RT Journal Article
SR Electronic
T1 Evidence of selection bias in preterm survival studies: a systematic review
JF Archives of Disease in Childhood - Fetal and Neonatal Edition
JO Arch Dis Child Fetal Neonatal Ed
FD BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health
SP F79
OP F84
DO 10.1136/fn.84.2.F79
VO 84
IS 2
A1 D J Evans
A1 M I Levene
YR 2001
UL http://fn.bmj.com/content/84/2/F79.abstract
AB OBJECTIVE To determine by how much selection bias in preterm infant cohort studies results in an overestimate of survival.DESIGN Systematic review of studies reporting survival in infants less than 28 weeks of gestation published 1978–1998. Studies were graded according to cohort definition: A, stillbirths and live births; B, live births; C, neonatal unit admissions. Proportions of infants surviving to discharge were calculated for each week of gestation.RESULTS Sixty seven studies report data on 55 cohorts (16 grade A, 23 grade B, 16 grade C). Studies that are more selective report significantly higher survival between 23 and 26 weeks of gestation (grade C > grade B > grade A, p < 0.01), exaggerating survival by 100% and 56% at 23 and 24 weeks respectively.CONCLUSION To minimise the potential for overestimating survival around the limits of viability, future studies should endeavour to report the outcome of all pregnancies for each week of gestation (terminations, miscarriages, stillbirths, and all live births).