Hi everyone, this week I will be the moderator for this discussion board, I'm excited to see what all your beautiful minds have to say about the earliest signs of pregnancy with sonography. Keep in mind not to just post a list of things, explain how you came up with that and what role does it have in pregnancy? Think of some possible things that can go wrong if we have one sign but not another, what have we learned so far that can effect a viable pregnancy? What can be mistaken for a pregnancy and what part of an early pregnancy should not be mistaken as pathology? Be creative but on topic with your responses. 

As we discussed today in lecture, the first thing we might see is the "intradecidual sign", which is essentially a tiny bubble that indicates some sort of pregnancy reaction is happening. However this is not super reliable. It does nothing to signify viability or if the pregnancy is even intrauterine.

Further research also brought me to "decidual cyst" and "pseudogestational sac". I found this article on Radiopaedia that explained pseudogestational sac and listed decidual cyst as a differential. Can anyone differentiate these? Or are they the same thing? It was a little unclear...

The gestational sac, which is the chorionic cavity, is usually the most notable first sign of a pregnancy with the "double decidual sac sign". However until there is a confirmed "healthy" yolk sac (usually see around 5-5.5 weeks), a healthcare provider likely wouldn't call it as pregnancy.

I'm really curious to hear about experiences of those who are in clinicals and what they have seen for OB scans!

The earliest sonographic sign that could suggest pregnancy would be the visualization of the gestational sac around the 4th week. For some, this may be a clue that the pregnancy is forming, but would not be definitive proof until a week later when the secondary yolk sac is seen within the gestational sac. I recall Dr. Wilson saying she would simply describe the sonographic appearance of the gestational sac and not refer to it as an intrauterine pregnancy until after the secondary yolk sac has formed. By week 6 the fetal pole should be noted with the presence of cardiac activity.

Another sonographic landmark to indicate gestation is by locating the double decidual sac sign which is created by the presence of the decidua capsularis and decidua parietalis. I am also curious to know if a corpus luteum cyst could be considered a sonographic sign since it is typically present throughout the first trimester if it were accompanied by another sign like the gestational sac. I know these two can often be mistaken for one another, but if both are present maybe it could be a sign?

Although there are many potential sonographic indications of pregnancy the most reliable in my opinion would be around week 5 to 5.5 when you should be able to document a gestational sac along with an enclosed secondary yolk sac! Please let me know your opinions on the corpus luteum, I know they can occur outside of pregnancy, but do you think they could be significantly if a gestational sac was also present?

We may be able to detect pregnancy with sonography, at 11 days after conception. Sonographically, we would find the intradecidual sign, a round fluid collection within an echogenic area, beside the endometrial cavity. I say 'may be' because, if I am correct, this sonographic appearance is also the same as an ectopic pregnancy. Although, the most reliable sign for a diagnosis by the healthcare provider that this patient is pregnant is viewing the gestational sac at 5 weeks or with the gestational sac and yolk sac at 5.5 weeks.

Also, the presence of the gestational sac will be correlated with HCG levels, a hormone produced by the placenta that also signifies a positive pregnancy.

The earliest signs of pregnancy is first the formation of the gestational sac which is seen at 4 weeks,grows at about 1mm a day until the 9th gestational week, and has a double decidual sac sign around it. Then the yolk sac forms at the 5th week, which should be measured between 2-5mm and not to exceed 6mm if there are not issues such as a nonviable pregnancy. The fetal pole then forms at 6 weeks, which is where a fetal cardiac movement can be visualized and measured. In some normal pregnancies the fetal cardiac heart beat is not seen until the fetal pole measures 4mm in length. The gestational sac with a double decidual sac sign is the most reliable for a healthcare provider to diagnose pregnancy. 

Here's an ultrasound image found online that demonstrates the gestational sac with the yolk sac and fetal pole within it. Does the gestational sac look as if its round and an appropriate shape for a viable pregnancy? I remember from Dr. Wilson's lecture that if the gestational sac started to look as if it were compressing then it may not be a good sign for the pregnancy. This gestational sac doesn't look very compressed to me, but may be something to still document since it looks as if its starting to compress near the fetal pole?

Some early sonographic signs of pregnancy could be a gestational sac that has a double decidual sign. Or even a cyst like sac and a positive HCG test could indicate there is a pregnancy but could possibly be too early to tell or is ectopic. However, more reliable signs would be the visualization of a yolk sack within a gestational sac with a double decidual sign, a fetal pole and even cardiac activity. I believe also that a corpus luteal cyst with the above findings may also correlate to a pregnancy. Here are some examples 

Sac or Cyst within the Uterus & Corpus Luteal Cyst

Gestational Sac with double decidual sign, Yolk sac

Gestational Sac with double decidual sign & Fetal Pole

One of the earliest signs we might see on an ultrasound is the double decidual sac sign. This sign appears as two echogenic rings and is from the decidua capsularis and decidua parietalis. This shows that the uterus has begun preparing for pregnancy. However, this sign alone is not definitive of an intrauterine pregnancy.

