What causes hot flashes in pregnancy?

Circulation. The hot flashes you may be experiencing while pregnant are not the same as those experienced by women in menopause. Menopausal hot flashes are due to lack of estrogen. Pregnancy is a high estrogen state. Most likely the hot flashes in pregnancy are due to changes in your circulation and increased heat generated by the baby.
Hormones. Commonly, the hormones during pregnancy can cause the hot flashes you are experiencing.