More US women delaying pregnancy

New US government data confirms the trend: the average age when women have their first babies continues to increase.

For the last four decades, women, on average, have been having first babies later in life than ever before.

In 2012, the latest year for which data are available, there were more than nine times as many first births to women 35 and older than there were 40 years ago. Among younger women – those under 30, and, particularly, those under 20 years old – first births have actually declined.

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"We've been seeing this for a while now, but it's somewhat breathtaking to see how broadly it has occurred among both age groups [those 35 to 39, and those 40 to 44]," said T.J. Mathews, a demographer with the National Centre for Health Statistics (NCHS), part of the US Centres for Disease Control and Prevention, which issued the report in the NCHS Data Brief.

The data was compiled from US state birth certificates nationwide, taken from the Natality Data File of the National Vital Statistics System. The analysis includes data on all births occurring in the United States, including maternal and infant demographics, and health characteristics for babies born in the country.

Family sizes declining

The findings suggest possible medical and lifestyle implications, experts said.

The fact that more first births are occurring among women 35 and older suggests family sizes will be declining, since the ability to conceive drops with age, noted Mathews.

"The number of births delayed might mean you're really not going to have three children," Mathews added.

• For women 35 to 39, first birth rates rose sixfold from 1973 to 2006 (from 1.7 to 10.9 per 1000 women).
• For women 40 to 44, the rate increased more than fourfold from 1985 through 2012.
• First birth rates rose among older women of all races and origins. Among those 40 to 44, increases in first birth rates rose 171% among blacks and 130% among whites.
• For Asian/Pacific Islanders in both age ranges, the rate of first birth in 2012 was almost double that of the next highest group. "They're having first births at an older age than other population groups," noted Mathews.

Geographical variations

Some states saw a greater increase in first births among older women. For example, the first birth rate for women 35 to 39 in Washington DC, New York, North Dakota, Oregon, Rhode Island, South Dakota, Washington, and Wyoming rose at least 40 percent from 2000 to 2012.

During the same time period, the first birth rate for women 35 to 39 increased 30 to almost 40% in nine states, according to the report. Only four states saw no increase in first births among this age group: Arizona, Idaho, Mississippi and Oklahoma.

And the first birth rate for women aged 40 to 44 rose at least 60% in Washington, DC, Minnesota, Nebraska and South Carolina from 2000 to 2012, the investigators found.

"The risk of infertility is probably the most important thing people need to know. They should understand that if they're delaying childbirth beyond age 34, there's a very real possibility they may need in vitro fertilization, and that's not an easy thing to go through," said Herway.

She also cautions women to realize that as they age, they may not be able to get pregnant using their own eggs. "If they want to get pregnant [after 34], some may not be able to do it with their own genetic material," she added.

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Not smarter than Mother Nature

Obstetricians and gynaecologists refer to pregnancies among women older than 34 as "advanced maternal age" or "geriatric" pregnancies, said Herway. "It doesn't sound good; you're just 34 and you're already considered advanced age."

Herway, who noted that she herself hasn't found time yet to have children, warns women against waiting too long to have their first child.

"We have so many things I can test for and medications I can give you, but when it comes down to having children, Mother Nature allows us to have babies at a certain age for a reason. I don't think we're smarter than Mother Nature," Herway said.