Maternity units have been urged to investigate after figures revealed differences in care for mothers and babies across Britain.
Findings of the National Maternity and Perinatal Audit (NMPA), the largest of its kind in the world, show the vast majority of women in England, Wales and Scotland have a safe birth.
But the number of babies requiring additional support and mothers experiencing adverse outcomes such as bleeding and severe tears differ across services.
The Royal College of Obstetricians and Gynaecologists (RCOG) said while some disparity in care is expected, "unwarranted or unexplained" differences should be investigated.
The data, which covered 696,738 births between April 2015 and March 2016, showed 3.5% of women sustained third or fourth degree perineal tears during vaginal births.
But this figure ranged from 0.6% to 6.5% across maternity services.
While hospitals reported 1.2% of babies in Britain required additional support in the minutes after they were born, some units recorded figures as low as 0.3% and others as high as 3.5%.
In England and Wales, 2.7% of women giving birth experienced a major haemorrhage. This figure ranged from 1.1% to 5.6% of women across services in the two countries.
Professor Lesley Regan, president of the RCOG, said: "While the UK is a safe place for women giving birth, this report shows variation in care and outcomes for women and babies in maternity services in Britain.
"Some variation is expected and can drive new improvements, but unwarranted or unexplained variation requires investigation.
"We urge all maternity units to examine their own results and those of their neighbours both to identify role models and to drive quality improvement locally."
The data, which was collected from 149 of 155 NHS trusts and boards providing care in England, Wales and Scotland, covered approximately 92% of births during the period.
The audit noted that some variations can be attributed to differences in data quality, completeness and the risk profile of women in different units.
Jan van der Meulen, professor of clinical epidemiology at London School of Hygiene and Tropical Medicine (LSHTM) and chair of the project, said: "This national audit, the largest of its kind in the world, makes it possible for the first time to compare the care that maternity units in England, Scotland and Wales provide to 750,000 pregnant women and their babies each year.
"In some hospitals, the quality of the clinical data needs to be further improved so that the audit can provide an accurate picture of the care that they provide.
"The audit's results will be a great help to improve the quality of maternity services."
The NMPA was commissioned by the Healthcare Quality Improvement Partnership on behalf of NHS England, the Welsh government and the Health Department of the Scottish government.
It is a collaboration between RCOG, the Royal College of Midwives, the Royal College of Paediatrics and Child Health and the LSHTM.
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