First-trimester screening for fetal triploidy at 11 to 14 weeks: a role for fetal biometry

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Abstract
Objective Intrauterine growth restriction in triploidy has been reported as early as in the first trimester. This study was undertaken to evaluate the ability of first‐trimester crown rump length (CRL)‐based charts to detect triploid fetuses. Material and Methods Analysis of fetal biometry in cases of triploidy diagnosed in the first trimester over the last three years. Biometry for abdominal circumference (AC), head circumference (HC) and biparietal diameter (BPD) was analyzed in relation to both gestational age (GA)‐based charts and to CRL‐based charts. Results Five cases of fetal triploidy were diagnosed at 11 to 14 weeks. Screening based on nuchal translucency (NT) and maternal age showed a risk > 1/300 in only one of the 5 cases of triploid fetus. In all of these five cases, CRL‐based biometry was grossly abnormal, although it was abnormal in only two of these five cases in relation to GA‐based charts. Conclusion First‐trimester CRL‐based biometry charts seem to reflect early asymmetrical growth delay in triploidy more accurately than GA‐based charts. CRL‐based biometry is likely to improve the early detection of triploid pregnancies without leading to dating error. Copyright © 2005 John Wiley & Sons, Ltd.