LONDON — The Delta variant of COVID-19 is dominating cases worldwide, and health officials in some countries are sounding alarm over its impact on pregnant women.

Several of England's top health officials issued a joint statement on Friday urging pregnant women to get vaccinated against the coronavirus. They pointed to new data showing that 98% of expectant mothers admitted to the hospital with Covid-19 in the country since May were unvaccinated.

The World Health Organization (WHO) has also previously said that infected, pregnant women face an increased risk of developing severe COVID-19 compared with non-pregnant women of a similar age.

One concern is that risk might be even higher with the Delta strain, which has been shown to be more contagious and can cause more severe disease compared to the earlier variants of the virus.

The latest data gathered by the UK Obstetric Surveillance System (UKOSS) showed the number of pregnant women that are being admitted to hospital with COVID-19 is increasing in the UK due to the Delta strain.

"Compared to the original Covid virus the new variants (alpha and then delta) caused progressively more severe disease in pregnant women," Andrew Shennan, professor of obstetrics at King's College London, said in a statement to the UK's Science Media Centre.

"This included need for ventilation, intensive care admission and pneumonia, more than 50% more likely to occur," he added.

The data collected by UKOSS show that around 33% of women in hospital with COVID-19 needed respiratory support and that 15% needed intensive care.

The UKOSS data only includes pregnant women. However, the group said that while the increase in hospitalizations was broadly in line with the current rise in COVID-19 hospital admissions in the UK's general population, the data highlights an increase among pregnant women needing care for acute symptoms. — CNN