Joann P. Galst Ph.D.

Fertility Factor

A Mathematically Determined Age to Start Trying to Conceive


Posted Sep 06, 2015

A Mathematically Determined Age at Which Couples Should Start Trying to Conceive.


Joann Paley Galst, Ph.D.

A recent European study has used a mathematical model to determine at what age a woman should start trying to conceive depending on how many children she and her partner want, how important this number is to them, and whether or not they would consider using IVF, if needed. For example, for a 90% chance to have one child, couples should start trying to conceive according to this model when the woman is 35 years of age or younger if they are willing to use IVF. For two kids with the IVF option, the latest starting age is 31 and for three kids, 28 years. Without IVF as an option, they would need to start earlier, i.e., 32 years of age for one child, 27 for two, and 23 for three. If couples are willing to accept only a 75% chance of success, they can start 4-11 years later.

This study appears to produce robust results, but come on, seriously??

What are women supposed to do with this information, really? It’s not like deciding the best time to book a vacation. The decision to start a family is based on multiple factors, with age typically not the primary variable. Life has a way of throwing obstacles in our way, for example, education, career, finances, childcare availability, and relationship obstacles, such as whether one has a partner, whether one and one’s partner feel ready to take on the very real and serious responsibility of raising a child from which, once a child is born, there is no turning back.

We do know that young people have unrealistic views regarding fertility (i.e., that it declines later than it actually does) and the success of IVF (i.e., that IVF offers guarantees to all women who cannot conceive, which it does not). So, while both women AND men need to be informed that achieving and sustaining pregnancy may become more difficult as a woman gets into her mid- to upper- 30’s and 40’s, our private intimate lives are not typically decided based on mathematical models or algorithms. So, women and men, be informed, but make the decisions that are right for you at the time that is right for you. And, pressure and fear may result in children being brought into the world when their parents don’t want them, certainly not the best outcome for anyone involved.

Women, consider a fertility check. All you need is a blood test timed to your cycles to get two measures (FSH and AMH) that can let you know if you can hold off a bit or if it’s more prudent to start trying to conceive sooner or consider freezing your eggs. A male fertility check just needs a semen sample. And couples need support to establish both their careers and their families at the same time so they can start their families earlier if they wish – better parental leave, easier access to affordable childcare, no disadvantaged position at work for women who continue to work but choose to start their families earlier, partners who also recognize the need to commit to the relationship and to starting a family if it is right for them. Couples should not have to make a tradeoff between career and family.


Habbema, J Dik F, Eijkemans, MJC, Leridon, H, te Velde, ER. Realizing a desired family size: When should couples start? Human Reproduction, 2015; 30(9): 2215-21. doi: 10.1093/humrep/dev148

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