Choosing your baby's sex: What the scientists say

Some parents-to-be secretly hope for one sex over the other. Some even want to tilt the odds in their favor. Learn what scientists say about methods for influencing a baby's sex, and read up on the folk wisdom, too.

Can we choose the sex of our child?

Yes, choosing the sex of your child is technically possible, thanks to advances in fertility treatments that allow doctors to identify male and female embryos. Sex selection is an option for couples who want to avoid passing sex-linked genetic disorders to their children. It also might appeal to parents who have children of one sex and want to have a child of the other sex. (This is sometimes called "family balancing.")
But today's sex-selection options aren't equally effective, affordable, or available. The most accurate sex-selection methods are the most expensive (tens of thousands of dollars) and often mean you have to undergo invasive infertility treatments and take fertility drugs with potential side effects.
If you're serious about trying one of these techniques for family balancing, you'll have to meet strict requirements. At some fertility clinics, you won't be eligible unless you're married and already have at least one child of the opposite sex you're trying for. And some clinics have age limits, but all will run hormone tests to see if you're still fertile.
Keep in mind that Mother Nature has already tipped the odds a bit in favor of boys: According to data from the National Center for Health Statistics, approximately 105 boys are born for every 100 girls.
Read on for more information on how today's sex-selection methods work, whether you may eligible to try them, and how much they cost.

Overview: Infertility treatment and high-tech sex selection

Infertility treatment is one way to try to choose your baby's sex.  Artificial insemination (AI) and in vitro fertilization (IVF) are two types of infertility treatment which can also use sex-selection techniques.
These treatments require you to invest significant time and money, and often mean you have to take fertility drugs. Be sure you understand what's involved before deciding whether high-tech sex selection is right for you.
AI is a type of treatment that places sperm closer to the site of fertilization. There are various AI methods, but intrauterine insemination (IUI) is the most common.
When you have IUI, your doctor uses a thin tube (catheter) to insert sperm directly into your uterus. You may also need to take fertility drugs.
In IVF, fertilization takes place outside your body. (In vitro means "in glass.") IVF starts with a round of fertility drugs to stimulate your ovaries to produce multiple eggs for fertilization, instead of the single egg typically released each month.
When your eggs are ready to be retrieved, a doctor gives you an anesthetic and inserts an ultrasound probe through your vagina to check your ovaries and follicles (the fluid-filled sacs where eggs mature). Then your doctor inserts a thin needle through the vaginal wall to remove the eggs from the follicles.
After that, your eggs are fertilized with sperm in a petri dish. Three to five days later, your doctor places the fertilized eggs – now embryos – in your uterus by inserting a thin tube through your vagina and cervix (the opening to the uterus). The number of embryos inserted depends on your age, the quality of the embryos, and your reproductive history.
As a general rule, if you're younger than 35 and the embryos look healthy, no more than two are transferred.

Preimplantation genetic testing

What it is
Preimplantation genetic testing is a procedure that can be done during IVF to remove one or two cells from an embryo and test them for genetic or chromosomal disorders. There are two types of tests – preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS). Both can be used to screen embryos for sex, but which test you have depends on the reason you want to choose the sex of your child.
In PGD, parents with serious inheritable genetic disorders can have their embryos tested and reduce their risk of having a child with the same condition. Sometimes it's important to determine the sex of an embryo because certain genetic disorders are sex-linked and mainly affect males.
For example, if a couple is at risk of having a son with Duchenne muscular dystrophy, PGD can identify male embryos with the abnormal gene. Then these would not be implanted in the uterus.
In PGS, embryos from parents who are presumed to have a normal number of chromosomes are tested for chromosomal disorders, such as Down syndrome. PGS can also screen embryos for sex, so some fertility clinics offer this test for nonmedical reasons, including family balancing.
Effectiveness
PGD and PGS are almost 100 percent accurate at determining the sex of the embryo.
How it's done
During an IVF cycle, eggs are fertilized with sperm in a petri dish. A single cell or cells are later removed from each of the resulting 3- to 5-day-old embryos and tested for genetic disorders or a normal set of chromosomes as well as the sex chromosomes X and Y.
In a regular IVF cycle, scientists try to determine which embryos have the best chance of implanting by looking at them under a microscope. But in preimplantation genetic testing, the embryos are tested thoroughly for genetic or chromosomal abnormalities and sex.
By transferring only healthy embryos to the uterus, you're less likely to miscarry or have a child with a genetic disorder. Prenatal tests, such as  amniocentesis or chorionic villus sampling (CVS), are still offered if you're 35 or older to check for genetic abnormalities.
For IVF, doctors usually transfer more than one embryo to your uterus – the number depends on your age, the quality of the embryos, and your reproductive history. (If you're 40 or older, typically three to four embryos may be transferred.) But if you have PGD or PGS, doctors usually transfer fewer embryos because they've already weeded out the ones that are unlikely to implant or result in a healthy pregnancy.
Pros

• If you do get pregnant, PGD and PGS ensure with almost 100 percent certainty that you'll have a baby of the sex you desire.
• Following a PGD or PGS cycle, remaining embryos of both sexes can be frozen. These can be used in the future if you miscarry or decide you want more children. Frozen embryos have a success rate similar to fresh transfers, but the procedure is less invasive and significantly cheaper.

Cons

• A single round of IVF with preimplantation genetic testing can cost more than $20,000.
• The procedure is invasive, and having eggs removed from your ovaries can be painful.
• Fertility drugs can have uncomfortable side effects, including weight gain, bloating, swelling, and blurred vision.
• As with any IVF pregnancy, you're more likely to have multiple births. According to the latest statistics from the U.S. Centers for Disease Control and Prevention, out of all infants conceived through IVF (and related procedures involving multiple embryo transfers) about 46 percent were twins or other multiples.  However, the possibility of multiples may be lower with PGD and PGS because in many cases only a single embryo is transferred.
• In women younger than 35, about 46 percent of fresh IVF cycles result in a live birth, and that percentage goes down as you get older. (Most IVF centers report higher success rates with PGD and PGS because abnormal embryos are excluded.)
• You'll need to decide what to do with the unused embryos: freeze, discard, or donate for adoption or research.

Cost

The average cost of a single IVF cycle is $12,400, according to the American Society for Reproductive Medicine. Preimplantation genetic testing adds another $5,000 to $8,000 to the tab. Check with your insurance – part of the expense may be covered.
Availability
Some fertility clinics offer preimplantation genetic testing only for medical reasons, and not for sex selection. Other centers allow you to use PGS to choose the sex of your baby, even if you don't have a medical reason to do so. Call fertility clinics to find out their policy on sex selection.
For more information
Read the American Society for Reproductive Medicine's report on sex selection and recommendations for its use.

Ericsson method

What it is
This technique, named for pioneer Ronald Ericsson, aims to separate faster-swimming, boy-producing sperm from slower-swimming, girl-producing sperm. In theory, the sperm placed directly into your uterus through AI will become the desired sex of your baby.
Effectiveness
Ericsson claims his technique is 78 to 85 percent effective when it comes to choosing boys and 73 to 75 percent effective for selecting girls.
How it's done
First, a sperm sample is poured on a gluey layer of fluid in a test tube. All the sperm naturally swim down, but the boy-producing sperm tend to swim faster and reach the bottom sooner.
Once the fast and slow swimmers are separated, you're inseminated with the sperm that may help you conceive a baby of the sex you desire.
Pros

• Inexpensive compared to higher-tech methods.
• Noninvasive.
• Relatively safe.

Cons

• There's no guarantee of success. Ericsson has published extensively and claims a success rate of approximately 75 to 80 percent. But evaluations of the test haven't been published by other fertility experts or proven independently.
• AI is not as effective as IVF, and it may take many cycles to achieve a pregnancy, depending on your age and fertility.

Cost
Approximately $600 per insemination.
Availability
This technique is available to everyone at clinics in California, Florida, Maine, Michigan, New Jersey, and New York. Look for one in your area.

