There is no age when any medical group “recommends” stopping having children.
So, I’m kind of passionate about this, so forgive me with starting with a little Biology 101: Genes are the instructions for how our bodies grow, develop and function. Genes are organized onto chromosomes. Humans have 46 chromosomes and they come in pairs. You get one of each pair from your mom and the other from your dad. So when a person goes to make an egg or sperm your body has to cut the nuber of chrosomes in half so that when the egg and sperm join up in an embro, you have the correct nuber of chromosomes.
Men are constantly producing new sperm. Women are born with all the eggs they will ever have. So a woman’s age is the same age as her eggs. As eggs age they have a greater likelihood to have the wrong number of chromosomes. This is called aneuploidy. When a pregnancy has aneuploidy there is usually a miscarriage. This is often before a pregnancy is recognized, but can be later. There are certain aneuploidies that can survive to term. The most common aneuploidy is Down syndrome (an extra copy of the twenty first chromosome) but Trisomy 13 and Trisomy 18 can also survive to term and are much more medically serious than Down syndrome.
So the increase incidence of “birth defects” in women who are older is actually an increased risk for aneuploidy. It’s not like the rate of all birth defects goes up with age. And this risk increases gradually throughout a woman’s life. There is no threshold when you hit a certain age. The difference between 34 and 35 is about the same as the difference between 33 and 34. Nothing magic happens at 35 or 40 or any age. And at 35 the risk for a liveborn child with an aneupoidy is only about 0.5%, meaning that there is a 99.5% chance that the mom’s age would not contribute to any health concern in the child.
The increase rate of aneuploidy is also the biggest reason for decreased fertility as a woman gets older given the aforementioned miscarriages that can result from most aneuploidies. This risk is also gradual over a lifetime with no threshold. There ave been studies done at IVF clinics, and if you screen embryos for aneuploidy and implant embryos without aneuploidy, the pregnancy rates are the same for women in their 20s and women in their 40s. That being said, there are some health concerns (high blood pressure, diabetes, etc.) which are more likely to be seen in older womeb that can complicate conception and pregnancy, but if you don’t have those complications, that doesn’t apply to you.
Since aneuploidy is an incorrect number of chromosomes there are standard tests to look for this. Some are screening tests (maternal serum screening, nuchal translucency, non-invasive prenatal screening – Maternity21) that will increase or decrease your risk. Other tests are diagnostic (like CVS or amniocentesis) and can tell with relative certainty if a pregnancy is affected by an aneuploidy. If a couple is concerned about aneuploidy, at whatever age, they should dicuss these options with their OB.
There are many many reasons why people might not want to have children after a certain age. And that is perfectly fine. I, personally, would like to be able to retire early and that would be difficult while raising a child, so I have my reasons as well. But understand the medical facts before assuming that you can’t have a healthy child after 30 or 35 or 40 or 45. I once had a patient who was having her first child at age 48 and the baby was perfectly healthy. Not saying that’s for everyone, but it happens (and, yes, it was a natural coneption – they assumed she was too old to get pregnant and so didn’t use contraceptives). If you would like to learn about these risks, make an appointment with your OB or a local genetic counselor. They can discuss things in detail.