The proposal would protect women's jobs during and after maternity leave
The European Commission has proposed extending fully-paid maternity leave from 14 weeks to 18 weeks.
The commission, the EU's executive, also said the same maternity benefits should apply to self-employed women.
The commission said longer maternity leave would encourage women to return to work after having children.
Critics have said small businesses will struggle to meet the costs and that national governments should decide on such matters, not the EU.
Maternity leave currently varies from 14 weeks in Germany to 18 months in Sweden, with many countries offering less than 18 weeks.
The proposed new rules would guarantee that women in the 27 EU countries would not be sacked during or immediately after maternity leave.
Governments would be free to offer new mothers more time off, but would have to pay them at least as much as sick leave.
"Our proposals to improve maternity leave will help women to combine work and family life, improving their and their family's quality of life," said EU Social Affairs Commissioner Vladimir Spidla.
Mr Spidla also said encouraging mothers back into work would help offset Europe's ageing work force.
But it is not up to "Brussels to tell British mothers and fathers how much leave they should take," said Conservative MEP Philip Bushill-Matthews.
"Small businesses will struggle to afford this extra cost," said Mr Bushill-Matthews, the Conservative employment spokesman in the European Parliament.
"Ultimately some of the smallest businesses may think twice about employing young women through fear of them going on maternity leave," he said.