A third of mothers surveyed for a new study have reported suffering a crisis pregnancy.
Up to 30% of those experienced unfair treatment at work while pregnant, while almost half said financial worries added to the crisis, the research found.
Some 2,300 mothers across the country were quizzed on a range of areas, including the attitude of their employers, maternity leave and how they were treated on returning to their job.
The Economic and Social Research Institute's (ESRI) Dr Helen Russell, one of the study's authors, said a significant minority of pregnant women faced unfavourable treatment at the hands of employers.
"This includes inappropriate workloads, loss of salary or bonuses, denial of promotion through to dismissal," Dr Russell said. "Such experiences can have significant financial, emotional and health costs for the women involved."
Crisis pregnancy refers to either an unplanned pregnancy or a planned pregnancy that has become a serious problem to the woman because of a range of concerns, including desertion by the father, lack of support from parents or financial difficulties.
The joint Health Service Executive and Equality Authority research, prepared by the ESRI, is the first nationally representative survey of women's experiences at work during and after pregnancy.
The survey also found women who earned more, were better educated and had an employed partner were more likely to take longer maternity leave and receive top-up payments from employers.
Women with lower wages took less maternity leave as financial pressures forced them back to work. And 21% of women who returned to work after pregnancy felt their opportunities for training had decreased.
The Irish Congress of Trade Unions (Ictu) said discrimination in the workplace must be tackled. David Joyce, equality officer, said: "The report is welcome as it provides clear evidence that discrimination is alive and well in the Irish workplace and provides us with an opportunity to finally end these practices."