Fetal Response to Cephalopelvic Disproportion

Abstract

Summary A group of African primigravidae undergoing trial of labour were studied along with a control group to assess the specific fetal responses to the possible excessive head compression encountered in cephalopelvic disproportion (CPD). Depending on the outcome of labour, the patients were placed in one of three groups: major CPD, minor CPD and primary uterine dysfunction with no CPD. Particular attention was directed to the fetal heart pattern evoked and the degree of head moulding produced. In the pbresence of marked CPD, the fetus initially responded with early prolonged fetal heart rate decelerations. These continued and as labour progressed, the late decelerations and falling pH typical of hypoxia developed. The early prolonged dip was a steep deceleration which started early, had no time lag and returned to the base line rate late in relation to the end of the contraction. An objective scoring method described the amount of head moulding present. A score of 6 was considered to represent marked moulding. If the patient was still undelivered after a further two hours of strong contractions with no head descent, then it had become excessive. On its own account, excessive moulding should be regarded as a sign of fetal distress.