Fibrin bands in intrauterine gestational sac

• TVS scan shows multiple, fine strands within the intrauterine gestational sac. 
• These strands were not visualized in transabdominal ultrasound. The higher resolution of the TVS probe is the reason for their visualization. 
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• Sonography of a 6-week intrauterine gestational sac shows the presence of fibrin bands within the sac. These are thin strands of fibrin that can be seen within the gestational sac.
• The presence of fibrin bands (significance): is not uncommon and is generally considered a normal finding in early pregnancy. They are thought to be a result of the normal breakdown of the embryonic membranes. Sometimes, (rarely), these may be due to breakdown of a demise of a twin embryo. 
• In this case, the sonography also reveals the presence of a large maternal ovarian cyst. While ovarian cysts can be common in pregnancy, a large cyst can increase the risk of complications such as torsion or rupture.
• It is important to note that, the obstetrician must closely monitor the patient with regular sonographic evaluations to ensure that the cyst is not causing any harm to the developing fetus or the mother.

Prognosis :

• Depending on the size and location of the cyst, the obstetrician may decide to take a conservative approach and wait for the cyst to resolve on its own or may recommend surgery to remove the cyst if it poses a significant risk to the patient. 

What are the differential diagnoses?

1. Subchorionic Hematoma: A subchorionic hematoma is a collection of blood that forms between the chorion (a membrane that surrounds the embryo) and the uterine wall. This can be a common cause of bleeding during pregnancy and may be seen on ultrasound as fibrin strands.

2. Missed Abortion: A missed abortion is a pregnancy loss in which the embryo has stopped developing, but the products of conception (gestational sac, placenta) are still present in the uterus. Fibrin strands may be seen within the gestational sac.

3. Blighted Ovum: A blighted ovum occurs when a fertilized egg implants in the uterus, but the embryo does not develop or is reabsorbed by the body. Fibrin strands may be seen within the gestational sac.

4. Ectopic Pregnancy: An ectopic pregnancy is a pregnancy in which the fertilized egg implants outside of the uterus, most commonly in the fallopian tube. Fibrin strands may be seen within the gestational sac in the fallopian tube.

5. Molar Pregnancy: A molar pregnancy is a rare abnormal pregnancy in which a tumor develops in the uterus instead of a fetus. Fibrin strands may be seen within the gestational sac.

6. Pseudogestational Sac: A pseudogestational sac is a fluid-filled sac that can be seen on ultrasound, but it does not contain a viable pregnancy. Fibrin strands may be seen within the pseudogestational sac.

7. Amniotic bands: Amniotic bands are not usually seen at such an early stage. Also they should be little more thicker. The general medical literature excludes amniotic bands in a 6 weeks gestational sac. 

All the above possibilities are excluded in our patient as the findings on sonography clearly show a viable embryo within the gestational sac in the uterine cavity.

Final diagnosis: viable intrauterine pregnancy at 6 weeks with a large ovarian cyst. Fine fibrin strands present in gestational sac don't appear to be significant. 

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Sonography of early gestation sac