It's that awkward question that many couples often hear: 'When are you having a baby?' It can pop up at dinner parties, family celebrations or even the grocery store.

But now more than ever, women are waiting longer to have their first child.

According to the Pew Research Center, in 1990 there were more births to teenagers than to women 35 and older. By 2008, the numbers reversed with 14 percent of births happening among older women and 10 percent in teens.

Today, one in five women has her first child after 35. So why are all these women waiting to have a baby?

There are many different reasons, says Dr. Natalie Gregory, a physician at Lowcountry OB/GYN. 'Primarily the same reasons I waited, too,' admits the 35-year-old mom of two who had her first daughter at 32.

"Women are going farther with education and getting more demanding jobs. We are getting married later in life," Gregory says. "We are focusing on our careers and relationships, buying homes, traveling, saving money and becoming successful in other ways prior to becoming mothers."

Heather Antos agrees. Antos gave birth to her first daughter, Elliot, in November at age 36. Married to her husband, Ron, since 2004, the couple were open to having kids but weren't interested in starting right away.

"I wanted to feel financially secure and as ready as possible to support our family and to save for her future," she says. "We love to travel and we wanted to go as many places as we could. I also knew the kind of mom that I wanted to be was a model of my mom. I want to be involved in everything with Elliot, and I knew that in my earlier years, I wasn't ready to be devoted like that."

When they made their decision to try to conceive, Antos heard a medical description that made her wince. "I was told often that I'm of ‘advanced maternal age.'"

Gregory, who often sees women in their 30s and 40s having their first child, warns all of her patients that fertility starts to decrease in the early 30s. 'It may take longer to conceive after the mid-30s since ovulation can be less regular. Women in this age range may have had issues with fibroids, abnormal Pap smears, infections, endometriosis or prior surgeries that could make conceiving and carrying a pregnancy to term more difficult.'

For former television anchor Cathy O'Hara Harrison, her passion for her career is what kept her from having children in her earlier years. Harrison married her husband, Kevin, in 1996 but didn't consider having children until much later, and her road to having children wasn't so easy.

At 40, she decided it was time to start trying. "One day, that gong went off and I wanted to have a child," says Harrison, who turns 50 this year. "I saw my contemporaries having children, and we started to try but found out I had endometriosis. Instead of in vitro, we decided to adopt."

The two adopted their first daughter, Maisie, in 2004 and their second daughter, Juliette, in 2008.

"Everything took a back seat to my career in the earlier stages and then as I got older, I began to realize what you do as a profession is not as important as who you want to be on the inside. As my love affair for all things news started to wane, I came into my own. I wanted to be a positive person and I started to change. I saw a shift,' she says. 'Had I had a child in my 20s, it would have been a disaster."

Today, Harrison works full-time for a national travel website and admits she's gained more wisdom and patience as she's gotten older, which helps her to be a better parent.

"Being an older parent, I don't want to be out dancing or hitting the town. I love nothing more than spending time with my girls making crafts, baking and just being with them," Harrison says.

How does she feel when she's on the playground with younger moms? "I admire young moms; parenting is a hard job no matter what. They don't make me feel any different. I think mothers have a bond that no matter what, you will find something to talk about."

Gregory often hears concerns from her patients about being the 'old mom' at the playground, but she focuses on the bright side.

"I see (older moms) thankful for having waited for the perfect man to be the father of their child. I see women who thought they would never have children blossom into amazing mothers later in life," says Gregory. "Mostly, I hear the same thing from all mothers, regardless of when women have their babies, that it is the most rewarding, difficult, demanding, awesome, fulfilling and life-changing thing they have ever done."

Like Harrison and Antos, Vladia Jurcova Spencer, a 37-year-old public relations agency owner, didn't feel ready in her 20s to have a child and is thrilled she waited to have her son, Oliver, who will turn 2 this year. Her pregnancy was easy, but her physicians made sure she was aware of the complications. But they couldn't prepare her for what parenting would truly be like.

"I was not prepared for how hard being a parent is. I am still learning every day. Being a mom is a full-time job,' says Spencer, who worked in high-pressure public relations posts. 'I have held some intense positions ... but none was as demanding as being a mom. But it is all worth it."

Now Spencer works from home and can enjoy time at the park with her son and husband Anthony. She would not have it any other way.

"Since many of my friends are mothers over 35, I know now that we can have it all: career, business, baby, family, travel and fun. It's OK to wait," Spencer says.

If you're thinking of starting a family in your 30s or 40s, here's Antos' advice: "Don't believe the hype and don't let yourself get caught up in being classified as advanced maternal age. It doesn't mean you can't have a child."

Ryan Nelson is on Twitter @Ryan_NelsonSC, Facebook and Google Plus.