How Long Can you wait to have a baby — historical data

From: Karen Reeds []
Sent: Wednesday, June 26, 2013 10:19 AM
Subject: Re: how long can you wait to have a baby — historical data

Courtesy of my daughter (due in August!)

> JEAN TWENGE The Atlantic JUN 19 2013
> Jean M. Twenge is a professor of psychology at San Diego State
> University and the author of The Impatient Woman’s Guide to Getting
> Pregnant.
> “The widely cited statistic that one in three women ages 35 to 39 will
> not be pregnant after a year of trying, for instance, is based on an
> article published in 2004 in the journal Human Reproduction. Rarely
> mentioned is the source of the data: French birth records from 1670 to
> 1830. The chance of remaining childless-30 percent-was also calculated
> based on historical populations.”

Karen Reeds


Comment from Daphna Oren-Magidor []

It is certainly true that demographic studies have used historical data in
order to look at dropping fertility rates. This is true not only for this
French study, but also for other notable demographic studies of fertility,
such as J. Trussell and C. Wilson, “Sterility in a Population with Natural
Fertility,” Population Studies 39: 2 (1985).

However, it is perhaps worthwhile understanding what historical-data studies
usually aim to do. The purpose of studies that use historical data is to
figure out how fecundity works in populations that practice natural
fertility, i.e in which there are no effective means of contraception on the
one hand, and no effective fertility treatments on the other hand. It is
assumed that such populations offer a view of what the body “actually” does,
without any additional aids or hindrances. Now, granted, this fails to take
into account the fact that modern nutrition and health systems may allow for
greater natural fertility. For example, the age in which girls begin to
menstruate (i.e – to become potentially fertile) has been steadily dropping.
It is not unlikely that the age in which women stop being fertile is
similarly become more delayed and that women’s natural fertility today is
greater than it was two or three or four hundred years ago. And yet, it is
important to understand where the data are coming from and what they are
used for.

This is not to say that I have any particular objection to Twenge’s
conclusions – other, perhaps, than the fact that they don’t seem
particularly new to me. They seem to echo what I’ve seen on websites
regarding conception etc.

However,  I’m not entirely sure if using historical-data studies is as
irrational as Twenge suggests. If nothing else, when we look at Western
Europe, especially places like England, some marriage patterns were
surprisingly similar to our own. The average age of marriage in large parts
of early modern Europe was roughly 23-24 for women, and 27-28 for men. In
other words, not unlike today, many couples did not start having children
until well into their 20s. Thus, it is not necessarily true that people
would be done with their childbearing at an early age. And given the lack of
effective contraception, it is unlikely that people could entirely avoid
getting pregnant if they were having sexual activity.

It is also worth noting that early modern guides to conception were
surprisingly supportive of women conceiving late. For example, The English
Midwife notes that ” “there are however many Women, which seem Barren for a
long time. yea till 35 or 40 years old, and sometimes longer who yet at last

Again, this is not to argue with Twenge’s conclusions, but merely to give
some perspective to the question of historical data and fertility.


Published in: on July 1, 2013 at 10:50 am  Leave a Comment  

The URI to TrackBack this entry is:

RSS feed for comments on this post.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: