188 Obstetrics and Gynecology Board Review •••
❍ How might the measurement of amniotic fluid volume be artificially increased?
By not maintaining the transducer perpendicular to the floor.
❍ How might the measurement of amniotic fluid volume be artificially decreased?
By applying excessive pressure on the maternal abdomen with the transducer.
❍ What is oligohydramnios?
Less than normal or diminished amniotic fluid volume.
❍ What is the incidence of oligohydramnios?
0.5 to 8% of all pregnancies.
❍ What MVP is consistent with oligohydramnios?
<2 cm.
❍ What AFI is consistent with oligohydramnios?
<5 cm, or less than 5th percentile for a particular gestational age.
❍ What AFI is consistent with severe oligohydramnios?
<2 cm.
❍ What are some clinical findings pointing toward the possibility of oligohydramnios?
- Fundal height less than estimated gestational age.
- Fetal parts easily palpated through maternal abdomen.
- Ultrasound examination demonstrates fetal crowding and poor visualization of fetal anatomy
❍ What subjective ultrasound criteria have been used to determine oligohydramnios?
- Absence of fluid pockets throughout the uterine cavity.
- Crowding of fetal limbs.
- Absence of pockets surrounding the fetal legs.
- Overlapping of the fetal ribs (in severe cases).
❍ Name some causes of oligohydramnios.
- Congenital anomalies, especially related to renal system dysfunction (eg, renal agenesis, polycystic kidneys,
genitourinary obstruction, dysplastic multicystic kidneys, or posterior urethral valves in males). - Chromosomal anomalies.
- Fetal anuria or oliguria due to decreased renal perfusion.
- Intrauterine growth restriction.
- Side effect of certain drugs [eg, indomethacin, NSAIDs, angiotensin-converting enzyme (ACE) inhibitors].
- Maternal dehydration.
- Severe preeclampsia.
- Postdate pregnancy.
- Ruptured membranes.