Probability of pregnancy by age

By Razib Khan | July 31, 2011 2:25 pm

I just finished reading My Fertility Crisis, which is excerpted from a longer piece you can get on Kindle for $1.99. The author is a single woman in her early 40s who is going through IVF treatments, without success so far. She outlines the choices she made over her life which may have influenced her current situation.

After reading the piece I came back to an issue I’ve wrestled with before: it’s often really hard to find information on probability of pregnancy online in the form of charts. The reason is that there’s so much information, and much of it is skewed toward people who are undergoing treatment for infertility. But why look when you can generate your own visualization? I  found a pregnancy probability calculator online which I cross-validated with some of the literature. Here is the best case scenario for probability of pregnancy if you are trying in the natural fashion (the probabilities exclude women who are clinically infertile, which is a rather slippery category strongly dependent on age, so the older cohorts are probably much larger overestimates than the younger ones):

The main focus is really the decade of the 30s for women. Here is a figure from Ovarian Aging: Mechanisms and Clinical Consequences which shows a finer-grain decline in fertility:


An issue mentioned in the piece above is that there is a focus on the successes of IVF as opposed to the failures. I don’t really buy that narrative. But, there is a tendency not to focus too much on the fact that many IVF successes for women in their 40s are due to donor eggs. A clear example of this phenomenon is that very few in the media highlighted the likelihood that Elizabeth Edwards’ last two children were conceived with the help of donor eggs. She was 49 and 51 when they were born.

Recently a friend asked me about the value proposition of freezing eggs in the case of a 35-year-old female friend. I think it’s something that many people in the developed world really need to consider. Yes, the cost is going to be in the range of tens of thousands, but that’s the magnitude of a car, and far less than a home. A healthy child seems to me much more valuable than either of these objects to people who want to have children.

One of the implications that many people take away from these results is that society should aid those who wish to have children at later ages. I’m broadly sympathetic to this viewpoint. The type of people that I know personally are often in this class; they have delayed starting families to finish their extended educations and invest in their own human capital. In 15 states the law requires than health insurance cover infertility treatment. But we must not ignore the class ramifications of these policies. Mandating the coverage of infertility may alter the behavior of some individuals (just as the existence of ART has changed the stance of many people toward the “reproductive clock” more generally), but it is operationally a transfer from those who have children earlier, and are generally of lower socioeconomic status, toward those who have delayed childbearing toward later ages and are usually of higher socioeconomic status. The counterargument could be that higher socioeconomic status individuals pay greater taxes already.

The General Social Survey has a variable, AGEKDBRN, which asks respondents when their first child was born. Below I limited the data set as follows:

1) All responses are from the year 2000 and later

2) All responses are from women

All the x-axes on the plots are age of the mother when the first child was born, while the y-axes are proportions across classes. I’ve smoothed the data some. In the first plot ~10% of women whose family wealth is less than $100,000 had their first child at 20. For women whose family wealth as more than $100,00 the proportion was ~8%. For the last plot I categorized “Dull”, “Not Dull” and “Smart” with WORDSUM, which is a 10 question vocabulary test which has a 0.70 correlation with I.Q. The dull category encompasses the bottom 35% of the distribution, the not dull encompasses the middle 53% of the distribution, and the smart the top 12% of the distribution.

CATEGORIZED UNDER: Culture, Data Analysis, Health
MORE ABOUT: Fertility, GSS, infertility
  • Hansa

    This is very interesting, but it doesn’t seem to control for the age of aspiring fathers. Fertility also declines in men, and I would estimate that as women age so do their partners, multiplying the chances of infertility further.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    This is very interesting, but it doesn’t seem to control for the age of aspiring fathers. Fertility also declines in men, and I would estimate that as women age so do their partners, multiplying the chances of infertility further.

    this is a relatively minor effect in comparison to women. male decline is gradual. the difference between a 30 year old male and a 40 year old male is far less than a 30 year old female and a 40 year old female. you can look up the papers on this. this probably has more of an effect on mutational load of children, and so long term morbidity, than conception probability. future comments about this issue should be followed by a reference to the literature. i didn’t post that because i didn’t want to clutter the main effect. and am not interested in speculation.

  • http://iamnurdzilla.blogspot.com Adrian Blake

    Did the data allow for any more economic grouping eg less than $50k a year? Less than $30k? $100k is about £50k which to me is quite well off. Since you talk about the poor paying for the rich it would be interesting to see, if data allowed.

    Great post by the way. I’m a guy and you even got me worrying about the biological clock. The 2nd chart scared me a little, since my girlfriend and I want kids, but not till (an unspecified but faraway time) later.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    #3, yeah, but the sample sizes for “wealth” variable are small.

  • http://backreaction.blogspot.com/ Bee

    That’s an interesting compilation, thanks. I don’t find the first plot too insightful though because it’s very unclear what ‘trying’ is supposed to mean and how it was controlled for. The success rate of ‘trying’ depends on how you try and how hard you try. If it was ensured that all women tried by the same means, then still the y-axis is misleading. I’d recommend normalizing it to the 20-year rate. What I’m saying is that you can increase the success rate by various means, such as ovulation tests or hormone pills. In fact, if these helpers were not controlled for, then the decline is actually even steeper than shown above, since you’d expect the older women to try harder.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    In fact, if these helpers were not controlled for, then the decline is actually even steeper than shown above, since you’d expect the older women to try harder.

    yes. couples who are doing things like taking hormone boosting injections, etc., are presumably yanked out of the sample. the distribution after 35 is WAY too optimistic if you remove ART, but ART is so common after this age in the USA that it’s hard to tease apart the probabilities.

  • DK

    I was always curious about differentials in newborn problems (both developmental and genetic) between mother and father ages. Fig 12 above shows that something tends to happen to eggs after they get ~ 35 years old. Plus the probability of gestation-related problems probably increases significantly with age. With the sperm however, there is the issue of germline mutations. Particularly, I imagine, large scale aberrations during meiosis. There must be a huge amount of data with regard to child health as a function of parents age. Only question is, has anyone bothered to collect it? Anyone knows any specific refs?

  • http://blogs.scientificamerican.com/crude-matter/ EcoPhysioMichelle

    #7: tends to happen to eggs after they get ~ 35 years old
    The accumulation of genetic damage over the mother’s lifetime, among other things.

  • http://undistinguishedknowledge.blogspot.com/ John Turner

    This is very interesting, but it doesn’t seem to control for the age of aspiring fathers. Fertility also declines in men, and I would estimate that as women age so do their partners, multiplying the chances of infertility further.

    this is a relatively minor effect in comparison to women. male decline is gradual. the difference between a 30 year old male and a 40 year old male is far less than a 30 year old female and a 40 year old female. you can look up the papers on this. this probably has more of an effect on mutational load of children, and so long term morbidity, than conception probability.

    Razib is basically right, the time to pregnancy doesn’t change much for men from age 30 to 40. The increase in time to pregnancy starts going up drastically for men after that.
    Paternal age and reproduction:

    Although some studies show contradicting results, we conclude that increasing paternal age is associated with reduced fertility, at least in couples where men are older than 40 years and women are at least 35 years.

    Here are relevant charts:
    Paternal age and reproduction

    Parternal age and fertility, an overview of studies

  • Mary

    You know, I wish that someone would write up the first chart with the source of your numbers and upload it to Wikipedia.

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

ADVERTISEMENT

See More

ADVERTISEMENT

RSS Razib’s Pinboard

Edifying books

Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »