Don't get Chrissy Glen wrong.

After four years spent coping with the heartache of infertility treatments that didn't work, she considers herself blessed to have a healthy baby girl finally conceived through in-vitro fertilization.

Jenna is a gift, she says, but if they are lucky enough to produce another child, Glen and her husband, Tim, hope for a boy to balance the gender ratio in their family.

Two years ago, 16 of her eggs were mixed with his sperm in a laboratory dish, yielding seven embryos. Two were transferred into her uterus (only one implanted successfully), leaving five available for another shot at IVF.

Using a technique that tests the gender of their remaining embryos before they are placed in the womb, the Glens could all but guarantee themselves a boy next time.

"We would really like to have one of each," says the 34-year-old stay-at-home mom from Richboro, Bucks County. "So that is definitely something we are going to consider."

It's a brave new world in childbearing, where advances in reproductive technology mean Mother Nature doesn't necessarily determine whether the nursery gets painted blue or pink. By spending thousands of dollars, parents can now fulfill any secret desires they may have to choose their child's gender.

And, as access has increased to procedures that can nearly guarantee the sex of a child, so has the freedom of parents-to-be to say what they really want. It's no longer "I just want a healthy baby," but "I just want a healthy baby girl." Or boy.

In a time when elective cesarean sections are scheduled like conference calls and parents outsource everything from baby-proofing to potty-training, it's not surprising that women are turning to science to gain even more control over procreation, says Vicki Glembocki of Westmont, mother of two daughters and author of The Second Nine Months: One Woman Tells the Real Truth About Becoming a Mom.

This newfound power could help to break the silent taboo in our culture about gender preference, she says.

"You are only allowed to say that you want a healthy baby," Glembocki says. "It is almost viewed as being superficial or insensitive to care about gender - but a lot of people do."

Amy Jo Bader, a mother and writer from Bala Cynwyd, says she understands the drive some parents have to meddle in biological fate.

Bader, 29, has a 3-year-old son and an 18-month-old daughter, and won't hesitate to tell you why she wanted to get pregnant a third time. "I'm not yearning for one or another in an all-or-nothing kind of way, but I would love to have a sister for Lucy," says Bader, now expecting. "That is my main motivation for wanting another baby."

Indeed, the unrequited longing for a baby girl is the most common reason women in America are pursuing high-tech gender selection, according to infertility specialist Daniel Potter of Huntington Reproductive Center, whose daughterless mother wept after the birth of her third boy.

"These women have a memory slot in their consciousness that is taken up by the daughter they always imagined," Potter says. "If they can't get that baby girl, it is like a death, and they go through the classic stages of grief."

Log on to In-Gender.com, and you will find a "gender disappointment" support forum for people devastated when their baby was not the sex they wanted. "I had my ultrasound today and started crying on the table. . . . My dreams are totally shattered," one user wrote recently, after discovering she was having a boy.

Family therapist Nancy DePaul of the Council for Relationships in Concordville worries that parents too wrapped up in concerns about gender might be trying to fill a relationship hole in their own lives rather than fulfilling their child's needs. "I also fear a child would get the message that they weren't enough," DePaul says.

Just because you can guarantee the sex of your child doesn't mean you are guaranteed the relationship you seek, says Evelina Sterling, a professional infertility consultant and author of Budgeting for Infertility: How to Bring Home a Baby Without Breaking the Bank, scheduled for release in March.

"There's an assumption for people who spend large amounts of money on family-building that somehow they should get what they are paying for," Sterling says. "Biology doesn't always work like that. We have no control over what our children are going to end up being in the long term."

Still, such admonitions aren't stopping families from going to extraordinary lengths to pursue their gender dreams. And for those without the cash or moral stomach for high-tech methods, there are cheaper, albeit less reliable, options.

Couples visit Web sites such as choosethesexofyourbaby.com or selectbabysex.com to purchase instructional DVDs and kits, many offering money-back guarantees. They take "girl" and "boy" dietary supplements and consult with ancient Chinese gender calendars. They use special douches to alter the pH level of the vagina to make it hospitable to the right kind of sperm, and have sex in recommended positions.

