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Tests are gaining popularity to determine the sex of the unborn child. Most often, parents want to prepare for the birth of a baby, as well as feel a closer emotional connection. In addition, information about the sex of the fetus may be necessary in early pregnancy for medical reasons. In the event that a disease genetically related to the sex chromosomes can be transmitted in the family.
A baby sex test can help parents satisfy their curiosity. However, not all tests are equally reliable.
To use this method, you need to know not only the exact day of conception, but also the day of ovulation. All spermatozoa can be divided into 2 groups: carriers of X chromosomes and carriers of Y chromosomes. If the sperm from the first group “wins”, you will get a girl, if from the second – a boy.
The growing interest of families and medical professionals in the methods of determining the sex of a child in early pregnancy has led to the need to introduce safe and non-invasive research into a permanent practice. Invasive diagnostic methods cannot be used only for this purpose and without appropriate medical indications. Therefore, there are more and more different research options that allow you to determine the sex of the unborn child quickly and with high accuracy.
It is believed that the “girl” chromosomes are more tenacious, but slow, and the “boy”, on the contrary, are fast, but not tenacious. Maiden chromosomes can sit in the uterus and wait for ovulation, but boy chromosomes cannot.
If intercourse was 2-4 days before ovulation, you will have a daughter. If he was directly on the day of ovulation or a few days after it, expect your son.
What non-invasive tests to determine the sex of the fetus are there?
Studies to determine the sex of a child, also known as non-invasive gender tests, are presented in several versions:
- Urinalysis is based on the detection of fetal sex hormones.
- Ultrasound – a scan is performed using an ultrasonic sensor and the establishment of primary sexual characteristics.
- PCR test – using an analysis in the mother’s blood, the presence or absence of fragments of the Y chromosome is determined.
- NIPT is a non-invasive prenatal testing performed using molecular biological methods. [1]
Urinalysis is not widely used due to the fact that it is the least accurate of the listed, performed at home. Ultrasound is the traditional way to determine the sex of a child, but it is limited by two indicators: firstly, by the gestational age, its accuracy reaches its maximum level after 18 weeks; secondly, poor visualization of the fetus or excessive activity can interfere with the doctor [2] .
The PCR test is an effective and safe approach, but it does not provide any additional information [3] . A more informative method is NIPT, it allows you to determine the sex of the fetus with an accuracy of 99.8% in the earliest stages of pregnancy [4,5] . In addition, the test is able to identify the risk of chromosomal abnormalities.
Benefits of the NIPT Method
Non-invasive prenatal testing has been developed to screen for chromosomal abnormalities such as trisomies 21, 18 and 13 (Down, Edwards, Patau syndromes). NIPT has many advantages over other screening and/or sex determination methods. It is non-invasive (only a mother’s blood sample is required), so it does not pose a threat to a pregnant woman or child, and is also a more comfortable option, unlike invasive diagnostic methods. The test has high accuracy rates. A 2017 systematic review of singleton pregnancies found that the sensitivity and specificity of non-invasive prenatal testing for fetal gender is as high as 99% [6].
Execution principle
Non-invasive prenatal testing measures the amount and composition of freely circulating extracellular DNA (cfDNA) in a pregnant woman’s blood, which is a mixture of maternal DNA and a small percentage of fetal DNA.
A woman can donate venous blood for analysis after 10 obstetric weeks of pregnancy [7] . By this time, the concentration of fetal cfDNA in the mother’s blood reaches the minimum threshold value necessary for the qualitative performance of the study. Testing in this case can have a sensitivity of up to 99%.
Analysis steps:
- cfDNA is isolated from the blood.
- Fragments of the Y chromosome among cfDNA can be detected using the following methods: microarrays, next generation sequencing, PCR test or mass spectrometry.
- The obtained data is analyzed and the result is transmitted to the patient.
