Guest Author - Krissi Danielsson

Judging from the traffic figures, it seems that "miscarriage causes" is by far the most popular area of this site and one of high interest to readers. For this reason, this article will be the first of a multipart series looking at the various causes of miscarriage and what the current scientific thinking is on each.

As a disclaimer, I am not a doctor myself and am not qualified to answer specific medical questions about this material; it is gathered from research via Internet sources. I will provide a source list at the end of each part. This material is only intended for informational purposes and if you have any specific questions, please direct them to your doctor.

Now, let's begin.

What causes chromosomal anomalies?

Doctors often blame "random chromosomal abnormalities" for the large majority of miscarriages. Depending on whom you ask, specific doctors may chalk up anywhere from 40-75% of miscarriages to random errors in the chromosomes of a zygote or embryo. The baby may have missing sections of vital chromosomes or extra copies of specific chromosomes that either make the baby incompatible with life or cause a woman's body to reject the baby. Since so many miscarriages occur due to chromosomal abnormalities, most doctors don't run tests on women who have just one miscarriage. It makes sense if you think about it. Error happen in cell division, especially when cells are dividing into gametes, and if an egg and sperm combine with the wrong number of chromosomes, it can sometimes just be impossible to build a human being with missing or extra genetic instructions.

When miscarriages happen due to random chromosomal abnormalities, a woman usually has perfectly good odds of having a normal baby in her next pregnancy. To put it shortly, it's just bad luck. The pregnancy happened to occur with the wrong egg and or sperm.

After a first miscarriage, doctors commonly assume the cause was chromosomal anomalies. It's rare that any doctor will offer diagnostic testing after just one miscarriage, and it's most common that they will just tell patients to go home and try again. In many cases, this may be perfectly good advice, since statistics suggest that most women who have one miscarriage face almost no increased risk of having a second one. If chromosomal anomalies were indeed the cause of your loss, then there isn't anything you can do to prevent the miscarriage anyway.

Treating and preventing chromosomal anomalies

In most cases, as mentioned above, chromosomal anomalies are random and don't require special treatment. The next pregnancy will most likely be normal and result in a normal baby. However, in some patients, chromosomal anomalies may require treatment. If the mother or father has a genetic disorder, the chances will be much higher of chrosomal anomalies in the baby. A disorder such as "balanced translocation" in either parent could result in as much as a 50% odds of miscarriage every time a woman gets pregnant. (See the additional resources in the side bar for a thorough explanation of balanced translocations.) In other cases, one or both parents may have a high number of eggs or sperm with chromosomal anomalies for reasons such as age or exposure to environmental contaminants. Genetic karyotyping of both parents is a common component of a recurrent miscarriage workup after two or three losses or in cases that genetic testing on the miscarried baby reveals a chromosomal anomaly, and this test will reveal whether a genetic problem in the parents is the root cause of miscarriages.

If this is the case, the least expensive way to deal with the problem is to just keep trying. However, this could result in a whole string of miscarriages and pregnancy losses that is just too much for anyone to handle. One miscarriage is bad enough, but the prospect of having to face seven or eight or more in a row before achieving a healthy baby may just be more than you can take. If this is the case, you have a few options. You can use donor eggs or sperm, depending on which parent has the underlying chromosomal anomaly, but this can be costly and can have psychological implications for the parent who would have no genetic link to the child. You can also undergo a relatively new procedure of pre-implantation genetic diagnosis in combination with IVF, which is also costly and involves multiple invasive procedures -- as well as no guarantee of a viable pregnancy. (See the side bar for more information; this procedure will also be the subject of a future article.) Adoption can also be an option for couples that prefer it to lengthy fertility treatment or a prolonged period of trying to conceive.

As far as preventing chromosomal anomalies, in most cases, it isn't your fault or your partner's fault and there's no means to reduce the odds of it happening again other than those outlined above. However, a few lifestyle factors may increase the odds of chromosome problems. If your partner regularly smokes, this can increase the DNA fragmentation in his sperm. In addition, if you or your partner have been regularly exposed to any kind of radiation or severe environmental contaminants, this can also have an impact. In the absence of these factors, there's not much that can be done.

How can you tell if a miscarriage results from chromosomal anomalies?

As mentioned above, the only way to tell for sure if a miscarriage resulted from chromosome issues is to have the miscarried baby tested. This can be difficult to do unless a d&c was done after the loss to collect the tissue, and it is also expensive and not always covered by insurance. In addition, some doctors will only rule out chromosomal anomalies in miscarried male babies, because they can often not determine with 100% certainty that results indicating "normal female chromosomes" are not from the mother -- whereas normal results from a male source can obviously not be from the mother.

However, in some cases, there may be signs that the cause of a miscarriage was something other than "random" chromosomal anomalies, and in these cases it might pay to be persistent in demanding further explanation for a miscarriage cause. This excerpt from an article in Parents magazine has some indications that can tell you whether a chrosomal anomaly was more or less likely to cause your miscarriage.

If you have had two or more miscarriages in a row, it's always a good idea to find a doctor willing to do a recurrent miscarriage workup and who won't assume that chromosomal anomalies are causing your losses. This is especially true if you are under 35. Sadly, older mothers do face an increased risk of losses from chromosome anomalies, but it can't hurt to look for other causes in any cases of subsequent repeated miscarriages.

A final word on grief

Just in case the thought occurs to you or some "helpful" friend brings it up, it is 100% okay to grieve the loss of your baby in ALL cases of miscarriage -- even if you know for sure that there was a severe chromosomal abnormality. Sometimes clueless people, including doctors, will tell you that "it's for the best" that you lost the baby since there was something wrong with it or they may say "it just wasn't meant to be." They don't understand these comments are completely unhelpful and that you as a mother (or father) can love your child from the moment of finding out about the pregnancy, no matter whether that child's genetic makeup is normal or not. Ignore anyone tries to minimize your grief in the face of a miscarriage from a diagnosed or suspected chromosomal anomaly. It is ALWAYS okay to mourn the loss of your baby.

Up next...

The next installment in this series will be: lifestyle factors.

Discuss: Have something to say about chromosomal anomalies? Post here.