What is hyperemesis?
Hyperemesis gravidarum is the fancy term for "morning sickness" with nausea and vomiting. Increasing hormone levels with gastrointestinal dysmotility, and abdominal fullness with pregnancy contribute to this benign but bothersome condition. Up to 2% of pregnancies may be complicated by hyperemesis gravidarum. Some women are affected worse than others. This condition can interfere with proper nutrition.
What embryologic problem is seen on US?
A neural tube defect (NTD) is present. The developing embryo has a dorsal neural rube developed from neuroectoderm. A neural plate and groove form around 18 days and the neural tube "zips" closed to form the neuraxis with cranial cavity rostrally and spiral canal caudally in the next 5 days.
The cephalic end of the neural tube has three enlargements, or primary brain vesicles: prosencephalon (telencephalon, which forms the cerebral hemispheres, and diencephalon, which forms the hypothalamus and optic vesicles), mesencephalon (which gives rise to the midbrain), and rhombencephalon, from which the metencephalon (pons and cerebellum) and the myelencephalon (medulaa) arise.
The caudal end of the neural tube forms under the direction of PAX and MSX genes, forming a tube with a central canal contiguous with the brain vesicles. The sonic hedgehog (SHH) gene deals with ventral positioning. Initially, the spinal cord extends the full length of the vertebral canal, but eventually there is lengthening of the vertebral column and dura so that, in adults, the cord terminates at the L2-L3 level and spinal nerves run distally as the cauda equina. This makes it possible to do a lumbar puncture (LP) by inserting a needle below the cord termination to sample cerebrospinal fluid (CSF).
What laboratory test(s) on maternal blood or amniotic fluid could be abnormal?
The alpha-fetoprotein (AFP) is increased. About half of fetal serum protein is AFP and half albumin (in the adult, the major blood protein is albumin). A defect in the fetus (NTD or abdominal wall defect) allows AFP into amniotic fluid and from there it can diffuse across the placenta into the maternal circulation. Thus, it is not specific for NTDs.
Measurement of acetylcholinesterase (and total cholinesterase) is more specific for NTDs, since these substances represent biochemical products in neurotransmitter synthesis.
What would a karyotype show?
46, XX NTD's are typically not related to chromosomal abnormalities.
Name conditions seen with this category of embryologic abnormality.
Spina bifida - closed
Spina bifida - open: meningocele -- meninges herniate from the defect
Meningomyelocele -- meninges and cord herniate from the defect
Encephalocele -- brain herniates through a skull defect
Anencepaly -- lack of the fetal cranial vault
Iniencephaly -- head retroflexed
Exencephaly -- partial cranial defect
Rachischisis -- long open spinal defect
What could be done to reduce the incidence of this condition?
Supplementing the maternal diet before and during pregnancy with folic acid will reduce NTD's by at least half. Remind a pregnant woman that it is important to do everything she can to improve the chances for a good outcome, but there are no guarantees. When everything goes right, it feels like a miracle, all the more so if you know through medical training all the things that can go wrong. And if something does go wrong, you need to be very careful not to add any guilt or blame to the shoulders of someone who is already grieving and depressed. Counseling should be non-judgmental and supportive when things go wrong.
What are potential outcomes?
Spina bifida, closed - minimal
Spina bifida, open - neurologic problems, paralysis - the higher up the vertebral column, the worse the neurologic deficits; infection
Anencepaly - not survivable
What are options for the parents?
Continue pregnancy with or without planned intervention following delivery. If intervention is desired, then the parents can consult with a pediatric neurosurgeon regarding repair following birth.
Pregnancy termination can be considered if the parents feel that the defects are severe with a grave outcome.
Is there a maternal risk?
No, other than potential problems with delivery with anencephaly, which may lead to breech presentation because there is no head to descend into the lower uterus and turn the baby for a normal delivery.
What are options for the parents?
Improved imaging techniques for fetal medicine (greatly improved ultrasounds) are just like every single technological breakthrough in medicine: they introduce more ethical dilemmas, even as they seem to make medical decisions more clear. The information improves, but the value judgments that are also part of every decision don't keep pace. So now we can see neural tube defects and, once they've been detected, provide options for interventions allowing improved prognosis. But it will still be a tough time for parents. They can continue pregnancy with or without planned intervention following delivery. If intervention is desired, then the parents can consult with a pediatric neurosurgeon regarding repair following birth. Pregnancy termination can be considered if the parents feel that the defects are severe with a grave outcome.