Why is sciatic pain common during pregnancy?

Growth of the fetus. The placenta and baby get larger and compress nearby objects, and not unique to have back pain and even sciatica, but departs after labor and delivery.
Arched back in preg. There are many causes of back pain in pregnancy. As the abdomen protrudes people compensate with an increased back curve and poor posture. Having weak muscles in the abdomen and low back combined with tight hamstrings makes it worse. Stretching and prenatal yoga. Making friends with a local chiropractor trained in pregnancy care can help too. More info: http://macobgyn.Com/drpl/?Q=node/67.