Trying to Win the Baby-Gender Lottery? Turn to Science

A woman I know is convinced that the reason she has three sons and no daughters is due to the British food marmite that she loves to spread on her toast. This delicacy (black, tarry, boiled-down yeast extract) is salty as heck--and salt, she says, favors the birth of boys.

The odds of such a family lineup occurring just by chance, according to my trusty calculator, are about one in eight. But I’d heard of the salt link before and was intrigued enough to investigate.

Within minutes, I’d located a number of pastel-colored, stork- and angel-adorned Web sites offering lots of help and advice for parents who want to try to pick the gender of their child. Some of the sites claim that eating lots of salt does favor a boy because it alters the chemistry of the egg in a way that favors the entry of male-determining sperm.

But why stop at just eating salt? Timing of intercourse, acid or alkaline douches, whether the woman has an orgasm, drinking coffee or decaf--all of these and more are purported to push the odds in favor of having one gender or another.

The rationale is that there are basic biological differences between sperm that carry an X chromosome (which lead to female embryos when they fertilize an egg) and sperm with a Y chromosome (which lead to males). And, further, that these odd-sounding activities preferentially select for one type of sperm or the other.

Having located all this advice, we called some fertility experts to find out what they thought of it.

“I’ve always been intrigued by this stuff,” says Dr. Richard Paulson, chief of the division of reproductive endocrinology and infertility at USC’s school of medicine. “There are all these different theories--about how boy sperm are smaller, faster but not as hardy, and the girl sperm are bigger and slower but live longer and tolerate acid treatment.”

Much of the advice follows from these basic premises, Paulson says. It is argued, for instance, that the odds of having a girl increase if a couple has intercourse several days before conception and the woman douches with acidy vinegar--because the “less hardy” sperm will be dead by the time the egg arrives.

Alkaline douches, on the other hand, are said to nurture the Y-bearing sperm, and if intercourse is timed for right at ovulation, those speedy boy sperm will fertilize the egg long before the sluggish, X-bearing sperm gets anywhere close.

Unfortunately, Paulson says, these theories are completely wrong.”All the tricks--having orgasms, not having orgasms, acid and base douches--none of those work,” says Dr. Alan DeCherney, professor and chair of obstetrics and gynecology at the UCLA School of Medicine. “It’s just like people saying if you’re carrying low it’s a girl, if you have hiccups it’s a boy. There is an obsession with gender.”

Yet X-bearing and Y-bearing sperm do differ slightly: The X-bearing sperm have about 2.8% more DNA.

Based on this difference, researchers have also tried a medley of methods to separate the two types, such as forcing them to swim through thick mucus. The idea is that the slim, athletic Y sperm will wriggle along faster than the slightly stouter X sperm so they eventually separate into two distinct packs.

That doesn’t work either, says DeCherney, but other tricks--also based on DNA differences--do.

Reasonable for selecting girls, for instance, is a fancy-sounding technique out of Virginia that employs lasers and DNA-binding dyes and examines each sperm, one by one (which sounds like a job-and-a-half).

It sorts the sperm according to how much DNA each one has, flicking it off down one of two sperm-sized passages.

Even more effective is a method in which a single cell from an in vitro-fertilized embryo is DNA-tested for gender. Then the sex of choice is implanted. (This is a pretty controversial technique, and many fertility clinics won’t offer the service except for medical reasons.)

As for the future--who knows?

“I predict,” says Paulson, “that one of these days there’ll come a time when you’ll go into the supermarket, go to the medicine section and right next to the sanitary napkins will be a blue box and a pink box that you can take home and mix with sperm to do at-home selection for male and female.”

*

If you have an idea for a Booster Shots topic, write or e-mail Rosie Mestel at the Los Angeles Times, 202 W. 1st. St., Los Angeles, CA 90012, [email protected].