From Dr. Angle:

"Eggs that are genetically abnormal will give rise to embryos that are genetically abnormal. Genetically abnormal eggs/embryos will not produce normal babies. For example, one chromosome that appears to be very age-sensitive is chromosome 21. When there are abnormalities with chromosome 21 the result is Down’s Syndrome in the offspring. So, when we see abnormalities in chromosome structure in eggs we think it means that the embryos that result from fertilizing these eggs will probably have a lower likelihood of producing normal, viable, healthy babies.

There is a wide range of outcomes for patients so it is impossible to say what the actual percentage of abnormal embryos will be for any given patient who walks in the door. But all patients will have some percentage of their eggs that will carry these genetic abnormalities and thus be unable to produce a healthy baby. The actual percentage will vary from patient to patient.

We tend to see that embryos that are highly fragmented, slow to grow, and of poor quality are generally genetically abnormal. But this is not always the case. In addition, embryos that look absolutely beautiful as we watch them during an IVF cycle can also be genetically abnormal when analyzed by these kinds of Pre-Implantation Genetic analysis tests. However, the trend is that good quality embryos tend to have a better chance of being genetically normal and poor quality embryos have a greater chance of being genetically abnormal.

We also see that most patients produce some embryos that are very good quality and some embryos that are poor quality. In addition we see when we do PGD that some embryos carry a normal complement of chromosomes and some do not. We believe that some of these genetic abnormalities can be corrected with time by the embryos, however some cannot. We are really just beginning to understand these kinds of mechanisms.

So, in conclusion I would have to say that this is what we think is going on: every woman produces some eggs that are good and some that aren’t, every cycle, no matter what age she is. So, even if we can get the abnormal eggs fertilized they probably have only a limited ability to make a healthy baby. The number of healthy eggs will decrease as a woman ages. There is a lot of speculation as to what is the norm for young women, but we certainly know that women who are over 40 produce very few healthy, normal eggs, which is why they have higher miscarriage rates, higher rates of babies born with Down’s syndrome, lower pregnancies rates, and lower implantation rates."

One woman in the my network of Choice Mom experts is Nichi of My Heathy Beginning; she is a doula and healthy pregnancy consultant who herself experienced two miscarriages. Here is her advice: "Trust birth, trust pregnancy, trust your body and trust that there is a reason for everything. I can speak from the perspective of two miscarriages in the past five years, 18 months after each of my girls. From working as a doula to supporting friends, my belief was always to trust what your body was doing -- then I had to look myself in the eye during that first miscarriage and ask myself if I could trust what my body was doing. Though it was hard, I could. I really did. I trusted it and grieved the loss and, after the fact, for both miscarriages, saw later why I lost those babies. When people ask me how many children I have I typically say two, but my heart always says four."

Read this BBC article about new research that has helped researchers understand how eggs MIGHT be able to be corrected for age factors in the future.

For more on miscarriage, listen to these audio interviews with a doctor about the reasons, and with a Choice Mom about the experience. In the future you can use the "miscarriage" keyword in the search engine or at the top of this post.