Although premature separation of normally implanted placenta is considered the most serious complication of pregnancy, knowledge of uterine behaviour during this condition is meager, on the basis of electronic recording of intra-uterine pressure two type of contraction pattern has been identified.
In type I uterine tonus has values below 30mmHg
with a frequency of 4-9 contractions per 10 minutes.
In type II uterine tonus has a value of 30 mm Hg or more and a higher frequency.
Cases falling in type I react to the administration of oxytocin, while those in type II do not.
So uterine tonus and contraction frequency appear to be a good indicator of the functional status of uterine mmcle in abruptic placenta and its reactivity to oxytocic agents.