Computer-generated image from micro-MRI. Actual size of fetus at time of birth (crown to rump) is 360 mm . This image presents a right-sided, frontal view of the process of birth. Typically, the expected time of birth is about 266 days or 38 weeks after fertilization. During the stage of dilation, the mother's cervix must soften and widen to 10 centimeters in diameter to allow for the passage of the baby. The fetus is shown head-down, about to traverse the pelvic cavity which has expanded significantly. At birth, the skull bones are still incomplete and are connected by unossified fibrous tissue called fontanels. These allow the head of the infant to compress while passing through the birth canal. Once the head has emerged fully, the rest of the body is delivered with relative ease.