Objective To examine inequalities in preconception health between migrant women in potentially vulnerable situations and non-migrant women. Design National cross-sectional study. Setting Data from the National Health Service (NHS) Maternity Services Data Set (MSDS) version 1.5, using data submitted by NHS maternity services in England. Participants All 652,880 women with an antenatal booking appointment between 1/4/2018 and 31/3/2019 were included. Data regarding migration status were available for 66.2% of the study population (n=432,022). Outcome measures Prevalence of preconception indicators were compared between probable migrants (those with complex social factors and English not their first language), possible migrants due to English not being a first language (without complex social factors), possible migrants due to complex social factors (who speak English as a first language) and unlikely migrants (those who speak English as a first language without complex social factors). Complex social factors include recent migrants, asylum seekers or refugees, difficulty reading or speaking English; alcohol and/or drugs misuse; all those aged under 20; and/or experiencing domestic abuse. Odds ratios were calculated comparing preconception indicators among those identified as migrants compared to unlikely migrants. Results Women identified as probable migrants (n=25,070) had over twice the odds of not taking folic acid before pregnancy and of having their first antenatal booking appointment after the recommended 10 weeks gestation compared to unlikely migrants (n=303,737), after adjusting for area-based deprivation level, mothers age at booking, number of previous live births and ethnicity (odds ratio 2.15 (95% confidence interval 2.06 to 2.25) and 2.25 (2.18 to 2.32) respectively). Probable migrants had increased odds of previous obstetric complications and being underweight at booking, but lower odds of recorded physical and mental health conditions (apart from diabetes and hepatitis b), smoking and obesity in unadjusted and adjusted analyses. Conclusions Inequalities between migrant women in potentially vulnerable situations and non-migrants exist across many preconception indicators. Findings highlight the opportunity to improve preconception health in this population in order to reduce health inequalities and improve perinatal and neonatal outcomes.

All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: MM has support from the Medical Research Council [Grant number MR/W01498X/1]; DS is supported by NIHR Southampton Biomedical Research Centre; HD is National lead for lifecourse intelligence at the Office for Health Improvement and Disparities, Department of Health and Social Care; DB reports grants from the NIHR RfPB Programme, the NIHR HS&DS Programme and the NIHR HTA Programme and is Chair of Trustees of the MASIC Charity; FB reports grants from MRC, NIHR, Novartis Gene Therapies, Wellcome Trust and Public Health England and is a member of the Foetal, Maternal and Child Health Reference Group of the UK National Screening Committee and a Member of Bloodspot Advisory Group; SM reports being on the Advisory Group on Contraception for the NHSEI Advisory Group on postnatal care; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

MM is supported by the Medical Research Council [Grant number MR/W01498X/1]. For the purpose of open access, the author has applied a Creative Commons Attribution (CC BY) licence. DS is supported by the National Institute for Health and Social Care Research (NIHR) Southampton Biomedical Research Centre [IS-BRC-1215-20004]. The views expressed are those of the author(s) and not necessarily those of MRC, UKRI, NIHR or the Department of Health and Social Care.

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