Pregnancy dating and viability

There are two ways of having a seven week ultrasound.One is via the abdomen – transabdominally and the other is through the vagina – transvaginally.

So obtaining accurate measurements and visualising them clearly on the screen is a little easier than when they are able to do somersaults and move around a lot. This is also more likely if you are having a transvaginal ultrasound. One of the reasons for this is because the heart needs to work harder and more efficiently to pump oxygenated blood around its much larger body and brain.

The quality of the equipment and the skill of the sonographer are very important when doing any pregnancy ultrasound.

A duration of only a week can make a significant difference in terms of what can and can’t be seen.

At seven weeks of gestation it is still too early to identify what gender (sex) the baby will be.

This is the period of time which provides the most accurate assessment.

Generally, ultrasounds which are performed in the first trimester are within 3-5 days of being accurate in terms of assessing gestational age.

It is also useful for women who are experiencing pain or bleeding or for those who have had previous complications such as miscarriages or ectopic pregnancies.

You must be at least 6 weeks gestation for us to identify a heartbeat.

It is also impossible to do a thorough foetal screening assessment because it is still just too premature in terms of embryonic development.

However, general “mass” structures such as a head and body can generally be seen in the embryo at seven weeks.

Crown/rump length and gestational age are closely compared with each other until around the end of the first trimester.

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