One quarter of women (25%) are planning to take time out of their job at some point, with the main reason being to start a family, according to the report by Duncan Lawrie Private Bank.
But based on average salaries, a five-year career break could cause a woman to end up seeing her eventual pension fund shrink by £70,000 during a 40-year career, the study said.
One-fifth of women planning a career break said they had "no idea" how they were going to fund their time away from work.
The figures are based on a woman starting paying into a pension aged 25 and contributing 5% of her salary to a retirement fund each year.
Her starting salary would be £25,000, which would gradually increase over time.
After taking a career break aged in her early 30s, the woman would re-start her career on the same wage.
The survey of more than 2,000 people also found that 13% of men are planning to or are currently taking a career break - although more than half (53%) have already started setting money aside to cover the costs.
Richard Boyd, a chartered financial planner at the bank said: "For some, a pension might be one spinning plate too many to manage, but its importance cannot be underestimated. Those that do let the plate fall may live to regret their decision later down the line."
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