First Signs of Pregnancy on an Ultrasound Baby Scan

Everyone knows the first signs of pregnancy - nausea & sickness, tender breasts and a missed period amongst other signs. But what are the first signs of pregnancy on an ultrasound baby scan?

4 weeks:

The lining of the womb will become thickened and slightly brighter than in the "non pregnant" uterus.

We may see a small cyst on 1 of your ovaries - this is nothing to worry about and is called the corpus luteum [it is what is left behind after ovulation - and releases hormones to stop you from having a period].

5 weeks:

A small "black hole" (the gestation sac) will appear within the lining of the womb.

During this week a small circle will appear within the gestation sac - this is the yolk sac (just like the yolk in a chicken egg). This will provide nourishment for the developing embryo.

Next development we see is a small line / "blob" THIS IS THE EMBRYO!

At just over 6 weeks:

At just over 6 weeks gestational age, the embryo should develop a heartbeat (by the time the embryo measures 7mm it should be beating!)

Although sometimes we can scan and see things doing a transabdominal scan (tummy scan with full bladder) the best way to scan this early in pregnancy is to do a transvaginal scan (internal scan). This does not compromise your pregnancy in any way, but allows us to use a higher frequency ultrasound probe (thus we can see smaller things more clearly).

There are the occasions that even if we perform a transvaginal scan we may not be able to give you a definitive answer to the question - “Is this an ongoing pregnancy”.  As Sonographers, we work with the Royal College of Obstetricians and Gynaecologists guidelines.  Which mean that we may report:

•  “A pregnancy of unknown location “ ie you have a positive pregnancy test but we have not been able to visualise a gestation sac either inside (intrauterine) or outside (ectopic) your womb.

• “A pregnancy of uncertain viability”  i.e. there is a pregnancy sac in the womb (we maybe able to see a yolk sac and embryo or just a yolk sac) but there is no evidence of the baby's heartbeat.

In these 2 cases, our Sonographer will explain what she has seen and what it may mean; you will then be offered a follow up scan (at the appropriate time interval) to see whether the pregnancy has developed.

Early pregnancy baby scans are important to attain reassurance as a mother and to be able to take possible precautions where necessary to help with a safe and healthy pregnancy.