anencephaly

[ddw2013]

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This is from NBME12.
A 28-year-old primigravid woman at 16 weeks gestation comes to the physician for a routine prenatal visit. Physical examination shows a uterus consistent in size with a 14-week gestation. Ultrasonography shows fetal anencephaly. Which of the following most likely failed to occur in this fetus?
0 A) Closure of the rostral end of the neural tube
0 B) Development of the cerebellum
o C) Development of the midbrain
o D) Migration of neural crest cell derivatives to their adult positions
0 E) Migration of neurons into the cerebral cortex

The answer is A.
The physical exam show the uterus size is 14 week but it is actually 16 week. Does this mean poly- or oligohydramnios? I thought it is oligohydramnios since the uterus is smaller than it should be. But anencephaly cause polyhydramnios due to swelling defect. How can this be oligohydramnios? Can someone explain to me? Thank~

 

[dyspareunia]

Maternal malnutrition is associated with fetuses that are small for gestational age. Folate deficiency is associated with anencephaly. And maternal malnutrition can cause folate deficiency.

Does that work?

 

[ChessMaster3000]

This is from NBME12.
A 28-year-old primigravid woman at 16 weeks gestation comes to the physician for a routine prenatal visit. Physical examination shows a uterus consistent in size with a 14-week gestation. Ultrasonography shows fetal anencephaly. Which of the following most likely failed to occur in this fetus?
0 A) Closure of the rostral end of the neural tube
0 B) Development of the cerebellum
o C) Development of the midbrain
o D) Migration of neural crest cell derivatives to their adult positions
0 E) Migration of neurons into the cerebral cortex

The answer is A.
The physical exam show the uterus size is 14 week but it is actually 16 week. Does this mean poly- or oligohydramnios? I thought it is oligohydramnios since the uterus is smaller than it should be. But anencephaly cause polyhydramnios due to swelling defect. How can this be oligohydramnios? Can someone explain to me? Thank~

the terms oligo/polyhydramnios are really used clinically in the 3rd trimester. As you can imagine, due to dating errors and all sorts of other phenomena, you can't really conclude that a 16 wk fetus that looks like 14 wks is due to oligo.

 

[EazyE1907]

The main thing the question is trying to reinforce is maternal folate deficiency can lead to fetal malnutrition/immaturity, but more importantly to neural tube defects. just need to know your simple neuro embryology. no need to get bogged down on oligo/polyhydramnios. keep it simple.