There is no definite way to avoid having a baby with Down’s syndrome. There will always be probabilities, sometimes greater than others. A big factor is the age at which amother conceives. At age 25, probabilities are 1 in 1,250; at age 40 probabilities increase to 1 in 100 (Shriver 2007). Parents with Down syndrome, or with an abnormal 21 chromosome are also at higher risk of conceiving a child with the condition. Many tests can be done before the child is born so that the parents may prepare for the child’s special needs (Shriver 2007).
A series of two surveys on exposure to contraceptive pills prove that there may be an impact at or around the time of pregnancy on Down syndrome probabilities. A study done by Martinez-Frias and Read infer that that there will be a slight increased rate of Down Syndrome for maternal age group 20–29, a decreased rate for maternal age group 30–39 (Read).