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Fetal Hydantoin Syndrome: Causes, Symptoms, Treatment, Diagnosis

What is Fetal Hydantoin Syndrome?

Fetal hydantoin syndrome is also known as Fetal Dilantin syndrome which refers to the combination of defects that is caused to the development of the fetus, which is due to the side effects of phenytoin (PHT) which is an anti-seizure medication, the medicine helps in prevention of tonic-clonic seizures. All those mothers who consume this drug their children suffer from intrauterine growth restriction which leads to the development of the small head and develops minor mental retardation, it also leads to limb defects, causing some minor and major birth defects. Some children with fetal hydantoin syndrome may have growth problems and development issues. An effect known as methemoglobinemia is a very rare side effect observed. Heart defects are also noticed.

Symptoms of the Fetal Hydantoin Syndrome

The symptoms that are associated with fetal hydantoin syndrome vary from infant to infant; the physical features will also differ from an infant to another. There are chances that the symptoms of fetal hydantoin syndrome are not noticeable at birth but will be notified when a child starts to grow gradually. As soon as the child will grow the symptoms will be noticeable. There are many types of research that are being conducted to find a possible symptom of fetal hydantoin syndrome; many are discovered by the doctors and there are a few yet to be discovered. There are many symptoms that are not fully understood by doctors yet. The infant affected by this syndrome may be born small due to the growth disorder during the development of the syndrome. The growth disorder or deficiency can vary too from moderate to severe and can persist during the child growths. Some facial disorders like a short nose, increased distance between the eyes than normal, wide mouth, etc. can exist along with underdeveloped fingers and toes. There are some infants that have more than normal growth of facial hairs and body hairs. A delay in growth and development is noticeable which also leads to the delaying of mental abilities from other children. The growth deficiency includes poor growth in height, lowering of the position of the head, weight deficiency, and poor sightedness. A significant lowering in cognitive functions is observed among the suffering children. Various cases are seen where the child suffers from lip deformities, this is treatable by undergoing a surgery. Other symptoms of fetal hydantoin syndrome include the following:

  • Heart defects
  • Hyperactivity disorder
  • Abnormalities in behavior
  • Defects in kidney
  • Defect in eyes which may lead to myopia
  • Inguinal hernia, a condition where the muscular layers of abdominal walls are pushed by the lower portion of the intestine.

Researches continue to have full knowledge of all the disorders related to this syndrome.

Prognosis of Fetal Hydantoin Syndrome

The fetal hydantoin syndrome occurs in 10 percent of infants born to epileptic women those are treated with phenytoin during pregnancy. A pattern of minor anomalies is being recognized for the past 35 years. Though the percentage of children suffering from this syndrome is very less still prevention and awareness are important for diagnosis and intervention. The support from parents is an important factor which helps a child in copping the challenges faced by him or her.

Causes of the Fetal Hydantoin Syndrome

The consumption of anti-seizure medications such as phenytoin by the mother which is used for the treatment of epileptic seizures results in developing multiple defects in the fetus. The amount of consumption of phenytoin which causes the defects in the fetus is not determined until now. The drug is often given with some other anti-seizure drugs that cause development disorder in fetus. One cause can be the combined effect of some specific genetic and environmental factors. The fact that phenytoin causes the developmental disorder is not 100 percent proven some doctors believe that it can also be caused by by-products of phenytoin. The genetic influences that cause phenytoin disorder and other environmental factors such as smoking are also a part to be discovered that how they affect the growth of the fetus. A report says that the women with mutations in the methylenetetrahydrofolate reductase (MTHFR) gene will be at a greater risk of having a fetus with this syndrome[2]. Scientists have also discovered that the protein product of the methylenetetrahydrofolate reductase gene plays a role in the breaking down of phenytoin or its metabolites.

Diagnosis of Fetal Hydantoin Syndrome

The symptoms and physical deformations of fetal hydantoin syndrome may vary from individual to individual to a large extent. There are also cases where fetal hydantoin syndrome is not visible during the time of birth but becomes more evident as the individual grows up.

