During pregnancy, the flow of oxygen and nutrients to the baby and the removal of carbon dioxide and other waste gases from the baby is achieved through the placenta.
The placenta is an exceedingly complex organ which is comprised of both maternal and fetal blood circulatory systems.
Adequate blood flow to and from the placenta, and in both the maternal and fetal circulations, is necessary in order for the baby to receive enough oxygen and for it to be able to expel carbon dioxide and other waste gases.
Any alteration in placental function can lead to decreases in the delivery of oxygen to the baby, a condition known as fetal hypoxia.
Because fetal hypoxia can result from many maternal or fetal diseases or conditions which diminish a placental function, safe and careful obstetricians will rigorously assess their patients who are at risk for the development of fetal hypoxia.
Maternal hypertensive disorders during pregnancy, including pre-eclampsia and HELLP Syndrome, if undiagnosed or poorly managed can directly lead to impaired placental function and resultant fetal hypoxia.
Maternal hemorrhagic disorders, including hemorrhagic placenta previa or placental abruption, wherein the placenta prematurely tears away from the uterus, can directly and acutely result in fetal hypoxia.
Poorly managed diabetes mellitus is also associated with a greatly increased risk of uteroplacental insufficiency which can directly lead to fetal hypoxia.
Decreased levels of amniotic fluid, also known as oligohydramnios, can lead to the impingement or prolapse of the baby’s umbilical cord, thereby directly cutting off the flow of oxygenated blood from the placenta to the baby, resulting in fetal hypoxia.
If the hypoxia, or lack of oxygen, is mild or transient, the baby will typically be able to compensate without suffering any permanent injuries.
However, prolonged or severe hypoxia can lead to fetal asphyxia. In such cases, the baby’s compensatory mechanisms fail or otherwise are overwhelmed, directly leading to the risk of permanent and irreversible brain injury and the condition known as hypoxic-ischemic encephalopathy.
In those patients who are recognized as being at risk for fetal hypoxia, the safe and careful obstetrician will initiate a regimen of fetal surveillance to routinely assess the status of the baby.
Such fetal surveillance tests typically will include nonstress tests, so called stress tests, also known as oxytocin challenge tests and biophysical profile testing.
It has long been recognized that variations in the fetal heart rate, as determined from continuous electronic fetal heart monitoring, can reflect both fetal hypoxia and whether the baby is suffering from acidosis, that is, the build-up of acids in the blood as a result of impaired gas exchange.
Thus, in babies who are at risk for developing fetal hypoxia, safe and careful obstetricians will study the variability of the fetal heart rate and assess whether there are any decelerations of the fetal heart rate from its normal baseline level.
Minimal to “absent” variability, and/or the existence of “late” decelerations during labor, are considered by many safe and careful obstetricians to be ominous signs of potential fetal hypoxia.
Safe and careful obstetricians and obstetrical nurses will promptly respond to any signs of fetal hypoxia.
In many cases, a finding of fetal hypoxia will require the prompt delivery of the baby by cesarean section.
Unfortunately, in many cases, where fetal hypoxia is undiagnosed or delivery by cesarean section is unnecessarily delayed, prolonged fetal hypoxia leads to permanent and irreversible brain damage, also known as hypoxic-ischemic encephalopathy.
Thus, the prompt assessment of fetal hypoxia and delivery by cesarean section will in many cases be the only way to prevent a baby from suffering potentially devastating injuries such as brain damage and cerebral palsy.