Association of maternal serum alpha-fetoprotein with persistent placenta previa.

OBJECTIVE: To evaluate the relationship between maternal serum alpha-fetoprotein (MSAFP) and the risk of persistent placenta previa. METHODS: We conducted a retrospective cohort study of singleton pregnancies with sonographic evidence of placenta previa at 15-20 weeks' gestation, between October 1991 and August 2000. Only pregnancies with MSAFP determination at 15-20 weeks' gestation and non-anomalous live-born infants > or =24 weeks' gestation were included. Pregnancies in which Cesarean delivery was performed for placenta previa were considered persistent; this was the primary outcome. RESULTS: Of 275 women with previa at 15-20 weeks' gestation, 33 (12%) had previa at delivery. Trend analysis revealed a greater likelihood of persistent previa with increasing MSAFP values (p=0.01). Mid-trimester MSAFP <1 multiple of the median (MoM) was associated with a decreased incidence of persistence of 4%, significantly less than the risk at > or =1 MoM (16%; p=0.01). CONCLUSIONS: There is an association between increasing MSAFP values and greater likelihood of persistent placenta previa. An MSAFP value <1 MoM is associated with a reduction in the risk of persistence of previa to delivery.     

Association of maternal serum α-fetoprotein with persistent placenta previa

Objective: To evaluate the relationship between maternal serum α-fetoprotein (MSAFP) and the risk of persistent placenta previa.

Methods: We conducted a retrospective cohort study of singleton pregnancies with sonographic evidence of placenta previa at 15?–?20 weeks' gestation, between October 1991 and August 2000. Only pregnancies with MSAFP determination at 15?–?20 weeks' gestation and non-anomalous live-born infants ??24 weeks' gestation were included. Pregnancies in which Cesarean delivery was performed for placenta previa were considered persistent; this was the primary outcome.

Results: Of 275 women with previa at 15?–?20 weeks' gestation, 33 (12%) had previa at delivery. Trend analysis revealed a greater likelihood of persistent previa with increasing MSAFP values (p?=?0.01). Mid-trimester MSAFP <?1 multiple of the median (MoM) was associated with a decreased incidence of persistence of 4%, significantly less than the risk at ??1 MoM (16%; p?=?0.01).

Conclusions: There is an association between increasing MSAFP values and greater likelihood of persistent placenta previa. An MSAFP value <?1 MoM is associated with a reduction in the risk of persistence of previa to delivery.     

Placenta previa associated with severe bleeding leading to hospitalization and delivery: a retrospective population-based cohort study

Introduction: The aim of our study was to compare maternal and neonatal outcomes in women with placenta previa complicated with severe bleeding leading to hospitalization until delivery versus those without severe bleeding episodes.

Methods: This is a population-based retrospective cohort study including all pregnant women with placenta previa who delivered at our medical center in the study period, divided into the following groups: 1) women with severe bleeding leading to hospitalization resulting with delivery (n?=?32); 2) patients with placenta previa without severe bleeding episodes (n?=?1217).

Results: Out of all women with placenta previa who delivered at our medical center, 2.6% (32/1249) had an episode of severe bleeding leading to hospitalization and resulting with delivery. The rate of anemia was lower (43.8% versus 63.7%, p?=?0.02) while the need for blood transfusion higher (37.5% versus 21.1%, p?=?0.03) in the study group. The rate of cesarean sections was significantly different between the groups, and a logistic regression model was constructed in order to find independent risk factors for cesarean section in our patients.

Conclusion: To the best of our knowledge, this is the first study to evaluate the impact of severe bleeding on the outcome of pregnancies complicated with placenta previa. Our study demonstrates that, in women with placenta previa, severe bleeding does not lead to increased adverse maternal or neonatal outcomes.     

Low birth weight and preterm delivery in relation to early-gestation vaginal bleeding and elevated maternal serum alpha-fetoprotein.

