Placental implantation abnormalities and risk of preterm delivery: a systematic review and metaanalysis

Abstract

We sought to evaluate the extent of the association between placental implantation abnormalities (PIA) and preterm delivery in singleton gestations. We conducted a systematic review of English-language articles published from 1980 onward using PubMed, MEDLINE, EMBASE, CINAHL, LILACS, and Google Scholar, and by identifying studies cited in the references of published articles. Search terms were PIA defined as ≥ 1 of the following: placenta previa, placenta accreta, vasa previa, and velamentous cord insertion. Observational and experimental studies were included for review if data were available regarding any of the aforementioned PIA and regarding gestational age at delivery or preterm delivery. Case reports and case series were excluded. Studies were reviewed and data extracted. The primary outcome was gestational age at delivery or preterm delivery<37 weeks' gestation. Secondary outcomes included birthweight, 1- and 5-minute Apgar scores, neonatal intensive care unit (NICU) admission, neonatal and perinatal death, and small for gestational age. Of the 1421 studies identified, 79 met the defined criteria; 56 studies were descriptive and 23 were comparative. Based on the descriptive studies, the preterm delivery rates for low-lying/marginal placenta, placenta previa, placenta accreta, vasa previa, and velamentous cord insertion were 26.9%, 43.5%, 57.7%, 81.9%, and 37.5%, respectively. Based on the comparative studies using controls, there was decreased pregnancy duration for every PIA; more specifically, there was an increased risk for preterm delivery in patients with placenta previa (risk ratio [RR], 5.32; 95% confidence interval [CI], 4.39-6.45), vasa previa (RR, 3.36; 95% CI, 2.76-4.09), and velamentous cord insertion (RR, 1.95; 95% CI, 1.67-2.28). Risks of NICU admissions (RR, 4.09; 95% CI, 2.80-5.97), neonatal death (RR, 5.44; 95% CI, 3.03-9.78), and perinatal death (RR, 3.01; 95% CI, 1.41-6.43) were higher with placenta previa. Perinatal risks were also higher in patients with vasa previa (perinatal death rate RR, 4.52; 95% CI, 2.77-7.39) and velamentous cord insertion (NICU admissions [RR, 1.76; 95% CI, 1.68-1.84], small for gestational age [RR, 1.69; 95% CI, 1.56-1.82], and perinatal death [RR, 2.15; 95% CI, 1.84-2.52]). In singleton gestations, there is a strong association between PIA and preterm delivery resulting in significant perinatal morbidity and mortality.

Maternal vascular malperfusion of the placental bed associated with hypertensive disorders in the Boston Birth Cohort

“…Much evidence now supports the hypothesis that the placenta plays a central role in determining pregnancy outcomes, and maternal and fetal health [1–6]. Current research, arising from life course perspectives [7] and the fetal origins hypothesis [8], has extended the placenta’s impact to predict adult chronic diseases [9], and potentially transgenerational effects [10].…”

Prenatal diagnosis and management of vasa previa in twin pregnancies: a case series and systematic review

“…This occurs mainly when the cervix is effaced and dilated and the membranes rupture spontaneously or are ruptured artificially. It can lead to rapid fetal exsanguination and death [1][2][3][4][5] and the perinatal mortality of undiagnosed VP has been reported to be as high as 60%. 6 The incidence of VP has been reported to range between in 1 in 1200 to 1 in 5000 pregnancies but the condition may have been under-reported.…”

“…6 The incidence of VP has been reported to range between in 1 in 1200 to 1 in 5000 pregnancies but the condition may have been under-reported. [1][2][3][4][5] A recent systematic review of 10 cohort studies found that the incidence of VP is 0.6 per 1000 pregnancies. 7 Approximately 90% of women presenting with a VP also have a velamentous cord insertion (VCI) and 3-4% of women presenting with a VCI have a VP.…”

“…Both cord anomalies are 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 5 5 low-lying placenta. [1][2][3][4][5][6][7][8] VCI and VP type I are also more common in twin pregnancies and monochorionicity doubles the risk for VCI compared to dichorinicity. 11,12 Maternal smoking has been recently reported as a risk factor for VCI and thus potentially of VP.…”

“…2 The associated complications of prematurity are, in many cases, the result of iatrogenic preterm birth in an effort to prevent stillbirth. Antenatal hospitalization to allow for closer surveillance for signs of labor in a unit with appropriate neonatal facilities has also been proposed for all pregnancies presenting with VP from 30-32 weeks of gestation [3][4][5]31 but the evidence is weak and based on low-quality evidence.…”