Women who freeze their eggs to extend their fertility run the risk of spending a lot of money for a treatment with a small chance of success.
So-called social egg freezing (SEF) can be used to put off childbearing or because a woman has not yet found a partner.
But the Royal College of Obstetricians and Gynaecologists (RCog) has warned that egg freezing does not guarantee future live births and there are storage limits for how long eggs can be kept frozen, currently 10 years in the UK.
Egg freezing is not available on the NHS apart from in certain circumstances, for example a woman undergoing medical treatment that may affect fertility.
Rcog said said the best time to freeze eggs was in a woman's early 20s, before the quality of the eggs and depleted, and "certainly" before the age of 37.
Figures from Imperial College London and Chelsea and Westminster Hospital show that the proportion of frozen eggs which lead to a live birth among women under 36 was 8.2%.
It saidy said the figure fell even further – to 3.3% – when it came to women aged between 36 and 39.
Of the 1,173 egg freezing cycles that took place in Britain in 2016, only 32% of patients were aged 35 or younger.
"The majority of women are taking measures to preserve their fertility too late, as a 'last-ditch' effort, instead of a planned and informed choice in their early to mid-30s," researchers said.
"Egg freezing is indirectly encouraging women to have children at an advanced maternal age, which carries with it significantly increased risk of medical complications in pregnancy.
"This is especially relevant to women freezing their eggs when they are already in their late 30s."
The report and comments from RCog form part of an ongoing debate in BJOG: An International Journal Of Obstetrics And Gynaecology as to whether egg freezing should be offered to women approaching their late 30s.
Some experts argue that the treatment should be offered to women as they approach the end of their natural fertility cycle because they "should not suffer involuntary childlessness because they have not yet found a partner".
Health professionals from Imperial College London and the Centre for Reproductive and Genetic Health said: "Although delaying childbearing to physiological extremes for social reasons is a reproductive gamble, some women have no alternative, e.g. single women approaching the end of their reproductive years," they said.
"Single women approaching their late 30s, who desire biologically related children in the future, should consider social egg freezing.
"Not only does it extend the window of opportunity to find a partner but it also retains the possibility of using a sperm donor as a last resort.
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"Women should no longer be punished with childlessness for not finding a partner, nor should they feel pressured into a relationship because of their declining ovarian reserve.
"While it does not guarantee against involuntary childlessness, SEF extends the window of opportunity for single women to find a partner and offers them hope where their 'biological clock' would otherwise run out of time."
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