Pregnancy has inspired baby-prediction traditions for generations. From carrying high or low to craving sweets, these old wive’s tales offer playful ways to guess whether a baby is male or female. In today's world, social media has introduced ring tests, baking soda tests, Chinese gender calendars, skull theory, Ramzi theory and ultrasound “nub” guesses.
However, there is a key distinction between entertainment and evidence. The traditional signs are not reliable in predicting the sex of a particular baby. This guide clarifies the difference between popular myths and what science reveals, and outlines the accepted prenatal methods that families can discuss with their health care providers.
Quick Answer
Baby’s fetal sex cannot be accurately determined by old wive’s tales. Ring movements, urine reactions, cravings, belly shape, fetal heart rate, carrying position, Chinese calendars, etc., generally do not work any better than chance.
There are a few findings at the population level that have been linked to fetal sex. For instance, hyperemesis gravidarum (severe vomiting during pregnancy) has been reported to be more common in pregnancies involving female fetuses. But that doesn't imply that serious morning sickness can decide the sex of a particular baby.
Prenatal screening options for medically useful information include cell-free DNA screening from around 10 weeks, and ultrasound, including the second trimester anatomy scan. ACOG emphasizes that screening and diagnostic testing are different.
What Are Old Wive’s Tales for Gender Prediction?
Fetal Sex vs Gender: What These Tales Actually Attempt to Predict
Most ‘gender prediction' traditions are really an effort to predict the sex of the fetus, typically using features linked to chromosomes or genital structure.
Gender is a more general term that encompasses identity and social experience. There is no pregnancy symptom or ultrasound guessing game that will predict a child's future gender identity.
Why Most Predictions Have Close to a 50/50 Chance
When two broad outcomes are possible and a method has no genuine predictive ability, guesses can naturally be correct around half the time.
That's why these traditions can appear so accurate. If someone guesses right, he or she might recall the correct guess, but if he or she guesses wrong, it's easy to forget.
Tradition, Confirmation Bias, and Memorable Correct Guesses
An old wive’s tale can seem more true than it is due to confirmation bias. Information that is consistent with a person's beliefs is more likely to be noticed.
If multiple family members make predictions and one of them is correct, that prediction could be the family story even if the others were incorrect.
Why These Games Remain Popular at Baby Showers and Gender Reveals
The appeal is typically not scientific but social. Friends and family can make predictions and compare them, create scorecards or write predictions down until a medical result or birth gives them the answer.
Entertainment without Using the Results for Medical Decisions
It's okay to play these traditions. However, an invalidated prediction should never replace prenatal care, recommended screening, ultrasound examinations, or professional medical advice.
At-Home Gender Prediction Tests
Ring Test: Circles vs Back-and-Forth Movement
A traditional test is to hang a ring over the belly of the pregnant woman. Some say that circular movement foretells a girl and back and forth foretells a boy.
No validated biological mechanism has been established between the movement of the rings and fetal chromosomes or genital anatomy. Hand movement, positioning, and air currents can influence the result.
Baking Soda Test: Fizzing vs No Reaction
The baking soda test is mixing urine with baking soda and seeing if it fizzes (male) or if it fizzes a little (female).
It's just chemistry. It does not provide information about fetal chromosomes.
Why Urine pH Reflects Diet, Hydration, Medication, and Health
There are many factors that can affect urine chemistry, such as diet, hydration, medications and health conditions. So, urine pH is not a specific indicator of fetal sex.
Red Cabbage, Key, and Necklace Tests
Color changes, movement or symbolic interpretation are used in red-cabbage mixtures, key-position tests, and necklace or pendulum games.
They can be entertaining baby-shower activities, but they are not validated medical methods.
Why Pregnant People Should Avoid the Drano Test
The Drano test is particularly unsafe. Drain cleaners can contain very high concentrations of corrosive chemicals which can burn and cause permanent damage to tissues. No medical advantage can be found in this exposure of a pregnant person to these chemicals. Do not use drain cleaner as a pregnancy sex test.
Pregnancy Symptom Myths
Morning Sickness: The “Girl” Prediction and the Important Scientific Nuance
According to the old saying, if you have more morning sickness, you'll have a girl.
