Quantifying the Risk of Different Types of Perinatal Death in Relation to Gestational Age: Researchers at Risk of Causing Confusion

Opposing or complementary perspectives? Perinatal outcomes, causality, and time zero

“…However, I question the underlying assumption that ongoing pregnancies rates and birth‐based rates are opposing perspectives that need to be reconciled. Perhaps instead, they are complementary—different approaches, each useful to answer different types of questions . The two are related, and foetal time clearly precedes neonatal time, but one does not subsume the other.…”

“…For this reason, a denominator of live births at the index gestational age is argued to be a better analytical choice. In truth, neither denominator perfectly accounts for these various analytical considerations . It is this challenge Dr Joseph addresses in his article in this edition of Paediatric and Perinatal Epidemiology .…”

“…There is consensus regarding the appropriate denominator for events that occur before the onset of labour, such as antepartum stillbirth: foetuses, or ongoing pregnancies—a term that reflects that many such outcomes, such as preeclampsia—pertain to the mother or the pregnancy rather than the foetus per se. Controversy arises when considering postnatal outcomes . Including all ongoing pregnancies in gestation‐stratified analyses of such outcomes is argued to more clearly reflect the fact that aetiological process often begins before birth.…”

Methodological Challenges in International Comparisons of Perinatal Mortality

“…A third explanation for the intersecting perinatal mortality paradox, termed the collider stratification bias, proposes uncontrolled confounding of the relation between birth weight (or gestational age) and perinatal mortality as the cause for the mortality crossover [42, 43]. Although there is little consensus on the preferred solution for the paradox of intersecting perinatal mortality curves [44••, 45–47, 48••, 49], there is general consensus that maternal smoking, hypertensive disorders, and multifetal pregnancy lead to adverse fetal and neonatal outcomes at all gestational ages and birth weights.…”

No Rates Were Harmed in the Making of This Paper: Response to Critiques

“…Although most researchers agree on fetuses as the denominator for several endpoints (e.g. antepartum stillbirth, preterm birth, and pregnancy complications), risk of outcomes identified after birth is generally measured among live births, despite the limitations imposed by such a choice . These ‘conventional’ estimates are predictive and clinically useful but cannot be relied upon for causal interpretation, given how they often result in overall harmful exposures appearing to be protective at preterm weeks.…”