The eLIXIR (early LIFe data Cross-Linkage in Research) Cohort.

The foundations of health are established at the very earliest stages of life. If the developing embryo, fetus, newborn baby and young child are given the best possible start in life, this will provide protection against poor health when they are adults. To achieve these best beginnings, we have to understand what can go wrong at each of those key stages in early life. Some causes are more obvious than others; for example, being born prematurely can lead to breathing problems, but there are many other factors that can interact in a complex way to affect the child's mental and physical health for life. If we know what these factors are, we can work to prevent them or their harmful effects.

The eLIXIR study aims to establish a novel way of unravelling the complexity of harmful early life influences, using routine information from mothers' and babies' health records. Whilst a few people choose to opt-out of providing their records, the vast majority support our strategy. It has the advantage of including almost everyone in our maternity population, so that all ethnic and social groups are represented.

Having shown that we can link together mothers and babies' mental and physical health records from GP practices and hospitals, we are now ready to invite researchers from around the UK to use our data, and explore the early life influences that affect children's health and find ways of preventing disease in adulthood. eLIXIR started in 2018, and we already have data from more than 40,000 pregnant women and their children, and we will continue collecting mums' data until we have data from 100,000 pregnancies; this will take about 4 years. This very large study of mums and babies gives researchers the opportunity to undertake novel approaches to learning from the data, all within an electronic, trusted research space that protects the identify of the mums and babies at all times.

The people providing our data live in South East London, where mental and physical health problems are common. The mothers come from many different ethnic groups and are often socially and economically deprived. Therefore, by working in this community, eLIXIR concentrates on those who most need help, and its findings should be relevant to other disadvantaged communities across the UK. Indeed, we will test this out by working with other groups, in Wales, Scotland and North East England, who are also using routine health data to study mothers and their babies, and the future health of the children.

Another important element of the study is the collection of blood samples. We do not obtain these from all mothers and babies - just those who give permission to do so when they come to clinics in early pregnancy. We already have samples from more than 1400 participants who are similar in their characteristics to our population of mums. This store of blood samples is important, because there are many different kinds of measurements that can be done on them, to add to the information that we have from the GP and hospital health records.

Our plans will be realised by recognition as an MRC 'Longitudinal Population Study'. This would provide us with funding support for the eLIXIR infrastructure, primarily to fund staff who collect mums' and babies' information from different sources, link that information together in the trusted, safe space, or collect the samples. In the future, we plan for eLIXIR to become self-sufficient, as researchers from all over the UK access the information and samples, and contribute to these costs.

Aim.
Adversity in the earliest stages of life can lead to life-long consequence for the child's health. Through a longitudinal birth cohort achieved by linkage of routine electronic health records (eLIXIR), our aim is to provide UK researchers with a national resource with which to address responsible mechanisms and develop effective interventions. This will be facilitated through establishing the eLIXIR cohort as an MRC Longitudinal Population Study (LPS).

Methodology
We have developed an electronic health record linkage (eLIXIR) with data from pregnant women and their infants from two NHS Acute Trusts, a Mental Health Trust and GP practices in South East London. This antenatal population born in over 170 countries, has a high level of socio-economic deprivation, and 26% of the mothers are of Black ethnicity. In contrast to smaller, conventional birth cohorts, this 'dynamic' cohort accumulates more than 15,000 pregnancies/year. With >98% opt-out consent, the data are representative of our population demographic, and provide a pregnancy and life-course 'read out' of contemporary shifts in population profile, health and health care practice. An important additional layer of information is provided by an 'opt-in consent' bioresource. eLIXIR therefore offers a unique opportunity for researchers to address the abundant inequalities in mental and physical health, and their interaction, in UK women and their children, and the life-long consequences.

Scientific and Medical Opportunities.
Adoption as an MRC LPS will enable access for researchers across the UK engaged in life-course research, particularly those investigating interactions between physical and mental health that drive health inequalities. Also, with a network of collaborators undertaking similar linkages in different geographical settings, we shall agree on common methodologies to enable cross-evaluation of outcomes, whilst planning a joint LPS data-linkage UK facility for research.