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Prenat Diagn. 2010 Mar;30(3):235-40. doi: 10.1002/pd.2445.

First trimester aneuploidy screening in the presence of a vanishing twin: implications for maternal serum markers.

Author information

  • 1Prenatal Screening Unit, Clinical Biochemistry Department, King George Hospital, Goodmayes, UK. KevinSpencer1@aol.com

Abstract

OBJECTIVE:

To assess the impact of a vanishing twin on the levels of the biochemical markers used in the first trimester aneuploidy screening.

METHODS:

A retrospective analysis of free beta-hCG and PAPP-A levels in 270 women with a normal singleton fetus with ultrasound evidence of a vanishing twin pregnancy. Marker levels (as MoM) were compared in three groups-76 women with a second empty gestational sac, 194 women with a second gestational sac containing a dead fetus with a measurable crown rump length (CRL), and 1360 matched singleton pregnancies.

RESULTS:

In women with a second empty gestational sac, the median free beta-hCG and PAPP-A MoMs (0.968 and 1.040, respectively) were not significantly different from the 1.0 MoM in singleton pregnancies. In the group with a vanished twin with a measurable-CRL-there was a significantly increased median PAPP-A MoM (1.317) but the median free beta-hCG MoM was not changed (1.024). Modelling this bias in PAPP-A MoM the detection rate for trisomy 21 would fall from 85 to 75%.

CONCLUSION:

First trimester screening in the presence of a vanishing twin may lead to errors in risk estimation. In such circumstances it may be advisable to restrict screening to the use of nuchal translucency (NT) alone.

PMID:
20066674
DOI:
10.1002/pd.2445
[PubMed - indexed for MEDLINE]
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