What is the purpose of the ABCD study?

‘We follow a group of children born in 2003-2004 from the mother's pregnancy. We look at the development and health of these children, by analysing questionnaires filled in by their mothers, fathers and themselves and by taking physical measurements. The main aim of the ABCD study is to identify and analyse factors in early life, during the mother's pregnancy and at an early childhood age, which may explain later health and differnces in health.’

How many families are participating in the study?

‘During pregnancy, over 8,000 women participated. The original idea was to only follow the pregnancy. Not all pregnant women gave their consent for the follow-up. We now have about 5,600 children to follow. The first questionnaire was during the fourteenth week of pregnancy, afterwards we received feedback on the birth. Since we have had contact at 3 months, at 5/6 years, at 7/8 years, at 11/12 years and 15/16 years. We will follow the children until they are 25 years of age.’

Is the data from the research already being used?

'Yes, almost 200 publications have already been published. Since the beginning of the ABCD study, studies have been carried out with the results. For example in the first stage on the taking folic acid among pregnant women. Around 80% of Dutch women take folic acid, and less than 30% of Turkish and Moroccan women. Why is that? Language plays an important role. If you don't understand the language well, you don't get the proper information.’

Where are you now with the study?

‘We're working on a new data collection, the kids are now 15-16 years old. It's harder to reach the children now. When the child is 16, all you need is the child's consent. Previously, the parents could persuade their children to participate, but now we regularly receive unsubscriptions from parents who indicate that their child does not feel like it. If this is the case, it is still interesting for us that the mother participates, because she can provide information about her child. We expect it to be a temporary phase, during adolescence, and that the youngsters will want to participate again in a few years.’

Are the parents informed about the results of the study or their own child in the meantime?

‘That differs. We informed the parents about previous measurements such as blood test results. We do not report the questionnaire that the child completes back to the parents, because they want their privacy to be guaranteed. When the children are 15/16 years old, for example, there are questions about alcohol and drugs. We do report back to the child himself/herself. No right or wrong, but how they score in relation to their peers, for example when it comes to sleeping problems. They find that interesting to know. Every year we also send a newsletter and an annual review in which we tell them in a fun way about the progress of the ABCD study and the studies in which the data was used.’

How has the knowledge you have gained been translated into practice?

'We have made a major contribution to the trend that the first thousand days are essential for the child's development. For example, by demonstrating that the mother's excess weight is the most important determinant of the child's obesity. And that stress, feelings of depression and anxiety during pregnancy are predictors of behavioural problems of the child. These aspects also often remain present in a family; depression, anxiety and overweight usually play a role not only during pregnancy, but also when the child grows up.

It is important to come up with early interventions. Then, for example, you can offer support to the family in areas of nutrition, sleep and exercise. If you do this very early on, you will benefit the most. The earlier you are there, the better.’

What is the contribution of the Amsterdam University Fund used for?

‘We have now received three contributions from the Amsterdam University Fund. The first time to make lipid determinations in blood of pregnant women. Several studies have been carried out, for example to explain the effect of the mother's diet during pregnancy on that of the child. This time the contribution is intended to increase the non-response rate. At 11-12 years of age we also received a contribution for the same goal.

What we notice is that the response of the first 80 percent is as much money and effort consuming as the last 20 percent. That 20 percent is very interesting, there are, for example, non-Dutch families among them, and we would like to keep those in the study. That costs a lot of manpower and money. We call these families several times, come to the neighbourhood and offer questionnaires in their language. We often have to explain the study, because if the contact moments are a few years apart, people sometimes forget that they are participating in the study.’

What do you hope to achieve in this final phase of the study?

‘The most important thing is that we keep the group as large as possible and that we can continue to do research. It's getting more and more interesting, the children are getting older, and all kinds of transitions are going on. They will study later, get their first job and relationships. We would like to know what impact this has on their mental and physical health. Because we have so much data from the earlier period, we can analyse what the most important factors are to grow up as healthy as possible. Then you also know at which moments you should intervene and you can actually only say that when you have the results at an adult age.

We want to contribute to the healthy development of children growing up in Amsterdam. We hope that we can continue the ABCD study for a long time to come and take interesting measurements. We have always succeeded so far and we are confident that we will continue to succeed.’