NEW YORK (CNNMoney) -- After undergoing two costly rounds of in vitro fertilization a few years ago, Laura Whitlinger, now 46, was thrilled when she saw the images of two babies appear on her sonogram. But it didn't take long before she and her husband realized that this double blessing came with some very serious financial implications.
"The fact that they will be going off to college when I am 62 is frequently at the forefront of my mind. I will be 66 when they are done," said Whitlinger of her two-year-old twins. "It's overwhelming to think about. I think 70 is a more realistic retirement number now."
Getting pregnant in the first place had already dramatically drained the Whitlinger's savings, with each round of in vitro costing $20,000 (including medication).
"When you see 40-plus women in Hollywood having babies it looks so easy, but it's not. We had to make a complete lifestyle change to try to make this work," she said.
After giving birth to the twins, Lyle and Wyatt, the couple relocated from the small farm in Oregon, where they grew wine grapes, to Manhattan where Whitlinger's husband found a higher-paying job in health care that could help support them all.
Whitlinger, meanwhile, is staying home with her kids and watching her IRA languish. She hopes to pick up some freelance writing work and start contributing to her retirement savings again once the kids start school, but that's a few years down the road. Her husband, however, has just started putting money into a 401(k) at his new job, but it is far from enough.
Old moms, new problems
This tricky predicament is becoming increasingly common. Over the past couple years, a growing number of women have been postponing pregnancy into their late 30s, 40s and sometimes even 50s in order to pursue careers or to become more financially stable.
While birth rates among women under the age of 30 have declined over the past 10 years, births among women above the age of 40 are at the highest level in decades, according to the most recent data from the National Center for Health Statistics.
And because women older than 35 have a higher risk of giving birth to twins -- thanks in part to their age and to fertilization treatments like in vitro -- many of the women who wait until later in life to get pregnant find themselves not just with one, but two or three or four bundles of joy.
As a result of this and other factors, the U.S. multiple birth rate has surged by more than 70% from 1980 to 2008, according to the National Center for Health Statistics. Three decades ago, there was a pair of twins born for every 53 births. In 2008, it was one out of every 31 births.
And with every child costing an average of $226,920 to raise to the age of 18 (not including college costs), multiplying that by two, three, or even four can put a serious dent in one's nest egg -- especially at an age when you're supposed to be contributing about 15% or more of your income toward retirement savings.
Chelsea Gladden, 38, already had three children and had been taking time off of work to raise them, when she unexpectedly got pregnant for a fourth time -- with twins.
She and her husband had already dipped into their retirement savings much more frequently than they would have liked. Now she expects to have to work for the rest of her life in order to keep up with the medical bills, ballet classes, guitar lessons and school expenses that they inevitably face.
But Gladden still doesn't regret the unexpected retirement roadblock.
"The pregnancy was quite the surprise and now having the twins is amazing," she said. "I can't imagine our family without them."
Making it work
The good news, said Lule Demmissie, managing director of investment products and retirement at TD Ameritrade, is that aspiring mothers are becoming much more aware of the increased chance of multiple births when giving birth later in life, she said.
"The octo-mom syndrome is already out of the closet," she said. "Women are having responsible discussions about these procedures, and there's much more awareness about what doing it could mean, instead of treating it like the lotto."
When you're surprised by an extra child or two, Demmissie says there are many "course corrections" you can make to avoid sucking your retirement savings dry.
"You have to say to yourself, can I afford where I'm living? Can I afford the plan I had for my children's education? Can I correct some of my own current expenditures? Maybe I was planning on buying an Audi and being more plush with my spending -- now it's time to reconsider that," she said.
If you were expecting one child and had saved up enough money for private school or college, you may have to consider public schools or cheaper options after you have an extra child to support, she said.
And of course, working a little longer won't hurt your nest egg either.
"People are already working longer for many reasons ... so having another child is like a pressure cooker impact, and may cause people to work even longer," said Demmissie. "In the end, it's always a balance sheet discussion to figure out how to make it work -- it's never too late to correct your plans." 
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