Repeat miscarriages

FEMALE CAUSES
A miscarriage is considered to be the interruption of a pregnancy during the first 20 to 22 weeks and before the fetus weighs 500 grams. Most miscarriages occur during the first 12 weeks and are called early miscarriages. A miscarriage that occurs after 13 weeks is called a late miscarriage. Very early miscarriages are not always detected, as they can be mistaken for a late period. Most women who have a single miscarriage will not have problems with maintaining a pregnancy in the future. Up to 90% of women will get pregnant again and the pregnancy will continue to term. However, a small but significant percentage of women will go on to have another miscarriage. This is known as repeat miscarriage and refers to cases in which women have two miscarriages in a row, or when more than two pregnancies have not been carried to term.

Causes of repeat miscarriage:
Genetic causes:
In the human species, it is not uncommon for embryo disorders to occur at random. Most spontaneous miscarriages in early pregnancy are due to the presence of chromosomal anomalies. However, genetic factors are less common in cases of repeat miscarriages. Chromosomal anomalies in the parents are only found in 6% of repeat miscarriage cases. The most common anomalies include balanced translocations, inversions and aneuploidy.

Anatomical causes:
Uterine malformations can produce miscarriages in more advanced stages of pregnancy or lead to premature deliveries. These malformations can be due to the shape of the uterus, the absence or atrophy of one half of the uterus, a double uterus or the presence of a uterine septum.

Endocrinal causes:
Diabetes and hypothyroidism can cause miscarriages in women suffering from hormonal imbalance whose condition is not strictly controlled by a doctor. Hormone secretion by the ovary should maintain a spontaneous pregnancy through the first weeks. The corpus luteum produces most of the hormones the pregnancy needs to develop, the most important of which is progesterone. A deficit in ovarian secretion can cause the early loss of a pregnancy. However, if endocrinal problems were found to be present in an earlier pregnancy, a repeat miscarriage is unlikely as the condition can be monitored when the women becomes pregnant again. Women with polycystic ovarian syndrome have a higher chance of miscarriage because of hormonal imbalances related to excessive levels of luteinizing hormone (LH) during the first phase of the menstrual cycle.

Infectious causes:
It has been shown that many infections can produce miscarriages. Fortunately, few last long enough to be a factor in subsequent pregnancies. One possible exception is syphilis.
Immunological causes: Many repeat miscarriages attributed to unknown causes may actually produced for immunological reasons. The importance of the so-called antiphospholipid syndrome as a cause of repeat miscarriage has been mentioned in recent years. This condition includes the presence of antibodies in the mother´s bloodstream that are related to embryo death and to diseases involving changes in hemostasis (e.g., thrombosis, a reduction in the number of platelets, etc.) It is estimated that around 10% of repeat miscarriages are due to immunological causes.

MALE CAUSES
The causes of repeat miscarriages attributable to the male partner are chromosomal disorders present in the sperm. The exact cause can be determined through the use of blood tests (karyotype) and by studying the sperm (using the FISH technique). It may also be necessary to perform a biopsy on the testicle.
There is no specific treatment for these problems. Depending on the nature of the disorder, the embryos obtained through in vitro fertilization can be studied so that only healthy ones are used in the embryo transfer (PGD). In cases where this is not possible, the couple can be referred to the Semen Bank.