' gestation (P < or = .05 and P = .002, respectively) but not with increased risk of spontaneous preterm birth within 2 or 4 weeks of ultrasound examination. CONCLUSION: Women with prior early spontaneous preterm births who have short cervical lengths or funneling of the internal cervical os before 20 weeks' gestation are at increased risk of subsequent spontaneous preterm birth.     

Etiologies of preterm birth in an indigent population: is prevention a logical expectation?

To assess the expectations of preterm birth prevention, we determined the causes of preterm birth in a population of indigent women. We studied 13,119 singleton births in a predominantly black, indigent population occurring between November 1982 and April 1986 to identify the proportion of preterm births that may have been prevented using current treatment modalities. Forty-four percent of the preterm births occurred at 35 to 36 weeks' gestational age, a time when most practitioners do not attempt tocolysis. Of the remainder, 17% occurred before 35 weeks but were indicated for maternal medical or obstetric complications, and another 17% occurred before 35 weeks but followed spontaneous premature rupture of the membranes. Therefore, of the 1445 preterm births, we calculated that only 336 (23.2%) were theoretically preventable. A fourth of these presented at less than 3 cm cervical dilatation and were treated appropriately with tocolytics, but delivered anyway. Therefore, most of the potentially preventable births occurred in the group that presented with cervical dilatation of more than 3 cm. We conclude that improving the preterm birth rate significantly below current levels may be difficult to achieve.     

Number and gestational age of prior preterm births does not modify the predictive value of a short cervix

OBJECTIVE: This study was undertaken to determine whether the number and gestational age of prior preterm deliveries modifies the significance of endovaginal sonographic cervical length less than 25 mm for the prediction of recurrent preterm birth less than 35 weeks' gestation. STUDY DESIGN: Secondary analysis of a multicenter, blinded, observational study. Endovaginal ultrasonographic examinations were scheduled at 2-week intervals between 16 and 23 weeks' gestation in singleton pregnancies of 181 gravid women with at least 1 prior spontaneous preterm birth between 16 and 32 weeks' gestation. RESULTS: The earliest prior preterm birth occurred before 23 weeks in 61 women and at 23.0 to 31 weeks in 115; 5 had missing gestational age data. Cervical length was not different between these 2 groups both at the initial scan (median 38 vs 37 mm, P=.54) and considering the shortest ever observed cervical length over the entire study period (median 30 vs 30 mm, P=.97). Cervical length less than 25 mm was associated with spontaneous preterm birth less than 35 weeks for both groups (positive predictive value 80% vs 71%, P>.99). There were 134 women with 1 prior preterm delivery (74%) and 47 with 2 or more. Cervical lengths were not different between these 2 groups at the initial scan (median 36.5 vs 37 mm, P=.52) or over the entire study period (median 30 vs 32 mm, P=.31). The positive predictive value of cervical length less than 25 mm for subsequent spontaneous premature birth was not significantly higher in gravid women with multiple prior preterm births (100% vs 73%, P>.99). CONCLUSION: Neither the number nor the gestational age of prior preterm births modify the predictive value of a cervical length less than 25 mm at 16 to 19 weeks for recurrent spontaneous preterm birth.     

Estimating recurrence of spontaneous preterm delivery

OBJECTIVE: To identify factors associated with spontaneous preterm birth and to estimate the risk of its recurrence for the second through fourth births among women in Utah who had a first and any subsequent birth between 1989 and 2001, using a retrospective cohort study design. METHODS: Utah state birth records were reviewed to identify women with a first live birth and at least one subsequent live birth from 1989 to 2001. Recurrence risks for spontaneous preterm birth were calculated for first through fourth births. Then all parties (1-12) and multiple maternal risk factors were used to estimate recurrence risks for pre-term birth outcomes by multinomial regression. Recurrence risks for early and late spontaneous preterm birth were calculated. Recurrence also was evaluated as the fraction attributable to previous spontaneous preterm birth. Using the identified factors, the sample was divided and the model was estimated for a subset of births (1989-1999); its predictive value was tested on the remaining births (2000-2001). RESULTS: Women who experienced a spontaneous preterm birth before 34 weeks of gestation in their first or second live birth had the highest rate of recurrence. Spontaneous preterm birth before 34 weeks was the highest risk factor for recurrence of early spontaneous preterm birth (relative risk 13.56, 95% confidence interval 11.5-16.0), and, in general, risks were highest for recurrences of same gestational age outcomes. CONCLUSION: A history of a live spontaneous birth before 34 weeks of gestation is a strong predictor of subsequent spontaneous preterm birth. A model of clinical risk factors may be used to identify women at increased risk for recurrent spontaneous preterm birth.     

