Erez et al. BMC Pregnancy and Childbirth 2012, 12:82 http://www.biomedcentral.com/1471-2393/12/82 RESEARCH ARTICLE Open Access Early preterm delivery due to placenta previa is an independent risk factor for a subsequent spontaneous preterm birth Offer Erez1*, Lena Novack2, Vered Klaitman1, Idit Erez-Weiss3, Ruthy Beer-Weisel1, Doron Dukler1 and Moshe Mazor1 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 1.5-8.5)]. 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. Keywords: Preterm birth, Placenta, Recurrent preterm delivery, Vaginal bleeding, Short cervix, Placenta previa Background distress syndrome and anemia are associated with this Placenta previa is a risk factor for preterm birth, and abnormal placentation [15,16]. contributes to about 5% of all preterm deliveries. [1] The Most of the patients with placenta previa are delivered prevalence of placenta previa is 0.3-0.5% of pregnancies preterm [4,17], and these deliveries are regarded as indi- [2-10], and the risk for this complication increases cated preterm births due to excessive maternal according to the number of prior cesarean deliveries hemorrhage. Nevertheless, recent evidence suggests that [11-14]. Placenta previa is associated with an increased other mechanisms aside bleeding may lead to preterm maternal morbidity including the need for blood and birth in women with placenta previa [18,19]. Patients blood products transfusion, urgent cesarean section, and with placenta previa who delivered preterm had a higher cesarean hysterectomy. Moreover, a higher rate of peri- rate of intra-amniotic infection/inflammation than those natal mortality and morbidity, especially respiratory who delivered at term [18], suggesting that similarly to spontaneous preterm birth, intra-amniotic infection or inflammation may contribute to the process of preterm * Correspondence: [email protected] parturition in patients with placenta previa. Moreover, 1Department of Obstetrics and Gynecology, Soroka University Medical Center, School of Medicine, Faculty of Health Sciences, Ben Gurion University women with this complication who had a short cervical of the Negev, P O Box 151, Beer Sheva 84101, Israel length have an increased risk to deliver preterm [20-22]. Full list of author information is available at the end of the article © 2012 Erez et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Erez et al. BMC Pregnancy and Childbirth 2012, 12:82 Page 2 of 6 http://www.biomedcentral.com/1471-2393/12/82 Thus, the mechanisms leading to spontaneous preterm delivery. Preterm delivery was defined as delivery before parturition may play a similar role in patients with pla- complete 37 weeks of gestation, early preterm birth was centa previa who deliver prematurely. defined as delivery <34 weeks of gestation, and late pre- Placenta previa is a recurrent pregnancy complication; term birth was defined as delivery between 34 to 36.9 reports suggest a recurrence rate of 2.3-3.2% [23,24]. weeks of gestation. Small for gestational age (SGA) was The underlying mechanisms leading to this are not com- defined as birthweight below the 10th percentile [26]. pletely understood. Yet, it is not clear from the literature whether patients with placenta previa who deliver pre- Statistical analysis term are at increased risk for recurrent preterm birth. The rate of placenta previa, its recurrence, and the risk The objective of this study was to determine whether for preterm delivery at the subsequent delivery following women with placenta previa who delivered preterm are a placenta previa at the primary CS pregnancy, were at increased risk for recurrent preterm birth in the sub- determined as primary outcomes. sequent pregnancy. Maternal demographic characteristics, peripartum com- plications and perinatal outcome were compared between Methods women with and without placenta previa. Parametric and Study population, selection of patients non-parametric statistics were used for continues variables This is a retrospective population based cohort study in- according to their distribution. Chi-square and Fisher exact cluding all women who delivered subsequent to a pri- test were used to compare categorical variables. Variables mary cesarean section (CS) during the study period found to be significantly associated with placenta previa (1988–2010) at the “Soroka University Medical Center”, and preterm birth in the univariate analysis were included a regional tertiary medical center where all the births in a multiple logistic regression. A two tailed P value of take place, and met the inclusion criteria. This cohort 0.05 was considered significant. Analysis was done by SPSS (n = 9983) was divided into two groups according to the package (Chicago, IL, USA) and SAS software version 9.2 site of placentation at the primary CS: Patients with pla- (Cary, NC, USA). centa previa comprised the study group (n = 297), and those with normal placental insertion served as the com- Results parison group (n = 9686). The rate of placenta previa in the primary CS pregnancy The patients were identified in a computerized data- was 3.0% (297/9983), and 1.08% (108/9983) in the subse- base including all data concerning demographic charac- quent pregnancy. The recurrence rate of placenta previa teristics, medical and obstetric history, pregnancy among patients who had this complication at the pri- outcomes as well as, maternal and neonatal morbidity mary CS pregnancy was higher than among those with- and mortality of all the deliveries at our medical center. out it [placenta previa- 2.69% (8/297) vs. normal Women who lacked minimal prenatal care (less than placentation- 1.03% (100/9686) crude odds ratio (OR) of three visits in prenatal clinic), those with multiple gesta- 2.65 (95% CI 1.2-5.7)]. tions, and parturient carrying a fetus with known chromo- Women with placenta previa had a higher mean ma- somal or anatomical anomalies were excluded from the ternal age and grand multiparity rate than those with study. The Institutional Review Board of Soroka University normally implanted placentae in both pregnancies. The Medical Center approved the study. rate of prior preterm birth did not differ between patients with placenta previa and those with normal pla- Outcome variables and clinical definitions centation in neither of the pregnancies (Table 1). Parity groups were defined in the following order: prim- Therateofpretermdeliveryamongpatientswithpla- ipara, multipara (2–5 deliveries) and grand multipara (6 centa previa in the primary CS pregnancy was 55.9% or more deliveries). Gestational age was determined by (166/297) and 51.9% (56/108) among those who had pla- date of last menstrual period when reliable and sono- centa previa in the subsequent birth. In both pregnancies graphic confirmation carried out by the first 20 weeks of studied, the rate of severe prematurity (<32 weeks of ges- gestation and/or first trimester sonographic measure- tation) was higher among women with placenta previa ment of crown- rump length. Hypertensive disorders of than in those with normal placentation [primary CS - pregnancy were defined according the American College normal placentation 4.1% (395/9686) vs. placenta previa of Obstetrics and Gynecology (ACOG) criteria [25]. Pla- 16.9% (50/297), OR 4.13 (95%CI 3.15-5.41), p < .001; sub- centa previa was defined as a placenta that partially or sequent delivery- normal placentation 2% (195/9875) vs. fully covers the internal cervical os, or when the lower placenta previa 9.3% (10/108), OR 5.07 (95%CI 2.45- placental edge lies within 20 mm from it [3]. The loca- 10.18), p < 0.001] (Figure 1). tion of the placenta was diagnosed prenatally by ultra- Women with placenta previa who delivered preterm sound examination and verified during the cesarean at the primary CS pregnancy had a higher rate of Erez et al. BMC Pregnancy and Childbirth 2012, 12:82 Page 3 of