Subsequent birth outcomes after an unexplained stillbirth: preliminary population‐based retrospective cohort study

Abstract

The objective of this study was to determine whether women who have experienced an unexplained stillbirth have a higher risk of adverse perinatal outcomes in subsequent births. We compared 316 subsequent births to women with a previous unexplained stillbirth, with 3160 births to women with no previous history of stillbirth, matched by year of birth, in the period 1987-1997, from the South Australian perinatal database, using logistic regression analysis. There was no increase in the rate of stillbirth and no statistically significant increase in the rate of perinatal death (OR 1.62 [95%CI 0.63-4.20]) or neonatal death, although larger studies are needed to confirm this. However, after adjusting for age, parity, and hospital category of birth, women who had a previous stillbirth had increased incidences in subsequent births of abnormal glucose tolerance or gestational diabetes (a fourfold increase); induction of labour and elective Caesarean section; fetal distress and postpartum haemorrhage; and forceps and emergency Caesarean delivery and preterm birth, which were independent of induction of labour. Gestational age at birth and birthweight were also significantly reduced, suggesting a need for close monitoring of their future pregnancies.

Management of subsequent pregnancy after an unexplained stillbirth

“…54,55 Although low birth weight is more common in the next pregnancy after an unexplained stillbirth, it has been difficult to determine whether this results from a trend to early delivery or a true increase in the incidence of pathological growth restriction. 8,56,57 A study from South Australia reported an increase in the odds for very low birth weight (that is, below 1500 g) that would not be accounted for by very preterm birth in the post-stillbirth group, suggesting a true increase in the number of growth-restricted babies. 8 Frequent ultrasound examination is commonly undertaken in the next pregnancy after unexplained stillbirth, but it is important to advise women about the potential limitations of such tests.…”

“…8,56,57 A study from South Australia reported an increase in the odds for very low birth weight (that is, below 1500 g) that would not be accounted for by very preterm birth in the post-stillbirth group, suggesting a true increase in the number of growth-restricted babies. 8 Frequent ultrasound examination is commonly undertaken in the next pregnancy after unexplained stillbirth, but it is important to advise women about the potential limitations of such tests. Abnormal uterine artery Doppler studies in the second trimester are associated with adverse pregnancy outcomes, and a finding of increased uterine artery flow impedance before 24 weeks gestation can predate a clinical suspicion of growth restriction.…”

“…8 Undiagnosed diabetes is associated with a number of adverse outcomes of pregnancy, including fetal demise. This risk increases adequately high such that the condition should be sought early in the next pregnancy.…”

“…11 All studies of pregnancy outcome subsequent to unexplained stillbirth are reassuring in terms of perinatal mortality, but report increased rates of intervention and iatrogenic adverse outcomes such as prematurity, emergency cesarean section and post-partum hemorrhage. [7][8][9][10] There is likely to be a strong Hawthorne effect in such studies as the history of a previous stillbirth increases levels of surveillance in the next pregnancy and lowers the threshold to intervene. Optimizing fetal surveillance while minimizing the risk of false-positive results that might prompt unnecessary intervention presents the major challenge in this setting.…”

“…Although the odds ratio for recurrence of stillbirths from all causes is almost five, 6 studies of pregnancy outcomes subsequent to unexplained stillbirth have not reported any increase in the risk of perinatal death. [7][8][9][10] However, those studies found that pregnancy after stillbirth is characterized by increased rates of induced labor, elective and emergency cesarean section, preterm birth and low birth weight. These adverse outcomes might be at least partly the result of obstetricians having a low threshold for intervention.…”