A gestational sac is also an early sign of a pregnancy that may be seen around 4 weeks gestational age. This appears as an anechoic structure in the uterus. However, as we discussed in class, sometimes the intradecidual sign that may be seen is actually not the gestational sac. There may appear to be an anechoic "bubble" in the endometrium, which may mimic a gestational sac, but it actually isn't. With an ectopic pregnancy, the uterus may still respond as if it were an intrauterine pregnancy, and thus it still grows and develops in response to the hormonal changes. This is why it is very important not to call the anechoic structure a gestational sac or intrauterine pregnancy until a yolk sac is seen.

Perhaps the most important early sonographic sign for a pregnancy is the visualization of the yolk sac. The yolk sac appears inside the gestational sac as an anechoic structure with an echogenic outside ring. This structure will provide nutrients for the developing embryo and is a sign of a definitive pregnancy.

Early sonographic signs of pregnancy include the intradecidual sac sign, double decidual sac sign, and visualization of the yolk sac within the gestational sac. 

The intradecidual sac sign appears at around 4 weeks, and looks like a small anechoic fluid-filled “cyst” within the uterus, which represents the gestational sac
(which I believe is the sonographic term used to describe the chorion; but correct me if I’m wrong please!). It’s important to note that this anechoic structure should not be called a gestational sac until a yolk sac is seen.

The double decidual sac sign is formed by the decidua capsularis and decidua parietalis which appear as two echogenic rings surrounding the gestational sac. 

Visualization of the yolk sac is another early sonographic sign of pregnancy, and its visualization is important in being able to identify a gestational sac with more certainly, and in determining an IUP. 

I found it very helpful that some sources referred to the visualization of the fetal pole and yolk sac, as the “diamond ring sign, here is an image in case it helps anyone remember!

The earliest sign of a pregnancy is a gestational sac and that can be seen around week 4 of a pregnancy.  A gestational sac will appear as an anechoic ovoid or circular shaped area in the uterus. However, one should keep in mind that one cannot definitively say a patient is pregnant until a yolk sac is visualized within the gestational sac. A cyst can also be mistaken for a gestational sac and it is common for the endometrium to thicken when there is an ectopic pregnancy. If a patient's HCG levels are high or they are having pregnancy symptoms but no intrauterine pregnancy is seen then we should look thoroughly to make sure there is no ectopic pregnancy. Our job as sonographers is to try our best to find any abnormalities so that the patient and baby can be safe. When looking for a pregnancy, we must first complete a trans abdominal scan to get a good field of view and trans vaginal to get more details. Thoroughly examining the adnexa is very important for an ectopic pregnancy. Also, if an intrauterine pregnancy is found then it should be in the fundus area, ovoid shape, yolk sac should be fairly circular and decidua should be thick surrounding the sac. As we can see in the picture below, there is a anechoic gestational sac with a yolk sac inside and a thick layer of endometrium surrounding the sacs. 

Here is a very helpful video that I found for first trimester pregnancy: https://www.youtube.com/watch?v=4X6rcJwIFZg

The first sonographic sign that someone is pregnant is the visualization of the intradecidual sign. This can be seen as early as 11 days post conception and appears as a "round fluid collection eccentrically located within an echogenic area adjacent to the endometrial cavity. This sign marks the gestational sac. At 7 weeks, the "double decidual sac sign" is seen, which is produced by the decidua capsularis and the decidua parietalis. 

The sign that sonographers should look for to confirm an intrauterine pregnancy is the secondary yolk sac, with the gestational sac and double decidual sign accompanying it. This can be seen at about 5 gestational weeks with transvaginal scans and 6-7 weeks transabdominally. This should be the first implication, since without visualization of the secondary yolk sac, it could be an ectopic pregnancy or other pathology.

The earliest sonographic sign of of pregnancy is a small intrauterine anechoic, fluid collection with rounded edges which is the gestational sac at around 4-5 weeks. The next sign is a yolk sac appearing within the gestational sac which is an unequivocal sign of pregnancy that occurs around 5.5 weeks. At about 6 weeks the embryo appears adjacent to the yolk sac. These are the first early sonographic signs of pregnancy. Also the double decimal sac sign should be seen at around 5 weeks. The outer ring is the decidua and the inner ring is the chorion. Below I attached a YouTube video that really helped walk me through the steps of what an early normal and abnormal pregnancy appear as sonographically. SUPER HELPFUL!

https://www.youtube.com/watch?app=desktop&v=raIclmdJOPo

Hey Moderator Buddy! 

