Acardiac fetus: evidence in support of a vascular/hypoxia pathogenesis for isolated oral clefting.
BACKGROUND
The acardiac human fetus represents an accident of monozygotic twinning or higher multiple births due to an artery-to-artery and a vein-to-vein anastomosis in the monochorial placenta. Blood returning to the placenta through the umbilical artery of a normal cotwin is directed into the umbilical artery of the acardiac twin such that blood reaching the cranial end of the embryo is likely to be poorly oxygenated resulting in a number of structural defects including oral clefts. Although retrograde perfusion as a cause of hypoxia is unique to the acardiac fetus, there is ample evidence from animal studies that hypoxia is associated with facial clefting.


METHODS
Twenty-six acardiac fetuses were examined at UCSD Medical Center between 1974 and 2003.


RESULTS
In 12 of the 26, the cephalic end of the fetus was sufficiently intact to document the structures of the face. Of these, cleft lip +/- palate was present in five and cleft palate alone was present in one. In all six, the oral cleft followed the normal planes of facial closure. The cotwin in all six cases was normal.


CONCLUSIONS
This article suggests that decreased blood flow/hypoxia to the cephalic end of the fetus may be an important contributor to the development of cleft lip +/- palate and cleft palate alone in the acardiac fetus and raises the possibility that this may also be a mechanism responsible for oral clefting in singletons.
Division of Dysmorphology/Teratology, Department of Pediatrics, University of California, San Diego, School of Medicine, La Jolla, California 92093-0828, USA. klyons@ucsd.edu
Kenneth Lyons
KL
Jones
William S
WS
Webster
Keith K
KK
Vaux
Kurt
K
Benirschke
D000015:Abnormalities, Multiple / Q000473:pathology*; D009008:Abnormalities, Severe Teratoid / Q000473:pathology; D002971:Cleft Lip / Q000150:complications / Q000209:etiology* / Q000473:pathology; D002972:Cleft Palate / Q000150:complications / Q000209:etiology* / Q000473:pathology; D005260:Female; D005313:Fetal Death / Q000473:pathology; D005318:Fetal Heart / Q000002:abnormalities*; D005333:Fetus / Q000002:abnormalities* / Q000098:blood supply / Q000473:pathology; D006801:Humans; D000860:Hypoxia / Q000150:complications*; D021041:Placental Circulation / Q000502:physiology; D011247:Pregnancy