American actress Marisa Tomei won an Academy Award for her work in the 1992 movie My Cousin Vinny. People laughed when they saw her film character telling a boyfriend that they need to get married. Why marriage? Because her biological clock is ticking and she wants a baby.

"Well I hate to bring it up because I know you got enough pressure on you already. But ... we agreed to get married as soon as you won your first case. Meanwhile, ten years later ... my niece ... the daughter of my sister is getting married. My biological clock is ticking like this (stomp, stomp, stomp) And the way this case is going ... I ain't never getting married."

"Lisa, I don't need this. I swear to God I don't need this right now."

Using it this way, a biological clock means the time in a woman's life when she is able to bear children. In the not-so-distant past, most people thought that when a woman reached her 40s it was too late for her to have children. The time on her biological clock had run out.

Well, that has changed. These days some women are resetting their biological clocks. They are giving themselves more time to have children.

Make no mistake. Being a "Single Mother by Choice" is very different from younger women who find themselves pregnant, perhaps not by choice.

Generally speaking, single mothers by choice are older and well educated. They are usually financially secure and successful in their careers. So, they have the money. What they may not have is a partner.

These women find themselves in their late 30s or early 40s, single and wanting children.

This is the place in life where writer Kerry Reichs found herself several years ago. She says she did not plan to become a single mother. She says she just did not find the right partner.

"Well, you certainly don't wake up when you're a ten year old girl and think, ‘Someday I want to be a single mother all by myself.' So, what it was, I think I had a set of standards for the partner I was looking for and I didn't meet anyone that fit those standards. And, at 39 I found myself single, without children and I wanted them very much. So, I made the difficult decision that I could do this on my own."

Kerry Reichs says part of the reason she wrote her latest book, What You Wish For, is to tell a story about people creating their own nontraditional families. These families look very different from the traditional mother-father-child structure. One character in the book is a successful woman in her 40s who is single and who wants a baby. Just like Ms. Reichs.

She says it was a difficult decision. It meant giving up on the idea, the fantasy, of having the "perfect" family. In the end, she decided that she had the resources and the temperament, or mental ability to do it.

"It's difficult because you're letting go of the fantasy of the life you thought you would have – the husband, the house in the suburbs, the dog, and the partner in raising this child. You don't want to damage your kid. You really have to think carefully if you have the resources and the temperament to do it. And I did. I always wanted a kid more than the house, more than the husband, more than anything."

The National Center for Health Statistics is a division of the U.S. Centers for Disease Control and Prevention. In January, the Center published a report on births in the United States. The report states that the birth rate for women aged 40–44 generally has risen over the past 30 years.

The number of births to women aged 45–49 rose 14% in 2013, compared to the number in 2012. The birth rate for women aged 49 and over also rose in 2013 from one year earlier.

The report states that the increase in birth rates for women aged 35 and over during the last 20 years has been linked, in part, to medical developments. Modern medicine now makes it easier to get pregnant.

Helping women become mothers has become big business. There are adoption organizations for a woman who wants to care for someone else's child legally as her own.

For the women who want to get pregnant, there are fertility centers with doctors who can help. Kerry Reichs chose to get pregnant from an anonymous sperm donor. She says the experience was surreal, too strange to be real.

"It's very surreal ... selecting a sperm donor. It's a little bit like going on an online dating site to pick someone ... except you're never going to meet (him) but (he) will be the father of your children ... which is totally crazy."

There have also been changes in U.S. public opinion toward unmarried women having children. There is no longer a social stigma on a woman having a baby without a partner. But single mothers by choice do have their critics. Conservative groups and social commentators say that choosing to become a single mom is not good for the child, families or society.

"No, and one of the things you're seeing in the contemporary political debate in America is some accusations that single mothers are destroying the fabric of our society. I'm personally going to destroy the government as we know it by being a single mother."

Kerry Reichs says this is not a decision women come to easily. She says for many if not most women this is a decision of last resort, meaning there are no other choices for them.

"In telling this story in What You Wish For I really want to share the amount of gravitas that goes into the decision making. This is not a decision that any woman makes lightly. This is really a decision of last resort -- nothing cavalier about it. And I wanted to capture the stark fear but also optimism and confidence that goes into it. And to encourage every woman who find themselves in that difficult place of facing a biological clock but no partner that this is something that they can consider. That every person can consider."

Kerry Reichs is now pregnant with her second child.

I'm Anna Matteo.