Associations between pregnancy outcome and South Asian ethnicity in Aotearoa New Zealand, with a focus on perinatal mortality and placental pathology

Abstract

Aims: International and New Zealand (NZ) research has identified that women of South Asian ethnicity have increased perinatal mortality. We analysed differences in pregnancy outcomes and associated risk factors by ethnicity in NZ, with a focus on South Asian women, to better understand pathways leading to observed discrepancies in adverse outcomes. We hypothesised that South Asian women have a greater predominance of metabolic dysfunction contributing to inequities in perinatal outcomes. Methods: Clinical data from perinatal deaths between 2008 and 2017 were provided by the NZ Perinatal and Maternal Mortality Review Committee (PMMRC), while national maternity and neonatal data, and singleton birth records were linked using the Statistics NZ Integrated Data Infrastructure for all births. Women of South Asian (including Indian, Fijian Indian, South African Indian, Sri Lankan, Bangladeshi and Pakistani), Māori, Pacific and NZ European ethnicity were included in the analyses of this thesis, based on personal identification of each individual with one or multiple ethnic groups, as per the NZ Ministry of Health Ethnicity Data Protocols. Pregnancy outcomes and risk factors for stillbirth and neonatal death were compared between ethnicities, by migrant generation and religion. Placental pathology reports from the PMMRC were blinded, and analysed by ethnicity by an experienced perinatal pathologist using the Amsterdam Placental Workshop Group Consensus criteria. Finally, twenty-one placental, metabolic, inflammatory and cardiovascular early pregnancy biomarkers from the Screening for Pregnancy Endpoints (SCOPE) study biobank were compared between Indian and European nulliparous women. Results: South Asian women were at significantly increased odds of perinatal death, compared with mothers of NZ European ethnicity (aOR 1.63, 95%CI 1.43-1.85), however only at ≤24 weeks and ≥41 weeks gestation (p<0.05). Women of South Asian ethnicity also had significantly increased odds of preterm birth (aOR 1.09, 95%CI 1.03-1.16), small for gestational age (aOR 1.13, 95%CI 1.08-1.18) and gestational diabetes (aOR 6.42, 95%CI 6.08-6.77). Among perinatal deaths, placentas of South Asian mothers were more likely to show signs of histologic chorioamnionitis <28 weeks gestation (aOR 1.87, 95%CI 1.19-2.94), and features of maternal vascular malperfusion (aOR 2.60, 95%CI 1.10-6.16) and abnormal villous morphology (aOR 2.12, 95%CI 1.14-3.94) ≥28 weeks gestation, compared with NZ European. Despite limited numbers, these findings were correlated with a high rate of diabetic and anaemic disorders. In the SCOPE biobank we observed an overall pattern of pro-inflammatory and adverse metabolic early pregnancy biomarkers in Indian compared with European mothers. Conclusions: Women of South Asian ethnicity in Aotearoa NZ are at increased risk of perinatal mortality. A less favourable metabolic health profile may contribute to adverse pregnancy outcomes in South Asian mothers, although further research is needed to confirm this hypothesis