Functional asymmetry of the human myometrium documented by color and pulsed-wave Doppler ultrasonographic evaluation of uterine arcuate arteries during Braxton Hicks contractions.
OBJECTIVE
We hypothesized that arcuate arteries supplying placental and nonplacental myometrial portions would respond with different degrees of change in their resistance during Braxton Hicks contractions.


METHODS
We examined 20 healthy pregnant women between 18 and 24 weeks' gestation with pulsed-wave and color-flow Doppler during focal Braxton Hicks contractions identified by real-time ultrasonography by means of the characteristic thickening of the myometrium. Systolic/diastolic ratio was used as an expression of resistance. Statistical analysis was performed by Wilcoxon signed-ranks and Mann-Whitney test.


RESULTS
When the contractions are localized in the subplacental myometrium, the resistance of the arcuate artery did not differ during and after the contraction. In contrast, when the contraction involved only nonplacental myometrium, the resistance during the contraction was significantly higher and in some patients there was complete absence of flow during the diastolic phase. During subplacental myometrial contractions, the main uterine artery resistance was not affected. When the contraction involved the nonplacental myometrium, the resistance of the main uterine artery increased with more pronounced changes when the contraction involved the lateral myometrial wall ipsilateral to the uterine artery under examination.


CONCLUSIONS
We speculate that the differences in the degree of resistance change are the result of different degrees of contractility exhibited by the subplacental and nonplacental myometrium. We conclude that the intact human myometrium manifests functional asymmetry and our Doppler findings confirm previous in vitro studies.
Kofinas
A D
AD
Department of Maternal-Fetal Medicine, York Hospital, PA 17405.
Simon
N V
NV
Clay
D
D
King
K
K
D001158:Arteries / Q000502:physiology; D003116:Color; D005260:Female; D006801:Humans; D009215:Myometrium / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000502:physiology; D011247:Pregnancy; D012039:Regional Blood Flow; D016216:Ultrasonography, Prenatal; D014590:Uterine Contraction / Q000502:physiology*; D014655:Vascular Resistance / Q000502:physiology*