All pregnant women in Scotland are currently offered either a screening test in the first trimester of pregnancy in which measurement of biochemical markers in the mother’s blood is combined with the ultrasound measurement of nuchal translucency in the fetus or, for those women who do not present early enough in their pregnancy to take advantage of first trimester screening, a second trimester quadruple serum screen.
The aim of pregnancy screening for Down’s syndrome is to offer women, during pregnancy, a screening test which can identify those women with an increased risk of having a child with Down’s syndrome. The group at increased risk (above the defined cut-off level) can then be offered diagnostic tests and with high quality counselling, parents can then make informed choices. The definitive diagnostic tests offered require either amniocentesis or chorionic villus sampling. These are invasive procedures which carry a small, but significant, risk of fetal loss.
The protocols document contains standard national protocols for all healthcare professionals involved in the NHS Scotland Down’s and fetal Anomaly screening programme. In order to ensure equity of service across Scotland, NHS Boards are required to ensure that the screening service provided locally adheres to these protocols.
2015 – Fetal Anomaly and Down’s Syndrome Screening Protocols – v 1
The Crown Rump Length (CRL) and Head Circumference (HC) tables for calculating gestation can be found using the link below.
Crown Rump Length and HC dating tables