Page 117 - 86 human physiology part-2

Chapter 17

The exchange of gases, nutrients and oxygen takes place between the maternal blood and fetal
blood. There are 2 main arteries.

• Umbilical Vein

Vein that carries nutrients and oxygen away from the placenta to the growing fetus. It also carries
rich blood. There is only 1 main vein.

• Fetus doesn't use its lungs for gas exchange.

Umbilical Abnormalities

• Single Umbilical Artery

One artery instead of two will result in chromosomal abnormalities. Some of these defects include
poor fetal growth, preterm delivery, and still births. This can be detected by a routine ultrasound. If an
ultrasound is done and no other complications or abnormalities are detected, the baby will usually be
born healthy.

• Umbilical Prolapse

This condition usually happens when a cord is too long. The baby may be born prematurely or will
be breech.

• Umbilical Nuchal Loops

This condition happens when the umbilical cord is wrapped around the baby's head at least one or
more times. This can be detected when a baby is in stress or by a simple ultrasound. In most cases the
mother will have a cesarean delivery. In other cases the cord may be wrapped around the hands or feet.

• Vasa Previa

This occurs in one in every 3,000 births, which can become life threatening for the unborn baby.
This complication happens when the umbilical cord inserts abnormally in the fetal membranes of the
placenta, which appears abnormally shaped or positioned. Major risks include unprotected fetal blood
vessels cross the cervix, oftentimes rupturing the membranes. Also, lack of blood pressure due from
pressure, causes the loss of oxygen to the baby. Women who will be at risk for this would be those who
already have experienced placenta previa or have used in vitro fertilization.

• Umbilical Cord Knots

About 1% of babies are born with one or more knots in their umbilical cord. Some knots happen
during labor; others happen from moving around in the womb. Most knots occur when the umbilical
cord is too long. In some cases the knots can become tight, cutting off the oxygen supply to the baby.
Cord knots result in miscarriages and stillbirth in 5% and 10% of most cases. Most will require a
cesarean delivery.

• Umbilical Clotting

332 | Human Physiology