Normal first trimester ultrasound, scan at 6 weeks of gestation.

Normal first trimester ultrasound, scan at 6 weeks of gestation.

Hi guys, welcome to another post, today I will be talking about Normal first-trimester ultrasound and all you need to know before your first scan.

This post contains affiliate links, please read my disclaimer for more information.

OK, so assuming that you have a positive pregnancy test, HCG (  pregnancy hormone ) blood work that confirms pregnancy, next thing is an ultrasound to rule out gestational age, estimated due date, how many babies and also maternal organs are check to rule out Fibroids, ovarian cysts etc..

If you haven’t seen my previous posts about fibroids and ovarian cysts I will link down below for you:

All you need to know about Fibroids.

All you need to know about Ovaries, normal hormonal cycles, and common cysts.

So now back to the post, what are you going to see on the first ULTRASOUND scan ( 6 weeks of gestation )??


Gestational sac: The first structure seen on ultrasound, the gestational sac can be visualized as early as 5 weeks by Transvaginal technique. A normal gestational sac can be round or oval and is located within the fundus or mid portion of the cavity in the uterus.

img_2776Gestational sac within the cavity.

img_2777Ultrasound image of the gestational sac and yolk sac.

Yolk sac: The yolk sac is the first structure visible within the gestational sac. The yolk sac should always be seen when the gestational sac measures greater than 1.0 cm or 10 mm.

A normal yolk sac is round and should measure less than 6 mm. If the yolk sac measures more than 6 mm, is bizarre in shape or is calcified follow up scan is required since most pregnancies with Abnormal yolk sacs will fail.

img_2782Normal looking yolk sac.

img_2787Enlarged yolk sac.

img_2788Calcified yolk sac.

Abnormally Shaped Yolk SacYolk sac with a bizarre shape.

Embryo:  The second structure that becomes visible within the gestational sac is the embryo. Embryonic cardiac activity should always be seen when an embryo measures greater than 5 mm.

A normal fetal heart rate usually ranges from 115 to 160 beats per minute during the first weeks of gestation, It is measurable with ultrasound from around 6 weeks, the normal range varies during gestation, increasing to around 150 to 175 beats per minute at 10 weeks and decreasing to around 130 beats per minute at term.

A heartbeat of 100 BPM or less In the first ultrasound may indicate a pregnancy that is going to fail however a follow up is always recommended.


Ultrasound image of an Embryo at about 6 weeks of gestation.

Membranes: The amnion grows against the chorion and the membranes eventually fuse, usually by 17 weeks.


Most COMMON and usually harmless cause of vaginal bleeding on the first trimester is Subchorionic bleedings, it resolves by itself however precautions have to be follow.


Ultrasound image of subchorionic bleeding.

And remember if you see an image like this one:

you guess it !!!! YOU ARE HAVING TWINS…

img_2790Ultrasound image of Fraternal twins. ( I will explain this in another post )

img_2791Ultrasound image of Identical twins.

If is more than 2 babies GOOD LUCK!!!! LOL

All ready so this was Normal ultrasound at 6 weeks, next post I will be talking about Normal pregnancy Dating, protocol, and guidelines, how we measure the baby to have an accurate due date, this and more so I will see you next time, next post on Thursday, see you there…

zadi xo

Disclaimer: Due to HIPPA compliance and regulations all patient information is protected on this site, the majority of the Ultrasound images are my own however some Ultrasound images are obtained from copyright free sites as well as the other images used on the blog posts. Also the information provided on my blog is designed to provide helpful information about the topic and are made with the best of my knowledge therefore is not intended to diagnose or treat any medical condition, For diagnosis or treatments on any medical problems consult your own physician. The author is not responsible or liable for any mistreated pathologies or wrong treatments.

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Ultrasound sonographer for many years and mommy of 2 boys, I love my kids therefore I love what I do, help other women to achieve a healthy and successful pregnancy is my goal.

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