How times have changed: Understanding prenatal diagnosis and genetic counseling in 2016
By Debra Guinn, MD, and Tessa Pitman, CGC
So much has changed in the past 50 years. It used to be that you realized you were pregnant around two or three months and went through your pregnancy not knowing the approximate date you were to deliver, how many babies you were having or the sex of your baby. Most important, no one knew in advance if the baby needed special care.
The only technology available at the time was abdominal X-ray. An X-ray could help determine fetal number, position and information about the maternal pelvis – but it exposed the fetus to radiation. When it came time for the birth, your partner was in the waiting room and you delivered in an operating room. Eventually both you and your partner met your baby and learned the gender. Usually, the baby was normal and everything went as expected.
Babies who were not so fortunate – those with birth defects or genetic abnormalities, or who were born prematurely – were taken to the special nursery (now called the neonatal intensive care unit) where nurses and doctors started supportive care. The outcomes at that time were not great because there was no preparation and, in many cases, it took weeks or months to determine the diagnosis, treatment plan and prognosis. Sadly, some babies were not going to survive, and the families were the last to know.
Thankfully our technical and clinical abilities have improved immensely and now much can be done to prepare before birth for babies at risk. One of the first breakthroughs was using ultrasound (sound waves) to image the fetus. It was an enormous step forward. Concurrently, researchers developed blood tests that helped identify pregnancies at risk for Down syndrome, neural tube defects (hole in the spine) and other problems.
We have made incredible progress since the 1950s, and our mothers and babies are healthier as a result. Physicians caring for women with high-risk pregnancies are better prepared. We are board certified in general obstetrics and gynecology and do subspecialty training in maternal fetal medicine, also known as perinatology. Maternal fetal medicine specialists work directly with general obstetrical providers including obstetrician-gynecologists, family practitioners and midwives to identify women at risk for all types of complications and develop a plan of care specific to the family’s needs and concerns.
Prenatal diagnosis, or fetal medicine, is a very important part of our practice. It is our job to identify as many babies as possible who have birth defects, genetic defects and obstetrical complications before delivery. To do that, we use maternal history, ultrasound and genetic testing as indicated.
Ultrasound capabilities have improved to such an extent that we can diagnose half of all birth defects in the first trimester. This requires sonographers to follow a very specific protocol for ultrasound and use the most current ultrasound equipment. They must gain the experience and additional training and certification to increase diagnostic accuracy.
All ultrasound exams are not equal. The accuracy of an ultrasound depends on the sonographer who takes the images, the interpreter or person who reads the images, and whether they have special certifications in certain parts of the exam or the equipment. Ultrasound exams can be performed in specialized maternal fetal medicine units, radiology suites and your provider’s office. Detection rates will be determined by many factors. You do have a choice in where you have your ultrasound. Ask questions about accreditation and when you should expect to know the results.
The “routine ultrasound” is performed at or around 20 weeks in pregnancy. Patients commonly refer to this as their fetal “sex ultrasound.” In truth, the sex of the fetus is the least important thing. On average, an anatomy ultrasound for one fetus should take 30 minutes to one hour or more to complete. The sonographer should evaluate every part of the fetus from head to toe as well as the placenta, the uterus and the cervix. At times it is impossible to see everything because of the fetus’ position or the mom’s scanning characteristics, but we try hard.
We also use 3D and 4D ultrasound if it will help us identify a specific problem. At Montana Perinatal Center, we follow all national ultrasound protocols that address safety and imaging standards. We review every ultrasound with you immediately following the study, with rare exceptions. A report is then sent directly to your OB provider for review. If you have an ultrasound elsewhere and there are concerns, your OB provider will most likely refer you to a maternal fetal medicine specialist for evaluation and management.
Ultrasound alone is not sufficient. The detection rate for birth defects varies based on where your ultrasound is performed, and no unit will detect all birth defects. But another group of babies is at high risk and need immediate care – those with genetic conditions despite normal ultrasound exams. Every human being has a unique genetic code that determines specific attributes. We inherit our genetic code from both our mother and our father. Scientific understanding of genetics is increasing at a pace that is almost impossible to keep up with, but the more we know about genetics the better we understand disease and the best options for treatment. Genetic testing can help identify unique variations in one’s genetic code. This information can be used to design treatments for multiple medical conditions from birth to adulthood, including cancer. The trick is to understand what testing is available and the risks and benefits of testing.
