Medical Oncologist
CION Cancer Clinics
Prenatal diagnosis for a known family gene fault | CION Cancer Clinics
If the exact gene fault in your family is known, a pregnancy can be tested for it. A small sample from the placenta or the fluid around the baby is checked for that one change. No IVF is needed. This page explains the two ways to take the sample, who chooses this route and who does not, what Indian law allows, and why the hardest decision comes before the test. At CION Cancer Clinics, our team helps carriers and their families plan checks, next steps and support after a genetic result.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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On this page
- Can a pregnancy be tested for our family's gene fault?
- Who tests a pregnancy for a family fault?
- What happens, from planning to a result?
- The words you will meet, in plain language
- CVS or amniocentesis: how do they differ?
- What this page cannot tell you
- Four things families assume about testing a pregnancy
- Common questions about prenatal diagnosis
The short answer
Can a pregnancy be tested for our family's gene fault?
Yes, if the exact fault in your family has already been found. A small sample is taken from the placenta or from the fluid around the baby, and the laboratory checks it for that one change. It works with a natural pregnancy, so no IVF is needed.
Two ways to take the sample
Chorionic villus sampling, or CVS, takes a tiny piece of the placenta. It is usually done between the eleventh and fourteenth weeks of pregnancy. Amniocentesis takes a little of the fluid around the baby, usually between the fifteenth and twentieth weeks. Both use a fine needle guided by ultrasound, and both carry a small risk of miscarriage.
Decide what you would do before you test
This is the hardest part, and it comes first. A result showing the baby carries the fault leads to a choice about the pregnancy. Some couples would continue whatever the result. For them, a test with a risk of its own may change nothing. A counsellor will help you think this through before any needle is used.
Prenatal testing only looks for the known family fault. It is not a general check of the baby's health.Is it for you
Who tests a pregnancy for a family fault?
A small number of couples, for quite different reasons. Most carriers of a cancer gene fault never test a pregnancy.
Couples who would act on the result
One partner carries a confirmed fault, and the couple has decided they would consider ending the pregnancy if the baby carries it. Testing gives them that choice without IVF.
Couples confirming an embryo test
After PGT-M, a prenatal test is often offered to confirm the embryo result. Here the aim is reassurance rather than a new decision.
Faults that cause illness in childhood
A few faults cause tumours or serious illness early in life. So can inheriting faults in the same gene from both parents, which is more likely when partners are related by blood.
Knowing early can mean
- Planning checks from birth
- Choosing where the baby is delivered
Who it does not suit
Anyone whose report shows only a variant of uncertain significance, meaning nobody yet knows whether it matters. Also most couples who would continue the pregnancy anyway, because the procedure carries a small risk and the result can wait until the child is grown.
Not sure whether this applies to you?
Ask an oncologistFrom planning to result
What happens, from planning to a result?
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Counselling before pregnancy, ideally
A genetic counsellor confirms the exact fault and talks through every option. Doing this before pregnancy avoids rushing a hard decision.
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Telling the obstetrician early
As soon as the pregnancy is confirmed, tell your obstetrician about the family fault. The timing of CVS depends on it.
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The laboratory prepares
The laboratory needs the original report, and often a blood sample from the carrier parent, to check its test before the pregnancy sample arrives.
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The procedure itself
A short outpatient procedure at a registered centre, guided by ultrasound. Most women go home the same day and rest.
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The result and a second conversation
The result is given in person, with counselling, whatever it shows. Ask beforehand how long it usually takes.
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Support, whatever you decide
Couples who continue and couples who do not both need support. Your counsellor and obstetrician stay with you either way.
On your forms
The words you will meet, in plain language
- Prenatal diagnosis
- Testing a pregnancy for a specific condition, rather than screening for general risk.
- CVS
- Chorionic villus sampling. A tiny sample of the placenta, taken through the tummy or sometimes through the cervix.
- Amniocentesis
- A small amount of the fluid around the baby, taken through the tummy with a fine needle.
- Carrier
- Someone who has the family fault. A baby found to be a carrier is not ill and does not have cancer.
