{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,7]],"date-time":"2025-10-07T08:50:19Z","timestamp":1759827019758},"reference-count":25,"publisher":"Wiley","issue":"1","license":[{"start":{"date-parts":[[2009,1,28]],"date-time":"2009-01-28T00:00:00Z","timestamp":1233100800000},"content-version":"vor","delay-in-days":27,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Prenatal Diagnosis"],"published-print":{"date-parts":[[2009,1]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Background<\/jats:title><jats:p>In the Netherlands, prenatal screening for trisomy 21 in the first trimester of pregnancy for singletons is conducted through a combined test based on maternal age, nuchal translucency measurement and maternal serum free \u03b2\u2010hCG and PAPP\u2010A. In our clinic risk calculations in twins are currently based on the NT of both fetuses instead of the combined test. In this study we looked at differences in early first\u2010trimester free \u03b2\u2010hCG and PAPP\u2010A between mono\u2010 and dichorionic twins.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>A total of 202 twin pregnant women participated in the study and agreed to donate first\u2010trimester serum for research.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>The data of 200 twins with normal outcome were used for setting up reference values for free \u03b2\u2010hCG and PAPP\u2010A. Trisomy 21 was identified in the two remaining pregnancies. The overall median weight\u2010corrected MoM was 1.99 for free \u03b2\u2010hCG, and 2.14 for PAPP\u2010A in all twins. Monochorionic twins have a significantly lower free \u03b2\u2010hCG weight\u2010corrected MoM (1.53 vs 2.11; Mann\u2010Whitney U, <jats:italic>p<\/jats:italic> = 0.002) and a significantly lower PAPP\u2010A weight\u2010corrected MoM (1.59 vs 2.40; Mann\u2010Whitney U, <jats:italic>p<\/jats:italic> = 0.003) compared to dichorionic.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>This study strengthened the need to make a distinction between mono\u2010 and dichorionic twins for the risk calculation in Down syndrome screening as biochemical markers are significantly lower in monochorionic than in dichorionic twins. Copyright \u00a9 2009 John Wiley &amp; Sons, Ltd.<\/jats:p><\/jats:sec>","DOI":"10.1002\/pd.2184","type":"journal-article","created":{"date-parts":[[2009,1,29]],"date-time":"2009-01-29T03:40:20Z","timestamp":1233200420000},"page":"74-78","source":"Crossref","is-referenced-by-count":28,"title":["Early first\u2010trimester free \u03b2\u2010hCG and PAPP\u2010A serum distributions in monochorionic and dichorionic twins"],"prefix":"10.1002","volume":"29","author":[{"given":"I. H.","family":"Linskens","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"M. D.","family":"Spreeuwenberg","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"M. A.","family":"Blankenstein","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"J. M. 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