National Pregnancy and Infant Loss Awareness Month

For women and couples that have experienced a miscarriage or pregnancy loss, you know how devastating and heartbreaking it can be. When you have been struggling to conceive for an extended period of time, it is that much more heartbreaking. Recurrent miscarriage can compound the devastation exponentially. After multiple miscarriages, it can be almost impossible to throw yourself back into the grinder with the ominous expectation of another loss.

How Common Is Miscarriage?

It is rarely any consolation for couples trying to conceive after a miscarriage, but the fact is, miscarriage is very common. According to the National Institutes of Health, 15-20% of all pregnancies end in miscarriage. This rate climbs higher as a woman ages, due largely to causes we will discuss shortly.

What Are the Main Causes of Miscarriage?

If we are playing the odds, the first thing we look at is chromosome-related miscarriage. The most common cause of miscarriage is the presence of chromosomal abnormalities in the embryo/fetus. The American College of Obstetricians and Gynecologists estimates that about 60% of miscarriages are caused by an irregular number of chromosomes. When an embryo has too many or too few chromosomes, it almost always leads to either a failure for the embryo to implant in the uterus, or a miscarriage. There are a few chromosomal abnormalities where the fetus can survive to full gestation including Down Syndrome (three copies of Chromosome #21) and Turner Syndrome (only one sex (X) chromosome).

As a woman ages, the odds that her embryos will have chromosomal irregularities increases exponentially. Studies of IVF patients indicate that a woman in her 20s or early 30s can expect only about half of her embryos to have a normal complement of 46 chromosomes. As she progresses into her late 30’s and early 40s, that number decreases to about 10% chromosomally normal embryos. An embryo with exactly 23 matched pairs of chromosomes is referred to as “euploid.” When an embryo has too many or too few chromosomes, we call it an “aneuploid” embryo.

More often than not, an aneuploid embryo is a result of an aneuploid egg rather than aneuploid sperm. So as unfair as it seems, the female partner has by far the largest influence on the embryo’s chromosomal makeup. With relatively poor odds of producing a “normal” (euploid) egg, even in younger women, it is easier to understand why the incidence of miscarriage and pregnancy loss is so high.

Addressing Chromosomal Issues to Improve Pregnancy Rates After Miscarriage

The odds of a chromosomally normal egg fertilizing and progressing as a viable pregnancy are quite high, so the first line of attack is to maximize the chance that a normal egg is available for fertilization. The IVF process requires that eggs be extracted from a woman’s ovaries, fertilized in a lab and cultured for 5-6 days, prior to selecting one or more eggs for transfer back to the uterus. So if we had a way to access and analyze the chromosomal makeup of each embryo prior to embryo transfer, we could make sure to transfer only the embryos that were normal. Fortunately, we do have a way to test embryos for their chromosomal integrity prior to transfer.

Identifying Viable Eggs

To understand the process by which we can identify viable embryos, let’s do a quick refresher on the IVF process. In IVF, a woman is given medications that cause her ovaries to produce multiple mature eggs. The eggs are retrieved from her ovaries using an ultrasound guided needle and sent to an embryology lab for preparation and fertilization. It is at this point in the process that we can intervene to analyze the chromosomal configuration of each egg. After fertilization, the eggs (now embryos) go through a process of cell division, in which they divide many times over the course of 4-5 days. When the egg reaches the stage where there are at least 8 cells, a biopsy can be performed where one or more cells are taken out for analysis. At Caperton Fertility Institute, we can perform the analysis in our own embryology lab. Since each cell contains a complete set of chromosomes, we can identify the “euploid” embryos with 46 chromosomes and designate those for transfer to the uterus.

Taking the Guesswork Out of Selecting the Best Embryo

We used to rely on the physical appearance of the dividing embryo to make an educated guess about which ones were most likely to result in a viable pregnancy. There were a number of grading systems used by embryology labs, but they all relied on a visual inspection and evaluation rather than a chromosomal analysis of the embryos. Now, by identifying euploid embryos and transferring a single one to the uterus through the IVF process, we can eliminate a high percentage of miscarriages and increase the rate of healthy births – even after prior pregnancy loss. This saves the heartache of miscarriage, while also saving the time and expense that used to be invested in less effective forms of treatment.