Prenatal Diagnostic Testing

Causes & Risk Factors

Prenatal diagnostic testing is typically recommended in specific clinical situations, rather than offered as routine screening:

•  High-risk result on first-trimester screening or NIPT

•  Abnormal findings on fetal ultrasound

•  Previous pregnancy or child affected by a genetic or chromosomal condition

•  Known parental genetic variant or chromosomal rearrangement

•  Family history of an inherited disorder relevant to the current pregnancy

•  Advanced maternal age, in combination with other risk factors, in appropriate clinical context

Symptoms & When to Test

As with screening, diagnostic testing is driven by clinical indication and pregnancy stage rather than symptoms.

•  Chorionic villus sampling (CVS) — a sample of placental tissue obtained during a defined window in pregnancy, typically earlier than amniocentesis

•  Amniocentesis — a sample of amniotic fluid obtained during a defined later window in pregnancy

When Should You Consider Testing?

Diagnostic testing is generally considered after a high-risk screening result, an abnormal ultrasound finding, or when a known parental genetic risk makes a definitive answer clinically necessary — always under the guidance of your obstetrician or a genetic counsellor.

Why Tests Are Combined

Depending on the clinical question, a sample obtained via CVS or amniocentesis may be evaluated using more than one technique — karyotyping identifies large chromosomal abnormalities, while chromosomal microarray can detect smaller structural changes that karyotyping may miss, and targeted molecular testing is added when a specific familial genetic variant is being tested for.

Using a single technique alone risks missing abnormalities outside its detection range; combining approaches based on the clinical indication ensures the analysis matches the actual question being asked (broad chromosomal survey versus a specific known variant).

These procedures and the resulting genetic analysis are performed under appropriate specialist care, with genetic counselling recommended both before the procedure and after results are available.

Tests Available at NPL

Most reproductive hormone and genetic tests do not require fasting. However, some tests have specific timing requirements (such as a particular day of the menstrual cycle), and if other tests are ordered at the same time, fasting may be required for those investigations. Please follow the preparation and timing instructions provided by your doctor or NPL.

Home Sample Collection

Unlike routine blood tests, CVS and amniocentesis are invasive procedures that must be performed by a specialist obstetrician at a clinic or hospital — they are not available as a home collection service.

Once your obstetrician has obtained the sample, NPL arranges secure, temperature-controlled transport of the sample to our NABL ACCREDITED UNDER ISO 15189:2022 laboratory for genetic analysis.

Your digital report is delivered securely to your treating obstetrician and to you, along with access to download and share it as needed.

If you have questions about scheduling the procedure itself, please coordinate directly with your obstetrician; NPL can assist with queries related to sample processing and reporting timelines at +977 1 5970147.

When to See a Doctor

•  High-risk screening result requiring diagnostic confirmation

•  Abnormal ultrasound finding suggestive of a genetic or structural condition

•  Known parental chromosomal rearrangement or genetic variant

•  Before proceeding with CVS or amniocentesis — discuss risks, benefits, and alternatives with your obstetrician