Widening the definition of “at risk” babies based on predicted birth weight may reduce the number of stillbirths and infant deaths, according a study led by UK researchers.
The study found that birth weight at or below the 25th centile, or at or above the 85th centile was associated with greater risk of adverse outcomes such as stillbirths and infant deaths.
“We provide convincing evidence that how we define whether a baby is too small or too large needs to be re-visited”
Closer surveillance, or earlier delivery of babies with these predicted birth weight may reduce these adverse outcomes, suggested the study authors in the journal PLOS Medicine.
They noted that in developed countries one-third of stillbirths and infant deaths still occurred at full term, but no consensus currently existed about what defined a small or large foetus or infant at that point what birthweight thresholds should trigger surveillance or intervention.
The research, led by Dr Stamatina Iliodromiti from Glasgow University, used data from 979,912 term singleton pregnancies – a child born singly, rather than part of a multiple birth – over a 19-year period in Scotland, and compared them with a UK cohort including 10,515 pregnancies.
The researchers, also from the University of Bristol and the University of Cambridge, studied the associations of birth weight centiles with stillbirth, infant mortality, admission to the neonatal unit and low Apgar score – an assessment of overall wellbeing at birth.
Dr Iliodromiti said: “Currently babies that are predicted to be too small (most frequently less than the 10th centile) or too large (most frequently over the 90th centile) are considered at risk.”
“We provide convincing evidence that how we define whether a baby is too small or too large needs to be re-visited,” she said. “We anticipate that by redefining this, we can continue to reduce stillbirths.”
New ‘at risk’ definition may cut stillbirths and infant deaths
The researchers noted that customised birth weight centiles – accounting for sex, gestation, and maternal characteristics – were increasingly being adopted by many maternity units. But it had not yet been tested whether they predicted adverse outcomes better, said the study authors.
Although they were not able to assess fully customised centiles, the researchers did look at whether partially customised centiles – only allowing for maternal height and parity – performed better in predicting adverse outcomes.
However, they noted that they found that these partially customised centiles did not improve prediction performance.
Dr lliodromiti added: “Replication of the analysis with fully customised birth weight centiles that additionally account for maternal ethnicity and weight is required. We can then definitively answer whether customised birthweight centiles are beneficial.”