The cohort, in numbers
Of the 17 indicted babies: at least 11 were twins or multiples; 4 further co-twins had already died in utero before the events on the indictment. That makes the indicted pool a highly selected, high-risk multiple-pregnancy cohort, not a representative slice of neonatal-unit admissions. See our twins-and-multiples evidence page.
Across the full cohort of 17 + 4 = 21 babies (indictment + pre-indictment co-twins), at least eight of the 17 pregnancies involved small-for-gestational-age (SGA) concerns, affecting 12 of the babies.
The triplet pregnancy
Children O and P were two of the three infants in a monochorionic triamniotic (MCTA) triplet pregnancy — a pregnancy type with a roughly 1-in-100,000 incidence and among the highest perinatal-risk profiles in obstetrics. All three triplets shared a single placenta.
In such a pregnancy, selective reduction (the termination of the smallest or most compromised of the three) is the standard option offered to mothers. Complete termination of the pregnancy is also a standard option. For a mother to continue such a pregnancy implies she has been counselled about its risks and, almost always, has chosen to accept the substantial perinatal-mortality risk in the expectation of specialist tertiary antenatal care.
A mother in that position would, on any reasonable reading, want delivery at a centre with tertiary neonatal capacity — in the North West, that centre is Liverpool Women’s Hospital. The fact that the triplet pregnancy came to be delivered at the Countess of Chester, a Level 2 unit, is itself the first question the analysis raises.
Small-for-gestational-age patterns
SGA is a red flag in obstetric practice. Its presence should prompt enhanced monitoring, regular growth scans, Doppler flow studies, and — in cases of severe growth restriction — consideration of early delivery at a tertiary centre. In the indicted cohort SGA is over-represented: eight of seventeen pregnancies, affecting twelve babies. Five of those nine pregnancies (eight of twelve babies) had received some antenatal care at Liverpool Women’s Hospital.
Referral patterns between hospitals
In 2014–16, the referral landscape for high-risk pregnancies in the Mersey and Cheshire region underwent documented change. Liverpool Women’s Hospital, the regional tertiary centre, tightened its internal triage criteria. Some mothers whose pregnancies would, under earlier protocols, have delivered at Liverpool Women’s found themselves offered delivery at the Countess of Chester. The analysis is careful to note that the full documentary record is not available, but the pattern — more high-risk multiple pregnancies delivered at the Countess of Chester in 2016 — is consistent with such a change.
Liverpool Women’s internal targets
A separate strand of the analysis addresses Liverpool Women’s reported internal stillbirth and neonatal-mortality targets. Targets of this kind, set at the hospital-level, can indirectly shape referral decisions — a hospital with internal targets on stillbirth reduction has structural incentives to transfer highest-risk pregnancies out to other units before delivery.
The analysis does not allege any deliberate wrongdoing by Liverpool Women’s. It does argue that the system of referrals, targets, and specialist-unit thresholds is a necessary part of the explanation for why an unusually high-risk cohort came to be concentrated at a Level 2 unit.
Implications for the Letby case
None of this proves that Ms Letby did not do what she was convicted of. But it changes the probability-weighting of the background. Convictions built on a “pattern of deaths on one nurse’s shifts is statistically unusual” argument depend on the baseline rate being representative of a general neonatal-unit cohort. The indicted cohort is not that cohort. It is a highly selected, high-risk, pre-filtered cohort.
Combined with Prof. Gill’s statistical critique of the shift-rota chart and the Panel’s case-by-case medical review, this obstetric-referral analysis is now part of what the CCRC has in front of it.