Losing a pregnancy is heartbreaking, whether it happens early or late. And when you experience several losses, you may feel anxious, sad, and fearful about trying again.
Pregnancy losses can happen early (before 20 weeks) or later, and depending on the timing the causes can be very different. In this post, we will go over the work-up for early pregnancy losses, which are far more common than late losses.
About one in every six recognized pregnancies ends in a miscarriage.
But if you include those that are lost before women realize that they are pregnant, pregnancy losses may happen as often as 50% of the time. When miscarriages happen repeatedly, especially if you have had no previous successful pregnancy outcomes, you may be referred to see a Maternal-Fetal Medicine specialist for evaluation and counseling.
Here are some of the most common reasons that pregnancies fail early, and what we do to evaluate them.
Abnormal fetal chromosomes
Humans are supposed to have 46 chromosomes.
Sometimes, fetuses have an extra chromosome, as with Down syndrome. Or they may be missing a chromosome, as in Turner syndrome. Or they may have a complete extra set of chromosomes.
If your OB is able to collect fetal tissue after a miscarriage, this can be sent for chromosome analysis. Sometimes the tissue fails to grow, but when culture is successful, it can give us valuable information. If a chromosome abnormality is present, we talk to you about what the chance is of having this happen again. The answer varies according to the specific abnormality.
Translocations are chromosome rearrangements; they happen when a chromosome breaks, and the broken-off piece attaches to another chromosome. Or when two chromosomes exchanges pieces with each other.
In a balanced translocation, there is an even exchange, and cells end up with the right amount of genetic material. About one in every 500 of us carries a balanced translocation. Most translocation carriers don’t even know about them, but when their cells divide to form eggs and sperm, problems can arise. Some eggs or sperm will have extra genetic material, and some will have missing pieces. In pregnancies with unbalanced translocations, fetuses will usually be abnormal, or they will miscarry early in pregnancy. Translocations are frequently discovered when fetal chromosomes are analyzed after a pregnancy loss.
A simple blood draws from you and dad can check for translocations. If one of you carries a balanced translocation, you yourself may be perfectly normal, but there is a greater than 50% chance that future pregnancies will have unbalanced translocations, resulting in miscarriage or an abnormal fetus.
Some couples with translocations elect to use an egg or sperm donor, and some decide to just take their chances, with the understanding that they are at increased risk for miscarriage.
Progesterone is a hormone made by your body. It helps make the inside of your uterus hospitable for a growing embryo.
If there is an inadequate amount of progesterone circulating in the first few months of pregnancy, miscarriage is more likely to happen.
Blood can be drawn to assess your serum progesterone level. Levels vary according to where you are in your menstrual cycle. If your progesterone level is low, or if we can’t determine another cause for your pregnancy losses, we frequently place you on supplemental progesterone during the first trimester of future pregnancies.
Our chromosomes contain thousands of genes, which carry instructions for how our cells grow and function. An abnormality in a single tiny gene can cause fetal abnormalities or pregnancy loss.
Remember that we all have two copies of every gene, one from each parent. If you are a carrier for a genetic disorder, that means you have one normal and one abnormal copy of a particular gene. If both parents are carriers for an abnormality (in other words, they each have one abnormal copy of that gene), there is a chance that their baby will have two copies of the abnormal gene. And that means the baby will likely have that genetic disorder.
These diseases include cystic fibrosis, sickle cell disease, and hundreds of other disorders.
There is blood testing that can be done on both parents to see if you are carriers for any of the more common single-gene disorders.
The uterus forms from two tubular pieces of tissue that come together and form one pear-shaped organ. Roughly 1-2% of women have a uterus that is not the normal pear-shape. Below are some examples of how the uterus can be different:
When the uterus is abnormally shaped, pregnancy loss is more likely. Or sometimes, a muscle growth called a uterine fibroid can alter the contour of the uterus. If a fibroid distorts the inner surface of the uterus, early pregnancy loss can happen.
A dye test called a hysterosalpingogram (HSG) can be performed to assess the structure of the uterus. Or your OB may elect to perform hysteroscopy, where a tiny scope is placed up through the vagina into the uterus. This procedure can identify scar tissue, fibroids, polyps, or shelves of tissue called septa, all of which can affect the ability of the uterus to carry a pregnancy.
Women with hypothyroidism (an under-active thyroid gland) are at increased risk of early pregnancy loss. Symptoms of hypothyroidism may include fatigue, oily skin, constipation, and weight gain, but more often than not, no symptoms are reported.
So unless we are looking for it, thyroid disease goes undetected a lot of the time. A blood test can determine whether you have an overactive or under-active thyroid gland, and both these conditions are treatable.
The prevalence of diabetes is rising sharply and corresponds with the rise in obesity. Uncontrolled blood sugars are a well-known cause of miscarriage, birth defects, premature birth, hypertensive disorders, and heart disease.
A blood test called a hemoglobin A1C looks at your average blood sugar over a 2-3 month period. If this is elevated, you will need to be seen for diabetic education. You will be asked to check your blood glucose and follow a diabetic meal plan.
You should try to get your A1C as close to normal as possible before trying again to become pregnant.
Sometimes errors happen early in pregnancy which causes the fetus to develop abnormally. When I think about the thousands of things that can go wrong with development, it is miraculous to me that things go right as often as they do. If there is a major birth defect the fetus may stop growing and miscarriage happens.
When early pregnancy losses happen due to a birth defect, we can’t determine what went wrong, because the fetus is just too small for us to be able to tell. So this is frequently a diagnosis of exclusion; in other words, we can’t find any other cause.
When you are evaluated for recurrent early pregnancy loss, some or all of these issues may be discussed.
Or you may have additional studies to look at immune problems or inherited blood clotting disorders. I usually advise women to take a prenatal vitamin daily and add an extra milligram of folic acid, which can reduce the risk of some birth defects.
What I would like for you to remember is that most of the time, even if all our studies are normal and no particular cause is found for miscarriage, successful pregnancies do happen. Take heart, and hang in there.