One of the topics that tends to come up early in prenatal care for women over 35 is genetic testing. With a range of options available — from simple blood tests to more involved procedures — and varying levels of information they provide, it’s understandable that many women find this area of prenatal care both important and initially overwhelming.
The most important thing to know upfront is that genetic testing is a personal decision, not a mandatory one. The goal of offering these tests is to give women information so they can make decisions that align with their values and circumstances. No testing option is right for every woman or every pregnancy, and declining certain tests is always an option. What matters is having enough information to make a decision that feels right for you, ideally in conversation with a healthcare provider who knows your specific situation.
This article provides an overview of the main prenatal genetic testing options available to women over 35, what each can and cannot tell you, and considerations that often come up in the decision-making process.
Why Age 35 Is a Clinical Reference Point
The age of 35 has historically been used in obstetrics as a threshold for discussing additional prenatal testing, based on statistical patterns in chromosomal variation rates. According to guidelines from the American College of Obstetricians and Gynecologists (ACOG), the risk of chromosomal conditions such as Down syndrome (trisomy 21) increases with maternal age, though it’s worth understanding the absolute numbers rather than just the relative risk language.
For a woman at age 35, the risk of a pregnancy with Down syndrome is estimated at approximately 1 in 350. By age 40, that risk is approximately 1 in 100. While these rates are statistically higher than those at younger ages, they also mean that the large majority of pregnancies in women over 35 are chromosomally typical. ACOG currently recommends offering genetic screening and diagnostic testing to all pregnant women, regardless of age, and allowing women to make individualized decisions about which options to pursue.
Screening Tests vs. Diagnostic Tests: An Important Distinction
Before diving into specific tests, it’s worth clarifying the distinction between screening and diagnostic testing — a distinction that is fundamental to interpreting results accurately.
Screening tests assess probability. A positive or “high-risk” screening result means the pregnancy has a higher-than-average statistical probability of a certain condition — it doesn’t diagnose anything. Many pregnancies with high-risk screening results turn out to be chromosomally typical. Screening tests carry no procedural risk to the pregnancy.
Diagnostic tests provide definitive answers about whether a chromosomal condition is present. They involve analyzing the baby’s actual cells, which requires either a sample of amniotic fluid (amniocentesis) or placental tissue (chorionic villus sampling, or CVS). Diagnostic tests carry small procedural risks, which are discussed in more detail below.
Non-Invasive Prenatal Testing (NIPT)
Non-invasive prenatal testing, also called cell-free DNA testing or NIPT, has become one of the most commonly discussed screening options for women over 35. NIPT involves a blood draw from the mother, through which small fragments of fetal DNA circulating in the maternal bloodstream are analyzed for chromosomal patterns associated with conditions like trisomy 21, trisomy 18, trisomy 13, and sex chromosome abnormalities.
NIPT has high sensitivity and specificity for the conditions it screens — particularly for trisomy 21 in pregnancies with higher baseline risk (as in older mothers). However, it remains a screening test, not a diagnostic test, and false positives and false negatives can occur. A high-risk NIPT result is typically followed by diagnostic testing (amniocentesis or CVS) before any definitive conclusions are drawn.
NIPT can typically be performed as early as 10 weeks of pregnancy. For women over 35 whose primary interest is in chromosomal screening, NIPT is often the first step in the testing conversation with their OB/GYN or maternal-fetal medicine specialist.
First-Trimester Combined Screening
First-trimester combined screening combines a nuchal translucency ultrasound (measuring fluid at the back of the baby’s neck between 11 and 14 weeks) with two maternal blood markers — PAPP-A (pregnancy-associated plasma protein-A) and free beta-hCG. Together with maternal age, these factors are combined into a probability estimate for chromosomal conditions.
First-trimester combined screening has moderate detection rates compared to NIPT, which is one reason NIPT has become increasingly prevalent. However, the nuchal translucency measurement and first-trimester blood markers also provide other information — including potential associations with certain cardiac conditions in the fetus — that NIPT doesn’t offer. Many practices offer both, or discuss the options alongside each other so that women can make an informed choice.
