Some midwives believe pregnancy itself could be the trigger

The same number said they knew at least one expectant mother who was a victim of domestic violence.

Many felt they lacked the time and training to deal with those cases, the survey of 700 midwives found.

The Royal College of Midwives' Frances Day-Stirk said domestic violence in pregnancy was a major health issue and early intervention was needed.

Experts think domestic violence may be one of the most common pregnancy complications.

"This is an increasingly common occurrence and complication rather than a rare event," she said.

Lack of time

"Domestic violence in pregnancy is a major health issue, requiring early interventions to prevent further harm to the mother and unborn baby."

VIOLENCE HELPLINE Free 24-hour National Domestic Violence Helpline: 0808 2000 247

Gill Aston is a midwife with more than 20 years' experience and a lecturer at Kings College, University of London.

In the course of her work, she said she had seen bruised women who maintained they fell down the stairs and women with bruising who had been kicked in their pregnant abdomen.

Midwives must pick up on physical and behavioural hints and clues, she said, allow pregnant women to talk, and secure help for them.

Those figures are the tip of the iceberg because most people don't report it Gill Aston Midwife

The research figures were likely to be an underestimate of the true situation, she believes, as 25% of women experience abuse in their lifetime.

"Often women don't disclose. Sometimes behavioural cues are missed and even injuries can be missed," she said.

"Those figures are only the tip of the iceberg because most people don't report it to the authorities or the police."

All health professionals who deal with women during pregnancy - GPs, health visitors and midwives - must work together to help, she said.

'Shocking'

Of the midwives asked, 88% thought it was part of their job to provide the right support and information to violence victims but more than a quarter said they lacked the right training.

Dr Aston said time, training, having someone to refer cases to, and the national shortage of midwives all had an impact.

Although 10% of midwives who took part in the survey felt pregnancy could be a trigger to violence, Dr Aston said the major risk factor for women was already experiencing abuse before pregnancy.

Sandra Horley, of domestic violence victim support charity Refuge said: "These figures are shocking and unacceptable, but they are the reality.

"A violent pregnancy is a high-risk one. All parties must work together to ensure that the safety of the woman and her unborn child are the number one priority."

The research was conducted as part of a Home Office campaign to raise awareness of the 24-hour National Domestic Violence Helpline on 0808 2000 247.