Abstract

OBJECTIVES: Preeclampsia is associated with impaired trophoblast invasion and typical villous and vascular placental lesions. The primary aim was to conduct a systematic review in order to quantify the prevalence of placental histopathological lesions in pregnancies complicated by preeclampsia. METHODS: MEDLINE, EMBASE and CINAHL were searched electronically and relevant articles reporting placental histopathological lesions were assessed according to the following criteria: study design, number of pregnancies, type of preeclampsia and whether the pathologist was blinded to the clinical information. Prospective and retrospective case-control studies, including 100 pregnancies or more in total, were included. The number of the most prevalent histological lesions according to the Perinatal Section of the Society for Pediatric Pathology classification was extracted and categorized in two main groups, "villous lesions" and "vascular lesions". Random-effect meta-analysis of proportions was used for analysis. Between-study heterogeneity was assessed using the I(2) statistic. RESULTS: The search yielded 717 citations and a total of 8 studies were included in the review. In unblinded studies, the pooled prevalence of villous lesions was 11.6% (95% CI 6.4-18.1%) and 48.2% (95% CI 19.1-77.9%) in normal and preeclamptic pregnancies, giving a pooled odds ratio (OR) of 7.59 (95% CI 2.16-26.62). In blinded studies, the pooled prevalence of villous lesions was 18.5% (95% CI 1.4-48.7%) and 42.0% (95% CI 13.3-74.2%) in normal and preeclamptic pregnancies, giving a pooled OR of 4.28 (95% CI 1.16-15.76). In unblinded studies, the pooled prevalence of vascular lesions was 8.1% (95% CI 4.5-13.2%) and 37.3% (CI 3.1-82.4%), giving a pooled OR of 20.34 (95% CI 11.53-35.89). In blinded studies, the pooled prevalence of vascular lesions was 9.8% (95% CI 0.7-27.8%) and 38.9% (24.1-54.8%), giving a pooled OR of 7.08 (95% CI 2.55-19.61). CONCLUSIONS: The prevalence of both placental villous and vascular histopathological lesions is higher, by a factor of four to seven-fold, in preeclampsia compared to normal pregnancies in blinded studies. Greater differences are reported in unblinded studies. Despite the fact that the probability (point prevalence) of finding abnormal placenta pathology is higher in preeclampsia, placental lesions are not specific to the diagnosis of preeclampsia.