How important is what happens to you in fetal and neonatal life in determining whether you develop heart disease later in life? I found myself thinking about that question a great deal back in the early 90s when the BMJ published many studies by David Barker, who in 1986 published the “Barker hypothesis” that fetal and neonatal experience was important in determining whether you later developed heart disease. Then David went to America, and the hypothesis seemed almost to leave with him. But last week I found myself thinking about the question again.

David was a great salesman. He would come and see me when I was the editor of the BMJ and convince me that his papers were hugely important. I liked him and was interested in his hypothesis, but I tried not to favour him. He did, however, publish a lot of papers in the BMJ—most of them with large datasets, complicated statistics, and small effects—and many people, including fellow editors, thought that we were soft on him. We even published a book of his papers.

His salesmanship extended way beyond the BMJ, and I remember his colourful lectures. I even think I remember him selling his hypothesis so hard that he said that if you had made a solid start in early life then it didn’t matter if you smoked.

Time moved on. David’s unit closed. He went to America. I left the BMJ, and the fetal origins of disease left my life.

But it’s crept back. I learnt that David and his hypothesis had been written up in positive terms in the New Yorker, and I read and enjoyed the article. Then I started a job where I was concerned with non-communicable disease in low and middle income countries. I do this with colleagues from the National Heart, Lung, and Blood Institute from the US, and I discovered that they are very interested in the Barker hypothesis.

Then last week I spent a whole day discussing the early origins of health with people who know a lot about it, and I’m writing this, as I write most things, to try and digest what I’ve learnt.

There is no doubt that what happens to you in fetal and neonatal life does influence your chances of developing cardiovascular disease in later life. But what is the size of the effect? We know that smoking, poor diet, physical inactivity, and the harmful use of alcohol are important risk factors for developing heart disease and other non-communicable diseases, and we have a sense of scale. Is what happens to you in early life more or less important than them?

That, I was told, is probably the wrong question. Rather what happens to you in early life sets you on a trajectory. If your mother is young and poorly nourished, smokes during pregnancy, has a poor diet, and is stressed, and then you are not breastfed, then you’ll be on a trajectory that will put you at high risk of developing heart disease, a risk perhaps four times that of somebody who has an optimal experience in early life. Children born in low and middle income countries are much more likely to have a bad “first thousand days” than children born into high income countries.

So can we do anything about it? There are many interventions that are highly likely to give children a better start: discourage teenage pregnancy; empower adolescent girls; improve the nutrition of young women; promote contraception; improve antenatal care; teach women about nutrition and possibly growing food; and encourage breastfeeding. These are all good things in themselves and have long been encouraged by those concerned about maternal and child health. Should they be given extra encouragement and perhaps extra resources because of the benefits they will have in later life?

Probably they should—because maternal and child health in low and middle income countries is often targeted at reducing mortality. But you can be alive but still at high risk of developing heart disease in later life. And we don’t quite know the effectiveness of these different interventions. Probably what we need is a large controlled trial with different combinations of interventions and an outcome measure of changes in biomarkers between birth and two years – the trajectory of the child.

These discussions are being held in the context of the forthcoming United Nations high level meeting on non-communicable disease. It surely makes sense to bring to the attention of the meeting and policy makers the importance of the first thousand days, but we need to know more about the scale of the effect and the effectiveness of interventions.

The morning after the meeting I read in Robin Lane Fox’s book The Classical World, about how girls in Sparta “would be trained in running, wrestling, and other sports, some of which were undertaken naked (argukably to prepare them to be mothers of fit, healthy children). So what the Spartans knew we must rediscover.

Richard Smith was the editor of the BMJ until 2004 and is director of the United Health Group’s chronic disease initiative.