This is one myth that has some scientific basis. Studies have shown a correlation between hyperemesis gravidarum and female fetuses. But it doesn't mean that if a woman has a bit of an upset stomach, she's having a girl, and if she has a lot of an upset stomach, she's having a girl.
Fetal Heart Rate Above or Below 140 Beats per Minute
One of the most popular pregnancy myths is the “above 140 means girl” rule.
NCBI revealed no significant difference in mean fetal heart rate in the first trimester of pregnancy between male and female fetuses. The researchers concluded that fetal heart rate is not a reliable test for fetal-sex prediction.
Carrying High vs Carrying Low
A high bump is traditionally associated with a girl, while carrying low is said to mean a boy.
In fact, the appearance of the abdomen depends on body structure, muscle tone, pregnancy history, fetal position and gestational age.
Round, Wide, or Pointed Belly Shape
A round or wide belly is sometimes assigned to one sex and a pointed belly to the other.
No reliable anatomical basis for the use of abdominal shape to determine fetal sex.
Fetal Movement, Energy Levels, and Sleep Position
Strong fetal movement is sometimes labeled a boy sign, while gentler movement is associated with a girl.
Other prediction games include maternal energy levels and sleeping position. None offers a validated method for sex determination of the fetus.
Why Symptoms Cannot Reliably Predict an Individual Baby’s Sex
Hormones, physical changes, metabolism, and other factors all play a role in pregnancy symptoms. Two people with the same sex can have very different pregnancies.
Cravings, Skin, Hair, and Other Body Myths
Sweet Cravings for a Girl vs Salty Cravings for a Boy
It is a common belief that sweet cravings are associated with girls, and salty/savory cravings are associated with boys.
Food cravings are not a test for the chromosomes. Hormones, nausea, food preferences, hunger and other pregnancy-related factors can affect appetite.
Pregnancy Glow, Acne, and the “Girls Steal Beauty” Myth
The proverb goes “girls take their mother's beauty”, and so acne becomes a girl prediction and glowing skin becomes a boy prediction.
Hormonal changes during pregnancy may affect the skin, but acne or what is known as a "pregnancy glow" is not a reliable indicator of fetal sex.
Hair Growth, Texture, and Body Hair Changes
Hair can become thicker or change in texture during pregnancy, and growth of body hair can also vary.
These effects are influenced by hormonal changes and individual biology rather than providing a dependable fetal-sex signal.
Linea Nigra Length and Skin Pigmentation
During pregnancy, a dark line may appear on the abdomen, called the linea nigra. It is not a valid way to predict fetal sex based on its length, darkness or direction.
Breast and Nipple changes
Some changes that happen during pregnancy include breast enlargement, nipple sensitivity, and areolar pigmentation. They range in severity from person to person. They cannot reliably distinguish male from female fetuses.
Mood Changes and Headaches
Old wive’s tales may include mood changes, headaches, fatigue, and irritability. These symptoms can have many causes during pregnancy and are not to be taken as an indicator of fetal sex.
Sympathy Weight and Couvade Symptoms
Some partners experience pregnancy-like symptoms such as nausea, appetite changes, fatigue, or weight changes. This phenomenon is sometimes called couvade syndrome.
Although these symptoms are present, they are not indicative of the baby's fetal sex.
Calendars and Ultrasound Theories That Sound Scientific
Chinese Gender Calendar: Maternal Age and Conception Month
The Chinese gender calendar is a combination of the mother's age and the month of conception that is used to determine the sex of the fetus.
It can seem more scientific than a mere superstition due to the dates and calculations involved. But studies do not validate it as a predictive tool.
What a Study of Over 2.8 Million Births Revealed
A large population-based study examined 2,840,755 singleton births in Sweden from 1973 to 2006. Researchers found that the Chinese lunar calendar was no better at predicting fetal sex than tossing a coin.
This big sample is helpful because it shows how much better large, well-designed studies are than anecdotes.
Mayan and Age-at-Conception Prediction Methods
In the Mayan calendars and other age at conception methods, the maternal age, timing of conception, or a combination of dates are used.
No biological mechanism has been established to link these calculations with fetal chromosomes, so they should be considered entertainment.
