Age and Pregnancy

Age and


More people are investing in their careers or other interests, so they may want to postpone starting a family. They may have questions about their fertility and the affect of age on future pregnancies. It can be hard to separate fact from fiction. Here are the facts.

What is meant by "high risk"?


Many people have heard that pregnancy is “high risk” for women over 35.  The term “high risk pregnancy” makes it sound like a woman over 35 has a high risk in pregnancy for any health problem or birth defect.  However, the primary risk that specifically increases with a mother’s age is the risk for an extra or missing chromosome.  Although it is true that other obstetric risks can develop because of underlying health conditions that are more common as people age, like diabetes or high blood pressure, the primary concern for pregnancy in a healthy woman as she ages is for chromosomal problems.  That may be reassuring for some women because the age-related risk for chromosome problems is still relatively low. For example, a woman who is 35 at delivery has a less than 1% chance to have a live born child with a chromosomal problem.

Here Are the Facts about Age and Pregnancy

Maternal Age & Infertility*

Menken, et al. Science 1986

Leridon Human Reproduction 2004

*There are different methods for measuring infertility. For this chart, infertility was defined as not conceiving within 12 months among married couples not using contraception. Research methods vary between studies and result in different rates, represented here with ranges.

  • The greatest chances for most pregnancies is a healthy baby.

  • Women are born with all their eggs.

  • As eggs age, problems arise with the chromosomes, the packages of genetic material inside the egg.

  • There is nothing magical that happens for pregnancy at 35 years of age. The effect of a mother's age on pregnancy is gradually increasing over time.

  • As women age, the chances to conceive is gradually decreasing, and the chances for a chromosome problem is gradually increasing.

  • Age-related infertility starts to drop more quickly at about age 32.**

  • The chances for a chromosome problem when the mother is 35 years old at delivery is still less than 1%. (See the table below.)

Maternal age-related risk for a live born child with a chromosome problem

  1. Hook EB Rates of Chromosome abnormalities at different maternal ages. Obstet Gynecol. 1981 Sep;58(3):282-5.

  2. Hook EB, Cross PK & Schreinemachers DM. (1983). Chromosomal abnormality rates at amniocentesis and in live-born infants. JAMA , 249, 2034-8. PMID: 6220164

Options for Women Having Children Over 35

​Learning about age and pregnancy can be scary for some people. It's important to remember that the greatest odds for most pregnancies is a normal, healthy baby.  Knowing the facts earlier (even before pregnancy) can empower people with more choices in their family planning. 

  • Egg freezing and IVF are options for people to have families later. However, experts say that these options won't make up completely for the drop in fertility, so it is important for people to understand the choices they are making when deciding timing of pregnancy.**

  • Genetic testing in IVF allows for screening embryos for chromosome problems. In this type of testing, embryos without chromosomal problems are the priority for transfer to the woman's uterus during the IVF cycle.

  • If a woman is already pregnant, genetic screening during pregnancy is offered to look for some common chromosome problems.

  • Other factors can affect the risk for birth defects. The Mainstream Genomics' Family Screens provide a Personalized Screening Plan based on both biological parents' family medical history.

Hear from an Expert

**SOGC Committee Opinion 2012