The reason of more than 60 percent of miscarriages, which occur during the first trimester of pregnancy, remains unexplained. Some people consider that the reason may be something that happened to them recently, for example some illness, exposure to something harmful, or fall, caused the miscarriage to occur. It is also assumed sometimes that the reason lies in genes, that some chromosomes did not get replicated in a right way. However, this all is rarely true, because as a rule by the time a miscarriage gets diagnosed or begins, the baby has already been lost for some period of time.
There are several possible causes of early miscarriage:

Hormones
When people communicate about some hormonal problem, the miscarriage is most likely to occur during the first 10 weeks of pregnancy, because after two months and a half the placenta has already taken the production of hormones over and any hormonal deficiency may not be considered as a factor. The most common problem of miscarriage is low progesterone level. And, unfortunately, it is not easy to be treated. All progesterone suppositories, although they are prescribed frequently enough, have not been proven to be much helpful and they may even become the reason of a nonviable pregnancy to last longer than it should.
 However, there is one situation, in which progesterone may be considered as a sure solution – it is women, suffering from a luteal phase defect, when the corpus lutem, which gets formed together with the egg during the period of ovulation, does not produce the hormones, necessary to sustain a normal development of pregnancy. Therefore, it should also be noted, that for the majority of women it does not usually make an every – month problem. As a rule the situation becomes corrects itself with the next egg and the next corpus luteum during the next period of ovulation. However, in case if this problem is a permanent one, it is possible to be diagnosed with the help of two separate endometrial biopsies. In order to act correctly, progesterone is to be started 48 hours after the ovulation occurs. And by the time a woman, suffering from a luteal phase defect, has a missed period, it becomes too late to save her pregnancy.

Therefore, it should also be noted, that low level of progesterone hormone is considered to be only a symptom, and not a reason of a nonviable pregnancy. When the level or progesterone is low, doctors may prescribe some kind of progesterone suppositories out of patient pressure, however the application of these suppositories is usually controversial, and in most cases it does not produce any effect. If there any suspected progesterone problem, Clomis is considered to be the most widespread treatment. Clomid is a pill, which is to be taken five days before a woman’s menstrual cycle begins. However, in 25% of women there is a cervical mucus decrease from taking this drug, which can influence their fertility in a negative way; this is why they should better avoid taking this medicine.
The reason of other hormonal problems may be an untreated thyroid disorder, however, this problem is quite an easy treatable one, and the function of a thyroid gland is not difficult to be tested. 

Chromosome Defects
When the woman’s egg unites with the man’s sperm, and they create the first cell, many factors come in to play. Even in those cases, when the egg and the sperm have perfect chromosomes, an abnormality crop can occur during the first few cell divisions, the sequences of which may be devastating. The reason of about 60% of early miscarriages is some certain chromosome defects, which cause a recently fertilized egg to die.
 If a woman has a wish to find out whether there were any problems, connected with chromosomes, she can do it easily by testing the tissue, obtained from the miscarriage. However, it is necessary to point out, that the analysis is to be conducted right away when the tissue comes out, otherwise the cell will stop growing and the test will not work. In case of a first miscarriage, there is no need to go to great length to save the tissue, as not every doctor is going to make any analysis of it, and chromosomal reason for this miscarriage usually gets assumed without any testing conducted.

Still even after a woman has a D&C procedure, and when the doctor sends the tissue of a miscarriage right after it was sucked out, there is a risk that it might not work. However, if a chromosomal defect does become the reason of a miscarriage, a woman may have at least a mall measure of comfort in being aware of the fact that although this beloved and precious baby has been lost, the chances that she will experience another miscarriage are extremely small. However, not everything is so good, as in women, who are older than 35, chances of having a repeated miscarriage increase drastically.

In accordance with some recently conducted investigations, after the second trimester of pregnancy begins, the number of miscarriages, which are cause by genetic factors, drops significantly, and the risk of having it is less than 10%. If a woman had suffered several miscarriages in a row, than her chances of this being her problem are low enough, and make only about 7%, however, in women, who are older than 35, chances of having a repeated miscarriage increase drastically.