Baby’s First Pictures: Decoding the First Trimester Ultrasound

In this week’s episode of Taco Bout Fertility Tuesday, Dr. Mark Amols takes you on a guided tour of your baby’s very first pictures—the first trimester ultrasound. From the tiny gestational sac to the yolk sac (your baby’s first lunchbox), to the fetal pole and that reassuring flicker of a heartbeat, Dr. Amols explains what each step really means and when you should expect to see it. You’ll also learn:

• Why we stop checking hCG once we see the sac
• What it means if a yolk sac is missing or measures unusually small or large
• How to understand the fetal pole and when to expect a heartbeat
• Growth benchmarks from “grain of rice” to “strawberry”
• Why being 3–7 days behind may (or may not) be concerning
• How and why the placenta forms, and when we can actually see it
• What nuchal translucency is, what causes it, and what it does—and doesn’t—mean

One ultrasound is just a snapshot, but together they create the story of the first trimester. If you’ve just found out you’re pregnant—or you’re supporting someone who has—this episode will help you decode what’s on the screen and know what to expect in those exciting early weeks.

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Join us next Tuesday for more discussions on fertility, where we blend medical expertise with a touch of humor to make complex topics accessible and engaging. Until then, keep the conversation going and remember: understanding your fertility is a journey we're on together.

