This article is from the Choosing Your Baby's Sex FAQ, by Roger A. Hunt firstname.lastname@example.org with numerous contributions by others.
The following summary of the methods outlined in Dr.
Shettles' book is based partly on an excellent
summary posted by misc.kids.pregnancy contributor Ana
Silva in September 1995, and partly on my
modifications. Thanks for permission, Ana!
--------- BEGIN SHETTLES SUMMARY ---------
Basically, men produce two types of sperms, the X
(female) and Y (male). According to Dr. Shettles'
studies the y-sperms are smaller, weaker, but faster
than their sibling x-sperms, which are bigger,
stronger, but slower.
Based on this fact, there are several things you can
do to "favor" the conception of boys or girls:
(1) The most important aspect of all is timing of
intercourse during the monthly cycle. The closer to
ovulation you have sex, the better the chances to
have a boy, because the y-sperms are faster and tend
to get to the egg first. If you have sex 3 days or
more before ovulation, the better your chances to
conceive a girl, because the weaker y-sperms tend to
die sooner and the x-sperms will be available in
greater quantity whenever the egg is released. On
the other hand, having sex from 2 days before
ovulation, through a few days after ovulation, is
better for conceiving a boy. Around the 2-day point
-- 48 hours before ovulation -- seems to be the 50/50
(For those with a precise turn of mind, Shettles
clarifies even further [p. 187]: from zero to 24
hours before ovulation, intercourse is more likey to
result in a boy; from 24 to 96 hours before, a girl
is more likely; and the further away from that 24-
hour dividing line in either direction, the better
(2) Position of intercourse and depth of penetration
are important, partly because of acidity/alkalinity
of the woman's reproductive tract (see sec. (6)
below). The closer to the entrance to the vagina, the
more acidic the pH of women's tract. Also, deep
penetration places the sperm closer to the egg, and
gives those aggressive boy sperms a head start :-).
So, a shallow penetration will favor girls and a
deeper will favor boys. Shettles recommends
missionary-position for a girl, and rear-entry (dog-
style) for a boy.
(3) Women's orgasms can also be important. This also
has to do with pH. When a woman has an orgasm, the
body releases a substance that makes the environment
more alkaline, favoring boys. Shettles recommends no
female orgasms when trying for girls!
(4) The sperm count is another factor. Obviously, a
low sperm count to begin with doesn't favor either
sex. But a high sperm count favors boys. Shettles
recommends three things:
(a) When trying for a boy, the man should not
have an ejaculation for 3 days before reaching the
target date a day or two before ovulation.
(Intercourse earlier than 3 days before ovulation
should be with a condom only.) For girls, have sex
every day from the first day after your period ends,
and stop 3 days before ovulation. (No intercourse
even with a condom during that time.)
(b) Shettles recommends that for boys, the man
wear loose underwear only -- that is, men who usually
wear briefs or other tight underwear should switch to
boxers. The idea is the same as wearing boxers to
increase overall fertility -- the testicles need
cooler temperatures for sperms to survive, and the Y-
sperms, since they are weaker, will be helped more
than the X-sperms by this method. However, Shettles
does NOT recommend the opposite, that men wear briefs
for a girl -- this will just decrease overall
(c) Also, for a girl, the man is supposed to
take a hot bath immediately before intercourse.
"Room temperature" is fine for a boy. The idea is
the same as the briefs versus boxers -- give the X-
sperms an advantage.
(5) In trying for a boy, Shettles recommends a nice
cup of caffeinated coffee for the man, right before
intercourse -- he isn't clear on how or why this
works, but apparently it gives the Y-sperms a jolt!
(6) Concerning douching and the pH of the women's
reproductive tract: A more acidic environment favors
girls, since it will kill the weaker y-sperms first,
leaving a greater quantity of x-sperms available to
fertilize the egg. On the other hand, a more alkaline
environment favors boys. (Note: Some women are
naturally very acidic and have a hard time conceiving
Shettles *formerly* recommended two douching-methods
(involving vinegar or baking soda) to help alter
vaginal pH. However, in the most recent update (c.
1989) of his book, he no longer recommends douching
at all. His comment (pp. 179-180) is that one can
get equally-good results with or without the douches
(Because many on the newsgroups who responded in
Sec. 3.3 below were using the older versions of
Shettles' book, there are a number of anecdotes
including the use of douches as well as other
Shettles methods. It's important to emphasize
that, although it won't do any harm if done
properly, Shettles no longer recommends douching
as part of his methods. He does strongly
recommend that nobody begin douching, for *any*
reason, without consulting her health-care
Well, these are the big ones. Read the book for other
details. If you can determine the time of ovulation
and follow the rules presented in his book, Dr.
Shettles claims a success rate of 70-75% for girls
and 75-80% for boys (better than the "normal" 50%).
As you see, it's not 100%!!!
Also, Shettles recommends a "practice" period of 3-6
months, to make sure the couple has all the
techniques down properly.
--------- END SHETTLES SUMMARY -----------