Will it be difficult to deliver a baby with a big head? This has always been a worry for mothers who want to give birth naturally. In fact, whether the baby can be born smoothly is closely related to the baby\’s head and the mother\’s pelvis. Only when these two parts cooperate with each other can delivery be successful. Let’s take a look at the relationship between the fetal head and the pelvis during childbirth. In general prenatal examinations, the data we get about the size of the fetal head is only the biparietal diameter of the fetal head measured by B-ultrasound, and the head circumference.