In this cohort study, the data collection will be based on six methods (physical examinations, questionnaires, tests, clinical data, biological samples, and survey of living environment) that complement each other in order to cover multiple aspects of determinants of health and health outcomes. We will use standardised questionnaires and protocol applied by birth cohorts in Europe, which will facilitate publication of results of our analyses in leading international journals and also will ultimately make it possible for pooling data and conducting joint-analyses with European cohorts in future.

Because of the costs and practical reasons, it will not feasible to collect all the desired data (as listed below) for all planned mother-child pairs for the cohort. We will therefore use a novel 3-level nested design:

A. General cohort:

a survey of 150,000 pregnant women across all designed centres for which we will collect data on:

1. Physical examination
2. Questionnaires
3. Tests
4. Clinical data
5. Biological samples
6. Living environment

B. Broad sub-cohort:

10,000-15,000 pregnant women selected from the general cohort in large centres for which in addition to the data that we collect for the general cohort, we will collect data on

1. Tests
2. Biological samples

C. Omics sub-cohort:

5000-7000 pregnant women selected from the broad sub-cohort for which in addition to the data that we collect for the general cohort and broad sub-cohort, we will collect data on

1. Tests
2. Biological samples:
3. Living environment