A dating scan is performed around week 8 of pregnancy but can be done as early as 5 weeks.
It is used to confirm due dates, assess the viability of the pregnancy, check the number of embryos, provide maternal reassurance, and to rule out ectopic pregnancy (fetus developing outside of the womb).
The gender of the fetus can also usually be established during this scan.
Usually conducted from week 28 of pregnancy, the growth scan is used to check the baby’s growth by measuring its head, abdomen, and thigh bone.
65 and 85% of trisomic fetuses will have a large nuchal thickness.
among those fetuses whose nuchal translucency exceeds the normal values, there is a relatively high risk of significant abnormality.
This means that combined first trimester screening will not give us a definitive answer.
dating scan will also show if you're expecting twins, triplets or more.
"first-trimester screening for trisomy 21 combining biochemistry and ultrasound at individually optimal gestational ages.
Combined first trimester screening assesses the risk for your baby having certain chromosomal abnormalities (trisomy 13, 18 and 21).
This testing combines the nuchal translucency ultrasound with specific blood tests.