[The study of making decision in the timing of delivery for patients of placenta previa through dynamic monitoring the length of cervical canal by perineal ultrasound].

Objective: To investigate the value of dynamic monitoring of cervical canal length by transperineal ultrasonography in the decision-making of the timing of delivery in patients with complete placenta previa, then to provide clinical guidance for complete termination of placenta. Methods: A total of 130 patients with complete placenta previa from 28 weeks to 30 weeks of gestation between January 2014 and October 2017 in Jiaxing Maternal and Child Health Hospital were selected. There were 66 patients in the experimental group and 64 in the control group, closely monitor the patient's vital signs, abdominal pain, abdominal distension, vaginal bleeding and fetal intrauterine conditions. In the experimental group, the length of the cervical canal was monitored by perineal ultrasonography at 2 hours and 12 hours after admission. This led to termination of the pregnancy. The control group was instructed to terminate the timing of pregnancy based on the patient's abdominal pain relief symptoms and vaginal bleeding. Compare the maternal and fetal outcomes of both groups. Results: The length of the cervical canal was (31.3±1.3) mm when the experimental group was admitted to the hospital, and the length of the cervical canal after the use of the retention drugs 2 h and 12 h was (32.1±0.4) mm and (32.2±0.4) mm, respectively.Compared with the length of the cervix at the time of admission. There was no significant change in the length of the cervical canal after the application of the retention drug 2 and 12 h(all P >0.05). The delivery week of 11 patients in the experimental group did not exceed 34 weeks, and 28 cases in the control group, and there was significant difference between the two groups. Compared with the control group, the difference of birth rate did not exceed 34 weeks, birth weight and hospitalization time decreased significantly (all P <0.05). However, there was no significant difference in maternal outcomes between the two groups. Conclusion: Through monitoring the length of the cervical canal by perineal ultrasound can make a better decision for the patients of complete placenta previa to chose the time of delivery.