OBJECTIVE: To determine whether early-gestation vaginal bleeding and elevated maternal serum alpha-fetoprotein (MSAFP) are independent risk factors for adverse infant outcomes. METHODS: We conducted a cohort study of 201 women with an elevated MSAFP (at least 2.0 multiples of the median [MOM]) and a second-trimester ultrasound evaluation at Swedish Hospital Medical Center between January 1989 and March 1991, and 211 women with MSAFP levels below 2.0 MOM who had also undergone ultrasound evaluations during the same period. RESULTS: Stratified analyses demonstrated that early-gestation bleeding and elevated MSAFP were independent risk factors for the delivery of both preterm and low birth weight infants. Compared with women with no history of early-gestation bleeding or elevated MSAFP, women with early-gestation bleeding alone had a relative risk (RR) of preterm delivery of 4.3 (95% confidence interval [CI] 1.5-12.1); non-bleeders with elevated MSAFP had an RR of 4.6 (95% CI 1.9-10.9). A combined history of early-gestation bleeding and elevated MSAFP was associated with an almost sixfold increased risk of preterm delivery (RR 5.8; 95% CI 2.2-15.6). Analyses restricted to women with normal-appearing appearing placentas by second-trimester ultrasound evaluations yielded similar results. CONCLUSIONS: These findings support an earlier report documenting the independence of early-gestation bleeding and elevated MSAFP as predictors of adverse infant outcomes.     

The effect of placenta previa on neonatal mortality: a population-based study in the United States, 1989 through 1997

OBJECTIVE: The purpose of the study was to explore the associations of placenta previa with preterm delivery, growth restriction, and neonatal survival. STUDY DESIGN: A retrospective cohort study was performed of live births in the United States (1989-1991 and 1995-1997) that used the national linked birth/infant death records from 22,368,235 singleton pregnancies. The diagnosis of previa was restricted to those live births that were delivered (> or =24 weeks) by cesarean delivery. We evaluated gestational age and birth weight-specific risk of neonatal deaths (within the first 28 days) in relation to placenta previa. Fetal growth was assessed in centiles of birth weight (<3rd, 3rd-4th, 5th-9th, 10th-90th, and >90th centile), adjusted for gestational age. All analyses were adjusted for the confounding effects of the year of delivery, maternal age, gravidity, education, prenatal care, marital status, and race/ethnicity. RESULTS: Placenta previa was recorded in 2.8 per 1000 live births (n = 61,711). Neonatal mortality rate was 10.7 with previa, compared with 2.5 per 1,000 among other pregnancies (relative risk, 4.3; 95% confidence interval, 4.0,4.8). At 28 to 36 weeks, babies born to women with placenta previa weighed, on average, 210 g lower than babies born to women without placenta previa (P <.001). Compared with babies born to women without previa, the risk of death from placenta previa was lower among preterm babies (<37 weeks of gestation), with a crossover at 37 weeks where the mortality rate was higher for babies born to women with placenta previa than for babies born to women without placenta previa. This crossover also persisted in an analysis by birth weight and term births (delivered at > or =37 weeks of gestation). Mortality rates for term births were higher among babies born to women with placenta previa than among babies born women without placenta previa who were at the 10th to 90th centile (relative risk, 1.9; 95% confidence interval, 1.3, 2.8), and those at >90th centile (relative risk, 3.6; 95% confidence interval, 1.3, 9.6). Among preterm births, however, placenta previa was not associated with increased neonatal mortality by fetal growth centiles. CONCLUSION: The risk of neonatal mortality was higher for babies born to women with placenta previa than for babies born to women without placenta previa who were delivered at > or =37 weeks of gestation. Pregnancies that are diagnosed with placenta previa must be monitored carefully, especially as they approach term.     

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.     

Natural history of placenta previa ascertained by diagnostic ultrasound.

