Objective: To describe the time sequence of changes in fetal monitoring variables in intrauterine growth restriction and to correlate these findings with fetal outcome at delivery.
Methods: This was a prospective longitudinal observational multicenter study on 110 singleton pregnancies with growth-restricted fetuses after 24 weeks of gestation. Short-term variation of fetal heart rate, pulsatility indices of fetal arterial and venous Doppler waveforms and amniotic fluid index were assessed at each monitoring session. The study population was divided into two groups: Group 1 comprised pregnancies with severely premature fetuses, which were delivered < or =32 weeks and Group 2 included pregnancies delivered after 32 completed weeks. Logistic regression was used for modeling the probability for abnormality of a variable in relation to the time interval before delivery. Trends over time were analyzed for all variables by multilevel analysis.
Results: Ninety-three (60 in Group 1 and 33 in Group 2) fetuses had at least three data sets (median, 4; range, 3-27) and had the last measurements taken within 24 h of delivery or intrauterine death. The percentage of abnormal test results and the degree of abnormality were higher in Group 1 compared to Group 2. Amniotic fluid index and umbilical artery pulsatility index were the first variables to become abnormal, followed by the middle cerebral artery, aorta, short-term variation, ductus venosus and inferior vena cava. In Group 1, short-term variation and ductus venosus pulsatility index showed mirror images of each other in their trend over time. Perinatal mortality was significantly higher if both variables were abnormal compared to only one or neither being abnormal (13/33 (39%) vs. 4/60 (7%); P = 0.0002; Fisher's exact test).
Conclusion: Ductus venosus pulsatility index and short-term variation of fetal heart rate are important indicators for the optimal timing of delivery before 32 weeks of gestation. Delivery should be considered if one of these parameters becomes persistently abnormal.