Skull Theory and Fetal Head Shape
There is a theory that fetal head shape on ultrasound can be used to determine fetal sex, known as skull theory.
Fetal anatomy and appearance on ultrasound will vary by gestational age, fetal position, imaging angle and individual. The casual interpretation of an ultrasound image is not a validated medical test.
Ramzi Theory and Placental Location
According to Ramzi theory, the position of the placenta or chorion in the first ultrasound examination indicates the sex of the fetus.
It is not a widely used clinical technique for the determination of fetal sex, although it is popular online.
Nub Theory: A Real Anatomical Feature but an Unreliable DIY Interpretation
The “nub” or genital tubercle is a true fetal anatomical structure. Scientists have investigated if its angle on a properly acquired ultrasound could help in early fetal-sex determination.
But, the professional interpretation, image quality, fetal position and gestational age are important. A social media picture should not be used as a substitute for a clinical ultrasound evaluation.
Why Social Media Ultrasound Guesses Are Not Medical Results
Online guesses can be based on incomplete images, miscalculated gestational ages, substandard image quality, or misidentified anatomical structures.
A qualified sonographer or clinician evaluates standardized views in a clinical setting. A cropped ultrasound shared online does not provide the same information.
Which Gender Prediction Claims Have Any Research Behind Them?
Severe Morning Sickness and Its Statistical Association With Female Fetuses
Severe pregnancy vomiting is one of the more statistically well-established traditional claims. A systematic review found that hyperemesis gravidarum was associated with a higher proportion of female offspring, with an odds ratio of 1.27.
Why a Population-Level Association Can't Predict an Individual Pregnancy
An association across groups does not make a symptom a diagnostic test. For instance, if a complication is somewhat more common in female fetuses, many pregnancies that have the complication may also have a male fetus.
Fetal Heart Rate Research and the Lack of Predictive Value
Fetal heart rate is a good illustration of the importance of scientific testing. Studies have shown that the average difference between male and female fetuses is not significant enough to be useful in predicting the individual fetus.
Nub-Angle Studies and the Importance of Gestational Age and Sonographer Skill
The use of ultrasound to determine fetal sex in the first trimester has been studied, with the accuracy of the procedure being dependent on gestational age and proper imaging.
This is different from interpreting a single ultrasound photograph using an online “nub theory” guide.
Evidence Quality vs Anecdotes and Online Accuracy Claims
Anecdotes can be interesting but cannot prove that a prediction method is effective. High quality evidence takes into account sample size, study design, statistical uncertainty, reproducibility, and potential sources of bias. Viral posts rarely provide this level of evidence.
Medical Ways to Learn a Baby’s Fetal Sex
NIPT from Around 10 Weeks
Noninvasive prenatal testing (NIPT or cell-free DNA screening) involves the analysis of DNA fragments that are shed from the placenta into the bloodstream of the pregnant person.
According to ACOG, cell-free DNA testing can start as early as 10 weeks and can be used to screen for common chromosomal conditions and sex-chromosome abnormalities.
Depending on the test and laboratory, fetal-sex information may also be reported.
Why NIPT Is a Screening Test and Not a Diagnostic Test
NIPT is a screening test, NOT a diagnostic test. ACOG notes that cell-free DNA screening can have false-positive and false-negative results and is not equivalent to diagnostic testing. If the screening test is positive, it may need diagnostic follow-up.
The 18-to-22-Week Anatomy Ultrasound
ACOG recommends the second trimester ultrasound be performed from 18 to 22 weeks to assess fetal structures. During this exam, genital anatomy may also be seen, depending on the position of the fetus and the quality of the image.
Why Ultrasound Results May Be Unclear or Incorrect
Fetal position, gestational age, image quality, maternal anatomy, and the experience of the person performing and interpreting the ultrasound examination can all affect ultrasound visualization.
Thus, even a professional ultrasound should be interpreted in the context of the clinical situation.
CVS and Amniocentesis: Diagnostic Tests Not Performed Only to Learn Sex
Diagnostic tests for genetic or chromosomal disorders include chorionic villus sampling (CVS) and amniocentesis. ACOG considers these procedures to be different from screening tests because diagnostic testing can identify if certain conditions are present.
