Abstract
To explore the association between fetal umbilical and middle cerebral artery (MCA) Doppler abnormalities and outcome in late preterm pregnancies at risk of fetal growth restriction. This was a prospective cohort study of singleton pregnancies at risk of fetal growth restriction at 32 + 0 to 36 + 6 weeks of gestation, enrolled in 33 European centers between 2017 and 2018, in which umbilical and fetal MCA Doppler velocimetry was performed. Pregnancies were considered at risk of fetal growth restriction if they had estimated fetal weight and/or abdominal circumference (AC) < 10th percentile, abnormal arterial Doppler and/or a fall in AC growth velocity of more than 40 percentile points from the 20-week scan. Composite adverse outcome comprised both immediate adverse birth outcome and major neonatal morbidity. Using a range of cut-off values, the association of MCA pulsatility index and umbilicocerebral ratio (UCR) with composite adverse outcome was explored. The study population comprised 856 women. There were two (0.2%) intrauterine deaths. Median gestational age at delivery was 38 (interquartile range (IQR), 37-39) weeks and birth weight was 2478 (IQR, 2140-2790) g. Compared with infants with normal outcome, those with composite adverse outcome (n = 93; 11%) were delivered at an earlier gestational age (36 vs 38 weeks) and had a lower birth weight (1900 vs 2540 g). The first Doppler observation of MCA pulsatility index < 5th percentile and UCR Z-score above gestational-age-specific thresholds (1.5 at 32-33 weeks and 1.0 at 34-36 weeks) had the highest relative risks (RR) for composite adverse outcome (RR 2.2 (95% CI, 1.5-3.2) and RR 2.0 (95% CI, 1.4-3.0), respectively). After adjustment for confounders, the association between UCR Z-score and composite adverse outcome remained significant, although gestational age at delivery and birth-weight Z-score had a stronger association. In this prospective multicenter study, signs of cerebral blood flow redistribution were found to be associated with adverse outcome in late preterm singleton pregnancies at risk of fetal growth restriction. Whether cerebral redistribution is a marker describing the severity of fetal growth restriction or an independent risk factor for adverse outcome remains unclear, and whether it is useful for clinical management can be answered only in a randomized trial. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.
Highlights
Poor third-trimester fetal growth is associated with adverse perinatal outcome[1,2]
Guidelines of the Royal College of Obstetricians and Gynaecologists on small-for-gestational-age (SGA) fetuses[7] state that ‘middle cerebral (MCA) Doppler may be a more useful test in SGA fetuses detected after 32 weeks of gestation’, but perhaps wisely do not define the parameters that should trigger a decision to deliver
In women who had the last Doppler measurement obtained within 1 week before delivery, the association of umbilicocerebral ratio (UCR) with composite adverse outcome was adjusted using logistic regression analysis for those parameters that differed significantly between women with and those without composite adverse outcome
Summary
The only therapeutic option is timely delivery This poses a dilemma as delivery too early risks the baby suffering the effects of moderate–late prematurity, whereas delivery too late risks further fetal compromise increasing the risk of suboptimal outcome or stillbirth. There remains little evidence on which to base the timing of delivery of such babies in the late preterm period. The key question is whether abnormal cerebral artery Doppler is a non-injurious response to fetal compromise or is itself a marker of compromise and ongoing damage necessitating early delivery. Without this information, it cannot be known if using these Doppler parameters to decide on intervention by delivery is beneficial for infant outcome. The usefulness of MCA Doppler and cerebral blood flow redistribution in improving perinatal and/or long-term outcome can be assessed only by randomization in a prospective study, but current data are insufficient to decide how such a trial should be designed
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