190 Obstetrics and Gynecology Board Review •••
❍ What is a common fetal heart rate tracing finding in patients with oligohydramnios?
Variable decelerations.
❍ Why are variable decelerations more commonly seen with oligohydramnios?
Cord compression due to lack of cushioning effect given by a normal amniotic fluid volume.
❍ What is the likely cause of oligohydramnios associated with asymmetric growth restriction?
Uteroplacental insufficiency.
❍ What is the mechanism by which uteroplacental insufficiency might cause oligohydramnios?
Chronic hypoxia causes shunting of fetal blood away from the kidneys to more vital organs, leading to decreased
fetal urine output, thus decreasing amniotic fluid production.
❍ What is the likely cause of oligohydramnios associated with symmetric growth restriction?
Chromosomal abnormalities.
❍ How does oligohydramnios make ultrasound assessment of the fetus more difficult?
Amniotic fluid easily transmits sound waves; therefore, ultrasound visualization of fetal anatomy is impaired by less
amniotic fluid.
❍ What can be done to improve the quality of diagnostic ultrasound in a pregnancy complicated by
oligohydramnios?
Intraamniotic placement of sterile saline (ie, amnioinfusion) may enhance visualization of the fetal anatomy.
❍ How does amnioinfusion help pregnancies complicated by oligohydramnios?
Amnioinfusion decreases the incidence of variable decelerations and consequently decreases the cesarean delivery
rate for nonreassuring fetal heart rate tracing.
❍ When might delivery be safely postponed in a term pregnancy complicated by oligohydramnios?
In an otherwise uncomplicated pregnancy with an AFI close to 5 cm and otherwise reassuring fetal testing and an
unfavorable cervix at 37 weeks gestation.
❍ What is polyhydramnios?
Synonymous with hydramnios, means abnormally excessive amounts of amniotic fluid.
❍ What is the clinical definition of polyhydramnios?
2 L of amniotic fluid measured at time of delivery.
❍ What is the incidence of polyhydramnios?
1% to 2% of all pregnancies.
❍ What MVP is consistent with polyhydramnios?
8 cm.