Placental pathology findings in perinatal deaths from 28 weeks gestation in Aotearoa New Zealand

A validation of placental pathology reports by ethnicity in New Zealand, through systematic analysis of histological slides

INTRODUCTION

Reliability studies of placental examination have shown differing interobserver agreement for certain pathological features, a lack of uniform reporting criteria and variable experience among pathologists. In previous analyses we have shown that placental pathology differs by ethnicity. This validation study was performed to investigate whether bias related to ethnicity is a feature of placental pathology reporting in New Zealand (NZ).

METHODS

199 of 1726 eligible perinatal death cases between 2008 and 2017 were selected at random for this audit-type study, including 51 cases from South Asian, Māori and NZ European ethnicity and 46 cases from Pacific mothers. Stored histology slides were blinded and re-examined by an experienced perinatal pathologist, and linked to the corresponding original pathology report. Interobserver agreement (overall, by ethnicity and by gestational age) was described by proportional differences and kappa coefficients.

RESULTS

Total interobserver agreement between original placental reporting and the validation review was 89.7 %, which differed by pathological feature. There was generally more underreporting than overreporting (3.6 % and 6.7 %, respectively). There was little disagreement by ethnicity (decidual vasculopathy [p = 0.03]), although there were more differences by gestational age (villous morphology [p < 0.01], chorioamnionitis [p = 0.03], high-grade villitis of unknown etiology [p < 0.01], and placental haemorrhage [p = 0.03]).

DISCUSSION

No systematic bias in placental pathology reporting in NZ was identified by ethnicity or gestational age, as observed differences could be related to the underlying prevalence of pathology. We identified more underreporting than overreporting of pathology in the original reports, emphasizing the importance of placental investigation by specialised perinatal pathologists.

An in-depth analysis of perinatal related mortality among women of South Asian ethnicity in Aotearoa New Zealand

BACKGROUND

International and national New Zealand (NZ) research has identified women of South Asian ethnicity at increased risk of perinatal mortality, in particular stillbirth, with calls for increased perinatal research among this ethnic group. We aimed to analyse differences in pregnancy outcomes and associated risk factors between South Asian, Māori, Pacific and NZ European women in Aotearoa NZ, with a focus on women of South Asian ethnicity, to ultimately understand the distinctive pathways leading to adverse events.

METHODS

Clinical data from perinatal deaths between 2008 and 2017 were provided by the NZ Perinatal and Maternal Mortality Review Committee, while national maternity and neonatal data, and singleton birth records from the same decade, were linked using the Statistics NZ Integrated Data Infrastructure for all births. Pregnancy outcomes and risk factors for stillbirth and neonatal death were compared between ethnicities with adjustment for pre-specified risk factors.

RESULTS

Women of South Asian ethnicity were at increased risk of stillbirth (aOR 1.51, 95%CI 1.29-1.77), and neonatal death (aOR 1.51, 95%CI 1.17-1.92), compared with NZ European. The highest perinatal related mortality rates among South Asian women were between 20-23 weeks gestation (between 0.8 and 1.3/1,000 ongoing pregnancies; p < 0.01 compared with NZ European) and at term, although differences by ethnicity at term were not apparent until ≥ 41 weeks (p < 0.01). No major differences in commonly described risk factors for stillbirth and neonatal death were observed between ethnicities. Among perinatal deaths, South Asian women were overrepresented in a range of metabolic-related disorders, such as gestational diabetes, pre-existing thyroid disease, or maternal red blood cell disorders (all p < 0.05 compared with NZ European).

CONCLUSIONS

Consistent with previous reports, women of South Asian ethnicity in Aotearoa NZ were at increased risk of stillbirth and neonatal death compared with NZ European women, although only at extremely preterm (< 24 weeks) and post-term (≥ 41 weeks) gestations. While there were no major differences in established risk factors for stillbirth and neonatal death by ethnicity, metabolic-related factors were more common among South Asian women, which may contribute to adverse pregnancy outcomes in this ethnic group.