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Is it a boy or a girl?

Facts and myths about predicting the sex of your baby. Terrible morning sickness? Definitely be a girl! No mood swings? Must be a boy… There are dozens of signs believed to indicate the sex of a baby still in utero, but we know most of these are based on folklore rather than science. Still, if these myths persist don’t they have some basis in fact? This article looks into eight of the most common beliefs.

A baby’s gender is determined when the egg is fertilized. An ultrasound test at 20 weeks into pregnancy is the most reliable way to discover the sex of a fetus, but a small minority of future parents decide to keep their child’s gender a mystery until the day of birth. Why do we want to know? And why is it that some of us just can’t wait? What lies hidden in our desire to know or not to know the sex of our babies in advance?

Nausea

The myth. The frequency of nausea a pregnant woman experiences can predict the sex of her baby. According to folklore, if a woman has no morning sickness in the first trimester, she should prepare to welcome a little boy. But if her morning sickness is severe, it’s likely that a little girl is on the way.

True or false? In fact, recent research suggests that feeling ill during pregnancy may indeed be linked to the baby’s sex. A study found that women carrying girls experienced more inflammation when their immune systems were exposed to bacteria compared with women carrying boys. This difference may impact the way women experience morning sickness. Those carrying girls may feel more unwell than those carrying boys. However, more research is needed to fully understand if there is a significant link between morning sickness and a baby’s sex.

Baby’s heart rate

The myth. If the fetal heart rate is greater than 140 beats per minute, it will be a girl. If it is slower, it will be a boy.

True or false? Scientists have measured the heart rates of dozens of babies in utero. Research shows there are no significant gender differences in any measured aspect of fetal heart rate variation.

Mood swings

The myth. Hormonal changes during pregnancy can often cause mood swings. Some people think that women carrying girls have higher levels of estrogen and are moodier as a result. 

True or false? There is scientific evidence that hormone concentrations in pregnancy can differ according to the sex of the fetus as early as three weeks after fertilization.

Studies have shown that hCG (human chorionic gonadotropin, the hormone home pregnancy tests respond to) is higher for female fetuses compared with males and remains elevated throughout pregnancy.

The symptoms of high hCG levels are so-called pregnancy glow (this hormone makes skin oilier) and morning sickness in the first trimester of pregnancy. Human chorionic gonadotropin also triggers an increase in the production of estrogen and progesterone. Even so, there is no scientific proof that levels of estrogen, which can cause mood swings, are higher in women carrying girls. Estrogen levels rise during pregnancy and fall after giving birth regardless of whether the baby is male or female.


Look at the moon!

The myth. Many people believe the lunar calendar influences the sex of the baby. Knowing the lunar phase at the time of ovulation/conception is enough to determine a baby’s sex:

  • If the moon is waxing (the period between the new moon and the full moon), the baby will be a boy.
  • If the moon is waning (the period between the full moon and the new moon), the baby will be a girl.
The sex of a future baby can be planned by engaging in sexual intercourse at the proper time for the required gender, assuming that the woman is ovulating at that time.

True or false? Although this method of determining the sex of a child sounds like fairy tale magic, it has been seriously researched and a correlation has been found. Lunar phases do influence a woman’s vaginal pH, meaning that a couple has a greater chance of having a boy if ovulation and conception take place during the full moon and of having a girl if the child is conceived when the moon is new.

Weight distribution

The myth. If a woman gains weight around her middle during pregnancy, she will have a girl, but if she gains weight just in the front of the body, it will be a boy.

True or false? Scientific evidence does not back up this theory. Where a woman gains weight during pregnancy depends on her body type.

The shape of the bump

The myth. If a pregnant woman’s belly is high and pointed, it certainly hides a little boy. But if it is round, wide, and low, her baby will be a girl.

True or false? The shape of a pregnant woman’s bump is determined by the size of the baby, by the position of the fetus, and by the number of pregnancies she has had.

