New Mathematical Model Shows When to Start Trying for a Family

October 30 2015 11:49am

Fertility Testing London


Researchers have created a computational model that determines when women should start trying to conceive for different family sizes.

The paper, ‘Realizing a desired family size: when should couples start?’ concludes that the age “at which a couple should start trying to become pregnant strongly depends on the importance attached to achieving a desired family size and on whether or not IVF is an acceptable option”.

The model suggests that if a woman wants a 90% likelihood of having one child without IVF, she should begin trying to conceive at 32 – later than a lot of suggestions in other contexts. However, if a woman wants a 90% chance of having three children without IVF, she would need to start trying to conceive at 23.

The study is based on natural fertility data from 58,000 women over 300 years. This means that there may be some flaws as the model is based on data from very different lifestyles to those experienced by modern, western women.

However, it does factor in that people don’t tend to have children in rapid succession so allows for gaps between conceptions. The chances of natural pregnancy fall to around 50% in a woman’s 40s, so this study is one of many that reinforce how important it is for women to consider whether they want a family in their 20s and 30s.

Young people are often optimistic about their fertility and how long they can delay the decision, especially with the advent of different fertility treatments. However, these treatments also have different success rates depending on age and overall health.

Information like the mathematical model created as part of this research will help to inform people and ensure that they can have the family they want with minimal treatments and invasive procedures.


Book a consultation with our doctors now.

Saturday morning and mid-week evening appointments now available!

Call our Patient Services Team on 020 33 88 3000

or email us at