oligohydramnios_flashcards (1)
What is oligohydramnios?
Oligohydramnios is a condition characterized by reduced amniotic fluid, defined as less than 500ml at 32-36 weeks or an amniotic fluid index (AFI) < 5th percentile.
What are some causes of oligohydramnios?
Causes of oligohydramnios include:
- Premature rupture of membranes
- Potter sequence
- Bilateral renal agenesis + pulmonary hypoplasia
- Intrauterine growth restriction
- Post-term gestation
- Pre-eclampsia
summarise Oligohydramnios
Oligohydramnios
In oligohydramnios there is reduced amniotic fluid. Definitions vary but include less than 500ml at 32-36 weeks and an amniotic fluid index (AFI) < 5th percentile.
Causes
premature rupture of membranes
Potter sequence
bilateral renal agenesis + pulmonary hypoplasia
intrauterine growth restriction
post-term gestation
pre-eclampsia
A 27-year-old primigravida presents for a routine midwife check-up. She is currently 26 weeks pregnant and she has not been compliant with her antenatal care.
On examination, the fundal height measures 18cm. Her blood pressure is 109/82mmHg and a urine dipstick is normal. The midwife refers her for an urgent scan which reveals oligohydramnios.
The mother is otherwise well and did not suffer from any symptoms during the pregnancy.
What is the most likely cause of the presentation?
Duodenal atresia
Fetal anaemia
Maternal diabetes
Renal agenesis
Trisomy 21
Renal agenesis
Oligohydraminos can be a clue that infants have renal agenesis (Potter sequence)
The correct answer is renal agenesis. This woman is presenting with oligohydramnios, defined as decreased amniotic fluid volume for gestational age. In this list, the only cause for it is renal agenesis. Renal agenesis causes the fetus not to produce urine, hence the liquid inside the sac will be diminished causing oligohydramnios.
This is usually seen in the context of Potter’s sequence, a rare fatal genetic disorder, characterised by severe oligohydramnios, resulting either from polycystic kidney or bilateral renal agenesis. This causes a specific appearance of the newborn, called Potter facies. The affected babies usually die within a few hours of birth or are stillbirths, and have wrinkly skin, low-set ears, flat noses and chins, and widely separated eyes with epicanthic folds.
Duodenal atresia is an incorrect option. This is a cause of polyhydramnios rather than oligohydramnios. In duodenal atresia, the fetus cannot swallow amniotic fluid, increasing the quantity free in the sac, and causing increased fluid for gestational age.
Fetal anaemiais an incorrect option. This is a cause of polyhydramnios rather than oligohydramnios. It can cause high-output heart failure if severe, which, in turn, leads to polyhydramnios.
Maternal diabetes is an incorrect option. This is a cause of polyhydramnios rather than oligohydramnios. Gestational diabetes cause the fetus to have increased urine output, increasing the quantity which is free in the sac, causing increased fluid for gestational age.
Trisomy 21 is an incorrect option. This is a cause of polyhydramnios rather than oligohydramnios. This is due to the fact that trisomy 21 is often associated with duodenal or oesophageal atresia, leading to the fetus being unable to swallow amniotic fluid, increasing the quantity which is free in the sac, causing increased fluid for gestational age.
