(CNN) -- Had she been born a generation earlier, Kim Hoffman might have had a shotgun wedding. As it turned out, she and Steve Miller took the time to plan their dream nuptials -- outdoors, on an organic farm, and with their 10-month-old daughter in tow.

Kim Hoffman and Steve Miller pose on their September 2005 wedding day with 10-month-old daughter, Sadie.

A pre-marriage birth certainly wasn't what her father wanted for his only daughter, said Hoffman, of Oakland, California. But seven months into her relationship with Miller, the unplanned pregnancy simply changed life's course.

"We would have headed down this path. The pregnancy just accelerated things," she said of the couple's cohabitation, the birth of Sadie and their 2005 wedding. "It was the way it was meant to be."

Along with magazine-cover grabbers like Angelina Jolie and Bristol Palin, Hoffman, today a 39-year-old mother of three, is part of a now record-breaking trend of women who give birth outside of wedlock.

Nearly 40 percent of babies born in the United States in 2007 were delivered by unwed mothers, according to data released last month by the National Center for Health Statistics. The 1.7 million out-of-wedlock births, of 4.3 million total births, marked a more than 25 percent jump from five years before.

Statistics such as these, which include for the second year in a row a bump in teen pregnancies, after a 14-year decline, leave Sarah Brown concerned. She worries about the children born to unwed parents -- about the disadvantages they often face, including increased likelihood of poverty and greater high school dropout rates. See the number of out-of-wedlock births by race and age »

"I wish people spent as much time planning when to get pregnant, with whom, under what circumstances as they do planning their next vacation," said Brown, the CEO and founding director of The National Campaign to Prevent Teen and Unplanned Pregnancy. "The stigma [of out-of-wedlock births] has eroded, and these numbers made me feel perhaps it's disappeared altogether."

That stigma Brown speaks of, however, isn't one that LaShanda Henry, 28, or the women in her family before her, would have known. Her parents never married. And her grandmother only had a wedding when she was in her 60s.

So when Henry, of Greenville, North Carolina, and her boyfriend of now five years, Jean Paul, had Christopher two years ago, there was no pressure to race down the aisle.

"Culturally speaking" taking vows wasn't expected, said Henry, who runs the Black Moms Club, an online social network, and the Web-only Mahogany Momma Magazine. "Do we want to spend that money on a wedding or a house? ... I guess it's about priorities. I was never one of those girls that dreamed about the wedding dress."

What she said about cultural differences and expectations might help explain some of the numbers. Other data released last month showed the percentage of unwed mothers differs from race to race. While 28 percent of white women gave birth out of wedlock in 2007, nearly 72 percent of black women and more than 51 percent of Latinas did.

"With the publicity of our first family," meaning the Obamas, Henry said in a discussion group entry, marriage might "slowly become more of a norm for all."

Henry's experience also echoes what Paula England, a Stanford University sociology professor, learned when she co-edited "Unmarried Couples with Children," which was published in 2007. That book traced for four years 50 unmarried couples, the majority of them black or Latino, that had babies in 2000, and the findings shot down some of her predictions.

England assumed many of the fathers would have high-tailed it out of the picture by the sixth month of pregnancy, leaving single mothers "truly single," the sociologist said. Instead, she found that in 80 percent of the non-marital births, parents stayed romantically involved and in 50 percent of the cases they were living together.

Still, the bulk of responsibility often falls to the mother. According to a 2008 survey by the U.S. Census Bureau, there are 9.8 million single mothers versus 1.8 million single fathers.

Support groups, such as Sisters Helping Sisters, exist to help single moms, providing them with resources, tips and empathetic ears.

Founded in 1997, the Kansas City, Missouri, program was the brainchild of Teri Worton Brooks, now 39. She was in her early 20s when she found herself with a baby boy to take care of on her own.

"I had no clue how to raise him and no clue how to better my life," she said. "But I knew there was a sisterhood among women. ... We could learn from one another."

The bulk of babies born to unwed mothers may be unplanned, but that doesn't take into account lesbian couples or women who've decided to go it alone. For many of them, the decision is the result of years of thought and emotional soul-searching.

When California Cryobank, which claims to be the world's largest sperm bank, opened its doors in the late 1970s, 99 percent of its business catered to couples grappling with male infertility, spokesman Scott Brown said. Now, that market in the sperm donor world accounts for less than 14 percent, according to projections by Charles Sims, the organization's co-founder and medical director.

About 50,000 women delivering babies each year are single moms by choice, said Mikki Morrissette, author of "Choosing Single Motherhood: The Thinking Woman's Guide," and founder of the online resource Choice Moms.

Many of these mothers choose to tap known or anonymous sperm donors as the biological clock begins to pound. Perhaps they are like Morrissette, who divorced in her early 30s, wasn't in a hurry to jump into another relationship and decided to have kids on her own.

While she and many other single mothers by choice can afford this option, David Popenoe worries about the example they're setting in a society where children still benefit most from married parents, he said.

Other women might look at these single mothers by choice and say, "'So many people are doing it, why shouldn't I just go ahead?'" said Popenoe, founder and co-director of the National Marriage Project at Rutgers University in New Jersey. "It's part of a slippery slope."

Janet Kaufman wasn't looking to influence anyone else; her personal decision, after loads of research, became a "practical matter."

The University of Utah English professor was in her mid-30s, single and figured even if she met someone immediately it might be a couple years before she'd feel comfortable having a child with that man.

Her parents offered encouragement. In fact her father proposed the idea of a donor. And her friends stepped up in ways she described as "just extraordinary."

"I had some concerns and fears," said Kaufman, 44, who ended up marrying one year after she had a second child by the same anonymous donor. "But I felt like with the right kind of support ... somehow I would make it work."

After her daughter's arrival came the question of how to discuss this situation with a child. She found her answer -- talk about it early and often -- through someone in the widespread network, Single Mothers by Choice.

Kaufman began explaining before her daughter, and later son, could talk. She found books, bearing titles such as "A Family Like Yours," which she read frequently, and even penned a story of her own. She knew from the start that she would always be honest.

"I'm sure they'll have a lot of feelings as they grow up, but I don't want it to be complicated by my not being open with them," she said. "In communicating with them about their origins, I'm also communicating with them about me -- the hopes I had, the dreams I had ... It's important for them to know how much they were wanted."

All About National Center for Health Statistics • Pregnancy and Childbirth • U.S. Census Bureau