The overall placing and management structure of a longitudinal birth cohort

In planning a longitudinal birth cohort study it is important to decide where the target population should be resident and where the organisation should be based, as well as how the study should be directed. In this paper we discuss the ways in which other birth cohort studies have made these choices and outline the advantages and disadvantages of different scenarios.     

Assessing diet in longitudinal birth cohort studies

Diet is an important component of a person's environment. It is important for adults and particularly for mothers during pregnancy and while breast feeding, and for children in utero and during later growth and development. Measurement of the type and amount of foods consumed is complex. Here we describe the different methods that can be used, when and when not to use each one, and the importance of validation studies.     

How many subjects are needed in a longitudinal birth cohort study?

One of the first decisions that needs to be taken when planning a birth cohort concerns the size of the study. This in turn will depend on the research questions to be answered and thence whether environmental exposures and outcomes are measured on a continuum or as dichotomous variables. Here we describe ways in which different birth cohorts have addressed this issue and explore the advantages of smaller detailed studies over larger less-detailed studies.     

Nesting sub-studies and randomised controlled trials within birth cohort studies

Although birth cohort studies can stand on their own, there are a number of different types of sub-studies that can add value to the overall project. These can be summarised within four main categories: (A) more detailed observations of relatively small subgroups aimed at describing mechanisms and processes; (B) nested case–control studies; (C) use of detailed observations to validate data collection by questionnaire or interview; (D) randomised controlled trials. For each category we give examples of ways in which they have been employed in current pregnancy birth cohort studies.     

Preparation, piloting and validation for a longitudinal birth cohort study

No longitudinal study should go into the field prior to detailed piloting and validation studies of the measures and techniques to be used. Preparation should also involve the training of staff, the acquisition of space and appropriate equipment, and liaison with the community and ethical committees as well as with scientific collaborators. Because different measures will continually be introduced as the participants age, the preparation, piloting and validation studies have to be ongoing. Here we describe some of the different strategies that should be used.     

The case for a coordinating centre for birth cohort studies

Designing, piloting and proceeding with a longitudinal birth cohort is a major exercise. Here we outline ways in which a resource centre could be initiated to provide advice and training, a library of appropriate instruments and publications, provision for cross-cohort comparisons and a biobanking facility. The resource should be available for cohorts planned in the developed and developing world, as well as those countries in transition. We discuss possible strategies for funding such a centre.     

The importance of biological samples in longitudinal birth cohort studies

Here we describe how measurements in biological samples can be used to provide direct measures of exposures to environmental pollutants, nutrients, infectious organisms and drugs of abuse, and to validate other less direct measures of exposure such as questionnaire responses. They can also be used as measures of outcome traits or intermediate phenotypes which may lie on the pathways to disease.     

Ethics and governance of a longitudinal birth cohort

All longitudinal birth cohorts should be undertaken with a detailed ethical strategy and policy on governance. Here we outline the various factors that should be taken into consideration and describe ways in which these issues may be addressed.     

巴西Pelotas的3次出生队列研究及其启示

巴西Pelotas出生队列研究是发展中国家持续时间最久、规模最大的一次出生队列研究。巴西Pelotas出生队列研究的内容相当广泛,涉及母婴健康状况、剖宫产率升高的原因、母乳喂养情况及其影响因素、健康的社会不均等性以及慢性病的影响因素等。该研究较好地反映了不同时代和不同社会阶层母婴健康状况的变化趋势,为全面了解发展中国家卫生保健的可及性和利用率,以及卫生政策的制定和实施提供了可靠的指导依据。     

Sources of data for a longitudinal birth cohort

This paper outlines the variety of data sources which can be utilised in a longitudinal study. Although a longitudinal study could be carried out using just one type of data, greater depth and accuracy can be achieved by including a variety of different sources of information.