Embryogenesis of fused umbilical arteries in human embryos.
OBJECTIVE
The objective of this study was to elucidate the embryologic basis of fused umbilical arteries in the human.


METHODS
Twenty-nine human embryo specimens at Carnegie stages 11 through 15 (4-5 weeks after fertilization) were examined histologically, with special reference to the development of umbilical arteries.


RESULTS
All embryos at Carnegie stage 11 and 12 had fused umbilical arteries, and 66% of Carnegie stage 13 embryos and 29% of Carnegie stage 14 embryos still had the condition. None of the embryos at Carnegie stage 15 or older had fused umbilical arteries, but there were always 2 arteries present in their umbilical cords.


CONCLUSIONS
Our data suggest that (1) a single umbilical artery splits into 2 as the developmental stage of the embryo advances, (2) that fused umbilical arteries represent a remnant of the embryonic phenotype, and (3) that fused umbilical arteries are embryologically distinct from true single umbilical artery.
Yamada
Shigehito
S
Congenital Anomaly Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan. shyamada@cac.med.kyoto-u.ac.jp
Hamanishi
Junzo
J
Tanada
Shozo
S
Tachibana
Mitsuhiro
M
Mimura
Rokuro
R
Fujii
Shingo
S
Shiota
Kohei
K
D002102:Cadaver; D006801:Humans; D014469:Umbilical Arteries / Q000002:abnormalities* / Q000196:embryology*