By Dr. Derrick Thompson (Obstetrician and Gynaecologist)
Every mother hopes for a normal, healthy baby. While most babies are born normal about 3 in 100 are born with a serious condition that may require expert medical care. To help you reduce your chances of having a child with a disability, I recommend you undergo the prenatal screening tests that are available to try and diagnose these conditions.
The main aim of these test is to see if your baby is at risk of suffering from Down syndrome or a neural tube defect. However, these tests can also indicate whether your baby might have other abnormalities such as cardiac or skeletal abnormalities.
Most carers now appreciate that a well-balanced diet and a folic acid supplement before you conceive (for at least 1 month and the first 3 months of your pregnancy) will significantly improve your chances of having a normal pregnancy and a healthy baby. For example taking 0.4-0.5 mg of folic acid a day in tablet form will reduce the risk of your baby being born with a neural tube defect by 70-75%.
Recent research has found that there may be a link between a mothers poor diet and poor health and an infant’s death from sudden infant death syndrome (SIDS).
Impaired development in two parts of the baby’s brain – one which controls breathing and waking, the other heart and breathing rhythms – may make these infants more susceptible to SIDS. There is no doubt that a fit, healthy mother improves her chances of having a normal healthy baby.
Down syndrome is a condition associated with varying degrees of intellectual disability and physical problems such as heart defects or impaired sight or hearing. Overall, Down syndrome occurs in about 1 in 700 pregnancies.
The most common neural tube defects are anencephaly and spina bifida. In anencephaly, the brain does not develop properly, and the baby does not survive. Babies born with spina bifida have an opening in the bones of the spine which can result in damage to the nerves controlling the lower part of the body. This can cause weakness and paralysis of the legs, and sometimes inability to control the bowel and bladder. There are varying degrees of severity of spina bifida, and many of the resulting deformities can be corrected.
In Australia, the United Kingdom and the United States of America, a neural tube defect occurs in 1 in 500-750 pregnancies.
Before submitting yourself to prenatal screening tests, you need to think about what you would do if there is an increased risk of you having an affected baby. Would you proceed to chronic villus sampling (CVS) where there is about 1 in 100 risk that the test could cause you to miscarry? How would you cope with a Down syndrome child? Would you have a termination? IF you would have a termination, is there any point in having the test?
Some couples feel that even if their baby were to suffer from Down syndrome, they would proceed with the pregnancy. Knowing the diagnosis would give them time to plan and prepare for the care of their affected child.
Cystic fibrosis is a common single gene disorder affecting 1 in 2000 babies. The condition causes recurrent respiratory infections, and death may occur in early adulthood. About 1 in 20 people carry the recessive gene for cystic fibrosis without any sign of the condition. Gene probes have been developed to diagnose this condition from cells obtained at CVS.
Thalassaemia is another inherited condition that can be diagnosed prenatally. This is a disorder of red blood cells which commonly affects people form Mediterranean countries and Southeast Asia. If both parents are carriers of the thalassaemia gene, either a gene probe of placental cells or an analysis of a fetal blood sample obtained at fetoscopy (when you are 18 weeks pregnant) can diagnose if your baby will have thalassaemia major. This condition causes severe anaemia and a shortened lifespan.