Accuracy of early pregnancy dating scans

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After 13 weeks gestation, the fetal age may be estimated by the diameter of the head and the length of the femur.

Dating is more accurate when done early in the pregnancy.

The scan can confirm the number of babies in the uterus, the embryo can be observed and measured by about five and a half weeks and a heartbeat usually detected by 6 weeks.

Scans at this stage in pregnancy are reassuring for women experiencing bleeding, pain or who have had previous miscarriages.

Transvaginal scanning may also be used to obtain a better image of the womb.

Nuchal translucency scan This is a scan which is usually carried out at 11-13 weeks and is a method of screening for chromosomal abnormalities without having an invasive test such as an amniocentesis.

If this does occur, the possible complications of or implications for the pregnancy will be fully discussed with the parents by a doctor or consultant and advice and guidance will be provided.This has an accuracy of about 70% and can lead to recommendations for further testing, such as an amniocentesis.Pregnancy Dating Gestational age is usually determined by the date of the woman's last menstrual period - assuming ovulation occurred on day fourteen of the menstrual cycle.Just wanting to know if any others have had an EDD from a scan that was different to the EDD calculated based on their LMP (last menstrual period).Which was correct in the end – the LMP due date or the estimated date of the scan?

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