The chances of giving birth to a healthy baby after using in vitro fertilization [IVF] depend on various factors, including:
* Maternal age. The younger you are, the more likely you are to get pregnant and give birth to a healthy baby using your own eggs during IVF. Women age 41 and older are often counseled to consider using donor eggs during IVF to increase the chances of success.
* Embryo status. Transfer of embryos which are more developed is associated with higher pregnancy rates compared with less developed embryos (day two or three). However, not all embryos survive the development process. Talk with your doctor or other care provider about your specific situation.
* Reproductive history. Women who've previously given birth are more likely to be able to get pregnant using IVF than are women who've never given birth. Success rates are lower for women who've previously used IVF multiple times but didn't get pregnant.
* Cause of infertility. Having a normal supply of eggs increases your chances of being able to get pregnant using IVF. Women who have endometriosis are less likely to be able to get pregnant using IVF than are women who have unexplained infertility.
* Lifestyle factors. Women who smoke typically have fewer eggs retrieved during IVF and may miscarry more often. Smoking can lower a woman's chance of success using IVF by 50 percent. Obesity can decrease your chances of getting pregnant and having a baby. Use of alcohol, recreational drugs, excessive caffeine and certain medications also can be harmful.
Melissa Keylon was in her 20s when she made a decision not to have children.
"I had always wanted kids, but when my mother passed away in 1999, I just lost that feeling. I don't know why -- maybe depression or thinking there was no way I could do it without my mother. After a while I just got used to saying I didn't want kids," says Keylon, 42, a kindergarten teacher in Chattanooga.
But things changed about five years ago when one of her students accidentally called her "Mommy."
"The little ones do this quite often," she says. "It always made me smile when this happened, but this time it really tugged at my heart. It finally hit that the only time I would ever be called 'Mommy' would be by accident."
Keylon began to question her decision about not having a child.
"It took me way over a year before I told my husband that I wanted to come off birth control and try to have a baby," she says.
She hoped her husband, Dale Keylon, now 50 and the father of a grown daughter and grandfather of two, would support her decision. He did. More than a year later, she became pregnant. The Keylon's son, Grayson Everette, is due on Dec. 18, three days before his daddy turns 51.
Keylon is among a growing number of women in their 40s who are having babies, many for the first time, studies show. According to data from the National Center for Health Statistics, in American women ages 40 to 44, birthrates have hit their highest point since 1967. Births have also become increasingly common among women in their late 30s.
Dr. Rink Murray, a reproductive endocrinologist with Tennessee Reproductive Medicine on Shallowford Road, says he's seeing more women in their late 30s and 40s wanting children than when he began his practice in 2008.
"A lot of these women are waiting until their older to have children because they're delaying marriage, with the average marriage now starting when couples are in their 30s," Murray says. "Women are also developing their careers and postponing having children. And a lot of women, who already have children, are getting married to men who either don't have children and want children, or the couple wants to have children together."
National Center for Health Science data also show that, as the number of older women giving birth rises, younger women are less likely bear children. Younger women are still more likely to have babies than older women but, in 2011, birthrates hit record lows among teens and women in their early 20s, the center says.
Older motherhood is not a new phenomena. During the 1940s and '50s, when baby boomers were being born, fortysomething motherhood was common, with many women having the last of their three, four or more children well into middle age. But those numbers cratered during the '60s and '70s, when the baby boom ran its course.
Misty Heinsman, who is 46 and pregnant with twins due in November, says she wanted to have children with her second husband, Rich Heinsman, who didn't have children until she gave birth nine years ago to their daughter, Ellie. Misty, who has three grown children from her first marriage, is also the grandmother of granddaughters ages 3 and 1.
A registered nurse, she says she struggled at first with the idea of with "starting over" raising children.
"Being a grandmother of two, having older kids who would be more like aunts and uncle, I worried about how difficult this would be on my body and, of course, the health and well-being of the child," Heinsman says. "On the other hand, I have the most wonderful husband and father that wanted more. He took my first three children as his own, after I had been raising them by myself for many years, and loved them. We had a daughter together, and tried for more, but it didn't happen."
So they went to a fertility specialist.
"After a few months there and their guidance, we were told that only one egg had fertilized out of 13 and that the chances didn't look good," she recalls. "We went ahead with the implantation and waited for what seemed an eternity (six weeks). We had an ultrasound. To our shock and awe, there wasn't just one embryo, there were two. The one embryo had split into identical twin boys."
Like Heinsman, many older women are turning to in vitro fertilization, a process that, between 2003 and 2011, saw its numbers rise by 50 percent among women 41 and older, according to Society for Assisted Reproductive Technologies statistics.
