The first ultrasound in pregnancy should be done no earlier than 8 to 9 weeks of gestation. On the other hand, it often happens that early ultrasound scans are done with such dubious results as to make the expectant mother anxious (most of the time for no reason).
The anxieties and worries they arise from seeing only the gestational chamber or not even that, or just a small dot, or not hearing the pulse.
The ultrasound scans performed too early, around 4-5 weeks of pregnancy, unfortunately, give very little useful information. If done at 4 weeks, they cannot even view the gestational chamber. At 5 weeks if you are lucky you will see a dot that confirms the pregnancy in utero.
For this reason, doctors do not recommend doing ultrasounds too early. Also because between the seventh and twelfth week an incredible development takes place on the fetus which gradually begins to take on human features. So what you see from 11-12 weeks of pregnancy is completely different, but certainly more exciting, than what you can see at 5-6 weeks.
Why might the doctor recommend an ultrasound at 6-7 weeks?
Although an ultrasound scan between 6 to 7 weeks is not done routinely, there are actually some important reasons why your gynecologist might request one.
The most common reason doctors require an ultrasound before 12 or 13 weeks is to accurately date the pregnancy.
If the pregnancy symptoms do not match the date of your last menstruation or there is any doubt about when it was conceived, measurements taken during an early ultrasound between 7 and 11 weeks of pregnancy) can be traced back to the gynecologist at the correct gestational time.
Other reasons that call for an early ultrasound include:
- Confirmation of single or twin pregnancy. Especially for couples who have undergone assisted fertilization treatments, the first ultrasound is anticipated.
- Confirmation of fetal heartbeat. If you have worrying symptoms, such as vaginal spotting or bleeding, your gynecologist will want to check if there is a threat of miscarriage or if the bleeding is due to other causes.
- Rule out an ectopic pregnancy. When an embryo implants outside the uterus, you can have normal pregnancy symptoms and a positive pregnancy test, even if the embryo is not viable. An ectopic pregnancy is a dangerous condition if it is not managed in time and early diagnosis is crucial.
- Check for complications: For example, if the doctor suspects that there may be a problem such as the presence of uterine fibroids, it is important to have this information immediately.
Ultimately don’t worry if your doctor requests an early ultrasound, maybe he just needs to gather as much information as possible so that you can experience a healthy and peaceful pregnancy.
What to expect when visiting
The world of social media is flooded with photos of pregnant ultrasound scans. All this often causes this moment to be idealized.
An ultrasound at 7 weeks of pregnancy or less will not be an idyllic experience, so it matters do not create too many expectations.
In most cases, the embryo is still too small to be clearly seen on an external abdominal ultrasound. A transvaginal ultrasound will be needed. This ultrasound is not painful, but it can be a little annoying.
The embryo is too small to have clear images. You may see the general shape of the embryo, but it is perfectly normal not to see anything that looks like a baby. Not for nothing at this stage many refer to the embryo as a “green bean”.
At 7 weeks it will be possible hear and see your heartbeat. It could have a rhythm of up to 110 beats per minute or more! If the embryo is in a visible location on the ultrasound, you will likely see a small flash or pulse on the screen. Usually at this stage they do not let you hear the pulse but only see the pulse.
What can you see after 6 weeks?
Recall that the seventh week of pregnancy ranges from 6 + 0 to 6 + 6.
- Gestational chamber. This is one of the first visible signs of pregnancy and refers to the fluid-filled space surrounding the embryo. The gestational chamber becomes visible starting from 5 weeks of pregnancy, confirming the intrauterine pregnancy by ultrasound. It will appear as a dark circular shape, in stark contrast to the whitish appearance of the inside of the uterus.
- Calf sack. Before an embryo can be seen inside the gestational chamber, the yolk sac should be identified. It is the first thing that develops inside the gestational chamber and supplies the baby with the substances it needs until the placenta develops. It will look like a small white ring or bubble inside the bag.
- Embryonic pole. This is the first indication that the baby is forming inside the gestational chamber. It has a thick, whitish shape attached to the yolk sac. Depending on how long it is, it can be curved or oblong. It can usually be detected within 6 weeks of gestation with a transvaginal ultrasound.
In the photo (source: Glowm.com) you can clearly see the embryonic pole and the yolk sac:
What measurements will be taken (and why)
In addition to detecting a heartbeat, the purpose of a 6-7 week ultrasound is to measure the gestational chamber and the embryonic pole to trace the gestational age.
The doctor will measure the size of the gestational chamber and the cranio-caudal embryo measurement (CRL), if it is visible. At 7 weeks the embryo should be around 5-9mm in size and the gestational chamber will be around 18-24mm.
From this point forward, fetal development proceeds rapidly and makes great leaps in size from week to week.
If the doctor detects a smaller or slightly larger gestational sac it could restore pregnancy. In any case, if the results are not clear, your doctor may ask you to schedule another ultrasound after a week or ten days, to evaluate the evolution of the pregnancy.
What could it mean if you don’t see anything
Whereas most women do not realize they are pregnant until at least 2-3 weeks have passed since conception (4-5 since the last menstruation), and that the very first thing that forms in the uterus is the chamber gestational, if an ultrasound is performed at 5 weeks only this will be visible.
If a woman has very irregular cycles and not knows when she ovulated, if you have an ultrasound scan 6 weeks after your last period but see only the gestational chamber and nothing else, don’t have to worry, in fact, it may be that she has recently conceived and needs to have her pregnancy restored. The doctor will see you the following week to check the evolution of the pregnancy and make a precise delay.
Having made this necessary clarification, we can only hide an ultrasound at 6-7 weeks it could also reveal that the pregnancy is not proceeding as hoped.
For example, if there are inconsistent signs, such as a large gestational chamber without a yolk sac or embryonic pole, it could mean an abortion is in progress or that it is a clear egg.
Are the twins visible so early?
Yes, transvaginally and especially if they are heterozygous, that is, they are twins derived from the fertilization of two oocytes by two spermatozoa.
If the twins are identical (homozygous), i.e. an egg has been fertilized but then split in two, there will be only one gestational sac; however, more than one yolk sac, embryonic pole, and heartbeat may be visible.
Keep in mind that ultrasound scans are not foolproof and at such an early stage the twin pregnancy may not be clear and visible.
Gestational chambers greater than one may not be visible until a subsequent ultrasound.
Dewald O, et al. (2020). Gestational sac evaluation.
Donovan MF, et al. (2020). Embryology, yolk sac.