One woman was on her second career and married to a man who already had children. She was certain she didn't want a child of her own. Then she hit 45, and suddenly having a baby was the only thing that mattered.
Other women were busy with medical, law or graduate school and then long hours at the office. Their 40s just seemed to sneak up on them.
Some of them spent years looking for a partner before choosing to become a single mother, or needed time to get used to the idea of a lesbian couple having a child.
Dr. Ingrid A. Rodi, a Santa Monica fertility specialist, understands why many of her patients have delayed childbearing until their 40s. At 53, she has lived through the social and medical revolutions fueling today's over-40 baby boom.
"Egg donation and fertility treatments make having children in your 40s more possible," she said. "But you start getting into progressive difficulties for mother and child."
The advice Rodi dispenses hasn't changed that much from that given to her own mother more than 50 years ago: If you're in your early 30s and want to have children, it's best to get the show on the road.
Not everyone, she said, welcomes the warning.
Although they make up only about 5% of overall births in California, births for U.S.-born women ages 40 to 44 have increased threefold since 1982, according to a recently published analysis from the Public Policy Institute of California, a nonpartisan think tank. Societal changes such as better educational and career opportunities for women are common reasons for delaying childbearing, said demographer Hans P. Johnson, the report's author.
But with those births comes greater risk.
Older mothers are more likely to develop high blood pressure and gestational diabetes and to give birth to premature and low- birth-weight babies. Even the use of donor eggs does not guarantee a healthy child -- or pregnancy itself.
Women begin to have fertility problems about 10 to 15 years before they experience menopause, Rodi said. The average age of menopause is 50 to 52, but it can range from 40 to 60. Women have no way of knowing for sure at what point in the spectrum they'll fall.
A string of well-publicized celebrity post-40 pregnancies makes it look easy: In February, "Desperate Housewives" star Marcia Cross gave birth to twins; actress Holly Hunter became a mother of twins last year; and Geena Davis had her twins in 2004.
But even in vitro fertilization rates decline with age when older women use their own eggs. (The newest fertility breakthrough, announced this year, may allow younger women to freeze eggs for use later.) According to the U.S. Centers for Disease Control and Prevention, the average chance for a 40-year-old woman undergoing assisted reproductive therapy to become pregnant using her own eggs was 23%, and to successfully carry the pregnancy through to birth, about 16%. Both rates dropped steadily with each one-year increase in age.
Using donor eggs, however, raises the chances for a successful live birth to 51% for women over 40, according to the CDC.
"Because it's so reliable, the number of women getting egg donation is going up every year," Rodi said. "And that is contributing significantly to the number of pregnancies in women in their 40s."
Donor eggs also eliminate some of the risks associated with older childbearing, said Dr. Richard Paulson, chief of the Division of Reproductive Endocrinology and Infertility at USC's Keck School of Medicine and a pioneer of egg donation. Aging eggs not only contribute to infertility and miscarriages but are more likely to have chromosomal abnormalities.
Despite the advantages of using donor eggs, admitting to doing so is one of the few remaining reproductive taboos -- among celebrity and regular moms alike.
And donor eggs aren't foolproof -- nor are they cheap. Treatment can cost from $10,000 to more than $25,000 per attempt, with high-demand donors such as Ivy League graduates and models commanding higher fees.
What's more, "virtually every complication associated with obstetrics is increased with increased maternal age, if you look at it statistically," Paulson said.
"But most of us believe that if women get good prenatal care and are carefully followed, the outcome is very good."
Dr. Alan R. Fleischman, medical director for the March of Dimes, an organization primarily concerned with the eradication of birth defects, is less optimistic.
"All of the complications of pregnancy -- high blood pressure, preeclampsia [a rapidly progressing hypertension that affects mother and fetus], fetal death, prematurity, low birth weight -- occur at higher rates in older women than in younger women," he said. "That's true with or without assisted reproductive technologies."
A 2004 study of Swedish women found the rate of premature births for women ages 40 to 44 to be 150% higher than for women 20 to 29, Fleischman said.
Prematurity is the leading cause of infant mortality in the United States, accounting for more than a third of all infant deaths, according to the CDC. Even those born just a few weeks early -- from 34 to 36 weeks -- are six times more likely than full-term babies to die during their first week, according to a study by the March of Dimes published in the November Journal of Pediatrics.
These babies are also at greater risk of breathing problems, feeding difficulties and trouble regulating body temperatures, Fleischman said. Extremely premature babies are more likely to have developmental problems, from minor to severe retardation, and to be disabled.
Among the complications that concern Fleischman most are those posed by multiple births.
Older women are more likely to conceive twins or triplets naturally as well as to use fertility treatments that result in multiple births, he said. And multiple births -- twins, triplets and higher-order multiples -- in turn increase all the other complications of pregnancy. According to the CDC, among all women using assisted reproductive technology, 15% of single births, 64% of twins and 98% of triplets or higher-order multiples were premature.
"I don't think [women] believe it's going to happen to them," Fleischman said. "I don't believe they are well-informed sometimes by their obstetricians and their general physicians about the risk."
The March of Dimes strongly recommends pre-conception counseling for older women, and if they decide to proceed with pregnancy, to have their obstetrician assess their risk of diabetes and high blood pressure. Before trying to conceive, the agency recommends that women get in the best physical shape they can and take daily vitamins, including folic acid, which has been shown to prevent birth defects. If they are planning to use reproductive technology, they need to understand the risks involved with multiple births.
Some fertility experts believe that awareness of the risks is already rising -- and that the boom in over-40s births may have peaked.
"What I'm curious about is whether this trend is going to continue or whether it is in fact going to reverse," said Paulson, who directs the USC Fertility Clinic. "We've raised the consciousness of the population to the fact that the biological clock is a reality."
Rodi agrees. She had her two children at 32 and 34, earlier than many of her contemporaries. But then, she was a fertility specialist.
"I remember having to think very clearly, 'It's time to get married,' " she said.
Even so, she and her husband, who is also a physician, waited to begin a family for five years, until they had completed their medical training.
That's not the case for many fledgling doctors today.
"Women in residency programs are having children today," Rodi said, "once it became clear that you couldn't postpone having children forever."