Results
Incidence
82 cases were reported to UKOSS in the one year study period (Figure1). One local reporter included a trichorionic triamniotic triplet pregnancy which was excluded; 81 MC (diamniotic) twin pregnancies were included in analysis. Data were collected from 47 centres. Case ascertainment via comparison with MBRRACE-UK data identified a potential additional 94 cases which centres were asked to investigate. Twenty-eight centres replied, with most potentially eligible cases not meeting the case definition (fetal demise was outside the study period, both twins died at the same time or the twins were not MC). Only three additional cases were identified which were included in the 81 cases analysed.
The characteristics of the study population are shown in Table 1. 22/81 (27%) sIUFDs were classified as spontaneous (i.e. no signs of TTTS, sIUGR or congenital/structural anomaly), 38/81 (47%) pregnancies with a sIUFD were complicated by TTTS, 5/81 (6%) with sIUGR, and 12/81 (15%) with a congenital/structural anomaly. In 4/81 (5%) cases it was not clear whether there was a preceding diagnosis of a complication of MC twin pregnancy, therefore they were classified as ‘unclear’. The median gestation at diagnosis of first sIUFD was 157 days, equating to 22+3 weeks (IQR 25th-75th: 134-186 days).