Placental localization by diagnostic ultrasound was performed at 16 to 18 weeks' gestation in 1,098 patients prior to amniocentesis for genetic indications. Placenta previa was diagnosed in 58 patients, 47 of whom went on to delivery uncomplicated by placenta previa. There were five patients with placenta previa at delivery, four of whom had third-trimester bleeding. One patient was diagnosed as having a normal placental implantation at midtrimester but placenta previa was demonstrated at delivery. The incidence of placenta previa at 16 to 18 weeks' was 5.3% and fell to 0.58% at delivery, indicating a 90% conversion rate. Thus the vast majority of cases of asymptomatic placenta previa remain so and convert before delivery. These patients should be observed with serial ultrasound at 6 to 8 week intervals until delivery or unequivocal conversion. No restriction in activity seems indicated unless the placenta previa persists beyond 30 weeks or becomes clinically manifest.     

Early placenta previa and delivery outcome

Ultrasound scan showed some degree of placenta previa in 503 patients. Of this group, 5.6% (28) had clinically significant bleeding or documented placenta previa at delivery. A scoring system based on placental localization was not successful in predicting who was at high risk for bleeding. However, the likelihood of clinically excessive bleeding did significantly increase if the placenta previa was noted after 30 weeks' gestation. The study did not find a greater incidence of small-for-gestational-age babies in women with low-lying placentas.     

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.     

High incidence of respiratory distress syndrome (RDS) in infants born to mothers with placenta previa

OBJECTIVE: To evaluate the incidence of respiratory distress syndrome (RDS) in infants born to mothers with placenta previa and to assess the risk factors for RDS. METHODS: Ninety-nine pregnant women with placenta previa who delivered by cesarean section at 30-35 weeks of gestation were compared retrospectively with 102 pregnant women matched for week of gestation and birth year, who underwent elective cesarean section. Maternal characteristics, neonatal outcome, and incidence of RDS were analyzed. Umbilical cord blood samples were collected at delivery and were used to determine cortisol, epinephrine, and norepinephrine levels. Student's t-test, the chi-square test, and Fisher's exact test were used for statistical comparisons. P < 0.05 was considered significant. The Mann-Whitney U test was used for comparison of continuous variables. RESULTS: Preeclampsia, histological chorioamnionitis, and premature rupture of membranes were significantly lower in the placenta previa group (placenta previa: 2.0% vs. control: 14.7%, P < 0.01; 14.1% vs. 30.1%, P < 0.01; 7.1% vs. 17.6%, P < 0.05, respectively). The incidence of RDS was significantly higher in the placenta previa group than in the control group (29.3% vs. 6.9%, P < 0.0001). The cortisol level in umbilical cord blood in the placenta previa group was lower than in the control group (median 7.3, range 4.4-14.9 microg/dl vs. median 10.6, range 4.9-30.3 microg/dl, P < 0.05). There were no significant differences in epinephrine or norepinephrine levels between the two groups. CONCLUSIONS: The incidence of RDS in infants delivered at 30-35 weeks' gestation by cesarean section was significantly higher in mothers with placenta previa than in women without placenta previa. This may reflect decreased fetal stress since the cord blood cortisol levels were found to be lower in women with placenta previa.     

Bacterial vaginosis and group B streptococcal colonization and preterm delivery in a low-risk population

OBJECTIVE: To evaluate the relationship between bacterial vaginosis (BV) and group B streptococcal (GBS) colonization in the 2nd trimester of pregnancy and preterm delivery. METHODS: 1,197 pregnant women between 22 and 25 weeks' gestation had a high vaginal swab for assessment of BV and GBS. Exclusion criteria were: previous preterm delivery, or mid-trimester abortion or termination of pregnancy, multiple gestation, oligo- or polyhydramnios, placenta previa, fetal abnormalities, uterine malformations, cervical incompetence, cervical cerclage, or receipt of an antibiotic effective against BV or GBS following the screening. All women had no risk factors for preterm delivery. The primary outcome measure in this analysis was spontaneous preterm delivery before 37 weeks' gestation. RESULTS: The preterm delivery rate was 8.7%, while the maternal BV and GBS colonization rates were 7.9 and 12.5%, respectively. Following adjustment for potential confounders BV was associated with an increased risk of preterm delivery (RR 2.19; CI: 1.21-3.98) (p = 0.01). On the contrary, GBS colonization was found to have a negative correlation with preterm birth (RR 0.43; 95% CI: 0.19-1.00). CONCLUSIONS: Although BV is a risk factor for preterm delivery, GBS colonization in the 2nd trimester of pregnancy has an inverse correlation with preterm delivery.     

