Contraindication for dilatation and curettage:
Ref. The Short Textbook of Pediatrics. Pg 650
 
Dilation and Curettage
Indications

Retained placenta after vaginal delivery (postpartum)
Retained products of conception after missed, incomplete, or inevitable abortion/miscarriage
Elective first-trimester abortion
Molar pregnancy
Evaluation of abnormal uterine bleeding

Contraindication

Untreated acute pelvic infection (endometritis, salpingitis, pyometra)
Coagulopathy
Possible fetal viability (except for elective termination)
Patient refusal