The infants who are affected with fetal hydantoin syndrome may remain small during the time of birth due to the lack of growth factors at the time of development. Growth deficiency severity may be slight to average and can be continued during the period of newborn.

There is no particular method of diagnosis that can help in diagnosing fetal hydantoin syndrome. Identification of a disease or disorder is done upon the proper detection of symptoms based on the available features in the affected infant in combination with a phenytoin exposure as a history during the time of gestation. It is a very significant fact that women who intake phenytoin during their period of pregnancy have a higher risk of having the baby with Fetal Hydantoin syndrome.

Treatment of Fetal Hydantoin Syndrome

The treatment of fetal hydantoin syndrome will differ from child to child depending on the particular symptoms that are shown. An integrated team may be need to work together such as pediatricians, surgeons doing oral surgery, plastic surgery, neurologists, psychologist, physiologist, and other professionals to get the desired outcome. It will need a cooperative process which will require a systematic plan inclusive of all aspects of a child’s treatment. The affected child can be benefited by therapies that include occupational therapy, physical therapy and speech therapy. The treatment for fetal hydantoin syndrome may also include behavioral therapy as a child suffering from this syndrome has a lot of behavioral changes. Apart from the treatment, one thing that will be beneficial to the child is the support and care from the family which includes more of psychosocial support[1]. If the child having fetal hydantoin syndrome suffers from cleft lip then it can be treated surgically; The first corrective surgery happens when the child is an infant, followed by a second surgery which will be related to cosmetic purpose only and is done when the child gets older. The surgical repairing process can be taken out in various stages or in a single operation which will vary accordingly keeping the child’s condition in mind. The palate surgery is scheduled during the toddler phase. The child is always made comfortable with all the happenings which help in speedy recovery of the child.

It is always recommendable to women prior as well as throughout their pregnancy period to be given the treatment of a single anticonvulsant as it has been found out that intake of more than one anticonvulsant puts the child at a greater risk of developing several birth defects. It is also advisable to women who take phenytoin to consume folic acid supplements at the same time both prior as well as after conception and throughout their pregnancy as a precautionary measure against deformations in the newborn. The medication given to infants with fetal hydantoin syndrome is directed towards particular symptoms that are evident. Treatment may need the combined efforts of a group of specialists. Pediatricians, plastic surgeons, psychologists, oral surgeons, neurologists, and different other healthcare professionals might be required to systematically and completely plan the child’s therapy.

Infants suffering from fetal hydantoin syndrome will be benefitted from developmental therapies starting at an early age to make sure that the affected child reaches their potential. Affected children may be benefitted from the physical, speech and occupational therapy. Different types of methodologies of behavioral and rehabilitative therapy may be advantageous. In addition medical, vocational as well as social services may be required along with the psychological support from the whole family.


Although fetal hydantoin syndrome is quite infrequent, when it is found in a child the effects are permanent due to the mutations in the gene and there isn’t a way to restore things back to normal. It is found that fetal hydantoin syndrome can occur due to the side effect of the phenytoin based medicine given to treat epilepsy; hence, one must be very cautious during pregnancy to consume these medicines and always consult a doctor during pregnancy to get the safest possible drug so that the harmful effects can be prevented. In case of unfortunate scenarios where the baby is found to have the problem, early diagnosis and intervention will be of great help. The child should be emotional supported by the family for a proper development and to make them feel safe and ready for the treatment as it involves multiple surgeries.


  1. Hegde, A., Kaur, A., Sood, A., Dhanorkar, M., Varma, H., & Singh, G. et al. Fetal Hydantoin Syndrome. The Journal Of Pediatrics, (2017). 304.
  2. https://rarediseases.org/rare-diseases/fetal-hydantoin-syndrome/
Sheetal DeCaria, M.D.
Sheetal DeCaria, M.D.
Written, Edited or Reviewed By: Sheetal DeCaria, M.D. This article does not provide medical advice. See disclaimer
Last Modified On:November 24, 2021

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