- PCPNDT Act
- The Indian law that controls prenatal testing. It allows testing for genetic conditions at registered centres and forbids revealing the baby's sex.
- MTP Act
- The Indian law on ending a pregnancy. It sets time limits that tighten as pregnancy advances.
Side by side
CVS or amniocentesis: how do they differ?
CVS
Amniocentesis
Done earlier, near the end of the first three months
Done later, in the middle months of pregnancy
Samples a tiny piece of the placenta
Samples the fluid around the baby
Gives more time to decide, within the law's limits
Leaves less time before those limits apply
Occasionally needs a repeat test to be sure
Sometimes used to confirm an unclear CVS
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Being straight with you
What this page cannot tell you
It cannot tell you whether to test a pregnancy, or what to do with the result. Those are your decisions, made with a genetic counsellor and your obstetrician, and they deserve time. No website should make them for you.
It cannot interpret a report
What your specific variant means, for you or for a baby, is a question for the counsellor who ordered the test. The same gene name can carry very different weight depending on the exact change.
It cannot give legal advice
Whether and until when a pregnancy can be ended depends on the MTP Act, the stage of pregnancy and the doctors' opinion. A carrier result for a cancer that begins in adult life raises questions that doctors weigh case by case. Ask your obstetrician early, before the result, not after.
Who this does not apply to
Most carriers of a cancer gene fault have children without testing the pregnancy at all. Choosing not to test is as legitimate as choosing to test.
Commonly believed
Four things families assume about testing a pregnancy
"If the baby carries the fault, the child will get cancer."
For most cancer gene faults, the fault raises risk in adult life. It does not settle the matter. Many carriers never develop cancer, and those who do are often found early.
"A scan can show whether the baby has the fault."
No scan can see a gene fault. Only a sample tested in a laboratory for the exact family change can answer that question.
"Prenatal testing is illegal in India."
Testing for genetic conditions is legal at registered centres. What the law forbids is using any test to find or reveal the baby's sex.
"We can decide what to do once we see the result."
Many couples find that far harder than expected, and time is short. Talking it through before the test makes the result easier to live with, whatever it shows.
Questions we are asked
Common questions about prenatal diagnosis
How risky are CVS and amniocentesis?
Both carry a small risk of miscarriage. For CVS it is thought to be less than one in two hundred pregnancies, and for amniocentesis about one in two hundred. Your obstetrician can tell you the figure for their own centre.
Is there a blood test instead of a needle?
Blood tests on the mother can check some conditions, but they are not yet a routine way to test for a family cancer gene fault in India. For now, CVS or amniocentesis is usually needed. Ask your counsellor whether anything newer applies to you.
Does it matter which parent carries the fault?
Not for the chance of passing it on, which is the same either way. It can matter for how the laboratory sets up the test. That is one reason the carrier parent's report and sometimes a fresh blood sample are needed.
Can we test the pregnancy without IVF?
Yes. Prenatal diagnosis works with a natural pregnancy, which is why it costs far less than embryo testing. The trade-off is that the choice is about a pregnancy that already exists.
What should we watch for after the procedure?
Mild cramps are common. Bleeding, a leak of fluid, a fever or strong, painful contractions need the obstetrician or the nearest emergency department the same day. Your centre will give you a number to call.
Will the centre tell us the baby's sex?
No. Revealing the baby's sex is a crime under the PCPNDT Act, and registered centres will not do it by any means. The test answers only the question about the family fault.
Can we test after an embryo test to be sure?
Yes, and many couples do. Embryo testing is very accurate but not perfect, so a confirming test is often offered. Some couples decline it because of the small procedure risk. Both choices are reasonable.
Where do we start?
With genetic counselling, ideally before the pregnancy. Bring the report that confirmed the family fault. Call the CION helpline if you are unsure who to see, and we will point you to the right counsellor.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
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Sources
- NHS — Chorionic villus sampling
- NHS — Amniocentesis
- PRS Legislative Research — The Medical Termination of Pregnancy (Amendment) Bill, 2020
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Talk to us
Planning a pregnancy with a known family fault?
Talk to us before the pregnancy if you can. We will arrange genetic counselling that sets out every option, including not testing at all. One helpline serves every CION centre.