FETAL MEGACYSTIS AT 10-14 WEEKS OF GESTATION

During the study period, 24 492 pregnant women attended the Harris Bir thright Research Centre at 10-14 weeks of gestation, at which time, in addition to the measurements of nuchal translucency thickness and cro wn-rump length (CRL), data on fetal abnormalities were recorded onto a computer database. Cases of megacystis were identified and the record s were reviewed. Additionally, the relationship of the longitudinal bl adder diameter with the CRL and the bladder diameter/CRL ratio (expres sed as a percentage examined with the use of data from 300 normal fetu ses at 10-14 weeks. Megacystis was present in 15 of the 24 492 pregnan cies (1 in 1633) and in these cases the minimum longitudinal bladder d iameter was 8 mm and the minimum bladder diameter/CRL ratio runs 13%. In the 300 control fetuses the bladder was visualized in 278 (92.7%) o f the cases and the longitudinal bladder diameter increased with the C RL (bladder diameter = 0.065 x CRL - 0.69; r = 0.47, p < 0.001), none of the measurements was more than 6 mm and the median bladder diameter /CRL ratio was 5.4% (range 0-10.4%) which did not change significantly with gestation (r = 0.1, p = 0.09). The bladder was visible in all ca ses with a minimum CRL of 67 mm. In three of the 15 cases with megacys tis, there were chromosomal abnormalities. In the chromosomally normal group, there were seven cases with spontaneous resolution, whereas in four cases there was progression to severe obstructive uropathy. The bladder diameter was 8-12 mm and the bladder diameter/CRL ratio 13-22% in all cases with resolution and in one case with progressive megacys tis; in the other three cases with progressive obstruction, the bladde r length was more than 16 mm and the bladder diameter/CRL ratio was mo re than 28%.