Reference ranges and standard percentile-curves for the Doppler indices RI and S/D ratio of the fetal middle cerebral artery. Color Doppler measurements in a perinatal centre.
OBJECTIVE
To perform reference ranges and standard percentile-curves for the Doppler indices resistance index (RI) and systolic/diastolic (S/D) ratio of the fetal middle cerebral artery, periodical color doppler sonographic measurements of 70 pregnant women in the 3rd trimester of pregnancy were done.


METHODS
600 Doppler flow measurements of the fetal middle cerebral artery between 28 and 40 weeks of gestation were performed. The patients had no previous obstetric complications, no apparent medical problems and no complications in pregnancy and labor. Percentiles curves were performed for the RI and the S/D ratio from the 10th percentile up to the 90th percentile.


RESULTS
In the 3rd trimester of pregnancy fetal cerebral circulation shows an increase of the diastolic component and simultaneous decrease in cerebral resistance. The average S/D ratio in week 29 is 8.0, in week 34 6.0 and in the 40th week 3.5. The RI decrement is from 0.88 to 0.67. Other groups demonstrated similar ranges however absolute data are different.


CONCLUSIONS
The increase in the diastolic component in the middle cerebral artery of the last third of the pregnancy demands reference ranges by using percentile curves. Knowledge of the reference range helps to discriminate between a normal fetal situation and disease. Because of different absolute ranges in the literature each perinatal centre should develop their own data.
Meyberg
R
R
Department of Obstetrics and Gynecology of the University of the Saarland, Homburg/Saar, Germany.
Ertan
A K
AK
Tossounidis
I
I
Friedrich
M
M
Schmidt
W
W
D000293:Adolescent; D000328:Adult; D002536:Cerebral Arteries / Q000196:embryology / Q000502:physiology*; D005260:Female; D005333:Fetus / Q000098:blood supply*; D006801:Humans; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D012016:Reference Values; D018615:Ultrasonography, Doppler, Color; D016216:Ultrasonography, Prenatal / Q000592:standards*