Pregnancy

Ultrasound at 6-7 weeks of pregnancy: what can be seen?

What can be seen during an ultrasound at 6-7 weeks of pregnancy and when it is useful to perform it.

The first pregnancy ultrasound should be done no earlier than 8, 9 weeks of gestation. Instead, it often happens that early ultrasounds are done with such dubious results as to make the expectant mother anxious (most of the time for no reason).

The anxieties and worries derive from seeing only the gestational chamber or not even that, or just a small dot, or not hearing the heartbeat.

The ultrasounds performed too early, around 4-5 weeks of pregnancy, unfortunately give very few useful indications. If done at 4 weeks they can’t even visualize the gestational chamber. At 5 weeks, if you’re lucky, you’ll see a dot that confirms pregnancy in the uterus.

For this reason, doctors do not recommend doing ultrasound scans too soon. Also because between the seventh and twelfth week an incredible development takes place in the fetus which gradually begins to take on human features. So, what you see from 11-12 weeks of pregnancy is completely different (and definitely 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 in 6 -7 weeks is not routinely done, there are actually some important reasons why your gynecologist may order one.

The most common reason doctors request an ultrasound before 12 or 13 weeks is to accurately date the pregnancy.

If your pregnancy symptoms do not match the date of your last menstrual period or there is any doubt as to when your baby was conceived, measurements taken during an early ultrasound (between 7 and 11 weeks of pregnancy) can gynecologist at the correct gestational age.

Other reasons for an early ultrasound include:

  • Confirmation of single or twin pregnancy.   Especially for couples who have undergone assisted reproduction treatments, the first ultrasound is anticipated.
  • Confirmation of the fetal heartbeat . If you have worrying symptoms, such as spotting or vaginal bleeding, your gynecologist will want to check whether it 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 may have normal pregnancy symptoms and a positive pregnancy test, even if the embryo is not viable. An ectopic pregnancy is a dangerous condition if not managed in time and early diagnosis is essential.
  • Check for complications: For example, if your doctor suspects that there may be a problem such as uterine fibroids, it is important to have this information right away.

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 from the visit

The social media world is flooded with pregnancy ultrasound photos. All this means that this moment is often idealized.

An ultrasound at 7 weeks of pregnancy or less will not allow you to see much, so it is important not to create too many expectations.

In most cases, the embryo is still too small to be seen clearly with an external abdominal ultrasound (ie by placing the probe on the belly). The gynecologist (or midwife) will then perform a transvaginal ultrasound, inserting the probe inside the vagina as in a normal gynecological examination before pregnancy.

During the exam, you may see the general shape of the embryo, but it’s completely normal not to see anything that looks like a baby. It is not for nothing that in this phase many refer to the embryo as a “bean” .

At 7 weeks it is usually possible to hear and see the heartbeat, even if today gynecologists prefer to wait until 10 weeks before letting the future mother listen to the heartbeat. The little heart could have a beat up to 110 beats per minute or more! While you may not feel it during the exam, if the embryo is in a suitable position on the ultrasound you will likely be able to see the heart beating, as a small flash or throb on the screen .

Ultrasound scan at 6 weeks: what can you see?

Recall that the seventh week of pregnancy goes from 6+0 to 6+6.

  • gestational chamber. This is one of the first visible signs of a pregnancy and refers to the fluid-filled space surrounding the embryo. The gestational chamber  becomes visible starting from 5 weeks of pregnancy   by 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.
  • Yolk sac. Before an embryo can be seen inside the gestational chamber, the yolk sac should be located. 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.

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 , in order to date the pregnancy and calculate the date of delivery .

The doctor will measure the dimensions of the gestational chamber and the craniocaudal measurement of the embryo (CRL), if it is visible.  At 7 weeks, the embryo should be around 5-9mm in size , while the gestational chamber should be around 18-24mm.

From this point on, fetal development proceeds rapidly and makes large jumps in size from week to week.

If your doctor finds a smaller or slightly larger gestational sac, they may re-date the pregnancy . In any case, if the results are not clear, the gynecologist may ask you to schedule another ultrasound scan after a week or ten days, to evaluate the evolution of the pregnancy.

What could it mean if you can’t see anything

Considering that most women do not realize they are pregnant until at least 2-3 weeks have passed since conception (4-5 since the last menstrual period) and that the very first thing that forms in the uterus is the gestational chamber , if you do an ultrasound at 5 weeks only this will be visible.

If a woman who has very irregular cycles and doesn’t know when she ovulated  does an ultrasound 6 weeks after her last menstrual period and sees only the gestational chamber, she shouldn’t panic : it may in fact be that she conceived later than she thinks and has need a pregnancy re-dating. The doctor will see you the following week to verify the evolution of the pregnancy and date the gestational age more precisely.

Having made this necessary clarification, we cannot hide that an ultrasound at 6-7 weeks could also reveal that the pregnancy is not progressing as hoped.

For example, if inconsistent signs appear, 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 the so-called  clear egg .

Are the twins visible so early?

Yes, transvaginally and especially if they are heterozygous , i.e. they are twins derived from the fertilization of two oocytes by two sperm.

If the twins are identical (homozygous) , meaning one egg was 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 infallible and at such an early stage a  twin pregnancy may not be clear and visible.

Gestational chambers larger than one may not be visible until a subsequent ultrasound.

Dr Kathryn Barlow

Kathryn Barlow is an OB/GYN doctor, which is the medical specialty that deals with the care of women's reproductive health, including pregnancy and childbirth.

Obstetricians provide care to women during pregnancy, labor, and delivery, while gynecologists focus on the health of the female reproductive system, including the ovaries, uterus, vagina, and breasts. OB/GYN doctors are trained to provide medical and surgical care for a wide range of conditions related to women's reproductive health.

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