Jennifer is a healthy 34-year-old woman who has been married for two years. She is working long hard hours to establish her legal practice and position herself for promotion in her law firm. It just doesn't seem like the right time to have a baby...or is it? What are the real risks (and benefits) of waiting longer to start a family? And if Jennifer isn't going to start now, should she freeze some eggs or embryos for later?
Everyone knows childbearing is riskier for older moms. But the odds of genetic problems, which usually come first to mind, are overblown. Here are the facts. Yes, the chance of Down Syndrome (DS) and other genetic conditions increases with egg age. For a 20-year-old woman, the chance of delivering a child with DS is about one in a thousand (0.1 percent). At 35 it is about half of a percent, and at 40 it rises to one percent. That means even at age 40, there is a 99 percent chance the pregnancy is NOT affected by DS. For families who would consider termination or who just want to know about their baby's health, options exist to check for these conditions during pregnancy. For most of the women I talk to, once they understand the actual likelihood of genetic conditions, these risks seem manageable, and aren't a major deterrent to getting pregnant.
What about medical complications? It is true that as you get older, you have had more years to develop conditions like high blood pressure, diabetes, and obesity. And these challenges do make pregnancy more complicated. If you have medical problems, a preconception appointment with your doctor or midwife is especially important, so they can give you personalized advice to prepare for the best possible pregnancy. Bottom line: the most likely result of pregnancy for an "older" woman who doesn't have major medical conditions is a healthy mother and baby.
So maternal medical problems and genetic conditions are not that big a deal for the healthy woman. But here is the indisputable (and some might say unfair) truth: fertility drops and miscarriage rises as you get older. And the slippery slope starts earlier than you might imagine. Fertility is highest in your twenties, decreases a little in your early thirties, and then falls rapidly starting around age 37.  The chance of first trimester miscarriage also goes up with age, with the lowest chances in the under 30 crowd, rising to an 80 percent chance of miscarriage if you conceive over age 45. 
So how are so many famous women able to have babies in their late forties and even into their fifties? Most of these are probably from eggs donated by younger women. Unfortunately, respecting the privacy of that decision gives the public a sense that a woman can have a baby into her fifties. The truth is, spontaneous pregnancy is quite unlikely after age 45.
Can freezing eggs resolve this tension between getting pregnant younger (for all the reasons listed) and waiting (for all the other great reasons)? Yes and no. Egg freezing is an important new fertility preservation option, although it isn't quite as reliable as fertilized embryo freezing. So the chances the eggs will "work" when you want them is not guaranteed. Embryo freezing requires that you have a partner now, or that you are willing to use donor sperm. Both are extremely expensive and out of range for many women (unless you work for one of the few employers that cover this in their health insurance plan). Additionally, some of the issues related to having babies later in life, like energy level, parental health, or wanting to retire before your child goes to college, are not resolved by this high-tech solution.
Some families choose to have children when they are younger so they have more energy and aren't elderly when the child still needs them, and so they don't have to worry as much about genetic problems, fertility, and medical complications. But others, like Jennifer, want to establish a career first, and wait to have more resources to meet their families' needs. Some women want children so much they are willing to go forward without a partner, while others wait to find that right someone. As you can see, individual values and preferences play into these very personal, emotional, and profound decisions.
So what timing is best for you? To think more about some of the factors that play a role in pregnancy and parenting, take my quiz "Am I Ready to Have a Baby?"
 ACOG Committee Opinion Number 589, March 2014
 ACOG Practice Bulletin Number 150, May 2015