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Underlying mechanisms of retained placenta: Evidence from a population based cohort study
Shirley Greenbaum1, Tamar Wainstock2, Doron Dukler1
1Department of Obstetrics & Gynecology, Faculty of Health Sciences, Soroka University Medical Center, Ben Gurion University of the Negev, Beer Sheva, Israel.
Objective:
To determine risk factors for retained placenta, and to identify supporting epidemiologic evidence for the three previously-proposed mechanisms: (i) invasive placentation, (ii) placental hypo-perfusion, and (iii) inadequate uterine contractility.
Design:
A retrospective population-based cohort study.
Setting And Population:
Israeli population in the southern district.
Methods:
Data were analyzed from a tertiary hospital database, between 1989 and 2014, using univariate tests and generalized estimating equation (GEE) multivariable models.
Main Outcome Measures:
Prevalence of retained placenta.
Results:
The study population included 205,522 vaginal deliveries of which 4.8% (n=9870) were complicated with retained placenta. Previous intra-uterine procedures and placenta-related pregnancy complications were found to be significant risk factors for retained placenta (history of cesarean section aOR=8.82, 95%CI 8.35-9.31; history of curettage aOR=12.80, 95%CI 10.57-15.50; pre-eclampsia aOR=1.25, 95%CI 1.14-1.38; delivery of a small for gestational age neonate aOR=1.08, 95%CI 1.01-1.16; stillbirth aOR=2.34, 95%CI 1.98-2.77). During labour, the risk for retained placenta was increased in presence of arrest of dilatation (aOR=2.03, 95%CI 1.08-3.82) or arrest of descent (aOR=1.55, 95%CI 1.22-1.96). Infections of the uterine cavity during labour were also found to be strongly associated with increased risk of retained placenta (endometritis aOR=2.21, 95%CI 1.64-2.97; chorioamnionitis aOR=3.35, 95% CI 2.78-4.04).
Conclusions:
Supporting epidemiologic evidence were found for all three underlying mechanisms. In addition, there is evidence to suggest that intrauterine infection and inflammation may also be a possible pathology associated with retained placenta.
Tweetable Abstract:
Risk factors for retained placenta support previously proposed mechanisms in a large cohort study.
