Dany P.L. Straetmans

Audit on nuchal translucency thickness measurements in Flanders, Belgium: a plea for methodological standardization.

To audit nuchal translucency thickness (NT) measurements for fetal aneuploidy screening in Flanders, and to estimate the impact of small variations in NT measurement on the screening result of two first‐trimester screening algorithms: maternal age + NT (Algorithm A), and maternal age + NT + pregnancy associated plasma protein‐A + free β‐human chorionic gonadotropin (Algorithm B).

Nuchal translucency thickness measurements for fetal aneuploidy screening: Log NT-MoM or Delta-NT, performer-specific medians and ultrasound training

Objectives: To evaluate in fetal aneuploidy screening the desirability of using Fetal Medicine Foundation (FMF) normal medians of nuchal translucency thickness (NT) measurements or performer-specific medians, and whether the NT measurements should be expressed as Delta-NT or Log NT-MoM values. Settings: First trimester-combined screening programme in a low risk population in Flanders, Belgium (Algemeen Medisch Laboratorium, Antwerp). Methods: Pregnancies unaffected by trisomy 21 (T21) were screened by FMF-trained or other ultrasonographers. Performer-specific NT medians were established for FMF-trained and other ultrasonographers. NCSS Statistical Software was used to establish probability plots for Log NT-MoM and Delta-NT values, relative to performer-specific references or to the FMF-reference. Results: A total of 16,096 pregnancies were evaluated. Six FMF-trainees and five other ultrasonographers each performed between 83 and 658 NT measurements. For the FMF-trainees, FMF-specific NT-MoM medians were close to one at a crown-rump length (CRL) between 50 and 80 mm, whereas the population-specific NT-MoM medians of the other ultrasonographers were close to one at a CRL between 40 and 80 mm. Performer-specific Delta-NT values fitted a Gaussian distribution between the 5th and 90th percentiles, while for the Log NT-MoM values this was between the 10th and 95th percentiles. Conclusion: We conclude that (i) the use of screening would benefit from performer-specific NT-medians based on Log NT-MoM values; (ii) the use of Log NT-MoM values is marginally better than the use of delta-NT MoMs; and (iii) NT measurements are valid at about 10 weeks (crown-rump length 40–45 mm) as well as at 11–13 weeks.

Dimeric Inhibin Serum Values as Markers of Ovarian Activity in Pill-Free Intervals

Levels of inhibin A and B as well as other hormones in serum samples obtained during the pill-free interval in women taking combined oral contraceptives (OC) were measured to asses the extent of ovarian activity during that period. Type of pill and day of pill-free interval were recorded during routine gynecologic check-ups, if patients were in the pill-free period and had taken their pills regularly in the previous cycle. In addition to inhibin A and B, serum levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), and progesterone were also quantified. Inhibin B levels rise significantly in parallel with rising levels of FSH, LH, and E2. Progesterone levels were completely suppressed and inhibin A levels rose slightly but insignificantly. Inhibins are sensitive biochemical markers of ovarian activity in pill-free intervals.

Sequential triage in the first trimester may enhance advanced ultrasound scanning in population screening for trisomy 21

To design a trisomy 21 screening protocol for sequential triage in the first trimester, and to evaluate whether it reduces the need for advanced ultrasound scanning to such an extent that this could be dealt with by a limited number of well‐trained sonographers only.

Single-step maternal serum screening for trisomy 21 in the era of combined or integrated screening

Single-step maternal serum screening (MSS) in the first (1MSS) or second (2MSS) trimester at maternal age ≧35 years was evaluated in the North Belgian region Flanders, where difficulties are encountered in the general introduction of combined or integrated screening algorithms. The fetal aneuploidy screening database of General Medical Laboratory AML in Antwerp was searched for 2MSS tests between 1992 and 1999 (α-fetoprotein, β-human chorionic gonadotropin (β-HCG) and unconjugated estriol, cut-off 1:300) and for 1MSS tests between 1999 and 2003 (free β-HCG and pregnancy-associated plasma protein A, cut-off 1:85). At ≧35 years, the detection rate for trisomy 21 (DR) was 93.8% (15/16) for 2MSS and the screen-positive rate (SPR) was 24.5% (504/2061). For 1MSS, these figures were 85.7% (6/7) and 17.7% (109/615) respectively. To detect one trisomy 21, missed by MSS at ≧35 years of age, an additional number of 1,557 and 506 primary invasive procedures would be needed for 2MMS and 1MSS respectively. We conclude that the performance of bothsingle-step 1MSS and 2MSS at maternal age ≧35 years in Flanders is excellent, even without the combination with ultrasound parameters or integration of first and second trimester parameters. The simplicity of both methods allows to consider them valuable options for fetal aneuploidy screening at advanced maternal age, until high quality combined or integrated screening is accessible to all pregnant women in Belgium.