Decreased Amniotic Fluid/Oligohydramnios

During the course of a normal pregnancy, the developing baby remains surrounded by amniotic fluid. It is generally felt that the volume of amniotic fluid will increase during the course of a normal pregnancy until approximately 36 weeks gestation, from which time there will be a gradual decrease.

The volume of amniotic fluid is typically assessed through ultrasonography and what is known as an Amniotic Fluid Index (AFI).

Decreased amniotic fluid levels during pregnancy, or oligohydramnios, is a condition which requires rigorous and careful monitoring and management by the responsible obstetrician.

Decreased amniotic fluid levels, or oligohydramnios, is associated with a number of conditions, many of which are significant to the health and well being of both the mother and her baby.

Poorly managed maternal hypertension, including the disease pre-eclampsia, can often result in uteroplacental insufficiency and decreased amniotic fluid levels.

Similarly, poorly managed maternal diabetes and resultant uteroplacental insufficiency can directly lead to decreased amniotic fluid levels, or oligohydramnios, even early in the pregnancy.

In many cases, it has been recognized that partial placental abruptions, where the placenta partially separates from the uterus, can also result in decreased amniotic fluid levels or oligohydramnios.

Several fetal conditions are also strongly associated with the development of decreased amniotic fluid levels. In particular, when the baby does not grow normally, a condition known as Intrauterine Growth Restriction, there is a strong association with the development of oligohydramnios.

Post-term pregnancies, that is, pregnancies which are allowed to continue well past 40 weeks of gestation, are also strongly associated with the development of decreased levels of amniotic fluid or oligohydramnios.

Chronic leaking of amniotic fluid can also directly lead to oligohydramnios.

It is generally recognized that the earlier in pregnancy that oligohydramnios occurs, the greater the risk to the well being of the baby.

Late in pregnancy, oligohydramnios may also be associated with thick meconium in the amniotic fluid. This places the baby at risk for aspirating meconium during the labor and delivery process. Aspiration of meconium into the lungs can lead to a respiratory disease known as “Meconium Aspiration Syndrome.”

During labor, the baby of a patient suffering from oligohydramnios may have what are known as “variable decelerations” of the heart rate. It is generally felt that such variable decelerations of the baby’s heart rate occur as a result of the compression of the umbilical cord during the process of labor and delivery. Such variable decelerations can often lead to a reduction of oxygen to the baby, resulting in hypoxia.

If oligohydramnios is assessed during the labor and delivery process, a safe and careful obstetrician will frequently utilize amnioinfusion, a process by which fluid is administered into the uterine cavity to prevent umbilical cord compression and to lessen the risk of meconium aspiration.

The failure of an obstetrician to diagnose and carefully manage a patient with decreased amniotic fluid levels, or oligohydramnios, can directly lead to a significantly increased risk of fetal death or permanent neurologic injury.

Because of the significant risks associated with moderate to severe decreases in amniotic fluid levels, or oligohydramnios, many safe and careful obstetricians will deliver their patients suffering from oligohydramnios well prior to term.

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