To investigate whether uterine contractions at the time of a Cesarean section have an impact on future presence and location of a cervical Cesarean scar.Methods
A targeted transvaginal ultrasound examination of the fetus, uterus and cervix was done in 2973 consecutive women at 14–16 weeks' gestation. The sonographer was blinded to the women's previous obstetric histories. The presence and location of a sonographic cervical hypoechogenic line, which probably represented a Cesarean scar, was recorded.Results
There were 180 women with a previous Cesarean section performed before the start of uterine contractions and 173 with a Cesarean section performed during contractions in labor. The cervical hypoechogenic line was more common in sections performed during contractions (75.7% vs. 52.7%; P < 0.001) and was more distally located from the internal os (17.9 ± 9.4 vs. 14.6 ± 9.1 mm; P = 0.01). A hypoechogenic line was observed in 21/2620 women without a previous Cesarean section, representing a false-positive rate of 0.8%.Conclusion
Cesarean sections, especially those done during uterine contractions, are actually performed through cervical tissue. This finding is in agreement with the physiological process of cervical effacement during contractions.