The Idea Behind It
The timing of intercourse definitely affects whether or not you get pregnant. Women ovulate (release an egg) only once a month. The days shortly before ovulation and immediately afterward are the best times to get pregnant.
The Whelan method adds another layer to timing. The idea is that sperm with Y chromosomes (which make boy babies) are more likely to fertilize an egg at certain times of a woman's cycle. At other times, sperm with X chromosomes (which make girl babies) are more likely to do the job.
The Whelan method was developed by Elizabeth Whelan, who holds a doctorate in public health. Her recommendations are based in part on the work of Dr. Rodrigo Guerrero, a physician from Colombia, who published two studies in the 1970s.
Guerrero studied the timing of conception in over 1,300 women. He used the basal body temperature (BBT) method to determine when ovulation occurred. BBT rises slightly shortly after ovulation.
Guerrero reported that when intercourse led to conception on the day basal body temperature rose, only 43.5 percent of births were male. The greatest chance of having a boy baby came with conception six or more days before the rise.
Following the Whelan Method
To follow the Whelan method, you'll need to follow your basal body temperature (BBT). You need a special thermometer which can measure changes as small as a tenth of a degree. You can find BBT thermometers at the drugstore or online.
Take your temperature every morning, as soon as you wake up. Plot each day's temperature on a graph so that you can see when it changes. Look for a change of about one half to one degree. It may take a few cycles to distinguish the ovulation-related rise from smaller fluctuations.
Once you know which day of your cycle your BBT is likely to rise, you can begin planning intercourse. Whelan says to have intercourse near the time of ovulation if you want a girl, and four to six days before your BBT rise if you want a boy.
Whelan gives full details in her book Boy or Girl.
Whelan Versus Shettles
The Shettles method is a popular low-tech way of choosing the sex of a baby. Research on whether it works is scanty, but many women swear by it.
The Shettles method is another timing-based method. However, the instructions are opposite to Whelan's. Shettles says to have intercourse around the time of ovulation to make a boy baby, and a few days before ovulation for a girl.
Guerrero argued that the data Shettles used was based on studies of artificial insemination. Guerrero own studies showed that gender selection based on timing did, indeed, work differently for artificial insemination than for natural intercourse.
So, who's right? There isn't any really strong science behind either method. Doctors will need to do more studies before anyone knows for sure.
Does It Work?
Whelan claims that following her plan to conceive a boy works 68% of the time. For girls, she says the success rate is 57%. Even if she's right, that's certainly not a guarantee.
Medical studies haven't proven that timing makes much of a difference. However, there is some research, more recent than Guerrero, that suggests having intercourse in the two days before ovulation does make having a girl more likely.
Other Methods for Gender Selection
The only sure way to choose your baby's gender is through either artificial insemination or selective abortion. Even then, it's possible to make a mistake.
Still, trying for a boy or a girl can be a fun part of planning a pregnancy. There are calendars, diets, other timing methods, and even suggestions for which sexual positions to choose. Check with your doctor first before trying any special diets, supplements, medicines, or anything else that could put you or baby at risk. Otherwise, as long as you'll be happy with a baby of either gender, you can enjoy the process.