Transcript

0:01

Today we talk about your baby's first pictures. What ultrasound actually shows in the first trimester and with all those early milestones really mean. I'm, Dr. Mark Amols, and this is Taco about Fertility Tuesday. If eightcg is a scoreboard that tells us the game is on, then ultrasounds are the highlight reel. They show us what's happening in real time. But one of the most important questions I get is what should I see at each step? And just as importantly, what does it mean if we don't see it yet? So let's walk week by week through the first trimester and decode what you can expect from those early ultrasounds. Now, as you know, prior to the first ultrasound, youre doing ACG levels every four to eight hours, watching them double and make sure theyre rising normally. The reason we dont do an ultrasound at that early stage is because you cant see the baby. Its just too small to see, even though its there. The first time you can see the baby is approximately around four to five weeks. Now, when I say see the baby, I mean seeing structures that represent the baby. The first structure we'll see is called the gestational sac. And this is a sac that's inside the uterus and usually comes around four weeks, five days to about five weeks. But this is just telling us that the baby is inside the uterus. It doesn't tell us this is a normal pregnancy yet because it's just a sac. So we can't confirm the pregnancy is healthy or viable, but we at least know its in the uterus and that tells us not the neck topic. Thats one of the reasons why we do those ultrasounds. Around five weeks, three days and five weeks, five days. Now, once we see the gestational sac, we dont need to follow Hg levels anymore because we can just watch the progression of what we expect to see in the ultrasound. There are times we may still use acg. If lets say something on ultrasound doesnt look right, we may want to check the ECG level to make sure its not dropping significantly. But once you see something in the ultrasound at that point, that's the main way you're going to watch the pregnancy evolve. The next step is around five weeks, three days to five weeks, five days. And this is where the yolk sac shows up. This is a critical step because this is what tells you that this is a normal pregnancy. If the yolk sac was missing, then that may be a sign of something wrong with the pregnancy, such as a blighted ovum so seeing it is a very important step. If you see a gestational sac and a week later you dont see a yolk sack, there is concern. Now, if you do a ultrasound, and lets say its five weeks, three days, and you only see the gestational sac, you dont need to be worried. It just may be a little early and you are not seeing the yolk sack yet. However, if you repeat the scan in one week and you still dont see the yolk sack at that point, that could be a sign that the pregnancy isnt developing normally. Now, whats the purpose of the yolk sack? The yolk sack provides nutrition until the placenta can take over. Think of it like the babys lunch sack. Now, whats interesting is the size of the yolk sack can be too small and too large. Its more of an association than actual causation. But if it is too large, it can sometimes point to something thats wrong, just like if it's too small. But don't put a lot of emphasis on this because it's not a direct correlation. as I said, it's just a bit of an association. Now, the next step is exciting. This is around six weeks, and this is when we expect to see the fetal pole. Now, in the beginning, before there was a heartbeat, the fetal pole will look like a little line, and then there'll be the yolk sack. It kind of looks like a ring, with a ring being the yolk sack and the little line being the part where it attach to your finger. Now, you don't have to be worried if you don't see a heartbeat yet. It could just be one day away. The only time we get worried about not seeing a heartbeat is when the embryo is measuring 7 mlime or crater. And then it does worry a little bit that we're not even seeing a flicker. But again, it's more of a concern, not absolute concern. Now, although the heartbeat can show up as early as six weeks, usually about around six weeks, three days, six weeks, five days, we tend to see it. Now, in the beginning, the heartbeat is going to be very slow. So if you come in on the early ultrasound, let's say, five weeks, five days, and there's a flicker, but the heartbeat is low. Do not be worried. That's normal. The heart just started beating. So it takes time for it to climb up into like, the 170s, 180s, and then eventually it actually starts coming back down. A, normal heartbeat is usually somewhere between about 110 and 180. But as I mentioned, very early on, especially around five weeks, five days, it's not uncommon to see it in the 90s or even at 100. So the point is, if you see an, early heartbeat, don't panic. If it ends up being low, it will catch up. So at this point, you now see an embryo, you see a yolk sac, you see a heartbeat. Now you can take a big, deep breath. Although there are no guarantees that things will keep going, statistically speaking, it's a good point. At this point, over the next few weeks, mostly what's going to happen is increase in the size of the baby and increased organogenesis, where all the organs will develop. If you get to the point where you're at eight weeks and still see a heartbeat and you didn't do any type of testing, your chances of a miscarriage are less than 6%. If you did PGTA testing, your chances are always less than 5% of a miscarriage. And if you get to 10 weeks, both the people who did PGTA and the people who did not do PGTA have the same chances of miscarriage at that point, which are both less than 5%. Now, this baby grows really fast. As I tell people all the time, a baby growing is faster than cancer growing. At about week six, the baby is about the size of a grain of rice, maybe 4 millimeter at the most. By week seven, a week later, it'around a centimeter, about the size of a blueberry. By week eight, it'almost doubled in size, 1/2 to 2 centimeters, it'about the size of a raspberry. And by week ten, it'a small strawberry in size around 3 to 4 centimeters. The point is, even a few days off can make a very big difference in what we see now. For many of you who undergone some type of fertility treatment, youre probably on some type of luteal phase support, such as progesterone, vasinal depositories, or even progesterone injections. The reason is because the placenta is