title: Are first-trimester screening markers altered in assisted reproductive technologies pregnancies?
abstract: OBJECTIVE
  To review the current literature on first-trimester screening with respect to specific issues for assisted reproductive technologies (ARTs) singleton and twin pregnancies.
  
  
  RESULTS
  A number of different first-trimester sonographic and biochemical markers have been validated in first-trimester screening for trisomy 21. Among sonographic markers, measurement of fetal nuchal translucency is the most investigated and least affected screening method in ART pregnancies, achieving comparable results in singletons and twins compared with spontaneous conceptions. The small deviation of nuchal translucency thickness observed in ART singletons did not influence overall screening performance, including the number of false-positive results. First-trimester maternal serum free β-human chorionic gonadotropin and pregnancy-associated plasma protein-A levels are more obviously altered in assisted conceptions and carry the risk of higher false-positive rates if not adjusted accordingly. The reason behind the alterations is currently not quite explored, but might be attributed to infertility and a higher incidence of placental disorders rather than to the use of ART. In twin pregnancies, chorionicity is an important confounding variable with evident impact on nuchal translucency measurements and maternal biochemistry, but both issues have not been sufficiently investigated in ART twins so far.
  
  
  CONCLUSIONS
  First-trimester measurement of fetal nuchal translucency in singleton and twin gestations is associated with similar screening results when compared with spontaneous conception. Adjustments for the mode of conception are required if maternal serum biochemistry is included in the screening algorithm. Further studies on assisted conception twins are essential to permit more conclusive results on this issue.
authors.affiliation: Department of Obstetrics and Prenatal Medicine, University Medical School Bonn, Germany.
authors.forename: Annegret
authors.initials: A
authors.lastname: Geipel
authors.forename: Ulrich
authors.initials: U
authors.lastname: Gembruch
authors.forename: Christoph
authors.initials: C
authors.lastname: Berg
mesh_terms: D015415:Biomarkers / Q000097:blood*; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D005260:Female; D006801:Humans; D048208:Nuchal Translucency Measurement; D011247:Pregnancy; D011248:Pregnancy Complications; D011261:Pregnancy Trimester, First / Q000097:blood*; D011272:Pregnancy, Multiple / Q000097:blood; D011266:Pregnancy-Associated Plasma Protein-A / Q000378:metabolism; D011296:Prenatal Diagnosis; D027724:Reproductive Techniques, Assisted
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A