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Prenatal diagnosis to facilitate gender selection is the diagnosis of gender in a fetus or embryo before it is born. If a baby of the desired gender has not been conceived, an abortion may be performed or the child may be placed for adoption.

Diagnostic prenatal testing is invasive (ie. amniocentesis, and chorionic villus sampling). Non-invasive methods are called "screens," and are less accurate. Invasive techniques include amniocentesis, which can be done from about 14 weeks gestation, and usually up to about 20 weeks, and chorionic villus sampling which can be done earlier (between 9.5 and 12.5 weeks gestation) but which is slightly more risky to the unborn child.

Methods of Prenatal Diagnosis

Non-invasive Methods

• Examination of the mother's uterus from outside the body. (i.e. Feeling the mother's 'stomach'.)
• Ultrasound detection - Commonly dating scans (sometimes known as booking scans) from 7 weeks to confirm pregnancy dates and look for twins. Later morphology scans from 18 weeks may check for the baby's sex and any abnormal development. The specialised nuchal scan at 11-13 weeks may be used to identify higher risks of Downs syndrome.
• Second trimester maternal serum screening (AFP screening, triple screen, or quad screen) can check levels of alpha fetoprotein, β-hCG, inhibin-A and estriol in the mother's serum. This cannot determine the baby's sex.
• First trimester maternal serum screening can check levels of free β-hCG and PAPP-A in the mother's serum, and combine these with the measurement of nuchal translucency (NT). Some institutions also look for the presence of a fetal nasalbone on the ultrasound. This cannot determine the baby's sex.
• Detection of fetal blood cells in maternal blood. With this technique it is technically possible to obtain a sample of the baby's DNA using blood cells from the fetus, that have made their way into the mother's bloodstream.

Invasive Methods

• Chorionic villus sampling - Involves getting a sample of the chorionic villus and testing it. This can be done earlier than amniocentesis, but is a more risky procedure.
• Amniocentesis - This can be done once enough amniotic fluid has developed to sample. Cells from the baby will be floating in this fluid, and can be separated and tested.
• Embroscopy and fetoscopy - These involve putting a probe into a women's uterus to observe (with a video camera), or to sample blood or tissue from the baby.