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ORIGINAL RESEARCH |
From the Department of Obstetrics and Gynecology, Memorial University of Newfoundland, St. John’s, Newfoundland, Canada, and Department of Obstetrics and Gynecology, Dalhousie University, Halifax, Nova Scotia, Canada.
Address reprint requests to: Joan M. Crane, MD, Grace General Hospital, St. John’s, Newfoundland A1E 1P9, Canada
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Abstract |
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Methods: This was a population-based, retrospective cohort study involving all singleton deliveries in Nova Scotia from 1988 to 1995. The study group consisted of all completed singleton pregnancies complicated by placenta previa; all other singleton pregnancies were considered controls. Patient information was collected from the Nova Scotia Atlee perinatal database. Neonatal complications were evaluated while controlling for potential confounders. The data were analyzed using 
2, Fisher exact test, and multiple logistic regression.
Results: Among 92,983 pregnancies delivered during the study period, 305 cases of placenta previa were identified (0.33%). After controlling for potential confounders, neonatal complications significantly associated with placenta previa included major congenital anomalies (odds ratio [OR] 2.48), respiratory distress syndrome (OR 4.94), and anemia (OR 2.65). The perinatal mortality rate associated with placenta previa was 2.30% (compared with 0.78% in controls) and was explained by gestational age at delivery, occurrence of congenital anomalies, and maternal age. Although there was a higher rate of preterm births in the placenta previa group (46.56% versus 7.27%), there was no difference in birth weights between groups after controlling for gestational age at delivery.
Conclusion: Neonatal complications of placenta previa included preterm birth, congenital anomalies, respiratory distress syndrome, and anemia. There was no increased occurrence of fetal growth restriction.
Placenta previa, an important cause of antepartum hemorrhage, is estimated to occur in 0.31% to 0.60% of pregnancies at delivery.1–14 Previous studies of complications of placenta previa might have limited current relevance. Almost all studies were conducted more than a decade ago.1–9,11,13–19 Although expectant obstetric treatment has not changed since then, there have been improvements in diagnosis20–22 and neonatal treatment.23,24 Those refinements might have changed the rate of neonatal complications. Previous studies examined women from individual centers, introducing possible referral bias. Some of those studies used birth certificate data or survey data,4,10 limiting the available variables. Even when important variables were included, most studies did not take into account the potential effects of confounding factors.1–3,5–8,14–19 The objective of this study was to determine the neonatal complications of placenta previa.
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Materials and Methods |
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Neonatal outcomes included perinatal death, congenital anomaly, birth weight, and preterm birth (defined as delivery before 37 weeks’ gestation). Congenital anomalies included cardiovascular, gastrointestinal, respiratory, otolaryngologic, genitourinary (including renal), dermatologic, musculoskeletal, neurologic, and chromosomal anomalies. Various specific measures of neonatal morbidity were evaluated, including respiratory distress syndrome (RDS), respiratory depression at birth, Apgar score less than 7 at 5 minutes, intraventricular hemorrhage, anemia, and length of hospital stay. Respiratory distress syndrome was defined as the presence of grunting, retractions, and decreased air entry before 3 hours of age, persisting beyond 6 hours of age, and not explained by any other disease. It was graded as mild (less than 35% oxygen), moderate (at least 35% oxygen or continuous positive airway pressure), or severe (mechanical ventilation). Respiratory depression at birth was defined as decreased respiratory effort requiring intermittent positive pressure ventilation. Intraventricular hemorrhage included all four grades and all subependymal hemorrhages, regardless of cause or predisposing factor. Neonatal anemia was defined as hemoglobin less than 140 g/L or hematocrit less than 42% in the first week of life, or hemoglobin less than 100 g/L or hematocrit less than 30% at any neonatal age before discharge.
Data were analyzed using SAS 6.11 (SAS Institute Inc, Cary, NC) statistical program to compare women with placenta previa to women without placenta previa who delivered in the same period. Continuous variables are given as median (not a normal distribution) and compared using the Wilcoxon rank sum test. Categoric variables are given as a percentage and compared using 2 or Fisher exact test where appropriate. Categoric variables are also given as and compared using crude odds ratios (OR) and 95% confidence intervals (CI). When neonatal complications other than mortality and major anomaly were examined, stillbirths were excluded (because neonatal complications would not be possible in that group). Multiple logistic regression was used to control for potential confounders, providing adjusted ORs.
