Women are being warned that they should consider starting a family before the age of 35 or they will risk missing out on motherhood.
According to a report by the Royal College of Obstetricians and Gynaecologists (RCOG) the optimal age for childbearing is between the ages of 20 and 35 as it is increasingly difficult for women to become pregnant after the age of 35. Women over 35 also have a higher risk of miscarriage and the report says women should be encouraged to consider having families during the period of optimum fertility.
The RCOG report says there is a growing trend for childbearing to occur at a later time in women's lives in many countries including Australia for manifold and complex reasons, including the availability of safe, effective contraception; in order to pursue further education; to build a career; to achieve financial independence, and to be in a stable relationship with a supportive partner.
The report says while women should be supported in their decisions on whether to have children or not and when to plan childbearing, they also need to know how fertility and pregnancy outcomes change with age - leading obstetricians and fertility specialists have previously warned that delaying having children until after this age is "defying nature".
The RCOG report outlines the issues associated with later motherhood and makes several recommendations including better education on the best age for childbearing and calls for more research into IVF methods and other assisted reproductive technologies.
The age at which women first become mothers continues to rise, but as women get older the number and quality of egg cells that are produced by the ovaries declines - as many as 10% of women are affected by early ovarian ageing.
The report says infertility and difficulty in conceiving can cause great emotional distress to couples and while women should ideally be free to choose when to start a family based on personal and professional circumstances, little can currently be done to reverse the underlying biological factors that determine reproductive ageing.
According to the RCOG report while in-vitro fertilisation (IVF) can potentially help many women conceive, like unassisted conception it is far less successful as women age - the live birth rate for women under 35 undergoing IVF is 31%, but the success rate is less than 5% for women over 42.
This is because the quality of the eggs harvested in assisted techniques such as IVF deteriorates with age and while these techniques stimulate the release of more egg cells they cannot compensate for the effects of reproductive ageing on egg quality.
While newer preservation techniques are designed to freeze eggs from younger women and allow postponed pregnancy at a later age, there is currently little evidence to support their use.