Does No Gestational Sac on the Ultrasound Mean I'm Not Pregnant?

Unfortunately, it's possible to have a positive pregnancy test but no baby on the ultrasound. If the gestational sac—which encloses the developing baby and contains amniotic fluid—isn't visible by around five weeks gestation, it might mean that you simply miscalculated your conception date, and it's too early to see the gestational sac.

But it might also indicate the pregnancy isn't viable, a miscarriage has already happened, or you're experiencing an ectopic pregnancy.

Learn more about when the gestational sac is usually seen during pregnancy. We also break down the different reasons why it might not be found on an ultrasound.

When Is a Gestational Sac Visible?

A gestational sac is one of the first signs of pregnancy that can be seen on a transvaginal ultrasound—usually by five weeks gestational age, but sometimes as early as four weeks. When identified on the ultrasound, the diameter of the sac is around 2 to 3 millimeters, and it looks like a white rim around a clear center in your uterus.

If you're also having quantitative pregnancy tests (serum hCG tests) the gestational sac usually becomes visible on transvaginal ultrasound when hCG levels have reached 1500 to 2000.

The next step on ultrasound is usually the appearance of the yolk sac within the gestational sac. The yolk sac functions as nourishment for the developing embryo and can usually be seen by five-and-a-half to six weeks gestational age on a transvaginal ultrasound.

Common Reasons for No Gestational Sac

Having a gestational sac doesn't say much about the health of your pregnancy, nor does it indicate whether an embryo is present or not. The gestational sac is essentially the structure that surrounds the fetus (when it becomes visible) and contains amniotic fluid.

If a gestational sac isn't seen on an early pregnancy transvaginal ultrasound by around five weeks gestational age, several things could be happening.

Too early in the pregnancy

The gestational sac is typically visible on a transvaginal ultrasound by five weeks of pregnancy, or by the time hCG levels reach 1500 to 2000. Before that, even in a viable pregnancy, there isn't going to be a visible gestational sac on an ultrasound.

Incorrect timing is one of the most common causes of a nonexistent gestational sac on an early ultrasound, especially in the absence of symptoms such as bleeding. When there's no confirmation of hCG levels or any definite evidence of dating, the pregnancy might still be in very early stages. In this case, a follow-up ultrasound is recommended.

If the pregnancy is definitely past five weeks, or the hCG level is higher than 2000, a finding of no gestational sac is more likely to indicate an issue.

Ectopic pregnancy

Whenever there's no gestational sac visible in the uterus, ectopic pregnancy is possible. This happens when the embryo develops somewhere outside of the uterus, usually in the fallopian tubes, and it's considered life-threatening. 

Ectopic pregnancy can be frightening, but keep in mind that the absence of a gestational sac is more likely to be related to wrong dates. Even if an ectopic pregnancy is detected, it can be managed well when caught early.

Miscarriage

If you experience early pregnancy bleeding or other miscarriage symptoms, this could mean you've had a very early miscarriage (also called a chemical pregnancy)—especially if no gestational sac is visible on the ultrasound. It's also possible the pregnancy tissue has already left the uterus.

If you have falling hCG levels along with no visible gestational sac, the diagnosis is almost certainly a miscarriage. As with an ectopic pregnancy, there are different treatment options available.

What To Do If There's No Gestational Sac

It can be difficult for health care providers to determine which of the above explanations is behind a pregnancy with no visible gestational sac. Therefore, it's completely natural to feel concerned and anxious, and perhaps even frustrated, as you wait for a diagnosis.

You may be told (or see on medical forms) that you have a "pregnancy of unknown location." This statement simply means that the ultrasound didn't show a gestational sac, and your medical provider isn't sure whether it's an ectopic pregnancy, a miscarriage, or a very early but otherwise normal pregnancy.

Most likely, you'll be asked to come back for a follow-up ultrasound and undergo monitoring of your hCG levels and possibly progesterone levels. Together, these repeat tests should give you a clear answer. The wait can be difficult, but it may be necessary for your health care provider to be certain of your diagnosis.