Prenatal Genetic Diagnosis for XLH

Prenatal Genetic Diagnosis for XLH

If you have a family history of X-linked hypophosphatemia (XLH) and are planning to start a family, you may want to consider prenatal genetic diagnosis.

What is prenatal genetic diagnosis?

Prenatal genetic diagnosis is a process to determine, before your baby is born, whether it will have a genetic disease like XLH.

As part of normal pregnancy checkups, your doctor assesses the health of the mother and the baby. They check your baby’s weight, size, and development at every appointment. For XLH, however, symptoms may not be apparent from early examinations, so a genetic test may be necessary to diagnose your baby before birth.

There are two techniques used to obtain a DNA sample from the fetus while it is still in the womb: amniocentesis and chorionic villus sampling (CVS).


In amniocentesis, the doctor takes a sample of the amniotic fluid, which is the liquid surrounding the fetus. The amniotic fluid contains cells from the developing baby. Clinicians can use these for genetic testing just as they would a blood sample or a cheek swab from an adult.

To obtain a sample of the amniotic fluid, the doctor inserts a needle into the uterus through the abdomen.


In CVS, the doctor takes a sample of the placenta. The placenta is an organ attached to the lining of the uterus during pregnancy and supports the baby’s development. The placenta contains DNA from both the fetus and the mother. Clinicians can use it for genetic testing of the fetus.

Your doctor will insert a needle into the placenta through the abdomen or vagina, using a syringe to “vacuum up” small finger-like projections called the chorionic villus, which clinicians then use for genetic testing.

CVS has some advantages over amniocentesis. The procedure is less likely to puncture the amniotic sac. Also, doctors can perform it earlier in the pregnancy than amniocentesis.

Risks of prenatal genetic testing

Complications can occur during either procedure, but are rare. Potential complications can include bleeding, infection, and damage to the amniotic sac or the fetus.

There also is a very small risk that either procedure may cause a miscarriage.

If you want to have a prenatal genetic test, your doctor will discuss the risks of each procedure and provide counseling if there are any factors that might make one procedure more of a risk for you or your baby.

What happens after amniocentesis or CVS?

Following the collection of the baby’s DNA, your doctor will send the sample to a laboratory for genetic testing. This process may take a few days to a few weeks. When your doctor has the results of the genetic test, he or she will meet with you to discuss the results and your options moving forward.

XLH inheritance

XLH is caused by a genetic mutation in a gene found on the X chromosome, so the disease is inherited in an X linked dominant pattern. Females have two X chromosomes while males have one X chromosome and one Y chromosome.

If you are a woman with XLH, then your children have a 50% chance of inheriting the X chromosome with the defective gene and developing the disease.

If you are a man with XLH, then your sons cannot inherit the disease, but all your daughters will inherit it.


Last updated: Aug. 21, 2020



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