Child deaths and maternal mortality rates have declined significantly since 2000, a report from a group of United Nations entities said on Thursday.

"Since 2000, child deaths have reduced by nearly half and maternal deaths by over one-third, mostly due to improved access to affordable, quality health services," said the report from the UN children's agency (UNICEF), the World Health Organization, the UN Population Division and the World Bank, known as the UN Inter-agency Group for Child Mortality Estimation.

Still, the new estimates show 6.2 million children under the age of 15 died in 2018, and over 290,000 women died due to complications during pregnancy and childbirth in 2017.

The report said that of the total child deaths, 5.3 million occurred in the first five years, with almost half of them in the first month of life.

Women and newborns are most vulnerable during and immediately after childbirth. It's estimated that 2.8 million pregnant women and newborns die every year, or one in every 11 seconds, mainly of preventable causes.

Children face the highest risk of dying in the first month, especially if they are born too soon or too small, have complications during birth, congenital defects, or contract infections, the report said.

About a third of the deaths occur within the first day and nearly three quarters in the first week alone.