Vanishing Twin Syndrome Workup

Updated: May 10, 2016
  • 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 pregnancy associated plasma protein-A (PAPP-A) and free beta-hCG. This may affect risk assessment for aneuploidy in the surviving fetus. [29]

Alpha-fetoprotein levels are elevated compared with values at similar junctures in both a singleton pregnancy and a normal twin pregnancy. [30]

The rate of rise of beta-human chorionic gonadotropin is slower than in a normal twin pregnancy. [31]

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. [32]

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. [33]

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. [25]

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Imaging Studies

Ultrasonography is used to confirm the diagnosis of early twin pregnancy. Follow-up ultrasonography reveals the pregnancy loss (vanishing twin). [12, 34] 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.

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Procedures

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

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Histologic Findings

Obtain histological samples of the placenta at birth since they may be the only evidence of vanishing twin syndrome with a reabsorbed fetus. [3, 8, 11]

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