"I've heard of things like this, but always in that hocus-pocus kind of way," says Lauren Rose, 34, of Center City, who is expecting her first child, a boy, next month. "But maybe I'm just not reading the right books or something."

Perhaps the best-known resource is physician Landrum Shettles' How to Choose the Sex of Your Baby, first published in 1960, which advises women to carefully coordinate intercourse with ovulation. His theory holds that male sperm, which swim faster, will win the race to the egg if sex occurs closer to its release from the ovaries.

None of these "natural" methods has more than a 50/50 chance of yielding the desired result, the same coin-flip odds that have always ruled gender selection, Potter says. But since they appear to succeed half the time, he says, believers are made.

After the birth of her daughter almost four years ago, martial-arts instructor Carrie Endara began tracking changes in her body temperature to determine when she was ovulating. Then she and her husband would have sex the day before and the day of ovulation to try to conceive a boy. Their 2-year-old son, Valo, was the result of these carefully plotted conjugal efforts.

"I can't say definitely that it worked," says Endara, 26, of East Norriton. "But the method was easy, and it didn't cost us anything."

If charting ovulation still seems like too much trouble, maybe diet holds the answer. A recent study by British scientists found that women who consume more calories near conception, and in particular eat more cereal, are more likely to have sons. Those who skip breakfast are more likely to have daughters, the researchers found, hypothesizing that evolution favors having boys around in times of plenty and girls during times of distress.

While there may be no harm in eating more Cheerios, Rose - who lost a second baby during pregnancy - says parents should keep in mind that healthy children are the ultimate goal, regardless of sex.

"That's the most important thing, boy or girl," she says. "Especially for those of us who have experienced the kind of sadness we have."

Build-a-Baby

Preimplantation genetic diagnosis (PGD)

Cell removed from embryos created in a laboratory dish through in-vitro fertilization (IVF) is tested for male or female chromosomes, and only those embryos of the desired sex are transferred to the womb.

Guarantee: 99.9 percent accurate.

Cost: About $4,000, not including an average of $10,000 for IVF.

Microsort technique

Experimental method in which fluorescent dye binds temporarily to DNA inside sperm cells. Since the X chromosome is larger than the Y and can bind more DNA, "girl" sperm fluoresce more brightly than their "boy" counterparts. The "sorted" sperm can then be used in IVF, or injected directly into the uterus through a catheter.

Guarantee: Improves the chances of having a girl to 89.5 percent, and carries a 73.6 percent chance for boys, according to Huntington Reproductive Center in California and Genetics & IVF Institute in Fairfax, Va., the two centers offering Microsort in a clinical trial.

Cost: $3,700 to sort one vial of sperm, not including an average of $10,000 for IVF or the cost of intrauterine insemination.

Sperm spinning, or Ericsson technique

Sperm are placed in a test tube atop a column of increasingly thicker layers of albumin and allowed to swim down into the solution. They can be separated into the faster male swimmers and the slower females.

Guarantee: Repeated medical studies have shown that the method does not alter the 50/50 X:Y ratio of sperm as claimed.

Cost: $600-$1,200 per attempt.

Time it right

The "Shettles" method says have sex two to four days before ovulation and you're more likely to have a girl, as only the slower but stronger female sperm will survive long enough to fertilize the egg. Have sex on the day of ovulation or just after and speedier male sperm will get there first. Some also swear by the O+12 method, which unlike Shettles, advises intercourse 12 hours after ovulation to conceive a girl. Make love once or twice a day if you want a girl, as frequent sex lowers the proportion of male sperm in the semen.

Guarantee: Advocates profess a 75 percent to 90 percent success rate with Shettles, but medical studies debunk these claims.

Cost: Free, except for any books and ovulation tracking supplies.

Pick your position

Deeper penetration could boost your chances of having a boy by depositing sperm near the opening of the cervix, favoring the fast-moving Y's. So the missionary position might be a better choice for having a girl.

Guarantee: No scientific evidence for efficacy.

Cost: Time and energy.