Placental abnormalities in type 1 and type 2 diabetes mellitus: a systematic review and metaanalysis of shear wave elastography

Objective: This study aimed to describe the placental changes occurring in women with preexisting diabetes mellitus and to determine if elastography can detect placental changes in vivo.

Data sources: PubMed, Embase, Medline, and Cochrane were searched to identify English language studies published until July 2020.

Study eligibility criteria: 1) For key question 1, studies that described histopathologic changes in placentas from women with known diabetes mellitus and 2) for key question 2, those that described structural-placental changes detectable by elastography in high-risk pregnancies (eg, those complicated by preeclampsia and/or fetal growth restriction), were included.

Methods: For key question 1, we grouped placental pathologies using the Amsterdam International Consensus Group definitions. For key question 2, we conducted a metaanalysis including all data from studies reporting placental stiffness in meters per second (m/s) or kilopascals (kPa). The mean difference (95% confidence interval) was calculated using a random effects model.

Results: Data were extracted from 14 studies of placental histopathology in women with known diabetes. In this group, a wide variety of placental histopathologic changes are described, though none are considered pathognomonic. The histopathologic changes including maternal vascular malperfusion, fetal vascular malperfusion, and/or infectious/inflammatory/other changes were divided into 3 broad categories on the basis of presumed etiology. A total of 15 studies reported the placental stiffness scores in women with a high-risk pregnancy vs those with a normal pregnancy. Only 1 reported stiffness scores for placentas in women with preexisting diabetes mellitus (N<10 women). Pooled analysis of 14 studies with available data included 478 "high-risk pregnancies" and 828 control or healthy pregnancies. Maternal-derived pathologies resulted in higher placental stiffness (mean difference 4.5 kPa [95% confidence interval, 3.16-5.87]) compared with control or healthy pregnancies. Fetal-derived pathologies also resulted in higher placental stiffness (mean difference of 6.5 kPa [95% confidence interval, 1.08-11.86]) compared with control or healthy pregnancies.

Conclusion: Shear wave elastography may provide an in vivo approximation of placental histopathology in women with certain kinds of high-risk pregnancies. A high-risk pregnancy may involve maternal- and fetal-derived pathologies. Further studies, particularly in women with preexisting diabetes, are needed to confirm this observation.