ABSTRACT
The fetus is entirely dependent on maternal/placental blood flow for intact survival. The placenta embeds in the wall of the womb and virtually covers a lake of maternal blood. The fetal circulation is separate from that of the mother, so exchange of oxygen and nutrients occurs from this maternal lake of blood across the walls of the small fetal blood vessels of the placenta. If the placenta becomes separated from the maternal blood supply (placental abruption), the fetus is at risk of hypoxic damage. This is the mechanism for fetal neurological damage with ante-partum haemorrhage. The placenta comes away from the wall of the womb, allowing the mother to haemorrhage, but also compromising oxygen supply to be fetus. Although the fetal circulation is separate the fetal blood vessels can be damaged, leading to fetal haemorrhage as well, which will further compromise the fetus. Such a haemorrhage may be obvious, causing vaginal bleeding; however, the placenta may break away from the womb, but contain the resulting haemorrhage. The maternal blood lake therefore enlarges, becomes relatively stagnant, and clots, causing compromise to the fetus that can range from intrauterine death to neurological damage. This placental abruption may have happened some time before birth, so that the baby is born in what appears to be good condition. The retroplacental clot may not be looked for or recognised, thus the cause of later cerebral palsy is missed.
