Most of the following complications are evident before onset of labor: Multifetal pregnancy Postterm pregnancy Prelabor (premature) rupture of membranes Abnormal fetal presentation Some of the following complications develop or become evident during labor or delivery: Amniotic fluid embolism Shoulder dystocia Fetopelvic disproportion Preterm labor Protracted labor Umbilical cord prolapse Uterine rupture (rare) Some complications may require alternatives to spontaneous labor and vaginal delivery.