It is less accurate than the combined test. This measures free beta-hCG, alpha fetoprotein (AFP), inhibin-A and unconjugated estriol (uE3) (see 'Serum markers for Down's syndrome', below). If a woman books later in pregnancy (when nuchal translucency is not as accurate, or if it is not technically possible to measure it) the quadruple test can be taken between 14 + 2 to 20 + 0 weeks of gestation.The serum screen measures free beta human chorionic gonadotrophin (beta-hCG) and pregnancy-associated plasma protein A (PAPP-A) (see 'Serum markers for Down's syndrome', below).The ultrasound scan can be carried out between 11 weeks + 2 days and 14 weeks + 1 day of pregnancy.The blood sample can be taken from the mother between 10 weeks and 14 weeks + 1 day of pregnancy.These can be used in combination (the combined test): There are two methods of screening for Down's syndrome: serum screening and ultrasound screening (nuchal translucency).The challenge of a prenatal screening programme is to identify women in whom a risk of Down's syndrome is sufficiently high to justify such an invasive test and to minimise the risk of miscarrying a healthy baby.Women found to be carrying a baby with Down's syndrome will be offered expert counselling and support, they may be offered a termination of pregnancy or they may choose to continue with the affected pregnancy with support.These procedures carry a risk of miscarriage (0.5-1% excess miscarriage risk for amniocentesis 1-2% for chorionic villus sampling). The aim of this screening programme is to identify those women at a higher risk of having a baby with Down's syndrome and to offer them diagnostic testing using either chorionic villus sampling (if less than 13 weeks of gestation) or amniocentesis (if beyond 15 weeks of gestation).There is at present some variation in the type and timing of the screening tests used in England, Northern Ireland, Scotland and Wales. All women, regardless of age, are offered screening for Down's syndrome.Information about amniocentesis and chorionic villus sampling.īe aware that parents may be ambivalent around the benefits of screening whilst acknowledging the advantages of knowing a diagnosis before delivery, they also may have concern for screening creating a less diverse population that has fewer support mechanisms for people with Down's syndrome.The screening pathway and next steps for screen-positive and screen-negative results, including information about the decisions that need to be made at each step and their consequences.An explanation of the risk score obtained following screening.The fact that screening does not give a definite diagnosis.Balanced and accurate information about Down's syndrome. Women should be given information regarding Down's syndrome screening at their first appointment with a healthcare professional. It is important that appropriate information, counselling and support accompanies testing and screening. Some people may decide against having diagnostic testing or even screening for Down's syndrome when offered the choice. It is important to emphasise that the decision to have any form of screening should be an informed one.
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