UBC Reports | Vol. 50 | No. 9 | Oct. 7, 2004

Becoming a Mum after 35

A UBC researcher wonders if we really know the risks of delayed childbearing

By Hilary Thomson

As the mums and strollers roll by, it’s obvious that more women over the age of 35 are having babies. In fact, there has been a 83 per cent increase from 1991 to 2000 for babies born to Canadian mothers over 35, according to the Canadian Perinatal Health Report, 2003.

In addition, many women wait until they are over 35 to have their first baby and a UBC researcher wonders if we know as much as we need to about the risks of delayed childbearing.

PhD student Sarka Lisonkova has launched a two-year study to look at impacts of delayed childbearing in B.C. It is the only population-based study in North America to examine trends in pregnancy outcomes as well as individual risk, multiple births, and newborns’ need for health-care services, in both rural and urban settings. She will compare statistics for mothers over 35 with those for mothers aged 20-35 years, and will also examine the whole spectrum of age categories.

“Women aren’t really told of the biological disadvantages -- particularly for the first baby,” says Lisonkova, who had her first child at 28. “There’s no arbitrary deadline for births, but risks do start to accelerate in later years.”

As reproductive organs age, function appears to diminish, says Lisonkova, and points to research that wanted pregnancies occur less frequently after the age of 35.

However, research findings vary as to risks posed by increased maternal age.

Some studies report greater risk of pregnancy complications such as premature delivery, stillbirth and low birth weight. Some risks might decrease, however, if mothers have already had a first child before the age of 35 years.

Other studies have reported no association between age and outcome when factors such as obesity, illness and prior reproductive problems are taken into account. Lisonkova will review the effect of such risk factors as smoking and fertility problems in her research.

In B.C., birth rates have dropped over the last five years for all age groups except mothers aged 35 years and older, who give birth to approximately 8,000 babies annually.

B.C. has the second highest proportion in Canada of live births to mothers over 35 years and the highest proportions for those 40-44 years.

Lisonkova is eager to find out at what age reproductive risks significantly increase and how risks may change over the decade 35-45.

“Maybe as new generations are getting healthier and living longer, the reproductive system functions quite well for longer,” she says.

“Or maybe this is true only for certain groups of women who stick to a healthy lifestyle and are free of illness or complicating conditions.”

Lisonkova says B.C. offers the opportunity to create a uniquely comprehensive study, thanks to resources offered by the B.C. Linked Health Database and the B.C Perinatal Database Registry. These databases allow her to study health services used by large population groups and link them to complete obstetrical data for approximately 200,000 births during the period 1998-2002. Using this and other B.C. vital statistics data, she will plot and compare a 10-year trend in health service use for babies of both older and young mothers.

Lisonkova believes that her study will help guide planning for maternal/infant health services and that differences between rural and urban areas may reveal valuable information to help allocate resources in the province. Findings on individual risk may assist physicians and other health-care professionals to recognize risks during prenatal care and delivery and will aid prenatal counseling and planning.

The study is supported by the Centre for Healthcare Innovation and Improvement, located at Children’s & Women’s Health Centre of British Columbia, an agency of the Provincial Health Services Authority. Funding for this research comes from a senior graduate studentship awarded by the Michael Smith Foundation for Health Research.