Final answer:
The interischial tuberous diameter less than 8cm indicates a narrow distance between the sit bones, which may signal potential complications during vaginal delivery due to a narrower pelvic structure.
Step-by-step explanation:
When the interischial tuberous diameter is less than 8cm, it refers to a situation where the distance between the ischial tuberosities, also known as the 'sit bones,' is less than the typical measurement. In obstetrics, this measurement is important as it can indicate potential difficulties during a vaginal delivery, because this diameter is part of the pelvis that the baby must pass through during birth. A diameter less than 8cm could suggest a narrow pelvis, which may increase the risk for complications during childbirth, such as shoulder dystocia or the necessity for a cesarean section.