How long does IVF allow a woman to delay having children?

The New Scientist has a new article up titled: When should you get pregnant? Computer knows age to start trying.

Happy with just one? The model recommends you get started by age 32 to have a 90 per cent chance of realising your dream without IVF. A brood of three would mean starting by age 23 to have the same chance of success. Wait until 35 and the odds are 50:50 (see “When to get started”).

The age a woman needs to start trying goes down significantly based on the woman’s unwillingness to accept the possibility of failure. Here is the data they present in table form:

Note how little IVF helps in this analysis.  A woman willing to accept a 50% risk of failing to have at least one child only gains one extra year she can delay starting to try to get pregnant (42 vs 41).  The same is true for a woman willing to take a 50% risk of failing to achieve a desired family size of 2 or three children (39 vs 38 and 36 vs 35).  IVF helps more for women who are more risk averse, but even here it only buys a few years.  A woman who is only willing to accept a 10% risk of failing to have at least one child has to start by age 32 without IVF, vs age 35 with IVF.  IVF helps the most for women who are most risk averse and want to have at least three children, raising the maximum age they should start trying from 23 to 27.

See the full article for more detail, but note that this model is regarding fertility and doesn’t take into account the risks of birth defects which are associated with older mothers.  The following chart presents data (archive) on this from Ask.com:

Also note that the ages in the table aren’t the age a woman should start looking for a husband;  these are the age she should start trying to conceive.  When considering when to start looking for a husband, these ages should be reduced based on the woman’s estimates of:

1. How long it will take her to find Mr. right once she starts seriously looking for husband material.
2. How long she plans on dating before becoming engaged.
3. How long she plans on being engaged before getting married.
4. How long she wants to be married before starting to try to get pregnant.

For example, assume a woman is confident that she can find Mr. Right just one year after she starts looking, plans on dating for one year before getting engaged, plans on being engaged for a year before getting married, and wants to wait a year after marriage before starting to try to get pregnant.  She should then subtract four years from the ages in the table to find the very oldest age she should start looking for a husband.  Using this example, if a woman wants to be highly confident (90%) that she will be able to have two children she should be looking for a husband by the time she turns 23.  With IVF she would have a few extra years, but should still be looking for a husband by the time she is 27.

There is however a confounding factor, because the longer a woman waits to start looking for a husband, the harder the husband search tends to be.  IVF can help a bit with delayed fertility but it can’t help an older woman find a husband.  A woman who is looking for a husband at 23 has a much larger pool of available men, and will find it much easier to fall in love than a 27 year old.  Since other women will have already picked first, the pool of available men will also be of lower quality (overall) for a 27 year old woman as well.

See Also:

• Charts on delayed motherhood
• How young should a woman marry?