Because we always fear the unknown, we will try to reduce your stress related to these tests by explaining what, when and why and the risks.
First, the prenatal screening test consists of two blood tests between the tenth and the sixteenth weeks of pregnancy. Combined with an ultrasound, this test gives you the probability that your baby has chromosomal abnormalities such as Trisomy 21. This test poses no risk to the baby or the mother. It measures the nuchal translucency where the baby’s neck is observed to detect an anomaly that would indicate an eventual chromosomal abnormality or malformations. This test has a rate detection of 85%. It was already offered systematically to women aged 35 and over because the risk of chromosomal abnormalities increases over time. However, a new program of the MSSS now offers this free test to women of all ages.
Depending on the result, a diagnosis test may be suggested. It’s the amniocentesis, it has a detection rate of almost 100% and it can be done after the 15th week of pregnancy. However, this test is a bit harder to take because unlike the screening test, it is invasive and may endanger the pregnancy. To detect anomalies, a sample of the amniotic liquid is taken by inserting a needle in the uterus. The risk of miscarriage afterwards varies between 0.25% and 1% according to different sources. Minor complications are more frequent (2-5 %) and include small losses of amniotic fluid, contractions and abdominal pain. Finally, if the test shows a chromosomal disorder, the woman must decide whether to continue or interrupt her pregnancy.
If you do not have a prenatal screening, the first ultrasound can be done during the 18th week. It helps to identify most abnormalities, the sex of the baby and his general development. Furthermore, it helps identify abnormalities of the mother like in the uterus, fallopian tubes or ovaries. Afterwards, between the 24th and 28th week of pregnancy, a test to detect gestational diabetes will be performed. A second ultrasound can be suggested at the 32nd week of pregnancy if you smoke, have hypertension or suffer from diabetes.
Finally, from the 35th week, you should have an appointment with your doctor every week to make sure that all is well.