Maternal serum Schwangerschafts protein-1 (SP1) and fetal chromosomal abnormalities at 10-13 weeks' gestation

Maternal serum SP1 concentration was measured at 10-13 weeks' gestation in samples from 87 pregnancies with fetal chromosomal abnormalities (trisomy 21 n = 45; trisomy 18 n = 19; trisomy 13 n = 8; Turner syndrome n = 7; 47,XXX or 47,XXY n = 4; triploidy n = 4), and in samples from 348 matched controls. In the control group, SP1 increased significantly with fetal crown-rump length (r = 0.20, P < 0.0001) and there was no significant association with fetal nuchal translucency thickness (r = 0.03). Similarly, in the group with fetal chromosomal abnormalities, SP1 increased significantly with crown-rump length (r = 0.31, P < 0.01) and there was no significant association with nuchal translucency thickness (r = -0.08). In the groups with fetal trisomy 18 and trisomy 13, the median SP1 (0.76 MoM and 0.57 MoM, respectively) was significantly lower than in the controls (z = 2.64 and z = 3.27, respectively); in 21% and 25% of the cases, values were below the 5th centile. In the group with trisomy 21 and other chromosomal abnormalities the median SP1 (0.96 MoM and 0.93 MoM, respectively) was not significantly different from controls (z = 1.17 and z = 0.67, respectively). Measurement of SP1 concentration at 10-13 weeks' gestation is not likely to be useful in the prediction of fetal chromosomal abnormalities.