Genetic Abnormalities

How a genetic disorder or chromosomal abnormality will affect the health of the mother and the baby will depend on the condition. Some genetic conditions may not cause any symptoms, and others can cause severe, life-limiting problems.

Some genetic disorders are passed down from parents to children through their genes. Sometimes there are sporadic changes in the DNA of a gene that cause the developing baby to be affected without a prior family history.

Before you conceive, you should talk to your doctor about steps you can take to help you have a healthy baby. Men and women can avoid exposure to harmful substances, such as ionizing radiation, alcohol, drugs, and certain chemicals. Preconception genetic testing can help you determine whether you’re at higher risk of having a baby with a hereditary genetic condition. If tests show you are at higher risk, you can use contraception to avoid pregnancy, have a spontaneous conception and use genetic testing during pregnancy to identify a affected baby, consider assisted reproductive technologies with an egg or sperm donor, or choose in vitro fertilization and test the embryos for specific genetic disorders before implantation.

However, no matter what steps you take, there is always a possibility that genetic abnormalities may occur. Anytime there is a pregnancy, there is at least a 3% risk for having a child with some sort of birth defect, mental impairment, or genetic abnormality.

Doctors can order genetic tests on the DNA from cells obtained by blood, amniotic fluid, placental tissue, cells inside the cheek, and other tissue. Different tests may use different sources of DNA. The type of DNA sample used and the tests performed depend upon the suspected abnormality. Once a DNA sample is collected, lab technicians are able to analyze the cells to look for changes in DNA, or in some cases, chromosomes.

In pregnancy, there are two main types of tests, screening and diagnostic, that help determine whether a developing baby has a genetic abnormality. Screening tests tell you the probability that your baby has certain disorders. Diagnostic tests tell you whether your baby actually has the disorder in question. Diagnostic tests are done on fetal cells floating in the amniotic fluid or cells from the placenta. The cells can be obtained through amniocentesis or chorionic villus sampling (CVS).

The genetic abnormalities looked for during testing depend upon things such as risk factors, the parents’ genetic carrier status, and specific disorders suggested by imaging tests. Some of the genetic abnormalities that can be diagnosed through testing are:

• Chromosome abnormalities, like Down syndrome
• Cystic fibrosis
• Fragile X syndrome
• Spinal muscular atrophy
• Sickle cell disease, or other blood disorders
• Tay-Sachs disease, or other disorders common in the Ashkenazi Jewish population
• Other disorders for which a couple has a family history

If abnormalities are detected, the parents are offered consultations to discuss the potential prognosis for their baby. They will then have to decide whether to continue the pregnancy (often without intervention or treatment until after delivery), end the pregnancy, or place the baby for adoption. If a birth defect is treatable before delivery, doctors may be able to offer a referral to a center that performs intrauterine surgical procedures. They may also recommend waiting until after birth.

Conditions that may be correctable prior to birth via intrauterine surgery include:

• Myelomeningocele (MMC) / spina bifida
• Twin-twin transfusion syndrome (TTTS)
• Some malformations of the lung
• Specific heart defects

Not all patients with the above problems are candidates for intrauterine procedures. Your doctor will provide guidance throughout the process.

Our maternal-fetal medicine specialists offer genetic counseling and testing. We have multidisciplinary teams of experts that include OB/GYNs, genetic counselors, pediatric cardiologists, surgeons, neurologists, interventional radiologists, neonatologists, and more.

Many parents get assistance from other parents through support groups, from organizations that specialize in certain abnormalities, and from therapists and other health care providers.