We learned that the earliest sonographic finding in the first trimester is the gestational sac at around 4 weeks. At this point the uterus should look nice and plump with a small sac that appears cystic adjacent to the fundus. There should be nothing in the sac at this point and would not even be called a gestational sac. 

The next finding that would be seen in the first trimester is the yolk sac which is another round echogenic structure with a sonolucent center. The yolk sac would be see around the 5-6 week and should be connected the the gestational sac. 

Another sonographic sign that might be seen simultaneously with the other structures is decidualiztion. From my understanding this is the maternals contribution and is made up of the endometrium basal layer. 

I believe it is reliable to diagnose a patient when the gestational sac is seen with a properly attached yolk sac. To also answer some of your questions Hailey, I think it is important not to mistaken the GS for a cyst in the endometrium or to mistaken it for fluid in the uterine cavity. I was wondering if you were unsure if a sonographic finding was an abnormality or a pregnancy how would you know if you couldn’t put color(in case it was a baby)? Might be a stupid question ..

The earliest definitive sign that a sonographer may see of a pregnancy would be in the yolk sac within the gestational sac. This, for me, would be the most definitive sign of an uterine pregnancy because an empty gestational sac could be fluid, a cyst, or a pseudosac. I make the distinction of uterine pregnancy because pseudosacs are created by the bleeding of decidualized endometrium from an ectopic implantation. A yolk sac would be seen at a little over 5 weeks gestational age, whereas the gestational sac could be detected earlier. 

Here is a great picture comparing the both:

Here is an article on pseudosacs for anyone interested:

https://www.wjgnet.com/2218-6220/full/v4/i3/58.htm#:~:text=A%20%E2%80%9Cpseudosac%E2%80%9D%20is%20a%20collection,pregnancy%20implantation%20(Figure%202).

Howdy everyone,

The earliest sign of pregnancy on sonogram is a small anechoic structure within the uterus (gestational sac). Even if there is an ectopic pregnancy a round anechoic area may exist in the uterus. In order to confirm an IUP (and rule out pathologies) we must see the yolk sac! It's important to remember that just because there is an anechoic structure in the uterus doesn't mean it's always a pregnancy. We have to be diligent while interrogating other areas as well.

This is an excellent overview of early pregnancy.

https://radiologykey.com/ultrasound-of-the-normal-and-failed-first-trimester-pregnancy/

Sarah

Since we don't really see many measurements in class I thought this is a good representation of how to measure early OB first trimester. I know everyone has a different way of measuring but if this is not the ideal way please lmk

According to our textbook for the class, a sign of a conceptus can be seen transvaginally as early as 3w4d GA when implantation is complete and the blastocyst is fully implanted in the decidua. It will look like a small, fluid collection with an echogenic border just off center of the endometrial cavity and is called the intradecidual sign. At this point, the chorionic cavity (aka gestational sac) is seen and is filled with chorionic fluid, giving it a cystic-like appearance. 

However, as Dr. Wilson was explaining in lecture, it is safer to definitively call a IUP when the secondary yolk sac is seen within the gestational sac, usually around 5-5.5 weeks GA. The secondary yolk sac (aka umbilical vesicle) is responsible for providing nourishment to the embryo and also hematopoiesis. Assuming the patient is being examined partially due to detectable hCG blood serum levels, we would suspect the patient is pregnant. At this early stage, we want to make sure to rule out an ectopic pregnancy as there are, to my knowledge, poor outcomes for ectopic pregnancies. Seeing the secondary yolk sac inside the gestational sac would prove it is an IUP and not ectopic. 

Here is a YouTube Video that walks through the sonographic signs of early pregnancy.

2. As early as 3 weeks and 4 days gestational age, the chorionic sac can be visualized using ultrasound. The chorionic sac, AKA gestational sac, is the first sonographic sign of intrauterine pregnancy. In ULS the term used for this image is intradecidual sign:

IMAGE 1 HERE ("intra")

It is important to note that this location is not within the endometrial cavity.

 IMAGE 2 HERE ("Sequence")

Between 5-6 weeks, the embryo adjacent to the yolk sac can be identified transvaginally. This is a good sign in terms of the prognosis of pregnancy because failure to identify the yolk sac once the gestational sac has reach 12mm suggest failed pregnancy. The location of embryo being in the uterus is important as well to rule out ectopic pregnancy. It is crucial to measure the yolk sac at this stage as well. When the yolk sac is greater than 6mm at the 5^th week is highlights an abnormal pregnancy.  Presence of cardiac activity is important at this time as well; normally measuring greater than 5mm with an average of 110 BPM. By 7 weeks the double decidual sign will be present. These criteria combined can confirm an intrauterine pregnancy.