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.     

Elevated maternal second-trimester serum alpha-fetoprotein as a risk factor for placental abruption

OBJECTIVE: To analyze the association of second-trimester maternal serum alpha-fetoprotein (MSAFP) and free beta human chorionic gonadotrophin (MSbeta-hCG) levels to placental abruption. METHODS: Fifty-seven women with placental abruption and 108 control women without placental abruption were tested for second-trimester MSAFP and MSbeta-hCG levels as a part of a trisomy 21 screening program. Discriminatory cutoff levels for MSAFP were sought to predict placental abruption. RESULTS: The median of the MSAFP multiples of median (MoM) (1.21) was significantly higher in the abruption group than in the control group (1.07) (p = 0.004). In multivariate analysis, elevated MSAFP remained an independent risk factor for placental abruption when adjusting for other risk factors (parity >/= 3, smoking, previous placental abruption, preeclampsia, bleeding in II or III trimester, and placenta previa). MSAFP >/= 1.5 MoM had a sensitivity of 29% and a false-positive rate of 10%. The levels of the MSbeta-hCG MoM did not differ between the cases and the controls. CONCLUSION: Although second-trimester MSAFP levels are higher in women with subsequent placental abruption, the clinical usefulness of this test is limited due to low sensitivity and high false-positive rate.     

Unexplained elevated midtrimester maternal serum levels of alpha fetoprotein, human chorionic gonadotropin, or low unconjugated estriol: recurrence risk and association with adverse perinatal outcome

OBJECTIVE: To determine if women experiencing an unexplained elevated maternal serum alpha fetoprotein (MSAFP; > or =2.0 MoM) or human chorionic gonadotropin (hCG; > or =2.0 MoM), or low unconjugated estriol (E3; < or =0.5 MoM) in one pregnancy are at increased risk for similar results in a subsequent pregnancy, and to determine if recurrence of these analyte extremes is associated with adverse perinatal outcome. METHODS: We identified all women delivering two consecutive singleton pregnancies at one hospital between 1992-1997 for whom second trimester trisomy 21 serum screen was performed in each pregnancy. All screens were performed in a single laboratory. Each pregnancy delivered after 20 weeks and had gestational age confirmed by ultrasound prior to 24 weeks. Subjects were excluded if a fetal anomaly or aneuploidy was present. Adverse outcomes included abruption, oligohydramnios, preeclampsia, preterm membrane rupture, preterm delivery, stillbirth, birthweight <10th centile, and admission to neonatal intensive care unit (NICU). RESULTS: A total of 538 women had 1,076 pregnancies meeting inclusion criteria; 12/515 (2.3%) of women with a normal MSAFP, 28/470 (6.0%) with a normal hCG, and 11/504 (2.2%) with a normal E3 in the first pregnancy had an anomalous result for the respective analyte in the second pregnancy. In contrast, only 4/23 (17.4%) patients with an elevated MSAFP (P = 0.003), 14/44 (31.8%) with an elevated hCG (P < 0.001), and 2/10 (20.0%) with a low E3 (P < 0.025) in the first pregnancy had the same analyte anomaly recur in the second pregnancy. The odds ratios for recurrent elevated MSAFP, hCG, and low E3 were 7.5, 5.3, and 9.2, respectively. Adverse perinatal outcomes occurred with similar frequency, regardless of MSAFP, hCG, or E3 results in consecutive pregnancies, using women with normal MSAFP, hCG, and E3 results in one or both pregnancies as controls. CONCLUSIONS: Women experiencing an anomalous serum analyte in one pregnancy are at significant risk to experience the same analyte result in a subsequent pregnancy.     

