Ruptured ectopic pregnancy
Active labor
Preeclampsia/HELLP
Placental abruption
Uterine rupture
Ovarian torsion
Surgical abdomen
Ectopic pregnancy if hemodynamically stable with OB follow-up
Spontaneous abortion if hemodynamically stable with adequate<unk>  control
Abdominal pain in pregnancy
The same abdominal pain differential as non-pregnant patients, plus:
Vaginal bleeding in pregnancy 
Ectopic pregnancy
Comorbid diseases in pregnancy
First trimester abortion
Nonpregnant vaginal bleeding
Complete abortion