FIRST TRIMESTER DATING SCAN

The first trimester screening is a non-invasive examination that combines a blood test and specialized ultrasound, to calculated the risk of the fetal chromosomal abnormalities (Trisomy 13, Trisomy 18, Trisomy 21).

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This is usually performed between 12-13 weeks.

The FTS is designed to screen for 4 groups of problems in pregnancy:

a) Risks of common chromosomal abnormalities (including Down syndrome [Trisomy 21], Edward syndrome [Trisomy 18] and Patau syndrome [Trisomy 13]) using Fetal Medicine Foundation (FMF) software. This allows the detection of 90% of Down syndrome, 90% of Edward syndrome and 90% of Patau syndrome.

b) Early structural abnormalities such as anencephaly (absence of skull), exomphalos (protrusion of intestines through an abdominal wall defect), megacystis (enlarged bladder), etc.

c) Risk of early pre-eclampsia requiring delivery 37 weeks (i.e. a serious condition during pregnancy characterised by high blood pressure with proteins in the urine). If left untreated, pre-eclampsia tends to progress and may become very serious. As the treatment of pre-eclampsia is delivery, we are most worried if the pre-eclampsia occurs early (i.e. before 37 weeks) which may require us to delivery early. If the risk of pre-eclampsia is raised, calcium supplementation of at least 1 g / day and low dose aspirin of 150 mg taken in the night reduce the risk of this complication.

d) Risk of fetal growth restriction before 37 weeks which may require early delivery. If fetal growth restriction is detection, the fetus needs to be closely monitored with fetal movement chart, regular measurements of the fetus and regular Doppler studies of the blood flow within the baby, and also cardiotocography (CTG) later in the third trimester.