This article is from the Choosing Your Baby's Sex FAQ, by Roger A. Hunt firstname.lastname@example.org with numerous contributions by others.
I found this while looking for something else, and
thought you needed it for your FAQ. :-) Not that it's
very useful, but possibly interesting.
Weinberg CR. Baird DD. Wilcox AJ.
The sex of the baby may be related to the length
of the follicular phase in the conception cycle.
Human Reproduction. 10(2):304-7, 1995 Feb.
MeSH Subject Headings
Adult, Cohort Studies, Female, *Follicular
Phase, Human, Infant, Newborn, Male, Pregnancy,
Prospective Studies, *Sex Determination, Time
"In a prospective study of normal couples
discontinuing contraception to begin a
pregnancy, the days of ovulation were estimated
by hormonal assay of daily urine specimens. No
hormonal interventions were used. Length of the
follicular phase (from onset of menses to
ovulation) was found to be related to the sex of
the baby among 133 pregnancies that survived to
delivery. Conception cycles with short
follicular phases (early ovulation) tended to
produce boys, while those with long follicular
phases tended to produce girls. This
relationship is consistent with other data and
could explain sex-related differences in the
length of gestation and the observed excess of
same-sex pairs among dizygotic twins."
I happened to ovulate two days late when I conceived
my [baby], though.
After getting different nonsensical news reports
about the New England Journal of Medicine article, I
went and got the real thing. The study was done
with fertile couples only. They tried to answer 4
[first three snipped] and (4) can a couple influence
the sex of the baby by altering the time of
They also didn't find any correlation between timing
of intercourse and sex of the child. So much for
the idea that the guy sperm swim faster than the gal
sperm (or vice versa?): at least not enough to matter
in the uterus under "normal" conditions.
By the way, they monitored the couples in the study
quite closely and estimated time of ovulation based
on chemicals in the daily urine specimens.
I'm not an expert on all of this by any means, but
this article is fairly straightforward.
[A.J. Wilcox, C.R. Weinberg, D.D. Baird (1995) Timing
of sexual intercourse in relation to
ovulation--Effects on the probability of conception,
survival of the pregnancy, and sex of the baby. NEJM
vol. 333 no. 23, pp. 1517-21. Pub. date 12/7/95].
There's an accompanying editorial pp. 1563-1564.
----- end individual responses --------------------