Hundreds of thousands of babies who died in the womb could have been missed out of international estimates on stillbirths, research suggests.

According to figures for 2015, an estimated 2.6 million babies a year worldwide are stillborn – dying at a point in pregnancy when most babies would survive outside the womb.

However, while the World Health Organization recommends countries collect stillbirth data from 22 weeks of pregnancy onwards, only data from 28 weeks or more is used for international comparisons and estimates.

Now research published in the Lancet shows this threshold means a huge number of stillbirths that occur earlier in pregnancy are not being recognised, with data from Europe revealing international estimates could be around 50% higher, at least for high-income countries, if stillbirths from 22 weeks are included.

“This work was to emphasise how many parents’ losses are not being acknowledged by the standard rates and also to look at stillbirths at those early in gestation,” said Dr Lucy Smith, first author of the research from the University of Leicester. “If we don’t have data on them, we can’t look at how we can design interventions to reduce those early gestation stillbirths – and they may have different causes of death, or different patterns.”

The study examined national data from 19 countries across Europe, and looked at stillbirths at different gestational ages from 22 weeks between 2004 and 2015.

Stillbirth rates varied from country to country – particularly before 24 weeks – and a handful of countries included late terminations in their data. Three, including England, did not have data for stillbirths before 24 weeks.

Nonetheless, the findings reveal that in 2015 alone more than 3,000 stillbirths occurred in Europe between 22 and 28 weeks of pregnancy, accounting, overall, for 32% of all stillbirths at or after 22 weeks.

The authors say gestational age used for international comparisons and estimates should be lowered to 24 weeks, and that countries should do better at collecting data from 22 weeks to allow researchers to better probe trends.

Prof Joy Lawn, of the London School of Hygiene and Tropical Medicine, who co-authored an accompanying commentary, said global figures for stillbirths could be 30-50% higher than current estimates if stillbirths from 22 weeks gestation are included.

“People have this idea that stillbirths are just meant to be and they happen quietly and nobody counts them. [But] we can count them, we can compare and it is a huge number,” she said, adding that many stillbirths are preventable.

“Part of the problem for stillbirths, especially the earlier ones, is if we don’t count them and don’t look at the trends, people don’t invest in changing them.”

But, she added, comparing data from 22 weeks could be difficult for low-income countries where babies are less likely to survive outside the womb at early gestational ages, and where data collection is already challenging.

Separate research, also published in the Lancet, explored the possibility of reducing the rate of stillbirth, based on raising awareness of foetal movement – an approach that has shown promise in Norway.

“One in 200 pregnancies ends in stillbirth in the UK and [it’s] clearly devastating for absolutely everybody involved and the wider family as well,” said Prof Jane Norman, first author of the study from the University of Edinburgh.

The study, involving 33 hospitals and more than 400,000 pregnancies over a two-year period from January 2014, investigated the impact of encouraging women to be aware of the movements of their baby in the womb and report any changes quickly so prompt identification, management and, if necessary, delivery of babies at risk of stillbirth could be carried out, with clinicians also given boosted advice.

However, after taking into account factors including maternal age, the researchers found the programme produced no significant reduction in the rate of stillbirths at 22 weeks gestation or later.

With the expectations high at the outset, the researchers say the study was not geared to confidently show only a small benefit, that not everyone might have stuck to the new programme, and that women might already have been looking out for reduced foetal movement.

The team say awareness and reporting of reductions in foetal movement is still important – it is already part of the NHS Saving Babies’ Lives Care Bundle.

But Lawn said the study suggests better monitoring of pregnancies is required by healthcare services.

“When a baby is in utero and they stop moving, you have probably already missed the event. The critical thing is more surveillance in pregnancy,” she said, adding that it is important women don’t feel blamed or stigmatised for a stillbirth.

But, she said, falling rates of stillbirths suggest improvements can still be made: “It is not ‘if this doesn’t work, nothing works’.”