Incidence of Preterm Delivery in Hong Kong Chinese

Summary: A retrospective analysis of the obstetric database between January, 1995 and December, 1996 was conducted to establish the rate of preterm birth and the incidence of babies with low birth-weight amongst Hong Kong Chinese in an obstetric teaching unit in Hong Kong, and to investigate possible risk factors for spontaneous preterm deliveries. In the series of 13,641 Chinese women who delivered during the study period, the incidence of preterm births before 37 weeks'gestation was 7.4% while the incidence of low birth-weight infants (<2,500g) was 6.4%. When only singleton pregnancies were included, the incidences of preterm births and low birth-weight were 6.5% and 5.1% respectively. This study has demonstrated results contrary to the belief that premature delivery is uncommon in a Chinese population. In addition, we have found that, similar to Caucasian populations, hypertensive disorders of pregnancy, gestational diabetes, antepartum haemorrhage and congenital malformation are significant risk factors for spontaneous preterm labour in singleton pregnancy in our Chinese population.     

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.     

Obstetrics and perinatal outcome of adolescent nulliparous pregnant women

OBJECTIVE: To study obstetrics and perinatal outcome in nulliparous teenage singleton pregnancies at a referral teaching hospital in the eastern province of Saudi Arabia. METHOD: All singleton births during 1996-2000 of nulliparous mothers aged < or =17 years at King Fahd University Hospital were reviewed (n = 102) and compared with births of a control group of nulliparous mothers aged 20-24 years who delivered during the same period (n = 102). RESULTS: The incidence of nulliparous teenage pregnancies was 0.8%. As compared with women aged 20-24 years, women of 17 years or less were at higher risk of very preterm birth (p < 0.05). The 5-min Apgar scores were not different between the two groups. Babies born to younger mothers had a significantly lower birth weight than those born to older mothers (p < 0.001); the incidence of a low birth weight (<2,500 g) was significantly lower in the control group (p < 0.04). There were no significant differences in distribution of mode of delivery, admission to the special care baby unit, antenatal complications, cesarean section indications, perinatal mortality rate, and early neonatal complications between the two groups. CONCLUSION: The increase in the very preterm births and the subsequently lower birth weight observed in nulliparous teenage women suggest that the maternal age may be a risk factor for very preterm births and associated long-term hazards.     

Fetal sex and indicated very preterm birth: results of the EPIPAGE study

OBJECTIVE: This study was undertaken to explore the association between fetal sex, mode of onset of labor, and principal cause of very preterm birth.Study design The analysis uses data on 2624 very preterm singleton births less than 33 weeks' gestation from a prospective study of all very preterm births in 9 French regions in 1997. RESULTS: Fifty-seven percent of the spontaneous births were male versus 50.8% of births after medical decision (P=.005). This pattern was explained by sex differences in causes of preterm birth. Male infants had a greater incidence of very preterm birth after spontaneous labor (relative risk [RR]=1.42 [1.21-1.66]), but one third less risk of indicated preterm birth associated with hypertension both with and without growth restriction (RR=0.73 [0.55-0.97] and 0.77 [0.60-0.97]). CONCLUSION: These results support previous reports of greater male susceptibility to preterm labor. The finding that pregnancies carrying female infants have a greater predisposition to indicated very preterm birth associated with hypertension has not been reported previously and merits further study.     

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.     

Preterm birth and maternal country of birth in a French district with a multiethnic population

OBJECTIVES: This analysis explores the association between preterm birth and maternal country of birth in a French district with a multiethnic population. DESIGN: Prospective observational study. SETTING: District of Seine-Saint-Denis in France POPULATION: 48,746 singleton live births from a population-based birth register between October 1998 and December 2000. METHODS: We compare preterm birth rates by mother's country of birth controlling for demographic and obstetric factors as well as insurance coverage and timing of initiation of antenatal care. MAIN OUTCOME MEASURES: Overall preterm birth rates and preterm birth rates by timing of delivery (<33 weeks versus 33-36 weeks of gestation), mode of onset (spontaneous or indicated preterm birth) and the presence of hypertension in pregnancy. RESULTS: Women born in Northern Africa, Southern Europe and South/East Asia did not have higher preterm birth rates than women born in continental France. Rates were significantly higher for women born in the overseas French districts in the Caribbean and Indian Ocean and Sub-Saharan Africa. Excess risk was greatest for early preterm births, medically indicated births and preterm births associated with hypertension. CONCLUSIONS: Patterns of preterm birth with relation to timing, mode of onset and medical complications among of Afro-Caribbean origin should be confirmed in future research.     

