9.2.1 Cephalopelvic disproportion (CPD)
Cephalic (pronounced ‘seff-ah-lik’) is from a Greek word meaning ‘the head’. Disproportion tells you that the size of the fetal head is different from the size of the mother’s pelvic brim.
Cephalopelvic disproportion (CPD) means it is difficult or impossible for the fetus to pass safely through the mother’s pelvis due either to a maternal pelvis that is too narrow for that fetal head, or a large fetal head relative to that mother’s pelvis (see Figure 9.1, and think back to the anatomy of the maternal pelvis and fetal skull which you learned in Study Session 6 of the Antenatal Care Module). The small (or contracted) pelvis in developing countries like Ethiopia is generally due to malnutrition in childhood persisting into adult life. Cephalopelvic disproportion cannot usually be diagnosed before the 37th week of pregnancy because before then the baby’s head has not reached birth size.