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How long can you wait to have a baby?

Posted on April 5, 2013 by Daniel at 2:22 am

familyLike many single women in their early thirties, Jean Twenge worried that she would miss out on motherhood. Recently divorced, she would be hit by bouts of full-on baby panic. She remembers having conflicting emotions when friends gave birth, casting longing looks at toddlers in the street and anxiously reading a magazine article about the state of her biological clock. The message was loud and clear; time was running out.

Today, at 41 and remarried, she is the mother of three beautiful daughters. “I needn’t have worried after all,” she laughs.

Received wisdom suggests that 35 is the magic age at which fertility drops off dramatically. The widely cited view that it is harder to have a baby after this age — a statistic that forces many women to leap into motherhood when they might not be ready to do so, pull back on their careers or to limit the number of children that they do have, or at least spend years panicking — is, she has discovered, based on information that is out of date and misunderstood.

The average age of women giving birth has steadily increased in the UK over the past 25 years. The average child-bearing age has risen from 23 in 1968 to 29.7 today. And there has been a 15 per cent rise in births to women in their forties over the past five years. But women are always warned against pushing the deadline beyond their mid-thirties. Several new studies suggest that women have more time than they realise to get pregnant.

The statistics that Twenge, a professor of psychology at San Diego State University and an experienced researcher, saw most often in medical books said that only two out of three 35-year-old women would be pregnant after a year of unprotected sex. “That meant one in three wouldn’t,” she says. “When you really want to have a baby, facing a one in three shot of being infertile is downright frightening.”

Twenge decided to go back to the source of the information. Searching through vast medical databases, she found that it was based on an article published in 2004 in the science journalHuman Reproduction.

What is rarely mentioned, she discovered, is that researchers had used church birth records in rural France between 1670 and 1830. “Isn’t that amazing?” Twenge marvels. “The statistics on which women today are making decisions about their careers, relationships and when to have children are based on a time before electricity, antibiotics, or fertility treatment.”

Even the advice given by The Royal College of Obstetricians and Gynaecologists, that the best age for childbearing is between 20 and 35, is based on this same study.

While the study allows researchers to look at data unaffected by contraception or IVF, there are obvious differences between women in the 17th century and now, says Twenge, such as “modern medical care and better diets”.

Twenge has published this and other research in her book The Impatient Woman’s Guide to Parenting and in a recent article inThe Atlantic. Not surprisingly, her work has received widespread attention in the US, particularly because it runs counter to what many women have been led to believe.

It has been hailed as good news for women who think they have to scale back their careers or have fewer children than they’d like to because they are standing on the edge of the fertility cliff. The Huffington Post’s women’s editor Margaret Wheeler Johnson said that Twenge has told many women “what they want to hear.”

Twenge says one of the reasons that this old science is still doing the rounds is because natural conception is hard to study and there is not much enthusiasm or funding for it.

On the other hand, she points out, there is an abundance of research on IVF, egg freezing and other means of assisted conception. “There’s a vested interest in having those techniques work as well as possible because fertility treatments cost a lot of money,” she says, pointedly. The recent studies on natural fertility that Twenge has pulled together present a more optimistic picture of older motherhood.

In a study published in Obstetrics and Gynaecology in 2004, researchers exam- ined the chances of pregnancy of 770 European women (born in the 20th century) and found that with sex at least twice a week, 82 per cent of 35 to 39-year-old women conceive within a year, compared with 86 per cent of 27 to 34-year-olds.

Two studies published this year also throw new light on thirtysomething female fertility. Noted epidemiologist Kenneth Rothman of Boston University followed 2,820 Danish women as they tried to become pregnant. Among women having sex during their fertile times of the month, 78 per cent of 35 to 39-year-olds got pregnant within a year, compared with 84 per cent of 20 to 30-year-olds. The difference does not seem dramatic.

A study carried out by the University of North Carolina School of Medicine, whose results were presented this month, found that among 38 and 39-year-olds who had been pregnant before, 80 per cent of white women of normal weight got pregnant naturally within six months. The percentage was lower among other races and those women who were overweight.

Twenge also found evidence contradicting the commonly held perception that women over 35 have a higher risk of birth defects. Although the rate of birth defects does rise as women age, she says, the risk is still very low.

Among 35-year-old women, 99.5 per cent of babies will be chromosomally normal at delivery, and 0.5 per cent, or 1 in 204, will not be. Among 40-year-old women, 98.5 per cent of babies will be chromosomally normal and 1.5 per cent, or 1 in 65, will not be. At 45, when very few women can still get pregnant, 95 per cent of babies will be chromosomally normal and five per cent, or 1 in 20, will not be. The majority of Down’s syndrome babies are born to women younger than 35, she notes. Their risk is lower but they have more babies.

All the indicators point to the fact that most 35 to 39-year-old women will be able to get pregnant naturally and deliver healthy babies, but it might take a few months longer than younger women.

“There are so many of us struggling with this issue and we’re being bombarded with conflicting advice, all of which points to our 35th birthdays as being the moment to fear, and it’s just not true,” she says. “Fortunately, fertility is still very high in a woman’s late thirties. I’m not saying fertility doesn’t decline with age. It does decline, but it doesn’t decline by that much, and it is still at a pretty high level in your late thirties.”

She says that she looks back now at the wasted time she and her husband Craig, an executive with Sony, spent worrying about her own fertility. She had her first child aged 35, her second at 38, and her third child at 40. “I was anxious every time, not just with my first baby, but even more so with the second and third. Every time, I thought, ‘I’m going to be too old and I’m not going to be able to have the family that I want to have’ and every time it turned out not to be true.”

Twenge says it took her and her husband five months to conceive their first daughter, three or four months for the second and only two months for their third.

Her main impulse for putting together the research, she says, was to help women have the best and most up-to-date information in order to make their life decisions. There is no single best time to have a child and every woman has to do what she calls “woman math” for themselves, she acknowledges.

“If it’s the right time for you and you’re in your early thirties, go for it. I would never presume to tell someone what to do,” she says. “But if you’re in your early thirties and you have a challenging career and you think, ‘I’ve got to have to have a kid now or it’s not going to happen’, don’t think that because it’s just not true. If it will be better for your career to wait a few years longer, the statistics suggest that should not be a problem.”

Listening to alarmist rhetoric and rushing into motherhood can have an effect on career trajectories and finances that adversely affect women’s lives in later years, she points out. One economist estimated that, on average, every year a woman postpones having children leads to a 10 per cent increase in career earnings.

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