Whether by natural methods or in vitro, the risks of a complicated pregnancy rises with age, but Murray says that staying physically active and being in good health greatly reduces potential problems.
"The older you get, the more opportunity you've had to develop diseases that can be exacerbated with pregnancy," including high blood pressure, excess weight and diabetes, among others, Murray says. "Pregnancy does put strain on the body and some women who are not healthy may not do well, but the vast majority of women who maintain their health do great."
There's no denying there's a risk for older mothers, Murray says, but even as the risk rises, it remains very small.
"The older you get, especially 35 and older, there is an increased risk of mortality (of the mother) during pregnancy," he says. "The risk when you're younger -- 7 in 100,000 young women die during pregnancy -- rises to 32 deaths in 100,000 for women 35 and older. One hundred thousand is a huge number. Pregnancy-related deaths, period, is a small number."
All women, regardless of their age, should be told the risks of pregnancy and make their decision based on the information, Murray says.
"The recommendation is you should offer testing to all women," he says. "We don't discriminate. There's not a magic cut-off age."
Despite their ages, Heinsman and Keylon haven't experienced severe complications with their pregnancies, although Heinsman acknowledges more discomfort this time around.
"I was in really good physical health before my pregnancy -- working out with a trainer, eating healthy," she says. "I have not had any issues with health, but a lot of discomfort (namely heartburn) and wanting to eat everything but I can't because of having no room. I can only sit for short periods of time due to losing circulation in my legs and needing relief from the four little feet that are kicking my ribs. I try to stay active, but it's hard."
For her part, Keylon says she's had "a great pregnancy," but she and her husband aren't taking any chances. They've gone to regular appointments with obstetricians, and even met with a genetics counselor.
"It was emotional hearing about all of the things that can go wrong and how those chances increase as you get older," she says. "We decided on a test called MaterniT21 instead of amniocentesis. We had the blood drawn that day and the results in one week. All is well with the baby and we also found out through this test that we were having a boy."
MaterniT21 is a new genetic blood test that tests the fetal cells circulating in the mother's blood and is less risky than amniocentesis.
"They actually are able to amplify the fetal DNA to figure out if the correct number of chromosomes are there," Dr. Melissa Lee, an obstetrician with Lee Memorial Health System in Fort Myers, Fla., told NBC. "More invasive testing such as amniocentesis have a higher risk of miscarriage, even if the risk overall is low.
"Unlike earlier tests, this one can be done as early as 10 weeks, when the fetus is a little more than an inch long," she says.
Heinsman advises women who are considering having children while in their 40s to do the research.
"Get all the facts and statistics -- not just with a woman's health issues during pregnancy, but seek the information on the quality of a woman's eggs after 40 to better understand the risks being taken," she says.
While some doctors may warn women about the risks of putting off motherhood to their 40s, studies show that older parents are more confident, less stressed and that their children do better on math and reading tests than children born to younger mothers.
Economist Amalia Miller at the University of Virginia calculated that, for every year a woman delays motherhood, she makes about 9 percent more in lifetime earnings. Delaying a baby for 10 years could nearly double a woman's lifetime income, Miller said.
"In some ways, I wish that we had decided to have a baby when we were younger, but now that it is happening, I wouldn't change a thing," Keylon says. "I believe that it was meant to happen now. We both have stable jobs. We are more financially stable than we have ever been. We have a home. We are not going to have to struggle like we would have had to when we were younger."
She and her husband began dating in 1992 and married in 1998, giving them more than 20 years of "just us," she says.
"We are more than ready to share our love and home with a child. We both know that things will change dramatically, but that's OK because of all the time that we have had of it just being us. I will continue to work. I love my job, my school, and my co-workers."
Heinsman says being in a place of financial stability at this time in her life is a "whole new world.
"We can provide whatever our children need with no hesitation. I didn't have that with my first three. I didn't get child support. I had wonderful people in my life that helped us."
For now, the Keylons have not yet discussed if they want more children.
"We are both just so happy that we are having this one," she says. "Our parents, both his and mine, are gone now. I'm quite sure that they would be over the moon happy about this baby."
But there have been comments from others.
"My husband has gotten more remarks about his age and starting our family than I have," she says. "I have only had one reaction that was especially hurtful. I know quite a few people who have had children in their late 30s and early 40s and none of them have any regrets."
Heinsman says she doesn't plan on having more children.
"I think if this was going to be a girl, then we would try one more time, but with a surrogate. But now, since we are having two boys, we are done. My work is cut out for me for the rest of my life," she says.
The Los Angeles Times contributed to this story.
Contact staff writer Karen Nazor Hill at khill@timesfree press.com or 423-757-6396.