More than 1,000 women in England and Wales take legal action every year claiming they were sacked for being pregnant, according to new research.
A new report by the Equal Opportunities Commission (EOC) into pregnancy discrimination in the workplace, published to mark the start of National Pregnancy Week, claims that women will continue to get a raw deal unless the Government acts to give more support to families and employers and improve awareness of the law.
The report found that pregnant women faced pay cuts, demotion, hostile treatment and unsafe working conditions.
The EOC has also found that more than a quarter of employers cannot cite a single statutory entitlement for pregnant women and that more than a third feel that pregnancy is "an undue cost burden on the organisation".
EOC Chair Julie Mellor said: "Our investigation has discovered that while the great majority of employers who know the law think it is fair, there are huge holes in many people's understanding.
"Some employers knowingly flout the law but many simply don't know what their responsibilities are or what help with costs is already available from the Government.
"It's not just families that benefit when pregnancy at work is managed successfully Ė it's in everyone's interests. Most families now rely on two incomes. Women make up nearly half of the workforce and make a major contribution to the success of individual businesses and the economy."
Almost a quarter of women who made an employment tribunal claim were dismissed within hours or days of telling their employer they were pregnant, while one in five who returned to work for the same employer after maternity leave returned to a lower grade or level of job.
Sex discrimination claims are estimated to have cost Britain's employers £4.3m last year
Among the women interviewed for the report was a former sales executive for a major national IT company who told the EOC: "I went from being the top salesperson in the company to being a liability. They weren't prepared to put in the time and effort that is needed to help the comeback. If they had, I'd have gone back to being the top salesperson"
Another woman said that after she announced her pregnancy, her manager told her: "You silly girl. Have you considered an abortion?"
The EOC called on the government to offer more support to employers and families, and to ensure that the law is properly followed.
Among the ideas that the EOC is exploring is asking the state to provide financial support for small businesses to spread the costs of pregnancy more equitably and remove some of their fears.