South Korea established the ban in 1987 to try to prevent abortions of female fetuses in a country where many prefer sons due to a Confucian belief that males carry on family lines.
However, the Constitutional Court ruled against the ban last month, saying South Korea has grown out of that preference for sons and the regulations restricts the basic rights of parents and doctors.
On Wednesday, 14 lawmakers - headed by the ruling Grand National Party's Rep. Lee Ju-young
- submitted a proposal that would allow doctors to tell parents genders of their unborn babies over 28 weeks old, said Kim Kwang-sup, an aide to Lee.
The proposal would still ban doctors' revelations of sexes of unborn babies under 28 weeks old to prevent abortions of babies with genders parents do not want, Kim said.
Kim said it is medically difficult to abort fetuses older than 28 weeks and there are health risks for mothers.
Abortion is illegal in South Korea but is widely practiced.
It was unclear when the National Assembly would vote on the proposal.
The court said the law should be revised by the end of next year. If the parliament fails to enact legislation reflecting the court's decision, the ban will be repealed, said Kim Bok-ki, a spokesman at the Constitutional Court.