 Hello everyone, this is Dr. Madhula Baput, Consultant Radiologist at the N13 Diagnostics and Baput Urology Centre, Thane, India. The focus of my interest is Diagnostic and Interventional Altersound and the aim of today's presentation is to highlight the normal sequential events which occur in the early first trimester. I hope you enjoy the video. I hope the video is beneficial especially to those who are beginners and have just begun their first trimester out to sounds. The aim of this presentation is to highlight the normal events that occur sequentially in the early first trimester. We all know that the first trimester is the period of rapid changes that begin with fertilization, formation of the blastocyst, implantation of the blastocyst, the embryonic period and the early fetal life up to 12 weeks. It's important to identify the normal sequential findings occurring in the early first trimester to establish a diagnosis of a normal viable pregnancy. It's important to recognize the ultrasound findings of pregnancy failure and also know the findings which are suspicious but not diagnostic of early pregnancy failure. So, as we all know it begins with implantation of the blastocyst. The blastocyst is a structure lined by trophoblasts and it contains an inner cell mass. So, this structure literally erodes the endometrium and implants which is when picked up by ultrasound as early as four weeks as a tiny rounded cystic structure within the uterine cavity. Now this as it grows is seen as an eccentrically placed implanted gestational sac. So, we can see here that the central white line is the collapsed uterine cavity and the gestational sac has embedded itself within one of the leaves of the endometrium. So, this is rightly called or described as the intra-decidual sac sign which helps us distinguish between a simple fluid collection which is also labeled as a pseudo gestational sac. As you can see on the left a pseudo gestational sac is a more of an oval or an oblong collection which is right in the center and you really don't see the collapsed uterine cavity whereas a gestational sac is more eccentrically placed and you can see the central white line which is the collapsed uterine cavity. The next sequential finding is the appearance of the yolk sac by around five to five and a half weeks. The yolk sac is an important structure as it once identified it confirms an intrauterine gestation. It's a regular cystic structure with a reflective rim and usually it does not exceed five to six millimeter and is an important structure in predicting outcome. So, next to appear in line is the embryo at around five and a half to six weeks which is seen opposed or closely juxtaposed with the yolk sac. This is often referred to as the yolk sac embryo complex. Now this which we see on ultrasound can be very well correlated with embryology wherein you see the yolk sac cavity very much in contiguity with the embryonic disc. Now we start seeing cardiac pulsations these can be seen as early as with a CRL of even two millimeter the lower limit of which is hundred beats per minute and this should be documented on M mode. So as we proceed to around seven weeks you see a sort of a feature less echogenic disc which is the embryo and around it you will see a thin white membrane which is referred to as the amnion. So further the yolk sac now separates and becomes extra amniotic and the amnion is beautifully visualized around seven to eight weeks gestation. So from a feature less disc you get a more of a human form by ten weeks wherein the limb buds are visualized and the spine is also more definable. So to sum up the events which occur in a normal early first trimester is first the appearance of the gestational sac wherein you see the intradesidual sac sign. If you don't see the intradesidual sac sign or if you have any doubts it's always better to follow up. Following the gestational sac is the yolk sac which develops when you see the yolk sac embryo complex which reveals cardiac activity that is the embryo reveals cardiac activity and thus you have an established early pregnancy. So knowing the normal events we now move on to diagnose early pregnancy failure and what are the criteria to be applied. Now all these criteria are from the Society of Radiologists in ultrasound consensus meeting 2012 which gives clear cut guidelines as to how you're supposed to report a first trimester ultrasound. Our aim is to prevent any inadvertent loss or termination of a potentially viable pregnancy. Many a times when we scan we find empty gestational sacs or we don't see an embryo within a gestational sac which is showing a proper residual reaction. So it's prudent to use a cutoff of 25 millimeter as the diameter with no visible embryo in diagnosing failed pregnancy. So any mean sac diameter less than 24 millimeters without an embryo as your first scan you should not label it as pregnancy failure but you should ask for a follow up. Then coming on to your crown rump length criteria without cardiac activity so whenever you see a CRL which is less than 7 millimeter and no cardiac activity it is always better to follow it up because no heart in a CRL less than 7 millimeter is suspicious though not diagnostic of early pregnancy failure. So on to your left you're seeing an image which is my first scan I see a gestational sac with a yolk sac. I've established that this is an intrauterine gestation early gestation but then I don't see the embryo so it's always advisable for a follow up and two weeks later I still see no embryo I only see the yolk sac so then this becomes a time-based criteria to call it a non-viable gestation. So only on one single scan wherein you're seeing the yolk sac but no embryo you cannot label it as a non-viable pregnancy. So guidelines for transversal ultrasound diagnosis of pregnancy failure in a woman with intrauterine pregnancy of uncertain viability. So what are the features diagnostic of pregnancy failure a crown rump length of equal to or more than 7 millimeter without a heartbeat a mean sac diameter of 25 millimeter or more and no embryo absence of embryo with heartbeat two weeks or later that showed a gestational sac without a yolk sac and absence of embryo with heartbeat 11 days or later after a scan showed a gestational sac with yolk sac. The findings which are suspicious but not diagnostic of early pregnancy failure include a scround rump length less than 7 millimeter with no heartbeat a mean sac diameter of 24 millimeter with no embryo absence of embryo with a heartbeat of seven to 13 days after the first ultrasound showed gestational sac without a yolk sac and absence of embryo six or more weeks after the last menstrual period and empty amnion and enlarge yolk sac a small gestational sac in relation to the size of the embryo all these criteria are suspicious but not diagnostic for early pregnancy failure. So it's important to carefully read these guidelines before reporting an early ultrasound in the first trimester. So this is one case of very less fluid or very less like a scene around the embryo wherein you have a very small sac and this should prompt you for a follow up and not just label it directly as something very much non viable. So you often see large yolk sacs we had this case recently wherein the embryonic length was only around 4 to 5 millimeter there was a large yolk sac accompanying so no cardiac activity scene we obviously know that these features are of bad prognostic significance but it's always always helpful to follow these patients up and this patient when she turned up on follow up was already bleeding and there was no gestational sac seen inside the uterine cavity on the subsequent follow up. So it's important to remember that you have features which are suspicious but not diagnostic and these must prompt you towards a follow up and a single scan with bad prognostic features must never be used to label early pregnancy failure. So our aim and our take home message is it's very very important to avoid any inadvertent termination of a potentially viable pregnancy it's important to take into account the sac size criteria the crown rump length criteria and very important the time base criteria to label a pregnancy as non viable. Thank you for your kind attention.