Although sciatica most commonly occurs during the third trimester, some women do develop it much earlier in their pregnancy, notes What to Expect. Early sciatic pain may be more common in women who have had a previous pregnancy, according to Cleveland Clinic.
Sciatic pain is caused by pressure on the sciatic nerve, which runs from the lower back down through the leg, notes Cleveland Clinic. Hormones during pregnancy cause a woman's ligaments to relax and loosen up so that she can give birth. This change sometimes pinches the sciatic nerve, resulting in a feeling of burning and shooting pain in the legs and lower back. This pain usually comes and goes.
Most sciatic pain due to pregnancy can be relieved by having the woman relax and lie on her side with the painful leg on top, according to the American Pregnancy Association. Hot and cold compresses can also ease the pain, so women can experiment to find which works best for them. Over-the-counter pain relievers may also help, but pregnant women should ask their doctors before taking any medication.
Although uncomfortable, sciatic pain during pregnancy is usually nothing serious, notes the American Pregnancy Association. However, constant nerve pain does need to be diagnosed by a doctor.