the baby'life support system, and it begins forming early, but doesn't fully take over to around 10 to 12 weeks. So in those early stages, because people with infertility can have higher chances of luteal phase defects, we usually will give you progesterone. In the very beginning, you cannot see the placenta. But later on, what you start seeing is this thickening around the sac. And as it becomes more defined near the end of the first trimester, you can then tell where the placenta is. So a lot of times, people will Ask me, well, where did the baby implant? The problem with that question early on is if you take a sandwich and you put a grape in between it and then you put both sides of the bread together while asking where it implant is impossible is touching both sides. It's not until the placenta starts to develop that that you can really tell which side itlanted on. Now what you can tell early on is where it implanted from the standpoint of near the top of the fundus or near the lower portion of the uterus. One of the most important things when it comes to ultrasound is dating the pregnancy. When people don't go through fertility, we don't know the D of conception. So we use the last menstrual period and we assume that, two weeks after the last menstrual period they ovulated and that's the data conception. But we know its not exact. But when you do know the exact data conception, such as with IVF or even with IUIs, the timing matters a little bit more. What do I mean by that? Well, if you got pregnant naturally and you went in for an ultrasound and lets say you were six weeks, six days, and the baby measured six weeks one day, if you were doing ivf, I would be concerned. But if you didnt do ivf, Id say, okay, maybe the timing was off. We don't really know when you had conception, but with ivf we know it's so close that really anything more than three days behind is concerning. Now when I say concerning, it doesn't mean that something is going to go wrong. It just means something isn't exactly right. We wouldn't expect to see that. If, it's five days behind, then I'm definitely concerned. The real question is, is the next ultrasound did the baby stay the same amount behind or is it getting further behind? Getting further behind is definitely worrisome. If it stays the same amount behind, then that means whatever happened cause the baby to, lets say stop growing. But from that point on its continued to grow at the same rate and its always going to stay behind because its already behind now. So the main point here is dont be worried if, for some reason youre 6 weeks, 5 days and then measure 6 week, 3 days, thats completely normal whether youe doing IVF, IUI or getting PREIT naturally. However, if you got pregnant naturally, then the baby can be up to a week behind and we don't worry because we know the dating isn't as accurate. So now we're about week 11 to 13 and this is when ultrasounds become really fun. Not only can you recognize the structures of the baby, such as arms and legs and the head, sometimes even starting to see a little bit of the nose, but now you see movement. You can see the baby jumping around. And it's pretty crazy when you see it. I always think about in the past when they didnt have ultrasounds and people couldnt see their babies move. I thought thats so crazy that they just didn't know anything that was going on in there and they just had to assume things were good. I feel like we were so fortunate now to have this type of imaging to give us the details and make us feel more comfortable and give us a chance to meet our baby a little bit earlier. Now, once we get into this stage, this is where some testing can be performed, such as nipts to check for things like genetics of the embryo, such as down syndrome, trisomy 13, trisomy 18, and another type of ultrasound called a Nucot translucency test. And this is where they look at the back of the babys neck to see how thick it is. The science behind this is, is that all babies do not have very good drainage systems. Talking like their lymphatic systems to pull the fluid out of their skin. If there are problems with a circulation or problems with the lymphatic system, the plumbing, then that could cause fluid to build up and cause the fluid on the back of their neck to get a little thicker than normal. Again, its supposed to be there. All babies have it. But some babies, such as ones with down syndrome, have heart problems or other types of chromosomal problems like trisomy 13, trisy 18 would cause that fluid to build up more. Now, if you have a thickened nucotranlucent, it doesnt mean that your baby is going to have a problem. What it means is that there could be an issue. And that's when you go into other tests. It doesn't mean your baby has down syndrome or some other genetic problem. It just means the fluid collection is building up. So there's some type of lmphatic or cardiovascular system that could be causing an issue. The next step is doing an amntcentesis or even what's called a CVs that you can do even a little bit earlier. That will then help you determine if that nuchal thickness is due to a chromosomal problem or just some other minor issue or major issue. Now, although it's beyond this podcast topic, the next ultraunder going have is going to be the anatomic scan, which happens a little bit later in the pregnancy, around 20 weeks. Well touch on that in a future episode. I think the important takeaway today is that one ultrasound is just a snapshot. Pregnancy is more like a movie. It takes multiple scenes to see how the story, unfolds. The first trimester might be filled with milestones, but its also filled with variability where a few days can make the difference between seeing nothing and seeing a heartbeat. So if youre in that spam where you maybe have blood test or youre waiting for that first ultrasound, remember the ultrasound is powerful but its not perfect. Sometimes the best medicine, its just patience. Hopefully this episode was helpful for you. I know a lot of times you would do on fertility topics, but I thought it would be nice to do things when people are pregnant and start talking about that for a few episodes. If you know someone who is wondering about an ultrasound or maybe they just found theyre pregnant, let them know about this episode. If you like this, tell your friends about our show and give us a five star review on your favorite medium. But most of all, keep coming back. I look forward to talking you again next week on Taco Bel Fertility Tuesday.