To identify the ultrasound-related risk factors for stillbirth in the third trimester.

Seventy-eight cases of stillbirth at Hangzhou First People's Hospital from January 2009 to December 2018 were enrolled in this study as a case group. One hundred and fifty-six normal pregnant women were included as a control group. The patients in the case group were further divided into two subgroups: high risk subgroup (with at least one clinical risk factor) and low risk group (without any clinical risk factor). The abnormal ultrasonic findings in the third trimester were collected and classified as abnormal umbilical cord, abnormal placenta, abnormal amniotic fluid, fetal anomalies, and maternal uterine abnormality. Logistic regression was used to perform statistical analyses, with odds ratios (ORs) of the included variables calculated.

In the case group, 51 cases were classified into the high risk subgroup and 27 into the low risk subgroup. Overall, only fetal anomalies detected by ultrasound could be considered as the independent risk factor for stillbirth (Y=-0.798+ 1.491X, OR=4.441, P=0.009). In the high risk subgroup, abnormal umbilical cord (OR=2.805, P=0.023), abnormal placenta (OR=3.386, P=0.028), and fetal anomalies (OR=8.909, P=0.002) could be considered as the independent risk factors for stillbirth (Y=-1.206+ 2.187×fetal anomalies+ 1.220×abnormal placenta+ 1.031×abnormal umbilical cord).

In the multiple abnormal findings by ultrasound, only fetal anomalies could be considered as an independent risk factor for stillbirth. For pregnant women with clinical high risk factors, abnormal umbilical cord, abnormal placenta, and fetal anomalies could be considered as the independent risk factors for stillbirth.