Ultrasound for spotting in early pregnancy is frequently done to exclude failure of the pregnancy, ectopic pregnancy and bleeding around the uterine cavity. Spotting can be normal related to implantation of the pregnancy or hormonal changes. Spotting in early pregnancy can also be a sign of something more concerning.
Ultrasound is the most common imaging test done to evaluate spotting in early pregnancy. Perhaps the most important condition to diagnose is ectopic pregnancy. This is when the pregnancy is located outside the uterine cavity. Most commonly inside the Fallopian tube. This can present with spotting and pelvic pain. When there is rupture of the ectopic pregnancy, life threatening bleeding can occur. Ultrasound will show a cyst or mass next to the ovary most commonly. There will often be fluid or blood in the pelvis.
Pregnancy failure or miscarriage can be detected with ultrasound in early pregnancy. There are criteria that radiologists use to diagnose failure based on size of structures and whether they see a heart beat. For example, when the embryo measures 7 mm on a transvaginal scan, there must be a heart beat. When the sac in the uterine cavity measures 25 mm on a transvaginal scan, an embryo must be seen. There are other measurements that make a miscarriage suspicious. If not diagnostic than a Follow up ultrasound and correlation with hormonal levels of beta HCG is needed to confirm in these cases.
A common cause of bleeding in pregnancy is subchorionic bleeding. This happens when there is bleeding between the uterus and membranes that surround the embryo. It is not known exactly why this occurs. Many subchorionic bleeds pose no harm to the pregnancy, especially when they are small. Subchorionic hemorrhages can be seen as collections close to the uterine cavity and sac. They are easily diagnosed on ultrasound.
There are causes of spotting in early pregnancy that are not related to the pregnancy as well. Fibroids, pelvic infections, amongst other causes can also result in spotting which ultrasound can sometimes diagnose. While spotting in early pregnancy can be a normal finding, it is important to exclude more threatening conditions outlined above.