They should not be performed routinely to determine the sex of the fetus, if possible, by safer, noninvasive methods.
Why Chromosomal Results, Genital Anatomy, and Gender Identity Are Different
Chromosomal information, anatomical sex characteristics, and gender identity are different concepts.
A prenatal test can tell you about chromosomes or fetal anatomy, but not about the future gender identity of a child.
Old Wive’s Tales Gender Prediction Scorecard
Signs Traditionally Said to Predict a Boy
Typical “boy” predictions are:
· Carrying low
· Cravings for salty or savory foods
· Fetal heart rate less than 140 bpm
· Pointed belly
· Increased fetal movement
· Smooth and shiny skin
· A Chinese calendar result predicting a boy
Signs Traditionally Said to Predict a Girl
Some common “girl” predictions are:
· Carrying high
· Sweet cravings
· Fetal heart rate >140 bpm
· Severe morning sickness
· Round or wide belly
· Acne or dull skin
· The act of rotating around in circles
· A Chinese calendar result predicting a girl
Most are unsupported. Severe hyperemesis is the notable exception in that research has identified a population-level association, but it remains unsuitable as an individual prediction test.
Record Your Predictions for Fun and Compare Them with Medical Results
If you have an old wive’s tale, make it a harmless prediction game with your family. Write down each person's guess before the medical result is revealed and compare the guesses after the medical result is revealed.
It can be a fun exercise to see how many of the approximately 50/50 guesses can appear more accurate than they really are.
Talk with Your OB/GYN or Midwife about Prenatal Testing
Discuss any questions about prenatal screening with an obstetrician, midwife, genetic counselor or other qualified health care provider.
When families transition from pregnancy preparation to newborn care, baby products can be helpful, too. A bottle washer at grownsy can be useful for regular bottle cleaning, and a bottle warmer can come in handy for families that like to drink milk or formula that is warmed.
A bassinet may be beneficial as an infant sleep area when it complies with relevant safety regulations. The American Academy of Pediatrics recommends that babies sleep on their backs on a firm, flat, non-inclined surface.
Conclusion
The old wive’s tales about fetal sex are a part of a long tradition of pregnancy storytelling. Though they can be fun at family gatherings, baby showers and gender-reveal parties, most have little or no scientific power to predict the sex of a specific baby.
Observations of the belly shape, cravings, fetal heart rate, ring movement, urine reactions, calendars, skin changes, etc. should not be used to replace prenatal screening or professional imaging.
The research also shows why nuance matters. The association of severe pregnancy vomiting with a higher proportion of female fetus at the population level is not strong enough to serve as an individual prediction test.
Evidence-based prenatal care provides much more reliable options when parents seek medically useful information. The second-trimester ultrasound is typically done between 18 and 22 weeks, and the cell-free DNA screening can start at around 10 weeks.
In short, enjoy old wives’ tales as traditions, but rely on qualified healthcare professionals and validated prenatal testing for medical information.
Reference List
American Academy of Pediatrics (AAP). How to Keep Your Sleeping Baby Safe: AAP Policy Explained. https://www.healthychildren.org/English/ages-stages/baby/sleep/Pages/a-parents-guide-to-safe-sleep.aspx
American College of Obstetricians and Gynecologists (ACOG). Current ACOG Guidance. https://www.acog.org/advocacy/policy-priorities/non-invasive-prenatal-testing/current-acog-guidance
American College of Obstetricians and Gynecologists (ACOG). Prenatal Genetic Screening Tests. https://www.acog.org/womens-health/faqs/prenatal-genetic-screening-tests
NCBI. Accuracy of the Chinese lunar calendar method to predict a baby's sex: a population-based study. https://pubmed.ncbi.nlm.nih.gov/20618730/
NCBI. Consequences of hyperemesis gravidarum for offspring: a systematic review and meta-analysis. https://pubmed.ncbi.nlm.nih.gov/21749625/
NCBI. The role of fetal heart rate in first trimester sonograms in prediction of fetal sex: a systematic review and meta-analysis. https://pubmed.ncbi.nlm.nih.gov/37573392/
