Asphyxia is a lack of oxygen supply to body tissues. Asphyxia can have negative effects on all of the organs, including the brain. Asphyxia can occur in the womb, during delivery, or immediately after birth. Lack of oxygen, depending on how severe it is and how long it lasts, can lead to serious injury in the brain and the rest of the body. At the same time, most babies can withstand a short period without oxygen without suffering short- or long-term harmful effects. Most commonly, these short periods occur during labour and delivery or immediately following birth.

Whether it comes in blood from the mother or through the baby’s lungs, oxygen is delivered by the baby’s blood circulation system to individual cells throughout the body, including the brain. Cells need oxygen to survive; an interruption to oxygen delivery, in the long-term, causes cell death. Cell death in the brain can have serious negative consequences, depending on its location and extent.

In the womb, the fetus’s oxygen needs are met entirely with oxygen extracted from the mother’s blood and delivered via the placenta and umbilical cord. Asphyxia can occur due to:

  • blockage or squeezing of the umbilical cord, reducing blood flow
  • low maternal blood pressure
  • a tear or separation of the placenta, called a placental abruption

During pregnancy, some women develop high blood pressure and pre-eclampsia, or high blood pressure accompanied by and excess of protein in the urine leading to a rapid swelling of the mother’s limbs and face. In many cases, this condition can be managed and may not be particularly dangerous to the mother or the fetus, however, at times pre-eclampsia can interfere with oxygen delivery to the fetus. If these types of events are of a short duration, the fetus will not likely face lasting damage. However, if these problems occur over a longer period of time, the baby’s brain may be damaged.

During birth, asphyxia may occur depending on how labour progresses. The causes are similar to those that can take place in the womb. During labour, particularly a long and difficult one, oxygen flow to the baby can be interrupted due to a squeezed umbilical cord or the placenta may become detached prematurely, cutting off its oxygen supply.

After birth, a baby’s oxygen needs must be met by his own lungs and blood circulation system. Often, premature babies have problems with their lungs or heart, or both, which have the effect of reducing the steady flow of oxygen to the cells within the body, including the brain. Many premature babies will not be able to breathe on their own immediately after birth and will need mechanical ventilation in order to receive enough oxygen. Poor blood circulation can also reduce the amount of oxygen individual cells in the body receive.

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Hilary Whyte, MSc, MB, BCh, BAO, MRCPI, FRCPC