Public Release: 

Assisted reproduction can't compensate for waiting too long to start a family

European Society of Human Reproduction and Embryology

Women who wait until 35 to start trying for a family were warned today (Thursday 17 June) that if they did not conceive spontaneously they could not depend on assisted reproduction to make up fully for the loss of natural fertility after that age.

Professor Henri Leridon, a demographer from the French Institute of Health and Medical Research (INSERM) and the National Institute for Demographic Studies (INED), reports in Europe's leading reproductive journal Human Reproduction[1] that, while the chances of rapid conception were still significant for women over 35, if they failed to become pregnant spontaneously, assisted reproduction could not fully compensate for the lost years.

He reached his conclusion after using a computer simulation model to study the odds on achieving a live birth naturally if a woman started trying to conceive at ages 30, 35 or 40 compared with the success rate if they turned to assisted reproduction technologies (ART) after four, three or two years respectively and assuming two attempts at IVF.

The complicated computer simulation[2] combined the monthly probabilities of conceiving, the risk of miscarriage and the probability of becoming permanently sterile through age.

"What it showed was that, under natural conditions, three-quarters of women starting to try to conceive at the age of 30 will start a successful pregnancy within one year. Two-thirds of those starting at 35 will be successful within one year and 44% of those starting at age 40 will succeed within one year. Four years after trying to start to conceive, 91% of 30 year-olds, 84% of 35 year-olds and 64% of 40 year-olds will have been successful.

"But, if women of 30 at first attempt at pregnancy turn to ART after four years of trying unsuccessfully, women of 35 turn to ART after three years of trying and women of 40turn to ART after two years of trying, then we find that ART will make up for only half of the births lost by postponing a first attempt at pregnancy from age 30 to 35 and less than 30% after postponing from 35 to 40 years."

The overall apparent[3] success rate of ART would be 30% (for those attempting pregnancy from age 30), 24% (from age 35) and 17% (from age 40).

Prof. Leridon said INSERM had done the study because it was important to answer a range of practical questions about the chances of either natural or artificially aided conception in order to provide efficient family planning advice and more precise information about the potential risks of postponing childbirth beyond a given age. In several European countries the mean age of childbearing is already close to 30 years.

"We concentrated on the proportions of women who conceive within four years because this is the mean delay before women in France turn to the most advanced forms of medical assistance."

"In summary," said Prof Leridon, "out of 100 women trying to become pregnant at age 30, 91 will have a child within 4 years without ART, another three will do so during the next two years thanks to ART and six will remain childless. Out of 100 starting at age 35, 82 will have a child after three years, another four thanks to ART and 14 will remain childless. Out of 100 starting at age 40, 57 will have a baby after two years, another seven after ART and 36 will remain childless. For those over 40 the number of births through ART is only slightly higher that it would be if they had tried for another two years to conceive naturally."

He said that results might be better if women aged 35 to 40 were encouraged to opt for ART faster than assumed in the computer model.

"The take home message if you are under 35 is 'be patient'. Even if you fail to conceive within a year your chances of conceiving subsequently are still substantial. More than half of you who are childless after one year will conceive during the next two years. But, if you are 35 or over the message is 'be impatient'. Your changes of conceiving naturally are still significant, but in the case of failure, ART will not fully compensate you for the years, and the chances of conceiving, that you have lost."


[1]. Can assisted reproduction technology compensate for the natural decline in fertility with age? A model assessment. Human Reproduction. DOI:10.1093/humrep/deh304.

[2]. The computer simulation model used (Monte Carlo) was based on the biological components of reproduction, plus nuptiality (including if needed, divorce, widowhood and remarriage), and birth control variables (e.g. the number of children wanted and effectiveness of contraception). It reconstructed the reproductive biology of a woman from marriage to the end of her reproductive period by submitting her to all relevant risks each month. A full explanation is given in the research paper.

[3]. The term 'apparent success rate' is used because some hypofertile women may conceive without any treatment.


1.  PDF version of this press release and full embargoed text of the paper with complete results can be found from 09:00hrs London time Tuesday 15 June at: or is available from Margaret Willson.

2. Human Reproduction is a monthly journal of the European Society of Human Reproduction and Embryology (ESHRE). Please acknowledge Human Reproduction as a source. Dr Helen Beard, Managing Editor. Tel: +44 (0) 1954 212404 Email:

3. ESHRE's website is:

4. Abstracts of other papers in ESHRE's three journals: Human Reproduction, Molecular Human Reproduction & Human Reproduction Update can be accessed post embargo from Full text of papers available on request from Margaret Willson.

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