Diagnostic Testing: Amniocentesis and CVS
For women who want definitive chromosomal information — whether because of high-risk screening results, a family history of genetic conditions, or a personal preference for certainty — diagnostic testing via amniocentesis or CVS provides conclusive answers.
Chorionic villus sampling (CVS) is typically performed between 10 and 13 weeks of pregnancy and involves sampling a small amount of placental tissue. Its earlier timing is one advantage for women who want earlier definitive information. The procedure-related miscarriage risk is generally cited at approximately 0.5–1%, though estimates vary by provider experience and technique.
Amniocentesis is typically performed between 15 and 20 weeks and involves sampling amniotic fluid. The procedure-related miscarriage risk is generally cited as approximately 0.1–0.3% in experienced hands. Amniocentesis can also detect neural tube defects through alpha-fetoprotein analysis, which CVS cannot.
Both procedures should be performed by practitioners with significant experience in these techniques, and the risk discussion should be individualized based on the provider’s experience and the specific pregnancy circumstances.
For more context on navigating early pregnancy decisions, our article on first-trimester decisions in pregnancy after 35 may be a helpful companion.
Frequently Asked Questions
Is prenatal genetic testing required after 35?
No. ACOG recommends that all pregnant women be offered genetic screening and diagnostic testing, but the choice of whether to pursue any testing — and which tests — is entirely the woman’s to make. Some women want comprehensive information; others prefer not to test or to test only for certain conditions. Discussing your values and priorities with your OB/GYN or a genetic counselor can help clarify what approach makes sense for you.
What is a genetic counselor and should I see one?
A genetic counselor is a healthcare professional with specialized training in medical genetics and counseling who can help interpret test results, explain risk figures in an accessible way, and support decision-making around prenatal genetic testing. Many women over 35 find a prenatal genetic counseling appointment extremely useful — either before deciding on testing or after receiving results. Your OB/GYN can provide a referral.
Can NIPT tell me the sex of my baby?
Yes, NIPT analyzes sex chromosomes and can indicate the baby’s sex with high accuracy as a byproduct of the chromosomal analysis. Whether this information is shared is usually a patient preference — most labs offer the option to either receive or decline sex chromosome results.
What happens if a diagnostic test confirms a chromosomal condition?
This is a deeply personal situation, and there is no single right response. Some families use the information to prepare for a child with specific needs; others face decisions about continuing the pregnancy. Genetic counselors, maternal-fetal medicine specialists, and other support resources are available to help families navigate this with accurate information and compassionate support. No one should navigate a diagnosis alone.
Key Takeaways
- Prenatal genetic testing is offered to all pregnant women but is a personal choice — understanding the difference between screening tests (which assess probability) and diagnostic tests (which provide definitive answers) is essential for informed decision-making.
- NIPT is a highly sensitive blood-based screening test that can be performed as early as 10 weeks and is widely used in pregnancies with higher baseline chromosomal risk, including in women over 35.
- Diagnostic tests (amniocentesis and CVS) provide definitive chromosomal answers but carry small procedural risks; the decision to pursue them typically follows a high-risk screening result or a personal need for certainty.
- The absolute risk of chromosomal conditions, even in pregnancies at age 35 and above, still means that the large majority of pregnancies are chromosomally typical — understanding absolute numbers alongside relative risk language is important.
- A prenatal genetic counselor can be an invaluable resource for interpreting information, understanding options, and making decisions that align with individual values and circumstances.
Medical Disclaimer
This content is for informational purposes only and does not constitute medical advice. Individual health situations vary significantly. Always consult a qualified healthcare provider before making decisions related to your health, fertility, or pregnancy.
About the Author
Emily Carter is a women’s health writer focused on fertility, pregnancy after 35, and sleep changes in midlife. She writes research-informed, non-alarmist content to help women navigate reproductive and hormonal transitions with clarity and confidence.