Down Syndrome Research Today is a free monthly online journal that collates and summarizes the latest research about Down Syndrome, including details on education, symptoms, treatment, information. | |||||||
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Does a "vanishing twin" affect first-trimester biochemistry in Down syndrome risk assessment?Chasen ST, Perni SC, Predanic M, Kalish RB, Chervenak FA Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Weill Medical College of Cornell University, New York, NY, USA. stchasen@med.cornell.edu OBJECTIVE: The purpose of this study was to evaluate the impact of spontaneous reduction in multifetal pregnancy on first-trimester maternal serum biochemistry. STUDY DESIGN: We evaluated first-trimester pregnancy associated plasma protein-A (PAPP-A) and free beta-human chorionic gonadotropin levels in singleton euploid pregnancies. Biochemical values in pregnancies with evidence of spontaneous reduction were compared to other singleton pregnancies. Mann-Whitney U, Student t test, Fisher exact test, and logistic regression analysis were used for statistical comparison. RESULTS: There were 41 cases (0.9%) of spontaneous reduction. Though spontaneous reduction was not associated with different levels of either analyte, reduction within 4 weeks was associated with higher levels of both PAPP-A (1.79 vs 1.18; P = .002) and free beta-hCG (1.28 vs 0.96; P = .03) compared with other pregnancies. Spontaneous reduction was associated with a higher frequency of PAPP-A >95th %ile (17.1 vs 4.7%; P = .003) and free beta-hCG >95th %ile (17.1% vs 5.0%; P = .004). Logistic regression identified independent associations between spontaneous reduction and both high PAPP-A and high free beta-hCG. CONCLUSION: Recent spontaneous reduction is associated with higher values of PAPP-A and free beta-hCG. These differences have the potential to affect risk assessment for fetal aneuploidy. Published 3 July 2006 in Am J Obstet Gynecol, 195(1): 236-9.
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