Risk factors for preterm birth in Vietnam.

OBJECTIVE: To identify the risk of preterm birth and possible determinants among women in Hanoi, Vietnam. METHOD: Prospective cohort study of 1709 women with singleton live births at Hanoi Obstetrics and Gynecology Hospital, Hanoi, Vietnam, June-October 2002. Logistic regression analysis was used to examine predictors of preterm birth (<37 weeks' gestation). RESULT: The risk of preterm birth was 11.8%. Physically demanding work during pregnancy, two or more prior spontaneous abortions, history of preterm birth, vaginal bleeding, inadequate prenatal care during the first 20 weeks of gestation, and history of intrauterine device use with removal less than 12 months before the current pregnancy were associated with increased risk of preterm birth (adjusted odds ratios between 1.8 and 2.6). CONCLUSION: Preterm birth is relatively frequent in this population. Beyond established risk factors, these data implicated agricultural work and physical work demands with preterm birth, as well as history of recent IUD use.     

Spontaneous preterm birth of liveborn infants in women at low risk in Australia over 10 years: a population-based study

Objectives  To describe a 10-year trend in preterm birth.
Design  Population-based study.
Setting  Australia.
Population  All women who gave birth during 1994–03.
Methods  The proportion of spontaneous preterm births (greater than or equal to 22 weeks of gestation and less than 37 completed weeks of gestation) was calculated by dividing the number of women who had a live spontaneous preterm birth (excluding elective caesarean section and induction of labour) by the total number of women who had a live birth after spontaneous onset of labour (excluding elective caesarean section and induction of labour). This method was repeated for the selected population of women at low risk.
Main outcome measure  Preterm birth rates among the overall population of women; preterm birth among all women with a spontaneous onset of labour; and preterm birth in a selected population of women who were either primiparous or multiparous, non-Indigenous; aged 20–40 years and who gave birth to a live singleton baby after the spontaneous onset of labour.
Results  Over the 10-year study period, the proportion of all women having a live preterm birth in Australia increased by 12.1% (from 5.9% in 1994 to 6.6% in 2003). Among women with a spontaneous onset of labour, there was an increase of 18.3% (from 5.7 to 6.7%). Among the selected population of low-risk women after the spontaneous onset of labour, the rate increased by 10.7% (from 5.6 to 6.2%) among first time mothers and by 19.2% (4.4–5.2%) among selected multiparous women.
Conclusions  Over the 10-year period of 1994–03, the rate of spontaneous preterm birth among low-risk women having a live singleton birth has risen in Australia.     

The preterm prediction study: granulocyte colony-stimulating factor and spontaneous preterm birth. National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network

OBJECTIVE: Granulocyte colony-stimulating factor is elevated in the amniotic fluid and plasma of women with chorioamnionitis and active preterm labor. We investigated the relationship between plasma granulocyte colony-stimulating factor and subsequent spontaneous preterm birth in pregnant women without symptoms. STUDY DESIGN: We performed a nested case-control study involving 194 women who had a singleton spontaneous preterm birth and 194 matched term control subjects from the patient pool (n = 2929) enrolled in the Preterm Prediction Study. Plasma collected at 24 and 28 weeks' gestation was analyzed for granulocyte colony-stimulating factor, and the results were compared with subsequent spontaneous preterm birth. RESULTS: Compared with term control subjects, women who were delivered of their infants spontaneously at <28 weeks' gestation had increased mean granulocyte colony-stimulating factor values at 24 weeks' gestation (84.7 +/- 38.4 vs 67.7 +/- 28.6 pg/mL; P =.049), and women who were delivered of their infants at <32 weeks' gestation had increased mean plasma granulocyte colony-stimulating factor values at 28 weeks' gestation (80.4 +/- 24.1 vs 55.9 +/- 16.5 pg/mL; P =. 001). At 24 weeks' gestation a granulocyte colony-stimulating factor value >75th percentile in control subjects (approximately 80 pg/mL) was found in 48.9% (23/47) of all women delivered of their infants at <32 weeks' gestation versus 14.9% (7/47) of the term control subjects (adjusted odds ratio, 6.2; 95% confidence interval, 1.8-20. 8). At 28 weeks' gestation a granulocyte colony-stimulating factor value >75th percentile was found in 36.8% (7/19) of women delivered of their infants at <32 weeks' gestation versus 5.3% (1/19) of term control subjects (adjusted odds ratio, 25.7; 95% confidence interval, 1.5-470.4). When measured at 24 or 28 weeks' gestation, granulocyte colony-stimulating factor did not predict spontaneous preterm birth at 32 to 34 weeks' gestation or at 35 to 36 weeks' gestation. CONCLUSION: In pregnant women without symptoms at 24 and 28 weeks' gestation, elevated plasma granulocyte colony-stimulating factor levels are associated with subsequent early (<32 weeks' gestation) spontaneous preterm birth, especially within the next 4 weeks, but not with late spontaneous preterm birth. These data provide further evidence that early spontaneous preterm birth is associated with an inflammatory process that is identifiable by the presence of a cytokine in maternal plasma several weeks before the early spontaneous preterm birth; however, later spontaneous preterm birth is not associated with this process.     

