Miscarriage is defined as a loss of pregnancy before the fetus becomes capable of independent life outside the uterus which is usually before week 20 of the pregnancy or if the fetus weighs less than 500 grams. There are several groups of miscarriage:
- Complete – when a woman experiences pain, bleeds and miscarriages, very often without a need for curettage;
- Incomplete – when a woman experiences pain and miscarriages begins with bleeding, but some pregnancy tissue remains in the uterus and a curettage is often necessary;
- Blighted ovum – when the sac develops but there is no baby inside and curettage is necessary;
- Missed ab – retained miscarriage, when a fetus appears but its heart stops beating and the pregnancy needs to be aborted;
- Septic miscarriage – a miscarriage caused by uterine infection.
With the appearance of affordable and widely accessible pregnancy tests women are able to notice what only medical workers used to know – that miscarriage is very often, so nowadays we know that around half of all pregnancies are miscarried. Pregnancy tests reveal the first category of miscarriage, the so-called biochemical pregnancies.
Biochemical pregnancies end very early, before they are visible on the ultrasound (which is possible around 5 weeks from the first day of the last period at the earliest). It is considered that biochemical pregnancies occur when the embryo dies immediately after forming and before it implants into the body of the uterus. They are very common and around 50 to 60 percent of all pregnancies are biochemical. We know that the pregnancy happened based on the positive beta HCG values (pregnancy hormone) in the blood or urine which stop being positive after a few days. Bleeding occurs (D&C is almost never necessary) and the pregnancy withers. Biochemical pregnancies were not very known of in the past because there were no such sensitive pregnancy tests and women used to wait for a few days after they miss their period to go see a doctor. If they would bleed, they thought they haven’t even been pregnant. The period after biochemical pregnancy may be heavier, clotted and more painful, but this is not a rule. Most often biochemical pregnancy has no symptoms because pregnancy symptoms usually occur around week 6.
The most common causes of biochemical pregnancies are:
- Chromosomal abnormalities – usually being the most common reason for miscarriage. The egg, or a sperm inseminating the egg, carry a chromosomal flaw which prevents the embryo to develop and it dies out;
- Uterine abnormality which can be congenital (septate uterus, double uterus, etc.) or acquired (fibroids) and may lead to embryo trying to implant in the unfavorable part of the uterus which causes the pregnancy to wither;
- Hormonal deficiency – some women have a second, luteal phase deficiency of hormones meaning that there are not enough hormones for the pregnancy to develop.
A large majority of women who have experienced biochemical pregnancy will later on give birth to a live baby so that, even though it carries feelings of loss at a time of occurrence, biochemical pregnancies are also a good sign for couples trying to conceive. Biochemical pregnancy causes us to worry if two or three such pregnancies occur in a short period of time. In this case you should contact your physician.
After the pregnancy is visible during ultrasound check or prior to week 20 of the pregnancy, about 15% of pregnant women will miscarry. After week 12 additional 1% miscarry. Such miscarriage is called clinical miscarriage. Women who already gave birth to a healthy baby and had no prior miscarriage are under a less than 12% risk to miscarry. The percentages grow with the number of previous miscarriage. This data is valid for young women. Past the age of 36, the risk of spontaneous miscarriage as well as infertility and giving birth to a baby with chromosomal flaw grows and the percentage of spontaneous miscarriage (both biochemical and clinical) after the age of 40 is 75%.
Most common cause of spontaneous miscarriage (in almost 70%) is chromosomal abnormality, similar to biochemical pregnancies where this percentage is even higher. The second most common cause of spontaneous miscarriage is infection and the rest lie in exposure to toxins (e.g. at workplace), hormonal issues, obesity, uterine abnormalities, systemic conditions in women (e.g. diabetes) and, very rarely, reasons connected to the immune system. Alcohol and stress are often mentioned as possible causes for spontaneous miscarriage, but there is no relevant scientific proof for this. Certain groups of women are considered to carry a higher risk to spontaneous miscarriage. They are women with polycystic ovaries, high blood pressure, thyroid disorders (hypothyroidism) or women taking antidepressants, smokers and drug users.
Symptoms of a spontaneous miscarriage include pain in lower abdomen, usually accompanied by severe cramps, and bleeding which may start out slow. After miscarrying, a woman will have her next normal period within the next 4-6 weeks. Next pregnancy can occur even prior to this period but it is advised to wait at least for three weeks before trying again, especially if D&C has been done.
There are women who have repeated miscarriages which are known as habitual miscarriages. Up to 5% of women will have recurrent miscarriages. Previously, repeated miscarriages were defined as having 3 or more of them, but considering the fact that women increasingly postpone getting pregnant and having a baby, usually faced with lack of time do this, gynecologists have decided to start diagnosing after 2 spontaneous miscarriages. The risks for women who have already had two or more spontaneous miscarriages and haven’t given birth to miscarry again are very high and are about 30-45%.
In most cases, we do a serious and detailed diagnostics in order to determine the case of miscarrying after two spontaneous miscarriages. More often than not we are not able to determine the exact cause, but we then monitor future pregnancies in a detailed manner and from the very beginning, usually committing women to a hospital for longer periods of time. What is important to remember is that despite this quite looming statistical data, most women who have had one or more miscarriages will eventually be able to give birth. That is why it is important not to feel guilt, anger or depressed feelings that are very often in couples experiencing a loss, but to find a way to overcome these feelings after a reasonable period of time assisted either by your closest family and friends or by a psychologist.