Genetic studies

The Hospital Clinica Vistahermosa has a Medical Genetics Unit with all the staff and equipment needed to be able to give an accurate clinical diagnosis and provide genetic counselling on hereditary diseases. This service also helps other departments diagnose genetic diseases in other specialities.

The Genetic Unit of Clinica Vistahermosa is one of the most advanced in Spain, not only does it work with the other areas of UR Vistahermosa, but also with other units and hospitals around the country.

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→ Genetic counselling

Genetic counselling is essential whenever there are genetic factors involved in the problems of a couple who come to the reproduction unit for help.

Members of the Reproduction Unit work together in the medical consultation and the genetic counselling provided on hereditary diseases and whenever it is deemed necessary and possible, the corresponding genetic alteration, gene mutation or chromosomal mutation, are studied in the laboratory.

→ Genetic diagnosis of infertility

Peripheral blood karyotype

Lymphocytes are cultured from a blood sample taken and then the peripheral blood karyotype is studied.

This is especially recommended for sub-fertile patients, when there have been recurrent miscarriages and when certain chromosome anomalies have been detected in children.

Y chromosome microdeletion study

Almost 20% of men with azoospermia have a microdeletion in one or various areas of the long arm of the Y chromosome, within the AZF region, especially in the DAZ gene.

The test consists in using molecular biology techniques (amplification by polymerase chain reaction: Multiplex- PCR), to study the mutations in different areas of the AZF region, including the DAZ gene.


  • Sub-fertile patients
  • ICSI candidates

Molecular study of other mutations

There is a growing number of hereditary diseases that are associated with sterility, such as cystic fibrosis, in which the mutant that is responsible for such has been identified.

During the medical consultation at the Unit, if we think that a mutation study should be carried out on a patient, their DNA is extracted from blood cells and then the mutation is studied by means of molecular biology techniques.

FISH – Sperm fluorescence in situ hybridization

This is a study of the DNA using fluorescent probes (specific or complementary centromeric DNA sequences) and microscopy (Fluorescence In Situ Hybridization), to detect the existence of numeric chromosome abnormalities in sperm. Normally the chromosomes 13, 16, 18, 21, 22, X and Y are studied.


  • Oligospermia and/or serious teratospermia
  • Patients with sex chromosome abnormalities
  • Patients who are translocation carriers – patients who have been treated with chemotherapy/radiotherapy
  • Recurrent miscarriages, when the cause of such is unknown

→ Prenatal genetic diagnosis

Karyotype test on amniotic fluid

This is a complete study that includes an amniocentesis and genetic testing. The patient is seen by a geneticist who prepares their medical report, gives them a detailed explanation of the test that is going to be carried out, the advantages and the disadvantages of such and provides them with genetic counselling whenever necessary.

This test can also prevent any mother-fetus Rh blood type incompatibility problems.

The radiologist team carries out the amniocentesis and after the genetic testing when the whole procedure is complete; the patient is given the results. The related-miscarriage rate is very low (less than 0.5 %).

In addition to this, we always study the alpha-fetoprotein in the amniotic fluid to make sure there aren’t any neural tube closure defects.

The karyotype test is recommended in the following circumstances:

  • Age: Women aged 35 and over
  • Other children with chromosomal birth defects
  • Chromosome abnormalities in parents
  • Family history of a genetic disorder
  • Increased risks of neural tube closure defects
  • Altered screening
  • Molecular diagnosis of monogenic diseases
  • Family history of a disorder associated to the X for which there is no specific test
  • Other pregnancies achieved with assisted reproductive techniques

Very recently the American Board of Medical Genetics published a document with advice on the prenatal screening for neural tube closure defects and aneuploidies stating that amniocentesis or chorionic villus sampling should still be made available for pregnant women aged 35 and over, as a method used to diagnose aneuploidy.

Chorionic villus sampling for fetal karyotyping

This is similar to the previous test if the material studied comes from a sample of the chorionic villus (placental tissue).

In this case, the karyotyping can be carried out a few weeks earlier than the amniocentesis (weeks 10-12 vs. 15-16), although the rate of related miscarriages after the sample has been obtained is higher (1%); only the extraembryonic material is examined, the AFP is not measured and the confined placental mosaicism can be a problem.

FISH in amniotic fluid

This is a study of the DNA using fluorescent probes (specific or complementary centromeric DNA sequences) and microscopy (Fluorescence In Situ Hybridization), to detect the existence of chromosomes without having to use cell cultures.

The big advantage of the test is that it is quick and results are obtained within 24-36 hours because it can be done without cell cultures, so the parents don’t have so long to wait and worry.

Normally the chromosomes 13, 18, 21, X and Y are studied because alterations to these cause 90% of the aneuploidies.

There are also specific probes that can detect certain mutations that are not captured on the resolution of conventional karyotyping but can be studied with FISH.

Prenatal study of monogenetic alterations

Many hereditary diseases are caused by mutations that occur in a specific gene and this can be passed down from one generation to another.

If the parents are affected by any of these diseases or is a carrier of a gene mutation, the molecular study on this mutation can be carried out on the cells taken from the amniotic fluid which is obtained by means of amniocentesis.

→ Pre-implantation Genetic Diagnosis (PGD)

PGD is the latest Assisted Reproductive Technique.

This technique was not originally meant for infertile couples, but rather those who have a high risk of transmitting certain diseases like hemophilia, cystic fibrosis, etc. onto their descendants. It is also used in cases of recurrent miscarriages.

The procedure involves carrying out an ICSI, followed by an analysis of the genetic material from one of the cells of each embryo obtained to determine which embryos are carriers of the corresponding abnormalities. Only those that do not have any genetic defects will be used, so as to prevent the disease being passed onto descendants. The pregnancy success rate for this technique is 40%.

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