We sought to determine whether umbilical cord complications, as evidenced by a
nuchal cord at the time of birth, affects
birth weight, placental weight and, therefore, the birth to placental weight ratio as a mechanism whereby fetal and placental growth may be differentially affected. The computerized perinatal database of St. Joseph's Health Centre, London, Ontario, was used to obtain the
birth weight, placental weight, umbilical cord
gases, and
nuchal cord status, for all term singleton liveborn infants between January, 1991 and December, 1994. The effect of no
nuchal cord versus
nuchal cord on
birth weight, placental weight, and the birth to placental weight ratio was determined, along with the interactive effects of gestational age and umbilical cord
gases, and the 'dose response' effect of the number of cord encirclements. Infants with the cord around the neck were smaller (P < 0.001), their placentas larger (P = 0.001), and their birth to placenta weight ratio also smaller (P < 0.001), with a 'dose response' relationship apparent as these effects were greater in those infants with more than one cord encirclement. Although gestational age and umbilical cord veno-arterial PO2 and PCO2 differences were also found to impact on
birth weight, placental weight, and the birth to placental weight ratio, these effects were independent of the effect of
nuchal cord complications. Umbilical cord complications is evidenced by a
nuchal cord at the time of birth, are associated with a decrease in fetal size relative to that of the placenta, although this is likely to be of little
biological significance for most
nuchal cord infants.