Doppler fetal circulation in pregnancies complicated by pre‐eclampsia or delivery of a small for gestational age baby: 2. Longitudinal analysis

Objective To observe the longitudinal changes in growth, and associated Doppler measurements, of the fetal circulation in pregnancies with a normal outcome and those complicated by pre-eclampsia, birth of a small for gestational age baby, or a combination of these complications. Methods Two hundred and ninety-two women had serial ultrasound scans performed from the 24th week of pregnancy. Measurements obtained included: the abdominal circumference, umbilical artery pulsatility index, the middle cerebral artery pulsatility index and time-averaged velocity, and the thoracic aorta pulsatility index and time-averaged velocity. Outcome measures included the birth of a small for gestational age infant, pre-eclampsia or a combination of these complications. Results One hundred and sixty-seven pregnancies ended in the normal birth of an appropriately grown infant at term, while 105 had a complicated outcome. They were divided into three categories: pre-eclampsia only (i.e. with the birth of an appropriately grown fetus, n= 13); small for gestational age only with no evidence of pre-eclampsia, n= 55; and pre-eclampsia complicated by the birth of a small for gestational age infant, n = 37. The group with pre-eclampsia complicated by small for gestational age was closest in characteristics to true clinical intrauterine growth restriction. A reduction in the abdominal circumference mirrored a rise in the umbilical artery pulsatility index and preceded changes in the middle cerebral artery and thoracic aorta. The greatest degree of change in the fetal circulation was observed during the three weeks preceding delivery. Ratios of the values obtained from the fetal and umbilical circulation demonstrated the greatest deviation from normal. Conclusions A reduction in fetal growth velocity preceded changes observed in the fetal circulation. Ratios of the fetal Doppler parameters provided the clearest evidence of deterioration in the fetal condition. The information provided may be of use in the diagnosis and management of the growth-restricted fetus.