Waking up with sudden leg cramps during pregnancy ? Those painful midnight surprises are very real ! Leg cramps are extremely common , especially during the second and third trimesters . They often strike at night, causing sharp pain in the calves or feet — and yes, they can be pretty uncomfortable. So, why do they happen? ✨ Causes of Pregnancy Leg Cramps: Changes in circulation due to the pressure from your growing uterus. Deficiencies in calcium, magnesium, or vitamin D .