Co-variables in first trimester maternal serum screening

✍ Scribed by Irene M. de Graaf; Howard S. Cuckle; Eva Pajkrt; Nico J. Leschot; Otto P. Bleker; Jan M. M. van Lith

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 57 KB
• Volume: 20
• Category: Article
• ISSN: 0197-3851
• DOI: 10.1002/(sici)1097-0223(200003)20:3<186::aid-pd776>3.0.co;2-a

✦ Synopsis

The objective of this study was to determined the in¯uence of maternal weight, maternal smoking habits, gravidity, parity and fetal gender on the level of maternal serum marker used in ®rst trimester screening for Down syndrome. A total of 2449 singleton unaffected pregnancies from two centres were studied. Maternal serum free b-human chorionic gonadotrophin (hCG) and a-fetoprotein (AFP) concentrations had been measured in all pregnancies, and pregnancy associated plasma protein (PAPP)-A levels had been measured in 924. All results were expressed as multiples of the gestation speci®c median (MoM) values after regression, using each centre's own medians. Information on maternal weight was available in 2259 pregnancies, on self-reported current cigarette smoking in 1364 (of whom 117 (8.6%) were smokers), on gravidity in 1371, parity in 1303 and fetal gender in 253. All three markers showed a statistically signi®cant negative association with maternal weight ( p<0.0005) and in the subsequent analyses MoM values were weight adjusted using standard methods. The median PAPP-A level in smokers was 0.81 MoM, a signi®cant reduction ( p<0.005); free b-hCG was also reduced (median 0.89 MoM) but not signi®cantly ( p=0.17), and AFP was unaltered. The median AFP level in primagravidas was highly signi®cantly greater than that in gravid women ( p<0.0005). In PAPP-A the reverse effect was seen but it did not reach statistical signi®cance ( p=0.15) and there was no effect for free b-hCG. Results of a similar magnitude and direction were found for parity. The median level of free b-hCG was higher ( p=0.0005), and the median AFP lower in female pregnancies. Maternal weight and, for PAPP-A, maternal smoking are important ®rst trimester screening co-variables. Gravidity, parity and fetal gender also seem to in¯uence one or more ®rst trimester markers.