Understanding Vanishing Twin Syndrome After Ultrasound & Bleeding

Question
Hi there, I had an ultrasound i was 8 weeks and it showed 2 sacs but 1 alive baby with a good heartbeat.
What happens to the other sac inside me?
Does my body get rid of it? I have been bleeding.
Would it do harm to the other baby?
Thank you

Answer
Dear Lilian,

From the information you have shared, what this sounds like is a vanishing twin situation. Vanishing twin syndrome is when one of a set of twin or multiple fetuses "disappears" in the uterus during pregnancy. This is the result of a miscarriage of one twin/multiple. The fetal tissue is usually then partially or completely reabsorbed by the mother. This gives the appearance of a "vanishing twin" on ultrasound.

The cause of vanishing twin syndrome is frequently unknown. Analysis of the placenta and/or fetal tissue frequently reveals chromosomal abnormalities, while the surviving twin is usually normal. A poorly implanted placenta may also be a cause.

If the fetus is absorbed completely, there are usually no complications to the pregnancy, other than first trimester vaginal bleeding. If the loss does occur within the first trimester, neither the remaining fetus nor the mother may have any clinical signs or symptoms. If there are symptoms, the most common symptoms include bleeding, uterine cramps and pelvic pain. The prognosis of the surviving twin is usually excellent, but it depends on the factors that contributed to the death of the other twin. If the twin dies in the second or third trimester, there are increased risks to the surviving fetus. This could include a higher rate of cerebral palsy and a threat to the continuation of the pregnancy. You are well within your first trimester.

Typically, no special medical care is necessary with an uncomplicated vanishing twin in the first trimester. Neither the surviving twin nor the mother would require medical treatment. As with any pregnancy, if your vaginal bleeding were to become very heavy with clotting or tissue and become accompanied by strong cramping, I would recommend that you let your doctor know or seek care.

I hope this has helped you and answered your question. I wish you well.

Brenda