Placenta previa, placenta accreta, and vasa previa

Placenta previa, placenta accreta, and vasa previa are important causes of bleeding in the second half of pregnancy and in labor. Risk factors for placenta previa include prior cesarean delivery, pregnancy termination, intrauterine surgery, smoking, multifetal gestation, increasing parity, and maternal age. The diagnostic modality of choice for placenta previa is transvaginal ultrasonography, and women with a complete placenta previa should be delivered by cesarean. Small studies suggest that, when the placenta to cervical os distance is greater than 2 cm, women may safely have a vaginal delivery. Regional anesthesia for cesarean delivery in women with placenta previa is safe. Delivery should take place at an institution with adequate blood banking facilities. The incidence of placenta accreta is rising, primarily because of the rise in cesarean delivery rates. This condition can be associated with massive blood loss at delivery. Prenatal diagnosis by imaging, followed by planning of peripartum management by a multidisciplinary team, may help reduce morbidity and mortality. Women known to have placenta accreta should be delivered by cesarean, and no attempt should be made to separate the placenta at the time of delivery. The majority of women with significant degrees of placenta accreta will require a hysterectomy. Although successful conservative management has been described, there are currently insufficient data to recommend this approach to management routinely. Vasa previa carries a risk of fetal exsanguination and death when the membranes rupture. The condition can be diagnosed prenatally by ultrasound examination. Good outcomes depend on prenatal diagnosis and cesarean delivery before the membranes rupture.     

Placenta Praevia: Does Uterine Activity Cause Bleeding?

EDITORIAL COMMENT": We accepted this paper for publication since it attempts to evaluate whether uterine contractions or 'taking-up' of the lower uterine segment initiate placental separation and haemorrhage in women with central placenta praevia. Obstetric practice in the USA is often different from that in Australia; certainly it is not our custom to manage women at home when central placenta praevia complicated by haemorrhage has occurred after the second trimester! The use of tocolysis for preterm labour in women with placenta praevia with or without haemorrhage is another regimen employed in this series that will interest readers.
Summary: Twenty-two women >24 weeks' gestation with a central placenta praevia were monitored to determine if an increase in uterine activity precedes bleeding in patients with central praevias. Monitoring of all subjects began at 26.3 ±4.4 weeks and continued until 37 weeks (or delivery if preterm).
All subjects had at least one haemorrhage, 7 women had 2, and 4 subjects had 3 episodes of bleeding. Only 3 patients delivered at term while the remainder (86%) delivered preterm. The gestational age at first episode of bleeding was 29.1 ±3.6 weeks and at delivery was 34.3 ±3.3 weeks. Nine women (41%) had an increase in uterine activity above baseline the day of or the day preceding the first haemorrhage. The increase in uterine activity was not statistically significant when compared to the 6 days prior to bleeding when all 22 patients were considered.     

Elevated maternal serum alpha-fetoprotein with low unconjugated estriol and the risk for lethal perinatal outcome

