Vanishing Twin Syndrome Workup

Updated: Apr 12, 2021
  • Author: Ann L Anderson-Berry, MD, PhD; Chief Editor: Christine Isaacs, MD  more...
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Workup

Laboratory Studies

Recent vanishing twin has been shown to increase levels of pregnancy-associated plasma protein-A (PAPP-A) and free beta-human chorionic gonadotropin (beta-hCG). This may affect risk assessment for aneuploidy in the surviving fetus. [31]

Alpha-fetoprotein levels are elevated compared with values at similar junctures in both a singleton pregnancy and a normal twin pregnancy. [4]

The rate of rise of beta-hCG is slower than in a normal twin pregnancy. [32]

If vanishing twin syndrome is diagnosed at the time of nuchal translucency ultrasound, biochemical screening markers may not be as precise as in singleton assisted-reproductive technique pregnancies. [33]

The use of biochemical markers may be indicated if, at the time of nuchal translucency, a vanishing twin is confirmed to have an empty gestational sac; however, if a dead fetus remains, biochemical markers are not accurate for screening. [34]

Other tests

Amniocentesis after diagnosis of a vanishing twin by prior ultrasonography has been reported to detect an XY cell by both FISH and real-time PCR in the sustained XX 20 weeks' gestation pregnancy. Take caution about interpretation of amniocentesis results because a vanishing twin fetus could lead to false-positive results. [27]

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Imaging Studies and Other Tests

Imaging studies

Ultrasonography is used to confirm the diagnosis of early twin pregnancy. Follow-up ultrasonography reveals the pregnancy loss (vanishing twin). [13, 35]  In addition, after diagnosing first-trimester bleeding, using ultrasonography before dilation and curettage is important. This ensures that bleeding does not signal the loss of just one fetus.

Chorionic villus sampling

Chorionic villus sampling may be helpful if the placenta has a mosaic makeup and there is a singleton at birth.

Histologic findings

Obtain histologic samples of the placenta at birth, because they may be the only evidence of vanishing twin syndrome with a reabsorbed fetus. [3, 9, 12]

 

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