Overview: At-home techniques

These low-tech methods are noninvasive and affordable, and you can do them in the privacy of your own home. All you need to do is chart your basal body temperature or use an ovulation predictor kit to determine when you ovulate. Then time sex accordingly.
So what's the catch? Their effectiveness is questionable at best.
Shettles method
What it is
Timed intercourse on specific days of your cycle.
Effectiveness
Shettles proponents claim the technique is 75 percent effective for choosing girls and 80 percent for choosing boys, but other experts are doubtful. Keep in mind that you always have about a 50 percent chance of conceiving a child of the sex you want.
How it's done
The theory is that sperm bearing a Y chromosome (for boys) move faster but don't live as long as sperm that carry X chromosomes (for girls). So if you want a boy, the Shettles method contends you should have sex as close as possible to ovulation. If you want a girl, plan to have sex two to four days before you ovulate.
Pros

• Does not require drugs or invasive medical procedures.
• Free or low cost.
• Safe.

Cons

• You must use an ovulation predictor kit to figure out when you're ovulating, or chart your basal body temperature to estimate the best time to have intercourse.
• There's no guarantee of success.

Availability
Anyone can try it at home.
For more information:

What it is
Timed intercourse on specific days of your cycle.
Effectiveness
Elizabeth Whelan claims her technique is 68 percent effective for choosing boys and 56 percent effective for choosing girls, but many experts are doubtful. Keep in mind that you always have a 50 percent chance of conceiving a child of the sex you want.
How it's done
The Whelan method directly contradicts the Shettles method. The theory here is that the biochemical changes that may favor boy-producing sperm occur earlier in a woman's cycle.
So if you want a boy, you should have intercourse four to six days before your basal body temperature goes up. If you want a girl, plan to have sex two to three days before you ovulate.
Pros

• Does not require drugs or invasive medical procedures.
• Free or low cost.
• Safe.

Cons

• You need to take your basal body temperature every day to figure out when you're ovulating, or use an ovulation prediction kit.
• There's no guarantee of success.

Availability
Anyone can try it at home.
For more information:

Sex-selection kits

What it is
These at-home kits are based on the Shettles theory. Separate girl and boy kits include a thermometer, ovulation predictor test sticks, vitamins, herbal extracts, and douches that are supposedly intended to favor a specific sex.
Effectiveness
Kit makers claim a 96 percent success rate, but some medical experts say the manufacturer's claims have no scientific merit.
How it's done
You track your cycle by using the thermometer and urinating on the ovulation predictor test sticks. Following the Shettles method, you have intercourse two to four days before ovulation if you want a girl and as close as possible to ovulation if you want a boy.
The douche is intended to change the vaginal environment to "influence the chances that either an X-carrying sperm or a Y-carrying sperm will be successful in fertilizing the egg." Vitamins and herbal extracts are also included to supposedly boost your odds of getting a child that is the sex of your choice.
Pros

• Does not require invasive medical procedures.
• Convenient.

Cons

• The success rate claimed by the makers is questionable.
• Expensive.

Cost
$199 for a 30-day kit.
Availability
Sex-selection kits are available through GenSelect.
For more information
Learn more about sex-selection kits at GenSelect's Web site.

The bottom line: What do the experts say?

High-tech sex-selection methods have stirred hot debate in the medical community. Some doctors think it's a great way to balance families, while others think we're heading down a dangerous path.
Mark Sauer, a fertility specialist and the program director at the Center for Women's Reproductive Care at Columbia University in New York, thinks that sex selection for family balancing is unethical and has no place in fertility treatments.
"I can't endorse the destruction of normal human embryos because they happened to be of the wrong sex," he says.
Not all fertility doctors agree with Sauer. Although the American Society for Reproductive Medicine officially opposes preimplantation genetic testing for nonmedical reasons, it acknowledges that sex selection shouldn't be condemned in all cases and doesn't favor making it illegal.
Low-tech sex selection has not sparked the same controversy, probably because these methods are far from foolproof, and the assumption is that couples practicing them are investing less – both financially and emotionally – in their success. But do they work?
These techniques range from Shettles and Whelan to folk wisdom (such as making love standing up and eating more meat if you want a boy, and eating lots of chocolate and having sex in the missionary position if you want a girl). The American Society for Reproductive Medicine says there's no evidence any of this can influence the sex of your baby.
"I tell my patients that if they want to try low-tech methods, give them a go," says Brian Acacio, a fertility specialist and medical director of the Sher Institutes of Reproductive Medicine in Los Angeles. "They probably won't hurt, and there's a 50 percent chance they'll work."