Sinusoidal pattern of uterine contractions in abruptio placentae.

Three cases of vaginal bleeding during labor associated with high-frequency uterine contractions (HFUC) in the third trimester of pregnancy are reported. Abruptio placentae was confirmed in all three cases. As HFUC was unrecognized as a sign of abruptio placentae, labor was allowed to continue in the first two cases and fetal demise ensued. The appearance of HFUC with vaginal bleeding in the third trimester of pregnancy should make the obstetrician highly suspicious of abruptio placentae. Labor should be terminated by cesarean section to prevent fetal death in utero.