Last updated on Jun 11th, 2021 at 05:33 pm

Couples who want to start a family usually have a gender preference, which is why the boy-girl recipe is so popular. In many cultures it’s considered important to have a boy first. Couples who have two (or more) children of the same sex, and plan to have one more, are more apprehensive about whether they will have a boy or a girl.

ALSO SEE: You might be able to predict your baby’s sex before conceiving, a new study finds

Where the boy-girl recipe comes from

It’s a well-known phenomenon that baby boys and girls come in spates. Little bundles of joy lined up in nursery bassinettes are sometimes predominantly pink, then a few days later, predominantly blue. An older midwife told me it had to do with the moon. A full moon, she said, was for girls, a new moon for boys. Her reasoning was that because a pregnancy is 10 lunar months, if a baby is conceived on a full moon, it will be a girl and babies conceived on a new moon will be boys. She was often right!

Author Colin Ronan in his book Lost Discoveries – A Forgotten Science of the Ancient World writes about a pregnancy test in Egypt that could also predict the baby’s gender. Bags containing wheat and barley were soaked in a woman’s urine. If she was pregnant, her urine would accelerate the growth of the wheat if the baby was a boy, or the barley if it was a girl.

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In the 1970s, Dr Landrum Shettles, after selling millions of copies of his book about choosing your baby’s sex, became known as the ‘father of gender selection’. His methods were based on: timing sex, position, douching and diet. Unfortunately he did not follow research guidelines and his methods were discredited.

Gender selection using fertility technology was made illegal in South Africa in 2012, ‘except in the case of serious sex-linked or sex-limited genetic conditions’. When a couple choose to have gender selection for medical reasons, they can choose preimplantation genetic diagnosis (PGD). This screens out embryos for a specific genetic mutation associated with the disease the family is at risk of passing on.

Modern, scientifically researched natural family planning (NFP) or the sympto-thermal method of natural contraception, is becoming popular. Doctors trained in NFP not only help couples to prevent a pregnancy without pills or injections, they’re finding that couples using the method methodically and successfully are also managing to plan their baby’s gender.

ALSO SEE: 6 fun ways to predict your baby’s gender

Is it the man or the woman who makes a boy or a girl?

In this game we have three players. The man (he makes the sperm and these can be either X for a girl, or Y for a boy), the woman (she provides the egg with only X sex-linked chromosomes), and the baby, who can be XX (girl) or XY (boy).

The man has two testicles where sperm are made. These are not gender specific, e.g. one for girl sperm and the other for boy sperm! Although it takes a full three months (72 days) for a sperm to develop, men are making millions of sperm all the time. At this production rate, there are bound to be mistakes and a high percentage of the three to five hundred million sperm ejaculated are rejects. Studies have shown that men who ejaculate between three and four times a week have healthy, motile sperm.

 Your partner can improve his sperm count by:

  • Wearing boxers – tight underpants keep the testicles close to the body where it’s hot. Sperm can overheat and die
  • Not sitting for too long or cycling – again, sperm overheat
  • Stop smoking (especially cannabis) and drinking alcohol
  • Having regular sex.

When a couple plan to have a specific gender, their sex life depends on the woman’s ovulation – a few days in the middle of her cycle when her body is fertile – and which sperm (the X or the Y) reaches her egg first.

 You will know when your body is fertile when:

  • Your body temperature dips, then rises slightly above normal
  • Your labia feels fuller
  • You have a wet and slippery vaginal secretion
  • High libido.

Healthy, motile sperm consist of a head, neck and tail. The head is covered with a little ‘helmet’ or acrosome to help the sperm burrow into the egg. The neck has little ‘energy tanks’ that help the long tail to swish from side to side, pushing the sperm forward at the speed of 20cm per hour! Y sperm swim a bit faster because they’re lighter, but they’re not quite as resilient as the X sperm.

X sperm swim a bit slower, but they’re more cautious. When sperm are released in seminal fluid (about one teaspoonful) and deposited into the vagina, their survival depends on whether the woman’s body is fertile or not.

Boy-girl recipe

To conceive a girl, the couple should have sex at the start of ovulation but before the egg is released (when her body temperature dips). When this happens, Y sperm who get to the fallopian tube first find it empty so they die. X sperm that swim up a bit later, find the egg waiting. X meets up with X and the baby is XX – a girl.

To conceive a boy, the couple should use a condom until the woman is sure that she has ovulated – some women feel a distinct pain in the pelvis called mittelschmertz. Her vaginal mucous will be very wet, slippery and stretchy like raw egg white. Position and diet are irrelevant. Penetration specifics don’t not make sperm swim faster and what you eat does not change semen or vaginal secretions. When sperm are ejaculated, the Y sperm quickly pass through the cervix – where they’re also energised by cervical mucous – and once recharged, race to the fallopian tube. When they get there, the egg is waiting, Y penetrates X. This equals XY – a boy.

More about the expert:

Sister Burgie Ireland is a qualified and registered nursing sister and midwife. She is also the author of ‘Daisy and the Flowerseller’, a children’s storybook and ‘Childbirth Education’, a fun pregnancy and birth guide. Learn more about Sister Burgie Ireland here.