Y Chromosome
Y ChromosomeNIPT

Y Chromosome

January 20, 2021


What is the Y chromosome?

The Y chromosome is one of the two sex chromosomes in human. The other is the X chromosome. The presence of the Y chromosome triggers development of the baby into a male. Human females usually have two X chromosomes, while males usually have one X and one Y.

Why is this analysis important?

Mothers can usually choose to find out the sex of their baby at their 20-week ultrasound scan which is offered by the NHS. However, the accuracy of the sex determination by ultrasound can vary greatly dependent on the sonographer’s experience, technique and the position of the baby in the uterus etc. Sex determination by identification of the Y chromosome using the non-invasive prenatal test (NIPT) is much more reliable with a sensitivity as high as 99.6%.


The results can show if the Y chromosome is “present” or “absent”. Depending on if you are carrying only one baby or twins, the results will be interpreted differently.

If the Y chromosome is “present”, this indicates that your baby is a boy. In case of twins, the presence of the Y chromosome indicates that at least one of the babies is a boy, but we can unfortunately not know if both twins are boys or if it is a boy and a girl. Unless the twins are monochorionic, which means that they share the same placenta and thereby identical twins and should therefore be two boys.

If the Y chromosome is “absent”, this indicates that the baby is a girl. In case of twins, this indicates that both twins are also girls.

Other Considerations

Receiving results on the Y chromosome is optional and free of charge. After purchase, you will be asked to tell us whether you want to know the sex of your baby or not. The NIPT test cannot detect genetic conditions related to the sex chromosomes.

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