Clinical presentation, investigation, underlying causes, and subsequent pregnancy outcomes among different phenotypes...

To evaluate the causes of miscarriage and subsequent pregnancy outcomes among different phenotypes of second trimester miscarriage.

Retrospective analysis of 170 consecutive second trimester miscarriages between 14 + 0 and 23 + 6 weeks recorded in the Clinical Data Analysis and Reporting System from 2012 to 2021. Cases were excluded if miscarriages occurred before 14 + 0 weeks of gestation, data were incomplete, or passage of the fetus happened before the clinical assessment. Cases were classified with a stepwise approach into three phenotypic groups including silent miscarriages (ST-SM), rupture of membranes (ST-ROM), and inevitable miscarriages (ST-IM) depending on the fetal heart pulsation and leakage of liquor at presentation. Clinical investigation of the underlying causes and the outcome of the subsequent pregnancy was then reviewed.

There were 97 cases of ST-SM, 21 cases of ST-ROM, and 52 cases of ST-IM. Placental histology and karyotype examination were more likely to yield significant results in the cases of ST-ROM and ST-SM (p < 0.05). The phenotypic examination identified different underlying causes including fetal anomaly, suspected cervical insufficiency, diabetes mellitus, and unknown causes (p < 0.001). Sixty-four cases achieved a subsequent pregnancy. Although women with history of ST-ROM and ST-IM received more cervical length monitoring and cervical cerclage than those with ST-SM (66.7% vs. 44.4% vs. 7.5%, p = 0.0002; and 16.7% vs. 22.2% vs. 2.5%, p = 0.031, respectively), the risk of recurrent second trimester miscarriage was higher in ST-ROM and ST-IM than in ST-SM (16.7% vs. 0%, p = 0.018).

The classification can differentiate different second trimester miscarriage phenotypes, which offers essential information to guide investigation panels of the underlying cause of miscarriages, and the prognosis and management of subsequent pregnancy. Future researches focused on second trimester miscarriage should report their findings according to different phenotypes.