Raised uterine resting tone in patients with abruptio placentae.

Uterine contractions were studied in 21 patients with abruptio placentae and intrauterine death. Contractions were examined in four 10-minute windows taken immediately prior to delivery, 30 and 60 minutes before delivery and at the beginning of the recording. Mean resting tone values for the 4 periods fluctuated between 23 and 25 mmHg. The mean contraction frequency for all the windows was 8 per 10 minutes. It is postulated that the high resting tone and frequent uterine contractions contribute to the high perinatal mortality associated with abruptio placentae.