Abstract
The present study aimed to describe the time sequence of abnormal changes in Doppler velocimetric parameters and its relationship with fetal heart rate recorded in growth-restricted fetuses. Fifteen singleton pregnancies with an ultrasound diagnosis of fetal growth restriction (abdominal circumference < 2SD) were evaluated prospectively and longitudinally. Fetal outcome included four perinatal deaths, seven emergency Cesarean sections due to abnormal cardiotocogram (CTG) and four admissions to the neonatal intensive-care unit. We observed 'early' Doppler changes (15 to 10 days prior to delivery) in the umbilical artery (UA), middle cerebral artery (MCA) and cerebroplacental ratio. 'Late' Doppler changes included absent or reverse end-diastolic flow in the UA, high resistance in the ductus venosus (DV) and decrease of umbilical venous blood flow. These changes appeared in 10% of cases 4-7 days prior to delivery and in up to 40% of cases on the day of delivery. Although occurring less frequently, umbilical vein pulsations, reverse 'a' wave at the DV and increased flow resistance in the MCA were also observed closer to delivery. 'Late' Doppler changes appeared in two-thirds of cases with 'early' Doppler changes and in 40% of cases with an abnormal CTG. These changes preceded the abnormal CTG patterns by 1-10 days. All perinatal deaths were of patients who showed 'late' Doppler changes (4/10), whereas an abnormal CTG without 'late' Doppler changes led to emergency Cesarean delivery because of the risk of loss of fetal well-being (7/10). From the time sequence observed we describe a standard model of Doppler changes in fetal growth restriction. It is obviously not a rule for fetal deterioration to take place the same way in every individual affected fetus. Nevertheless, it is apparent that 'late' Doppler changes usually precede an abnormal CTG and are associated with greater perinatal mortality.