Maternity services in England and Wales have been "overwhelmed" by a rising number of births, including more complex cases, according to a new report.
The State of Maternity Services, from the Royal College of Midwives (RCM), says there is a failure in England "to adequately address the chronic shortage of midwives".
While more midwives are being employed "these are simply being eaten up by the record-breaking baby boom".
Midwives are also dealing with more complex cases, in part due to the rise in the number of older mothers giving birth.
The number of births in 2010 to women over 40 (27,731) was the highest since 1948. This age group has seen a 71% rise in births since 2001, the study said.
It added: "This ageing of mothers means greater demands on maternity services as pregnancies to older women are more likely to involve complications, which demand more of midwives and others in the maternity team.
"Combined therefore with the baby boom, this has a multiplying effect on the workload heaped on midwives."
Each of the four parts of the UK has experienced a rising number of births over the last decade.
In England, the number of births has risen 22% since 2001 - or more than 10,000 extra babies born every month.
Scotland and Northern Ireland, even with a rise in the number of births, broadly have a sufficiently large midwifery workforce, the report said. England and Wales on the other hand have been overwhelmed by the rising number of births.