Must consider ectopic pregnancy in pregnant patient presenting with<unk>  pain and no documented IUP
Quantitative beta hCG and pelvic US
Also consider beta hCG and pelvic US if concerned for spontaneous abortion
Consider pelvic exam to check for open cervical os, protruding products of conception
Urinalysis
CBC, CMP, lipase,<unk>  imaging depending on the differential
Quantitative beta hCG and pelvic US
Consider pelvic exam to check for open cervical os, protruding products of conception
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