Serial first- and second-trimester Down's syndrome screening tests among IVF-versus naturally-conceived singletons.
BACKGROUND
It has been reported that second-trimester serum markers may be affected by assisted reproduction, leading to a higher false-positive rate.


METHODS
A total of 285 naturally and 71 IVF-conceived singletons which underwent a serial disclosure Down's syndrome screening programme were compared. The study protocol included first-trimester combined [nuchal translucency (NT), free beta-HCG and pregnancy-associated plasma protein-A (PAPP-A)] testing. The second-trimester triple serum screening included alpha-fetoprotein (AFP), intact HCG and unconjugated estriol (uE3). After excluding aneuploidies, miscarriages, anatomical anomalies and cases with incomplete follow-up, the serum samples of normal cases were assessed and correlated.


RESULTS
NT measurement was not significantly changed in either group. However, the IVF group had lower PAPP-A [0.96 versus 1.05 multiples of normal median (MoM)] and higher AFP (1.13 versus 1.07 median MoM). Both groups had similar rates of first-trimester false-positive results (FPR; 7 and 9% respectively), but the IVF group had a significantly higher mid-gestation FPR rate (10 versus 5%; Pearson chi2, P = 0.029). This has contributed to amniocentesis uptake rates of 15 and 13% for the IVF and natural conception pregnancies respectively.


CONCLUSIONS
The IVF group tended to have a significantly higher second-trimester FPR rate. To counterbalance this phenomenon, integrated first- and second-trimester screening tests or the use of NT alone might be a reasonable option that deserves further investigation.
Maymon
R
R
Department of Obstetrics and Gynecology, Assaf Harofe Medical Center, Zerifin, Israel. intposgr@post.tau.ac.il
Shulman
A
A
D000328:Adult; D004314:Down Syndrome / Q000175:diagnosis* / Q000196:embryology; D005189:False Positive Reactions; D005260:Female; D005306:Fertilization; D005307:Fertilization in Vitro; D006801:Humans; D008137:Longitudinal Studies; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis*; D011296:Prenatal Diagnosis / Q000379:methods* / Q000592:standards; D012016:Reference Values; D000509:alpha-Fetoproteins / Q000032:analysis
D000509:alpha-Fetoproteins; D011266:Pregnancy-Associated Plasma Protein-A