Growth hormone binding protein in normal and aneuploid pregnancy: a paradoxical decrease in trisomy 18

Objective To explore whether abnormalities in growth hormone binding protei n (GHBP) may underlie the growth restriction associated with fetal aneuploi dy. Design A retrospective casecontrol study. Setting Monash Medical Centre, Clayton, Victoria, Australia. Population Twenty-one trisomy 18, and 30 trisomy 21 pregnancies, and 170 ch romosomally normal pregnancies at 15-18 weeks of gestation representing thr ee to five controls per case matched for source, gestation and duration of storage. Methods GHBP was measured using a ligand immunofunctional assay. Results In the chromosomally normal pregnancies GHBP levels decreased sligh tly but significantly across the narrow gestational window studied. Compare d with controls, levels of GHBP, expressed as median (95% CI) multiples of the median (MoM), in the trisomy 21 pregnancies were similar, 1.0 (0.92-1.3 9) MoM and 1.27 (1.04-1.50) MoM, respectively; P = 0.061 (Mann-Whitney CI t est) but were significantly reduced in the trisomy 18 pregnancies, 0.68 (0. 51-0.84) MoM; P = 0.0014 (Mann-Whitney U test). Conclusions These data suggest that decreased levels of maternal growth hor mone binding protein, and by implication growth hormone receptor complement , may underlie the early severe growth restriction that is characteristic o f trisomy 18.