Updated

Nearly half of women who became pregnant through in vitro fertilization (IVF) after age 40 say they were "shocked" to discover they needed fertility treatments, a new study finds.

In the study, the researchers at the University of California, San Francisco interviewed women from 61 families — including heterosexual couples, lesbian couples and single women — who conceived and delivered children via IVF after age 40. The interviews were done between 2009 and 2011.

"We found that women did not have a clear understanding of the age at which fertility begins to decline," the researchers wrote in their study, published online Nov. 30 in the journal Human Reproduction.

Most women thought their fertility would last longer than it did. For instance, 31 percent said they expected to get pregnant without difficulty at age 40.

"Very few participants had considered the possibility that they would need IVF, and 44 percent reported being ‘shocked’ and ‘alarmed’ to discover that their understandings of the rapidity of age-related reproductive decline were inaccurate," the researchers wrote.

However, fewer than a quarter of these women said they would have tried to get pregnant earlier if they had more information about declining fertility, the study found. For women in the study, "personal-life circumstances would not have encouraged them to begin childbearing earlier than they did," the researchers wrote.

Along with a decline in the chance of conceiving naturally, the chance of successfully having a baby via IVF also declines with age — the chance of success with one cycle of IVF treatment drops from 41 percent at age 35, to 4 percent after age 42. Studies have shown the general public is not aware of the extent of this decline, the researchers said.

Three-quarters of the women said they felt lucky about successfully conceiving through IVF.

The researchers noted that their study participants were a selected group of women, and the study was retrospective. Studies that follow women forward over time, and test other populations are needed to confirm the results.

According to statistics from the Centers for Disease Control and Prevention, infertility affects nearly 12 percent of reproductive-age women in the U.S. Part of the reason for this is cultural trend of women delaying childbearing, according to the study. One in five women now has her first child after age 35, an eightfold increase compared with a generation ago.

When the researchers probed into why the study participants held mistaken beliefs about fertility, 28 percent said that incorrect information from friends, doctors or the media reinforced the idea that older women could easily become pregnant. For example, a 42-year-old woman recalled thinking, "Everyone’s having babies at 42 … all the superstars are having them," according to the study.

About a quarter of participants said their beliefs stemmed from messages about preventing pregnancy they had received since adolescence. One woman wrote, "It’s like, all of our lives we’re terrified we’re going to get pregnant too soon and have a child and ruin our lives … and, actually, it’s not that easy."

A quarter of participants also said their beliefs were based on their mothers’, sisters’ or their own previous fertility.

It remains unclear exactly what can be done to better educate women about fertility. Researchers have been slow to get information about fertility declines out to the public, according to the study. For example, a 1982 report from French researchers was the first large study to show a decline in artificial insemination success rates as women aged, but it wasn't until 2000 that the American Society for Reproductive Medicine (ASRM) recommended that women over 35 trying to conceive be counseled and treated more quickly than younger women.

And messages about declining fertility could also have "unwelcome social implications," the researchers said. A public education campaign that the ASRM undertook between 2000 and 2002 was criticized for pressuring women to have children before they were ready, and for undermining women's efforts to become educated and have careers.

However, the trend of women delaying childbearing has continued, and data show that IVF can only partly offset fertility declines. "These projections make a case for renewed attempts to educate women and men about the known parameters of fertility at all life stages," the researchers wrote.

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