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Results |
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). The crude OR suggested an increased risk of perinatal death with placenta previa, but when adjustments were made for maternal age, gestational age, and congenital anomalies, the risk of death was no longer significantly increased (Table 2). Placenta previa was significantly associated with major fetal anomalies, even when adjusted for maternal age.
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), the significant neonatal complications included RDS and anemia. Potential complications not found to be significant after controlling for the same potential confounders included respiratory depression at birth, intraventricular hemorrhage, and a low Apgar score at 5 minutes. As expected, preterm births and neonatal intensive care unit (NICU) admissions were significantly more frequent in the placenta previa group. Neonatal hospitalizations were longer in that group. Birth weights were lower in the study group, but were not significantly different when adjusted for gestational age (P = .15). |
Discussion |
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Other neonatal complications associated with placenta previa in previous studies include preterm birth, low birth weight, respiratory depression at birth, RDS, intraventricular hemorrhage, anemia, and low Apgar scores.2,3,5–7,14–19 None of those studies controlled for maternal age, gestational age, and congenital anomalies. When potential confounders were controlled for, neonatal complications of placenta previa included RDS and anemia. It might be that the circumstances of the deliveries of those infants (bleeding with or without fetal compromise) predisposed them to hypoxia and anemia, thus increasing the incidence of RDS.5 The present study confirmed that preterm birth, admission to NICU, and length of neonatal hospital stay were significantly increased in pregnancies complicated by placenta previa. After controlling for gestational age, birth weight did not appear to be adversely influenced by placenta previa. That finding contradicts previous studies that suggested a higher incidence of suspected fetal growth restriction1,15,17,18 and might be explained by improvements in obstetric ultrasound and treatment.
Our study took place when transvaginal ultrasound, maternal steroids for lung maturity, and neonatal surfactants were available. The perinatal mortality rate was lower than that in previous studies, and infants were more likely to be preterm but not growth delayed when gestational age was considered. Because our findings incorporated current obstetric and neonatal practices, knowledge of neonatal complications of placenta previa can be used to improve prenatal counseling and neonatal treatment.
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Footnotes |
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Received June 12, 1998. Received in revised form September 15, 1998. Accepted October 8, 1998.
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References |
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2. Cotton DB, Read JA, Paul RH, Quilligan EJ. The conservative aggressive management of placenta previa. Am J Obstet Gynecol 1980;137:687–95.[Medline]
3. Brenner WE, Edelman DA, Hendricks CH. Characteristics of patients with placenta previa and results of "expectant management." Am J Obstet Gynecol 1978;132:180–91.[Medline]
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8. Strong TH, Brar HS. Placenta previa in twin gestations. J Reprod Med 1989;34:415–6.[Medline]
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20. Leerentveld RA, Gilberts EC, Arnold MJ, Wladimiroff JW. Accuracy and safety of transvaginal sonographic placental localization. Obstet Gynecol 1990;76:759–62.[Medline]
21. Sherman SJ, Carlson DE, Platt LD, Medearis AL. Transvaginal ultrasound: Does it help in the diagnosis of placenta previa? Ultrasound Obstet Gynecol 1992;2:256–60.[Medline]
22. Farine D, Fox HE, Jakobson S, Timor-Tritch IE. Vaginal ultrasound for diagnosis of placenta previa. Am J Obstet Gynecol 1988;159: 566–9.[Medline]
23. Crowley P. Corticosteriods prior to preterm delivery. In: Enkin MW, Keirse MJNC, Renfrew MJ, Neilson JP, eds. Pregnancy and childbirth module, "Cochrane Database of Systematic Reviews." Review No. 02955, August 14, 1994. Disk Issue 1. Oxford: Update Software, 1994.
24. Mercier CE, Soll RF. Clinical trials of natural surfactant extract in respiratory distress syndrome. Clin Perinatol 1993;20:711–35.[Medline]
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