OBJECTIVE: To determine whether a combination of elevated maternal serum alpha-fetoprotein (MSAFP) and low unconjugated estriol (E3) concentration identifies pregnancies at particularly high risk for fetal abnormality or poor outcome. METHODS: Pregnancy outcomes were reviewed for women with elevated MSAFP (> or =2.0 MoM) from our database of 50,315 women who had received triple marker testing from 1993-1998. Outcomes for those with low E3 (< or =0.7 MoM) were compared with those with normal E3 (>0.7 MoM). The incidences of fetal death, neural tube defects, chromosome abnormalities, congenital abnormalities, preterm birth, small-for-gestational age (SGA), twins, and inaccurate dates were compared in the two groups using Fisher's exact test with P < 0.05 considered significant. RESULTS: Of the 50,315 women screened, 1,435 (2.85%) had an elevated MSAFP. Pregnancy outcomes were obtained in 94% of those with elevated MSAFP and 70% of all patients screened. Neural tube defects were present in 57 fetuses/infants (21 anencephalic, 29 spina bifida, 7 encephalocele) of which 46 (81%) had an elevated MSAFP. Of the 1,435 women with an elevated MSAFP, 199 (14%) had a low E3. Compared to those women with elevated MSAFP but normal E3, women with elevated MSAFP and low E3 were at significantly increased risk for fetal death (20.6% vs. 2.8%, relative risk (RR) 8.9), anencephaly (9.0% vs. 0.1%, RR 122.8) and chromosome abnormality (2.5% vs. 0.6%, RR 4.0). CONCLUSIONS: Pregnancies complicated by elevated second trimester MSAFP and low E3 are at a particularly high risk (32%) for lethal perinatal outcomes. Twins, while a common cause of elevated MSAFP, are rarely found when an elevated MSAFP is associated with low E3.     

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.     

Cervical dilatation and prematurity revisited

Cervical examination between 26 and 30 weeks' gestation is described as a method for identifying women at risk for delivery before 34 weeks. Blinded cervical examinations were performed in 185 consecutive women, and 15 (8%) were found to have cervixes dilated 2 or 3 cm. The incidence of delivery before 34 weeks' gestation was 27% in such women compared with 2% in those whose cervixes were undilated or 1 cm. Other factors linked to cervical dilatation included parity and prior preterm delivery. However, parous women with cervical dilatation remained at increased risk for delivery before 34 weeks' gestation. We conclude that early third-trimester cervical examination may be an important adjunct in identifying women at risk for preterm delivery.     

Optimal timing of antenatal corticosteroids in women with bleeding placenta previa or low-lying placenta*

Background: Administrating a single course of antenatal corticosteroids to women at risk of preterm birth between 24 and 34 weeks of gestation has been shown to decrease neonatal morbidity and mortality. There is evidence that the optimal timing for the administration of antenatal corticosteroids is within 1–7 days before birth as the effect of antenatal corticosteroids has been shown to decline 7 days after administration. Therefore, given that antenatal corticosteroids are the single most effective intervention in cases of preterm birth, efforts should be made to optimize the timing of administration of antenatal corticosteroids.

Objective: To test the hypothesis that the timing of antenatal corticosteroids in women with vaginal bleeding due to placenta previa or low-lying placenta can be optimized by identifying women at low risk of imminent delivery.

Study design: This was a retrospective cohort study of all women admitted to a tertiary referral center at 24–34 weeks’ gestation with vaginal bleeding due to placenta previa or low-lying placenta between 2003 and 2014. Multivariable logistic regression analysis was used to identify factors that are independently associated with delivery within 14 days from admission.

Results: A total of 202 women who met the inclusion criteria were admitted with vaginal bleeding in the presence of placenta previa or low-lying placenta during the study period, of whom 31 (15.3%) and 44 (21.8%) gave birth within 7 and 14 days from admission, respectively. The following factors were independently associated with delivery within 14 days from admission: complete placenta previa (odds (OR) 3.57, 95%CI 1.57–9.03), severe bleeding at presentation (OR 17.14, 95%CI 2.92–100.70), uterine contractions at presentation (OR 6.02, 95%CI 1.91–19.00), and cervical length <25?mm at presentation (OR 6.33, 95%CI 1.37–29.11). A predictive test based on the presence of ≥1 of these risk factors was associated with a sensitivity of 90.9% and a negative predictive value of 94.6% for delivery within 14 days of presentation.

Conclusions: In women presenting with vaginal bleeding due to placenta previa or low-lying placenta, it seems possible to identify a subgroup of women in whom the likelihood of delivery within 14 days is low. This information may allow for selective (rather than routine) administration of antenatal corticosteroids in this scenario, and may thereby contribute to the optimization of the timing of administration of antenatal corticosteroids.