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 rise in singleton preterm births in the USA: the impact of labour induction

Please cite this paper as: Zhang X, Kramer M. The rise in singleton preterm births in the USA: the impact of labour induction. BJOG 2012;119:1309-1315. Objective To assess the extent to which increased rates of labour induction and caesarean section have contributed to the recent rise in preterm birth. Design National birth cohort study. Setting USA. Population and sample Singleton live births, with primary analysis based on non-Hispanic white women. Methods Ecological study based on the 50 states and the District of Columbia during two time periods 10?years apart: 1992-94 and 2002-04. Main outcome measure Preterm birth (live birth <37?completed weeks of gestation), based on an algorithm combining menstrual and clinical estimates of gestational age. Results The state-level ecological analysis among non-Hispanic white women showed that the change in preterm birth rate from 1992-94 to 2002-04 was significantly associated with the change in rate of labour induction (r?=?0.50, 95% CI 0.26-0.68), but not with the change in rate of caesarean delivery (r?=?-0.06, 95% CI -0.33 to 0.22). Weaker but otherwise similar associations with labour induction were observed in Hispanic women and in non-Hispanic black women. Conclusions Increasing use of labour induction is probably an important cause of the observed increased rate in preterm birth.     

The relationship between cesarean delivery and gestational age among US singleton births

The increasing trend of delivering at earlier gestational ages has raised concerns of the impact on maternal and infant health. The delicate balance of the risks and benefits associated with continuing a pregnancy versus delivering early remains challenging. Among singleton live births in the United States, the proportion of preterm births increased from 9.7% to 10.7% between 1996 and 2004. The increase in singleton preterm births occurred primarily among those delivered by cesarean section, with the largest percentage increase in late preterm births. For all maternal racial/ethnic groups, singleton cesarean section rates increased for each gestational age group. Singleton cesarean section rates for non-Hispanic black women increased at a faster pace among all preterm gestational age groups compared with non-Hispanic white and Hispanic women. Further research is needed to understand the underlying reasons for the increase in cesarean section deliveries resulting in preterm birth.     

An assessment of key aetiological factors associated with preterm birth and perinatal mortality.

The 4 main causes of preterm births in 303 women with consecutive deliveries in Flinders Medical Centre were premature rupture of the membranes (39%), spontaneous preterm labour (22%), pregnancy-induced hypertension (17%) and antepartum haemorrhage (12%). Premature rupture of the membranes occurred with equal frequency in singleton and multiple pregnancies and there was no difference in the frequency of this cause between the pregnancies with live outcomes and those with perinatal deaths. Spontaneous preterm labour was more common in multiple pregnancies (39%) than in singleton pregnancies (22%). One in 3 of the preterm births and 79% of the pregnancies with perinatal deaths occurred at less than 32 weeks' gestation. As it is unlikely that any single obstetric and social intervention will be able to reduce these causes of preterm birth research must continue to find markers to predict premature rupture of the membranes and spontaneous preterm labour.     

Risk of preterm delivery in non-diabetic women with polycystic ovarian syndrome

Objective:To examine the risk and etiology of preterm delivery in women with polycystic ovary syndrome (PCOS).Study Design:Retrospective cohort study comparing preterm delivery rate among non-diabetic PCOS and non-PCOS women with singleton pregnancy. Multivariable logistic regression was used to identify predictors of preterm delivery among PCOS women.Result:Among 908 PCOS women with singleton pregnancy, 12.9% delivered preterm compared with 7.4% among non-PCOS women (P<0.01). Causes of preterm delivery among PCOS women included preterm labor (41%), cervical insufficiency (11%), hypertensive complications (20%), preterm premature rupture of membranes (15%), fetal-placental concerns (9%) and intrauterine fetal demise (5%). Maternal age, race/ethnicity and nulliparity were significant predictors of preterm delivery in PCOS, whereas body mass index and fertility medications were not.Conclusion:A higher proportion of PCOS women delivered preterm (12.9%) compared with non-PCOS women, with the majority of cases due to spontaneous preterm birth. Future studies should explore etiologies and strategies to improve pregnancy outcomes in PCOS.