Experimental study of umbilical cord length as a marker of fetal alcohol syndrome

Umbilical cord length has long been investigated as a potential marker of i ntrauterine events that may place the neonate at risk for future adverse de velopmental sequelae. Experimentally, significantly shortened cords have be en reported in association with prenatal exposure to common drugs of abuse. This study in rats reports the time course of effects on umbilical cord le ngth of a daily maternal ethanol gavage (3,200 mg/kg) from gestational day 6 through termination of pregnancy at either day 17, 18, 19, or 20. A total of 786 fetuses derived from 60 litters were examined. Control fetuses demo nstrated a linear increase in umbilical cord length and body weight gain du ring late gestation, findings that support previous studies. The body weigh ts of the ethanol-exposed fetuses were reduced significantly on all gestati onal days examined, indicating intrauterine growth retardation, a character istic of fetal alcohol syndrome. Similarly, acute fetal akinesia as well as long-term sequelae stemming from impaired neurological development would r esult from the elevated blood ethanol levels achieved in this study. The um bilical cords of ethanol-exposed fetuses were significantly shorter on gest ational days 19 and 20 in comparison to their controls, while cord lengths on days 17 and 18 were not shortened significantly. A stretch hypothesis ha s been proposed suggesting that the degree of fetal activity is the main de terminant of umbilical cord length. In rats, there is a physiologic diminut ion of the volume of amniotic fluid (oligohydramnios) in late gestation (da y 19 to term), which restricts fetal movements but does not appear to alter the linear relationships between gestational age and cord length in contro ls, thus arguing against the stretch hypothesis. However, cord lengths in t he ethanol-exposed fetuses plateaued in late gestation, suggesting possible adherence to a stretch hypothesis. This dichotomy is discussed emphasizing fetal growth and activity as well as intrauterine space. (C) 2000 Wiley-Li ss, Inc.