Just be prepared for a mountain of work.

"Do it! I'm glad I've done it," said record-breaking mom Janet Maslin-Bosher, now 60, who lives in west London with her toddlers, Sarah and James, born in September 2002.

Maslin-Bosher is the oldest woman ever to have twins.

New Yorker Aleta St. James is expected to give birth to twins today, three days before her 57th birthday. That would be a U.S. record.

Like any mom, Maslin-Bosher is proud, telling the Daily News yesterday that Sarah and James are "delightful, cheeky, alert, intelligent" kids.

But everything hasn't been easy: Her partner, Martin Maslin, died of a heart attack at 64, five months after the birth.

Maslin-Bosher, a former nanny and day-care worker, said nothing prepared her for the shock of having her own kids. "Fourteen nappies [diapers] a day, it's given me repetitive strain injury," she said.

"I do more than most young mothers do. I'm Superwoman!" she said with a laugh.

But even a woman of steel needs some help.

A baby-sitter takes the twins three days a week for a few hours while Maslin-Bosher studies antiques restoration. "It keeps me sane," she said. "You must have space for yourself."

Judith Bershak of Los Angeles, who had her daughter, Sarah Cook, at 50, agreed. "Don't think you can do it all single-handed," said Bershak, now 58.

But she has made adjustments. "I taught in the inner city. I couldn't do that and come home and be Super Mom, so I retired in 2002," Bershak said.

Her husband, David Cook, a deputy attorney general, is the breadwinner. He turns 39 tomorrow. She advised St. James to have a chiropractor lined up for back problems, accept all help offered - and ignore talk she's too old for motherhood.

"I hate when people say it's not natural to have a child at this age. What's natural? ... Talk of 'natural' is stupid," Bershak said.

Some doctors, however, question the wisdom of using donated eggs to, in effect, prolong a woman's reproductive years.

"You have to consider the issue of having a child come into the world when the healthy life span of the mother is uncertain," said Dr. Frederick Licciardi, director of egg donation at the New York University School of Medicine.

His program sets the pregnancy deadline at 50.

Barbara Brennan of Tennessee was 53 when she gave birth to twins in May as a surrogate mother for her daughter.

The reward of presenting her daughter with beautiful, healthy twins, Meredith and Pryce, was worth any pain, Brennan said.

"We are happy, well-adjusted people who are bringing children into the world for all the right reasons," she said. "It wouldn't happen if it was against nature."