The interpretation of the results is to confirm the presence or absence of fragments of the Y chromosome. If they are found, then the woman is expecting a boy, if not, then a girl.
By date of birth of parents
This is one of the most ancient methods. It was invented in Japan. For this test, you will have to find two special tables – the table of pair numbers and the main table of the test. Then follow the instructions:
- In the first table above, the months of birth are indicated for the man, and on the left – the women. Find the intersection of your months to determine the number of the pair.
- Find the couple’s number in the second table and check it against the month of conception.
- Get the baby’s gender and information on how likely that gender is. In some months, the chances of having a boy or a girl are almost equal.
Despite the antiquity of the method, he also sometimes makes mistakes.
Determination of the sex of the unborn child by blood
From the 7th week of pregnancy, the sex of the baby can be determined by a routine blood test. If a Y chromosome is detected in it, then a boy will definitely be born, because girls do not have such chromosomes. If the doctor “catches” the X chromosome, then the chances between the boy and the girl are equal, because the Y chromosome could simply not be caught. Due to this inaccuracy, even doctors are not advised to trust such a medical test.
This is an American test that was invented about 10 years ago. It is believed that it determines the sex of the baby with an accuracy of 87-95%, that is, it is not the most accurate option. But it is the simplest and safest. It’s easy to use. You need to collect some urine in a special container, wait for the specified time, and then check the color. He will indicate the sex of the fetus.
To make sure what the gender of your baby will be, you can take several tests at once. However, remember that the surest way to determine this is an ultrasound scan.
Reliability of NIPT results
NIPT demonstrates high sensitivity and specificity for screening for common aneuploidy and fetal sex determination [6] . Also, compared to other prenatal screening tests, it has a low false negative rate of 0.09 to 0.13% [8] .
List of sources used:
- Bowman-Smart, H., Savulescu, J., Gyngell, C., Mand, C., & Delatycki, MB (2019). Sex selection and non-invasive prenatal testing: a review of current practices, evidence, and ethical issues. prenatal diagnosis. doi:10.1002/pd.5555
- Behzad Mehr, R., Rezaie Keikhaie, K.; Behzad Mehr, R. (2020). Accuracy of Ultrasonography in Fetal Gender Determination in 11 to 14 Week of Gestational Age. Gene, Cell and Tissue, 8(1). doi:10.5812/gct.95381
- Perspectives of Pregnant People and Clinicians on Noninvasive Prenatal Testing: A Systematic Review and Qualitative Meta-synthesis. (2019). Ontario Health Technology Assessment Series, 19(5).
- Norton, ME, Jacobsson, B., Swamy, GK, Laurent, LC, Ranzini, AC, Brar, H., … Wapner, RJ (2015). Cell-free DNA Analysis for Noninvasive Examination of Trisomy. New England Journal of Medicine, 372(17), 1589–1597. doi:10.1056/nejmoa1407349
- Kearin, M., Pollard, K., & Garbett, I. (2014). Accuracy of sonographic fetal gender determination: predictions made by sonographers during routine obstetric ultrasound scans. Australasian Journal of Ultrasound in Medicine, 17(3), 125–130. doi:10.1002/j.2205-0140.2014.tb00028.x
- Mackie, F., Hemming, K., Allen, S., Morris, R., & Kilby, M. (2016). The accuracy of cell-free fetal DNA-based non-invasive prenatal testing in singleton pregnancies: a systematic review and bivariate meta-analysis. BJOG: An International Journal of Obstetrics & Gynaecology, 124(1), 32–46. doi:10.1111/1471-0528.14050
- https://harmonytest.roche.com/
- Yu, B., Lu, B.-Y., Zhang, B., Zhang, X.-Q., Chen, Y.-P., Zhou, Q., … Wang, H.-Y. (2017). Overall evaluation of the clinical value of prenatal screening for fetal-free DNA in maternal blood. Medicine, 96(27), e7114. doi:10.1097/md.0000000000007114