Friday January 28 2011
Fertility declines with age
“Don’t wait too long for a baby,” said the Daily Mail today. It reported on a new study saying that “women are six times more likely to suffer from fertility problems when 35 than 25”.
The news comes from a recent report by UK experts in obstetrics and gynaecology that discusses fertility and how age affects it. While the article is written well, it is not intended to be an exhaustive or systematic review of the evidence on fertility, but to provide an overview on the issue using selected evidence to support different points being made. In fact, much of the report affirms what is already known about fertility declining with age. The report also debates why women are choosing to have their children later, and discusses in general terms how adverse outcomes tend to increase with the mother's age.
Finally, as the trend towards older motherhood continues, the authors call for better fertility information to be given to all women to help them plan their pregnancies.
Where did the story come from?
This paper was written by Dr David Utting, a specialty registrar in obstetrics and gynaecology, and Susan Bewley, a consultant obstetrician. The doctors work in hospitals in London and their paper is published today in the latest issue of The Obstetrician and Gynaecologist, a peer-reviewed medical journal published by the Royal College of Obstetrics and Gynaecology. There is no report of any funding received to undertake this review.
The Daily Mail’s interpretation of this review as “a major study” is a little misleading. The obstetrics and gynaecology experts have written an article based on their experience and opinion, drawing heavily on previously published research about fertility. They have not conducted new research proving that fertility is “six times” lower in women aged 35 than in those aged 25. This figure is in fact derived from a statement made by the researchers when talking about a study published in 1997.
What kind of research was this?
This was an opinion piece or narrative review regarding the evidence by two experts in the fields of obstetrics and gynaecology. The authors were writing about fertility and have drawn on different studies and resources. They have cited 25 pieces of literature to support their arguments. The article is divided into several sections, including those about older mothers, declining fertility, increased adverse outcomes, the role of men’s fertility and assisted reproductive technologies.
Data from the Office for National Statistics is used to demonstrate how the age of a first-time mother has been increasing. Since around 1975, women aged 30 to 34 are more likely to enter into motherhood than any other age group. The authors give their opinions on some of the reasons for this, discussing the wider choice of reliable contraception and the results of a 2006 survey in which most women cited career and money as being reasons, with a number also highlighting the need to find a suitable partner.
The authors also present data on female fertility rate over time (since 1958), which shows this is decreasing. The Daily Mail homed in on this section with its headline: “Women are six times more likely to suffer from fertility problems when 35 than at 25.” This figure is based on a statement in the report: “At the age of 25, just 5% of women take longer than a year to conceive with regular intercourse, rising to 30% in those aged 35.” The researchers did not discuss the source of this statistic, nor the quality of the research that originally provided it.
The authors talk about the increase in adverse pregnancy outcomes for older mothers, citing research that shows an increase in the rate of miscarriage with increasing age. They say that there are other risks associated with age, and that this isn’t surprising given that older women “have had longer exposure to gynaecological insult such as sexually transmitted infections, pelvic inflammatory disease, endometriosis, development of fibroids, cervical surgery and the possibility of premature menopause”.
The authors included a short section on fertility in men, which said there is “a clear decline in motility, morphology and volume [of sperm] from the age of 50”. They note that the increasing age of the male partner is linked to increasing rates of miscarriage.
What were the basic results?
The authors make four key points at the start of their paper, saying:
- Fertility is unpredictable but declines with age.
- Women in the UK are having their first baby at an older age.
- Older women are at greater risk of miscarriage and other medical complications: this has implications both for obstetricians and gynaecologists.
- The “biological clock” ticks for men, too.
How did the researchers interpret the results?
The researchers say that “full, clear fertility facts need to be made available to women of all ages”. Preventing infertility would be better than having to treat it, they say, adding that the age at which women conceive is a key factor. Explaining this to women so that they can make fully informed choices can be done through education and social support for parenting. The researchers say that some of the graphs they present should be available in GP surgeries and at family planning clinics, “to remind clinicians and patients that the most secure age for childbearing remains 20-35”.
The authors go on to say that IVF cannot make up for the delay and physiological decline in the quality of a woman’s eggs, and that a realistic message to give is that under the age of 30, a woman is likely to have a baby from using IVF or other similar technologies, but over the age of 40 she is not.
This is an interesting discursive review of some of the research into fertility and ageing, particularly in women. It is not a systematic review and the studies cited by the authors are only mentioned briefly, are not critically appraised and no mention is made of their quality. The authors have made some important points, all of which serve to remind women and their healthcare providers that there is an age window in which fertility is naturally highest and pregnancy outcomes are likely to be more positive. In some cases, it is unclear in the article which age groups the authors are referring to, as the term “older women” used in the article is not well defined.
The Daily Mail has focused on a statistic that makes a good headline, but there are other interesting facts in the article too, including:
- Sixty percent of subfertility is thought to be caused by female factors, 30% by male factors and 10% by a combination of both.
- Of all babies born in 2007, 1.8% were born via assisted reproductive technology (such as IVF, treatment for poor ovulation, oocyte donation). Like fertility in general, the efficacy of these treatments also declines with age.
This is an interesting article summarising national trends in childbearing and discussing some of the effects that age has on pregnancy and the ability to conceive. As the authors originally intended, this review contains some useful facts and advice for practitioners about how to counsel women who are seeking family planning.
The review also highlights some of the medical and social issues people face when planning a family. The health of mother and baby are critical considerations in family planning, but social and practical choices can also present a range of different, and sometimes very difficult, decisions. It makes sense, as the authors suggest, to ensure that women are given clear information about the biological and medical outcomes of attempting to conceive at different ages, allowing them to adequately factor this information into the personal decisions they make.