One of the first signs of pregnancy that appears on ultrasound is the gestational sac.
The sac that encloses the developing baby and contains the amniotic fluid. It is found in the uterus, and on an ultrasound it appears as a white border around a clear center.
The gestational sac is formed around five to seven weeks after the last menstrual period in natural cycles, so it is usually visible between three and five weeks of gestational age using a transvaginal ultrasound.
A transvaginal ultrasound has a higher sensitivity and produces clearer images than a transabdominal ultrasound. The gestational sac is usually seen when your HCG (human chorionic gonadotropin) levels are between 1500 and 2000.
If a gestational sac is seen on your ultrasound, is this a guarantee of a normal pregnancy?
Visualizing a gestational sac is undoubtedly a positive sign of pregnancy, but it is not a guarantee that your pregnancy will be healthy and will continue normally.
For example, after the sac becomes visible, the next positive sign of pregnancy is a yolk sac that develops within it. The yolk sac provides nutrition to the developing embryo until the placenta takes over and, therefore, is an important indicator of the health of the pregnancy.
In some cases, a gestational sac will be detected in the ultrasound, but later a yolk sac will not be found. The yolk sac is usually visible on a transvaginal ultrasound between weeks 5 1/2 and 6 of gestation.
Possible reasons that may limit the detection of the gestational sac
If you do not see a gestational sac in your ultrasound, what does that mean? There are several possible reasons for the lack of a gestational sac. It could be that:
Your dates are late : This is a common reason and may simply mean that you need a repeat ultrasound later. It may be useful to compare this finding with HCG levels, which would probably be less than 1500 if you are not as advanced as you thought you were during pregnancy.
You have aborted : It could be that you had a very early miscarriage (chemical pregnancy) or that you are aborting. The decrease in HCG levels is also a sign of spontaneous abortion.
You have an ectopic pregnancy : If your HCG levels are between 1500 and 2000, but you do not see a gestational sac, it could mean that you have an ectopic pregnancy.
An ectopic pregnancy can be a medical emergency, and if this is a possibility, your doctor will want to do more tests and talk about treatment options.
What does an empty gestational sac mean?
Usually, an embryo is seen inside the gestational sac at 6 weeks of gestation.
One of the most common types of miscarriage, known as an anembryonic pregnancy, an empty sac or an affected ovum, occurs when a gestational sac does not contain an embryo.
In other words, an embryo could not develop. This type of pregnancy loss occurs early in the first trimester and often before a woman realizes she was pregnant.
It can be the result of an abnormal cell division, poor quality sperm or a poor quality egg.
In most cases, chromosomal abnormalities will cause the woman’s body to undergo a natural abortion without intervention. However, there are some cases in which a woman can choose a dilatation and curettage (D & L) to complete the miscarriage.
This procedure may be appropriate for women who want a pathologist to try to find a cause for the miscarriage, for those who believe it will help them cope better with the loss, or for the physical or medical concerns raised by their doctor.
If your doctor discovers an empty gestational sac on an ultrasound, you can confirm that your pregnancy is not viable; in other words, pregnancy will not result in the birth of a baby, since it is not progressing normally.
But sometimes (depending on the size of the gestational sac), it may be too early to determine that the sac is really “empty”. In this case, your doctor will ask you to return for a repeat ultrasound.
This can be a moment full of anxiety, but it is meant to guarantee a 100 percent accurate diagnosis (whether the pregnancy is viable or not viable).
In search of good progress
Early transvaginal ultrasounds are a relatively easy way to follow a pregnancy from the beginning, and together with the levels of HCG can give you and your doctor an idea of how your pregnancy is progressing.
The gestational sac is the first structure that doctors look for with an early ultrasound. When it is present (between 3 and 5 weeks of gestation), it can be a positive sign.
That said, sometimes a gestational sac is seen but it is empty, without evidence of an embryo at 6 weeks of gestation.
On the other hand, sometimes you do not see a gestational sac. The most common reason for this is inaccurate dates and it is simply too early.
But if a gestational sac is not seen at follow-up, or if HCG levels indicate that one should be seen, you may have a miscarriage or an ectopic pregnancy.
Pregnancy can be a happy time, but also full of anxiety when things do not go as you would like.
Lean on your friends and family. If you think you are having a miscarriage, have a withered egg or an ectopic pregnancy, it can be a big emotional blow.
This is especially true since many couples have not yet shared their pregnancy with family and friends, so they may feel very lonely. There are stages of affliction associated with spontaneous abortions, even when they occur early.
To that are added the often well-meaning but damaging comments like “you can always have another.” It is important to honor your feelings and grieve in the way that is best for you.