This is sometimes called a nuchal translucency scan.The nuchal translucency measurement can be taken during the dating scan.You may have simply conceived earlier or later than you thought you did (which can happen if your cycle is at all irregular or if you remembered your last menstrual period date incorrectly).Your doctor might want to repeat the ultrasound to make sure that your pregnancy is developing as it should.You won't be offered the combined screening test if your dating scan happens after 14 weeks.Instead, you will be offered another blood test between 14 and 20 weeks of pregnancy to screen for the risk of Down's syndrome.Every pregnant woman wants to know her due date, and a due date that is calculated from her last menstrual period often doesn't match the due date that is estimated by her first ultrasound (also known as a sonogram).
There are basically seven different ultrasound exams, but the basic process is the same.
An image of your fetus will appear on an accompanying computer screen and while looking at this image, the technician will take some standard measurements from different angles and listen for a heartbeat.
Don't worry: This type of exam is painless and risk-free, and seeing your baby for the first time will likely be an enjoyable experience.
As the pregnancy progresses, the accuracy of an ultrasound for predicting due dates decreases.
Between 18 and 28 weeks of gestation, the margin of error increases to plus or minus two weeks.
You may need to have a full bladder for this scan, as this makes the ultrasound image clearer.