By Deanne Gage
From the print edition, October 2012
Toronto-Based mom Kristin Roff had no intention of pursuing amniocentesis, a procedure that accurately determines certain chromosomal abnormalities in the fetus. After all, results from her prenatal screening tests found her baby, her second child, to have a low risk of any genetic disorders. But when a routine 20-week ultrasound revealed a bright spot on her fetus’s heart (known as echogenic focus), sometimes associated with Down syndrome, she reconsidered. “I wanted to know what to expect so I could best prepare,” says Roff.
While other screening tests give only ratios and probabilities, results from amniocentesis (amnio), are definitive, explains Kenneth Lim, MD, a specialist in maternal fetal medicine at BC Women’s Hospital and Health Centre in Vancouver. “You will find out whether the baby has a genetic disorder like Down syndrome or Trisomy 18. Amnio does not guarantee a healthy baby, but it does eliminate the possibility of certain things.”
Why is amnio offered?
Amniocentesis is not offered to all pregnant women, just most commonly to those whose chances of having a baby born with chromosomal disorders are greater than the risk of the procedure itself (which has about a one in 200 chance of causing a miscarriage). Generally, that qualifies moms-to-be who have certain family histories of genetic disorders, who received an abnormal result on other tests or those aged 35 or older. It is usually performed in the second trimester after 15 weeks, and is available in all provinces, but each amniocentesis centre will have slightly different criteria regarding to whom they offer the test.
Some moms-to-be who fall in these categories will decline the procedure. Dr. Lim gives the example of a woman who is currently 18 weeks along and has a history of a number of miscarriages. “You could tell her that her baby has a high genetic risk, but she may decline the amniocentesis because, to her, the risk of a miscarriage outweighs the benefits of a test,” he says.
What is amnio like?
The total time for the procedure is about 15 minutes. First, the doctor will perform an ultrasound to check the baby’s position and your placenta. Then, after sterilizing the area, a long, thin needle is inserted through your abdominal wall into the amniotic sac around your baby to retrieve a little more than a tablespoon sample of amniotic fluid. The cells in the fluid provide the information about your baby’s chromosomes. The actual needle insertion takes only a couple of minutes. Dr. Lim says the amount of discomfort varies from patient to patient. “The best description is an insect bite, followed by some menstrual cramping,” he says. Roff suggests your partner or support person accompany you to the procedure. “Emotionally, it can be a draining experience and you need that moral support,” she says.
Once the amnio is complete, the hospital may observe you for a few minutes before you head home for a day of rest and recovery. Most doctors recommend you book the day off work or find someone else to care for small children and take it easy.
It’s not uncommon to experience slight cramping or a mild fluid leak for the first 24 hours. The doctor or a nurse will give you information on what additional symptoms to look for, says Dr. Lim. “I usually ask that a patient contact us if there is any vaginal bleeding or fluid leakage, menstrual-like cramping, or fever or chills beyond what they would consider mild or slight.” You can usually resume your regular routine within 48 hours.
Complete results of your amnio are sent to your doctor or midwife in about two weeks. If a chromosomal abnormality is diagnosed, you’ll meet with your doctor, a fetal medicine specialist and a genetic counsellor to decide your next course of action. According to Sylvie Langlois, MD, a clinical geneticist also with BC Women’s Hospital, you’ll have the choice of terminating your pregnancy or learning more about planning for a special needs child. But the decision rests with you. Dr. Langlois says the timing of the testing is set up so that patients with abnormal chromosomal results can terminate the pregnancy (most occur prior to 20 weeks) if that is what the patient wishes. “There is typically time to get testing done, receive the results, think about options and make an informed decision,” she says.
After a stressful wait, Roff received her amnio results and four months later she gave birth to a healthy baby boy.
Looking for more? Check out our guide to pregnancy testing.