Screening process for Down’s syndrome during pregnancy

Posted: 16/03/2015

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During pregnancy all women in England are offered screening for Down’s syndrome. When this is offered, they should be given some information on what the screening will entail and what it can and cannot identify, and with what level of certainty.

The type of screening offered will depend on the number of weeks gestation of the baby when screening is requested. Between 11 and 14 weeks gestation, a scan known as a nuchal translucency ultrasound scan is offered together with a blood test. During the scan, measurements are taken of the back of the baby’s neck. The combination of the measurements and the blood test results give an indication of the level of risk that the baby will have Down’s syndrome.

Between 14 and 20 weeks gestation a blood test is offered which will again give an indication of the level of risk of Down’s syndrome. This test is less reliable than the earlier one and is most frequently used when a woman finds out she is pregnant after the time for the combined test has passed.

The age of the mother is an important consideration in assessing Down’s syndrome risk. As a woman gets older, her eggs are more likely to divide abnormally. At age 25, the risk for Down’s syndrome is one in 1,250 births. This risk increases to one in 385 at age 35 and jumps to one in 30 at age 45. Women who have a child with Down’s syndrome are more likely to have another baby affected with the condition. Also, mothers who have Down’s syndrome themselves are 50 percent more likely to give birth to a child with Down’s syndrome.

When a woman is identified as at a higher risk of having a baby with Down’s syndrome she will be offered additional screening in the way of chorionic villus sampling (CVS) or amniocentesis. These tests will confirm categorically whether or not the baby has Down’s syndrome. However, these tests are not without risk to the pregnancy, as they involve inserting a needle into the uterus. The woman has to make a personal decision whether she wishes to undergo these tests and to accept the (minimal) risk of losing the pregnancy.

During the above screening process an antenatal diagnosis of Down’s syndrome may occasionally be missed. This may be because the foetus’s particular presentation was such that it was impossible to identify the condition before birth or, alternatively, it may be that there was an error in care that led to this diagnosis being overlooked.

Helen Hammond, associate in the Penningtons Manches clinical negligence team, comments: “Finding out during pregnancy that your unborn baby will have a disability can be very distressing but it does offer the opportunity for a family to consider the difficult choice of whether they wish to continue with the pregnancy. If they do, it gives them time to prepare themselves for looking after a child who may have additional needs and medical problems.”

While raising a child with a disability can be very rewarding, it can also be very expensive, given the child’s additional needs and the fact that these needs may well continue for their entire life.

If you have concerns that your child’s Down’s syndrome should have been diagnosed before he or she was born and, had you known of their condition, you may have decided not to continue with the pregnancy, it may be possible for you to pursue a claim (known as a wrongful birth claim) for the additional cost of raising your child due to his or her disability.

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