Whether the new arrival is a boy or a girl, most parents do not notice their baby's blood being sampled because it happens so quickly. Within a few days of birth, a health-care worker deftly pricks the heel of the writhing bundle of joy and dabs a few blood spots onto filter paper. The sample is later used to check the newborn for rare genetic disorders.

This is newborn screening in the United States, which identifies problematic conditions in some 3,400 infants each year. In many ways, it is public health care at its best. In others, it demonstrates the sometimes fraught relationship between the medical and research communities and the public.

The problem is not only that many parents miss the heel-prick test at the time, but also that they can be unaware of it altogether. That might be acceptable if the blood sample taken from their child was destroyed after screening, but it is not. In fact, some blood is retained (sometimes indefinitely), stripped of identifying information and used for quality assurance and unrelated biomedical research. Usually this is done without the parents giving their explicit informed consent.

To be unclear about how newborn blood is collected and used is the fastest route to turn the public against sampling.

The United States is not the only nation that fails to insist on seeking the written permission of parents before sampling and screening babies. Only a few countries do. But as the News Feature on page 156 shows, the fact that the practice is widespread offers little defence against those who see the lack of consent as a serious problem.

One of those critics is the vociferous campaigner Twila Brase, a former nurse who hates the idea that the government could have the DNA of babies on file. Beneath her inflammatory suggestions that researchers are planning to test infants for a tendency to violence, she has a serious point. Parents must be better informed about the storage and use of these samples.

People want control over their genetic information and that of their children, and they are not getting it. Some parents might have been given a leaflet and some may even have signed a form, but as a recent review shows, state regulation of newborn screening is a mess (M. H. Lewis et al. Pediatrics 127, 703–712; 2011).

Only a handful of US states have laws that expressly allow parents to opt out of having blood spots retained for study. At least two changed their regulations only after litigation. And the chance to opt out can be presented at an inopportune time, when parents could struggle to make a clear decision. Although many health officials worry that giving parents a choice will encourage them to refuse the screening, there is evidence that most parents asked for permission will allow their children's blood to be stored for future research (B. A. Tarini et al. Public Health Genomics 13, 125–130; 2010). And the potential for biomedical research at a population level is vast. That is why the US National Institutes of Health recently set up the Newborn Screening Translational Research Network, to share data between state repositories and researchers.

To be unclear about how newborn blood is collected and used is the fastest route to turn the public against sampling of newborns for any purpose — including screening programmes. Witness the debacle in Texas, where five million samples had to be destroyed after newspapers published evidence that the state was trying to conceal it was passing on newborn bloodspots to the military.

The best solution may be to explain more clearly to parents that the use of baby blood for screening and for research programmes are distinct, and to give them more choice about what is done with samples after screening has occurred. The state of Michigan does this already through its BioTrust for Health programme, which allows parents to change their minds later.

But there must also be a greater effort to inform and educate parents about the benefits of both newborn screening and biomedical research on anonymous blood spots. To be effective, this cannot be relegated to the period immediately before and after a child's delivery, and should instead be started earlier in pregnancy.

Making these changes will not be easy. The medical infrastructure is complex enough without adding steps and opportunities for people to decide on procedures à la carte. But if parents are not given choice, they will begin to demand it.