What causes sciatica during pregnancy?

Pressure: There are a few causes of sciatica during pregnancy- among these are pressure on the lumbar plexus of nerves by the uterus/baby, increased pressure on the disks from increased weight in pregnancy, or simply increased stress on the piriformis muscle imitating sciatica. There are a few more but these are some of the more common ones.

Most common-pyriform: The fetus can compress the pyriformis muscle and cause it to spasm. It is easier to occur when the pelvis widens, already stretching this muscle. This muscle overlies the sciatic nerve (actually one third of people have sciatic nerve branches passing through it! when it cotracts-bingo, an abrupt onset of sciatica!

Lots of Reasons: When pregnant, there are so many things going on. Your hormones are very different causing your ligaments to stretch quite a bit especially in the pelvis resulting in pain. Also the baby's position can place stress on your spine resulting in bulging discs or even herniated disks causing the sciatica pain. Recommend seeing a pregnancy specialized therapist that can guide you through this.