Journal of Ultrasound in Medicine, Vol 14, Issue 5 361-366, Copyright © 1995 by American Institute of Ultrasound in Medicine
Doppler velocimetry of the fetal middle cerebral artery in patients with preterm labor and intact membranes
F. Ghezzi, A. Ghidini, R. Romero, R. Gomez, M. Galasso, J. Cohen and M. C. Treadwell
Perinatology Research Branch, NICHD, Bethesda, MD, USA.
A prospective cohort study was conducted to determine whether preterm labor
is associated with changes in the impedance to blood flow of the fetal
middle cerebral artery. Doppler velocimetry studies were performed in 194
consecutive patients with preterm labor and intact membranes. Pulsatility
indices of the middle cerebral artery and umbilical artery were determined
on admission. Results were expressed as ratio of the observed pulsatility
index to mean value for gestational age expressed as delta MCA PI and delta
UA PI, respectively. The prevalence of preterm delivery (< 37 weeks) and
delivery within 24 hours of admission was 55.2% (107/194) and 15.5%
(30/194), respectively. Patients with an examination-to-delivery interval
within 24 hours had significantly lower mean delta MCA PI than that of
patients delivered at > or = 37 weeks and > or = 4 weeks after the
examination (P < 0.01). Fetuses with a delta MCA PI at or below 0.88 had
a relative risk of 2 (95% confidence interval, 1.32 to 2.9) who were
delivered within 24 hours compared to controls (sensitivity 76.7%,
specificity 62.8%, positive predictive value 26.7%, negative predictive
value 93.5%). Stepwise logistic regression analysis indicated that the
relationship between delta MCA PI and examination-to-delivery interval
remained statistically significant after correcting for cervical dilatation
(P < 0.001). Our data indicate that preterm parturition is associated
with a decrease in the impedance to flow in the fetal cerebral circulation.
