In surgery, an incision across the midline from navel to symphysis pubis is avoided because of:

28.5 Disorders of the omphalo-mesenteric duct (Meckel's
diverticulum)

In fetal life the intestinal tract and the yolk sac are joined by the omphalo-mesenteric or vitelline duct. Remnants of this may
persist and present as: (1) A persistent discharge from the umbilicus which is occasionally faecal. (2) Gastro-intestinal bleeding
from ectopic gastric mucosa in Meckel's diverticulum. (3) Gut obstruction caused by gut twisting around a persistent vitelline duct,
as described in Section 28.3. You may occasionally have to resect and anastomose gut in connection with any of these three, or,
rarely, with the other abnormalities in Fig. 28-4.

And patent urachus
Surgery to close a defect of the bladder (patent urachus). The urachus is a tube
that connects the bladder to the umbilicus during fetal development. After birth,
the urachus normally closes and becomes a ligament. When the urachus fails to
close after birth, the tube remains open (patent), leaving an abnormal opening
(patent urachus) between the bladder and the umbilicus and increasing the
possibility of introducing bacteria and infection into the bladder.