The Department for Education and Employment has confirmed that the proposal is in response to cases such as that of Diane Blood, who fought a three-year legal battle for the right to be inseminated with her dead husband's sperm.
In common with some other occupational pension schemes, the teachers' scheme has long provided benefits for teachers' children. The proposed regulation would require a teacher's natural child to be born no more than 12 months after the death.
The unions have protested to the Government. Barry Fawcett, secretary to the teachers' panel on the pensions working group, said it would be unfair to expect a woman who had survived a car crash which had killed her partner to decide within three months whether to use his sperm.
He added: "The numbers are clearly going to be tiny. The principle of refusing children's benefits in these situations is appalling. It can't be justified on cost grounds."
A DFEE spokesman confirmed the regulation was drawn up "in view of frozen embryos and the possibility that children might be born some 10 ears after the death of the parent".
But he said it was too early to comment on other concerns which were raised by unions in a letter from the teachers' panel of the pensions working group. This is their last chance to have their say on the regulations, due for parliamentary approval in March.
The unions have scored one victory, with the DFEE agreeing that teachers who leave early on a reduced pension will not be penalised if they go back to work and start contributing again.
But they fear these teachers will not be allowed to buy into "top up" schemes, where they can purchase additional years of service to top up their benefits - even though there would be no cost to the pension scheme.
Marion Bird of the Association of Teachers and Lecturers fears the measure could discriminate against women and warned the union would take legal action if so.
The unions also fear teachers who have retired at the normal age may also have their pensions reduced as a result of subsequent earnings or purchase of "top ups". Another rule change could mean that the families of teachers who die in service will not get the full amount of any "additional voluntary contributions" those teachers have made.