It is true that on average baby boys weigh more at birth than baby girls, and a larger baby might make the belly slightly bigger. However, this difference in weight is so small it wouldn’t change the shape of the bump.

The position of the fetus in the womb has a greater influence on the shape of the belly. If the baby’s back is lying alongside the mother’s front, her belly will stick out. If the baby’s back is parallel with the mother’s back, the abdomen looks flatter. The position the future baby adopts is not dependent on its gender.

Also, pregnancy stretches the abdominal muscles and they stay flexible after pregnancy. Women who have already carried a child may notice that the belly grows big faster and earlier than with the first pregnancy.

Food cravings

The myth. Many women experience food cravings when pregnant. Some people think that sugar cravings mean a girl is on the way, whereas cravings for salty food indicate a boy.

True or false? There is no scientific evidence to suggest that food cravings during pregnancy can indicate the sex of the baby.

Little girls will steal your beauty?

The myth. According to legend, girls steal away their mothers’ beauty. But if a pregnant woman grows more attractive through her pregnancy, she can thank the little boy in her womb.

True or false? There is no evidence to support this! The same woman can look differently at different stages of her pregnancy—glowingly beautiful one day, but tired and exhausted the next.


Does the ultrasound test provide 100% accuracy in prediction of gender?

The baby’s gender is determined at the moment of conception—when the sperm contributed carries a Y chromosome a boy is conceived; if the sperm carries an X chromosome, the baby will be a girl.


Male and female genitalia develop in the same, way with no external gender differentiation until about nine weeks.

At nine weeks the genital tubercle begins to develop into a clitoris or penis. However, it is possible to see differentiated genitalia only at 14 or 15 weeks.

Starting at about 12 weeks, an ultrasound can help determine a baby’s gender based on the angle of the genital tubercle; this is sometimes called ‘nub theory’. Using this method, the sonographer looks to see whether the tubercle is pointing up toward the baby’s head, indicating a boy, or whether it remains flat, indicating a girl.

Ultrasound examinations are not intended to determine the sex of the child; they are primarily used to follow the course of pregnancy and the development of the child. But of course the ultrasound can be used to determine the sex of the child with great accuracy. Predictions are correct about 90 percent of the time.

Although it is possible to determine gender as early as 12 weeks, a number of circumstances may influence whether or not this is possible: The baby needs to be well-positioned for the ultrasound; the sonographer may not have time to wait until the baby moves into a better presentation to make a prediction. The clarity of the ultrasound images and the skill of the person interpreting them also play a role.


Sometimes the umbilical cord is taken for the penis, which is why boys are mistakenly predicted more often than girls.

The only way to be completely sure of the sex of a baby is to wait until the baby is born.

To know or not to know? Pros and cons

The desire to know the sex of an unborn child is motivated by emotion, and emotions make us care. Knowing whether to expect a boy or a girl can help personalize pregnancy. If parents can imagine a person, rather than a baby in the abstract, they may be better prepared for baby’s arrival: they can choose their baby’s name (usually associated with a specific gender) and shop for the person they visualise joining the family.

Parents who choose not to know their child’s gender during pregnancy emphasize that it is more important to have a healthy baby rather than to prepare for a boy or a girl. It is also thought that this stage is unique because the child is loved completely regardless of his or her gender.

For some the rush to know takes away a surprise that is worth the wait.

Sometimes the desire to know the sex of a child is linked to a gender preference.


Depending on the country and its traditions, a boy or girl may be more socially desirable or may present a greater financial challenge.

This is an ethically controversial issue as now, with the help of modern medicine, it is possible to have a child of specific sex or to prevent the birth of a baby of unwanted gender.

Experience in many countries has shown that gender-selective birth control can have unpredictable consequences, such as the dramatic surplus of males in some parts of Asia and Africa. Although it was once considered better to have a boy, now too many men are unable to find a female partner. This results in low self-esteem and other psychological difficulties, often leading to aggression and violence. Gender equality is the solution.

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