Screening and tests
What Happens After an Abnormal NT Scan?
An abnormal NT scan raises a question and does not give a final answer. Here is how doctors usually work through it, step by step.
Reviewed24 October 20268 min read
Screening and tests
NIPT in Twin Pregnancy: Is It Reliable?
NIPT can be used in twin pregnancies, but results are interpreted differently. Learn how reliable it is, its limits with twins and IVF, and what follow-up is advised.
In this guide
Non-invasive prenatal testing (NIPT) analyses fragments of placental DNA in the mother's blood to screen for chromosomal conditions. In twin pregnancies, interpreting NIPT is more complex because DNA comes from two placentas or one shared placenta, and the contribution from each baby can differ.
Why is NIPT more complex in twins?
Two sources of DNA
In twins, cell-free DNA comes from both placentas. If one twin has a chromosomal condition, its DNA may be diluted by the healthy twin's DNA.
Identifying the affected twin
NIPT cannot usually tell which twin is affected in non-identical twins.
Low fetal fraction
The proportion of fetal DNA from each baby may be lower, which can lead to a failed or inconclusive result more often than in singletons.
Vanished twin
If one twin stopped developing early, its DNA can remain in the mother's blood and cause a false result.
How reliable is NIPT in twins?
Studies suggest NIPT detects most cases of Down syndrome in twin pregnancies, with low false-positive rates. Data for trisomy 18 and 13 are fewer, so results are interpreted more cautiously. Some laboratories also report limitations for other conditions in twins.
Does chorionicity matter?
Yes. Monochorionic twins usually share the same genetic makeup, so a result generally applies to both. Dichorionic twins may be non-identical, so the result may apply to one or both. Chorionicity is best determined by early ultrasound.
What about IVF twins?
NIPT can be done in IVF twin pregnancies, though factors such as donor eggs or vanished twins should be shared with the laboratory and doctor.
Why is the NT scan still important?
The NT scan at 11 to 14 weeks assesses each twin individually, checks chorionicity and early anatomy, and helps interpret risks for each baby. It is strongly recommended in twin pregnancies.
What happens after a high-risk result?
Counselling and diagnostic testing, usually amniocentesis or CVS of each baby as needed, are recommended. A fetal medicine specialist performs these with care to sample the correct twin.
Putting it together
NIPT is a useful screening option in twin pregnancies when combined with expert ultrasound and counselling. Dr Malathi G. Prasad provides twin pregnancy scans, NIPT counselling and diagnostic testing in Trichy.
If your doctor has suggested this, our twin specialised clinic page lists what is included and how to book; the team is happy to talk it through first.
Related guides
Common questions
Sources
This guide is for general information and does not replace a consultation with a fetal medicine specialist.
In line with the PCPNDT Act, we do not perform or support sex determination.
Share this guideWhatsApp
Twin Specialised Clinic
Specialist monitoring and care for twin and multiple pregnancies.
Related guides
Card 1 of 3
Twin Specialised Clinic
Specialist monitoring and care for twin and multiple pregnancies.
About Twin Specialised ClinicBook your appointment
Call us, message us on WhatsApp, or send a request and our team will call you back to schedule your visit.
Mon - Fri: 9:00 AM - 9:00 PM