The relation of fetal colon and rectum diameters with labor in healthy late-third trimester pregnancies

To investigate the associations of fetal colon-rectum diameters with labor and fetal distress or meconium passage in healthy pregnancies in the late 3rd trimester.

A total of 162 healthy, singleton pregnant women at ≥36^0/7 weeks who were in the latent-phase of labor (n = 69) or those not in labor (n = 93, controls) at the time of ultrasound examination were enrolled. Fetal colon (ascending, transverse, descending, sigmoid) and rectum diameters, Doppler indices of materno-fetal vessels were measured. Data were analyzed according to the mode of delivery.

Fetal colon-rectum diameters were smaller in women in labor compared to controls (p = 0.001). Positive correlations were observed between fetal colon-rectum diameters and interval between ultrasound and labor onset in the control group except for those who had scheduled cesarean sections (C/S) (p = 0.001). Similar colon-rectum measurements were obtained in fetuses delivered via cesarean section due to fetal distress or to other indications (p > 0.05). In women who had uterine contractions during ultrasound examination; later delivered by vaginal route, no association was observed between Apgar scores and colon-rectum diameters during latent-phase (p > 0.05), and also there were significant positive correlations between different segments of colon-rectum diameters and duration of neonatal meconium passage (p < 0.05).

Fetal colon and rectum diameters are smaller during labor and the measurements tend to diminish as the labor approaches, but do not indicate fetal distress.