In perinatology, we combine ultrasound and genetic testing with the patient’s family history and reproductive history to evaluate a pregnancy’s specific needs. First and foremost, we speak to our patients. We record thorough histories of all potential exposure in pregnancy that may put the family at risk. Depending on your personal history, genetic counseling may be included in your care plan. The following is a brief summary of prenatal genetic counseling:
Genetic counseling is about being proactive and taking charge of your health. Understanding your risk for a particular genetic condition guides the appropriate next steps for treatment, management and, in some cases, prevention of associated medical problems.
Women of all ages can benefit from meeting with a genetic counselor to understand prenatal screening and testing options available to them. Some women are at an increased risk for having a child with a particular birth defect or genetic condition and will be referred to a genetic counselor. Some of the reasons a woman may be referred include:
- Will be 35 years or older at delivery.
- Had an abnormal maternal serum screen result.
- Had an abnormal result on an amniocentesis or chorionic villus sampling (CVS).
- Had an abnormal ultrasound.
- Prenatal exposures included certain medications, drugs, radiation or infections during pregnancy.
- From an ethnic background where some genetic conditions are more common.
- Have a history of multiple miscarriages or infertility.
- Have a previous child with, or family history of, a genetic condition, birth defect or intellectual disability.
- Have consanguinity (parents related by blood).
Genetic counselors can discuss the different prenatal screening and testing options available to you. There are different screening and testing options to further evaluate identified risks and provide clarity. It’s important to understand what information the different screening and testing options will and will not tell you about the baby. Just in the past few years, a new test has become available that allows us to screen for certain chromosomal conditions through a simple, noninvasive blood draw on the mother. It is a noninvasive prenatal test (NIPT). It works by analyzing cell-free fetal DNA circulating in maternal blood, and it screens for conditions like Down syndrome, but also for more severe chromosomal conditions such as Trisomy 18 and Trisomy 13. In many cases it replaces amniocentesis with its inherent risks – but limitations apply.
Carrier screening: All of us carry several recessive traits that were passed down by our loved ones. We are “normal” but can have a gene that is abnormal. If our “normal” partner also carries the same recessive gene, there is a 25 percent chance of the fetus being affected by the disease. Some of these conditions are treatable and others are fatal. We can test for many of these conditions prior to or during pregnancy. The type of screening offered is based on ancestry and family history.
Meeting with a genetic counselor doesn’t mean that you have to have genetic testing. Genetic testing is a complex process, and there are several important things for you to consider before that blood draw or cheek swab. Meeting with a genetic counselor is an important step before any genetic testing is done, and several professional societies recommend this. Additionally, some insurance companies require that a physician refer their patients for genetic counseling prior to any genetic testing. We respect your wishes and want to make sure you understand the value and the limitation of testing options. We do believe there are benefits to testing for your baby and your family, regardless of the result. Ultimately, it is your decision and we will respect it.
Genetics is a family affair. Identifying an inherited genetic condition in one person can have implications for other family members as well. While nearly every condition has a genetic component, not all genetic conditions are inherited. Most people tend to be fairly private about their health, so it is not uncommon for a patient to have very limited information about their family history. However, there are several other important aspects about the family history even when that information is limited. We encourage families to share medical histories from one generation to the next. It all starts with the courage and commitment of one family member.
A genetic diagnosis is part of who we are, but it certainly doesn’t define us. Having a specific diagnosis, rather than a nonspecific label of something like intellectual disability, is very important. A diagnosis can provide information on prognosis, associated problems to be vigilant about, and educational and developmental interventions. In addition, a specific diagnosis lets a family have a support group. They can meet and learn from other affected families about coping with the diagnosis while advocating for their child on a daily basis.
Ultimately, maternal fetal medicine specialists and genetic counselors work as part of your health care team. We partner with you, your family and your providers to provide you with important information and resources. We want nothing more than for you to be empowered to make informed decisions about how and where your family will be treated. We have the ability through ultrasound and prenatal genetic testing to see into the future. We no longer have to wait, unaware and unprepared, until a baby is born with complications.
We work together to develop the best plan for your family and improve the quality of life for your unborn child. Families with known complications who are well prepared for all eventual outcomes have a far better birth experience and transition as parents of children with special needs than those who choose to assume the best and go into delivery without a plan.
We are here to help you, if desired. Thankfully, we usually can provide reassuring information about your unborn baby’s health and concentrate on you having the birth experience of your dreams.
First published in 406 Woman magazine, Feb/March 2016