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The gestational sac is the first structure formed at the beginning of pregnancy that surrounds and shelters the baby and is responsible for forming the placenta and amniotic sac for the baby to grow in a he althy way, being present until approximately the 12th week of pregnancy. pregnancy.
The gestational sac can be visualized by transvaginal ultrasound around the 4th week of gestation and is located in the central part of the uterus, measuring 2 to 3 millimeters in diameter, being a good parameter for confirmation of pregnancy. However, at this stage it is still not possible to visualize the baby, which only appears inside the gestational sac after 4, 5 to 5 weeks of gestation. For this reason, doctors usually prefer to wait until the 8th week to order an ultrasound to have a more secure assessment of how the pregnancy is developing.
Gestational sac evaluation is a good parameter to verify that the pregnancy is progressing as it should. The parameters evaluated by the physician are implantation, size, shape and contents of the gestational sac. Check out other tests to evaluate the evolution of pregnancy.
Gestational sac size table
The gestational sac increases in size as the pregnancy progresses. During the ultrasound, the doctor compares the results of this test with the following table:
|Gestational Age||Diameter (mm)||Variant (mm)|
|4 weeks||5||2 to 8|
|5 weeks||10||6 to 16|
|6 weeks||16||9 to 23|
|7 weeks||23||15 to 31|
|8 weeks||30||22 to 38|
|9 weeks||37||28 to 16|
|10 weeks||43||35 to 51|
|11 weeks||51||42 to 60|
|12 weeks||60||51 to 69|
The reference values of the gestational sac size table allow the doctor to identify problems and anomalies of the gestational sac in advance.
Most common problems with the gestational sac
The he althy gestational sac has regular and symmetrical contours and good implantation. When it presents irregularities or low implantation, the chances of the pregnancy not evolving are great.
The most common problems include:
Empty gestational sac
After the 6th week of pregnancy, if the fetus is not visualized by ultrasound, it means that the gestational sac is empty and therefore the embryo has not developed after fertilization. This type of pregnancy is also called an anembryonic or blind egg pregnancy. Learn more about anembryonic pregnancy and why it happens.
The most common causes of a fetus not developing are abnormal cell division and poor sperm or egg quality. Usually, the doctor requests a repeat ultrasound around the 8th week to confirm the anembryonic pregnancy. If confirmed, the doctor may choose to wait a few days for a miscarriage or perform curettage, in which case hospitalization is required.
Gestational sac displacement
Displacement of the gestational sac can occur due to the appearance of a hematoma in the gestational sac, due to physical exertion, falls or hormonal changes, such as dysregulation of progesterone, high blood pressure, alcohol and drug use.
Signs of displacement are mild or severe cramping and brown or bright red bleeding. Generally, when the displacement is greater than 50%, the chances of miscarriage are high. There is no effective way to prevent displacement, but when it happens, the doctor will prescribe medication and complete rest for at least 15 days. In the most severe cases, hospitalization is necessary.
When to go to the doctor
It is important to go to the doctor if symptoms of intense colic or bleeding appear, in this case you should immediately seek the maternity hospital or emergency room and contact the doctor who is monitoring the pregnancy.The diagnosis of problems in the gestational sac is only made by the doctor by ultrasound, so it is important to start prenatal care as soon as the pregnancy is known.