Doctors more often recommend amniocentesis and chorionic villus sampling (CVS) to women over about age 35 because the risk of chromosomal problems (like Down syndrome) rises with maternal age and eventually becomes higher than the small procedure‑related risk of miscarriage from these invasive tests.

Age and chromosomal risk

As a woman’s age increases, the chance of having a baby with a chromosomal abnormality (aneuploidy) rises steadily; this increase becomes clinically significant in the mid‑30s and beyond. For example, the risk of Down syndrome is much higher at age 40 than at age 25, so the background chance of a problem is greater in older mothers even if the pregnancy otherwise appears normal.

Why 35 became the cutoff

Historically, age 35 was used as a threshold because at that point the estimated risk of Down syndrome roughly matched or exceeded the added miscarriage risk from amniocentesis or CVS, making invasive testing more justifiable. This led to a standard of care in which women who would be 35 or older at delivery were routinely offered these diagnostic procedures for chromosomal analysis.

Balancing benefits and risks

Amniocentesis and CVS provide a definitive diagnosis for many chromosomal conditions, which can guide decisions about continuing the pregnancy, preparing for a child with special needs, or planning delivery. Because older women have a higher baseline chance of such conditions, the benefit of certainty more often outweighs the small but real miscarriage risk of the procedures in this group.

How recommendations are changing

More recently, professional guidelines have shifted toward offering screening or diagnostic options to all pregnant women, not just those over 35, especially with the availability of noninvasive prenatal testing (NIPT). Even so, advanced maternal age remains one of the most common reasons that clinicians discuss or recommend amniocentesis or CVS.