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Miscarriage: Understanding the facts and dispelling the myths

Depression, General, Mental Health, Women's Health, Infant and Children | January 28, 2015 | Author: The Super Pharmacist

women, infant

Miscarriage: Understanding the facts and dispelling the myths

Miscarriage, or spontaneous abortion, is the loss of a foetus from the womb at a point before the natural end of a pregnancy. Most miscarriages occur in the first 23 weeks following conception. Some estimates indicate that this occurs in approximately 15% of pregnancies. These events are often associated with physiological or external factors over which the pregnant woman has no control, and is not responsible for. Some miscarriages occur without a discernible explanatory factor, and are known as idiopathic spontaneous abortions. Miscarriage may cause distress, anxiety and/or depressive symptoms, which may persist for six months or more. Some women may experience recurrent miscarriage, which may result in prolonged feelings of grief and loss. Estimates suggest that recurrent miscarriage affects up to 2% of women of reproductive age. Women who have experienced one or more miscarriages may be more susceptible to depression and anxiety during subsequent pregnancies.

Risk Factors

There are several variables that may contribute to the risk of spontaneous abortion and/or miscarriage. Examples include:

Diabetes: Recurrent miscarriage is associated with pre-existing diabetes. Some treatments, including insulin, are not effective in maintaining blood sugar levels in pregnancy. However, metformin, a newer medication, has been associated with safety during pregnancy, and may be associated with a reduced risk of spontaneous abortion.

Structural uterine anomalies: Variations in the shape and structure of the womb may affect the chances of conception and of carrying a foetus to full term. Common forms of uterine abnormality include:

  • Septate uterus, in which the internal part of the uterus is split in two (or nearly in two) by a band of tissue
  • Bicornuate uterus, in which both the external and internal parts of the organ appear to 'fold inwards'

These abnormalities are also associated with recurrent miscarriage. A study of 170 women with these conditions investigated the effect of surgery on the probability of successful pregnancy. The live birth rate in women with septate wombs who had received surgery was 81.3% compared to 61.5% in those who had not. There was no effect of surgery for women with a bicornuate uterus, but there was a tendency toward improvements in complete pregnancies and live birth weights.

Thyroid/parathyroid disorders: The levels of thyroid or parathyroid hormones appear to affect conception and foetal retention even in healthy women. A study including 1477 women with normal thyroid function undergoing insemination found that higher levels of thyroid-stimulating hormone (TSH) prior to conception was related to higher rates of full-term pregnancy. Thyroid dysfunction is associated with miscarriage and with growth disorders of infants born to patients. Foetal development problems are also related to maternal iodine deficiency, since iodine is required to form thyroid hormones. Some aspects of foetal growth are regulated by the thyroid. This regulation is entirely dependent on the mother's body until approximately 20 weeks into pregnancy. Interruptions or impairments of this may result in effects ranging from spontaneous abortion to impaired foetal brain formation. On the other hand, excessive thyroid activity may also result in complications with pregnancy. The ideal level of TSH in the treatment of these disorders during pregnancy is one maintained at below 2.5 mIU/L.

Antidepressants: Many types of antidepressants are contra-indicated during pregnancy, due to links between these drugs and foetal abnormalities and/or loss.

Selective serotonin re-uptake inhibitors (SSRIs) have been found to be associated with an increased risk of spontaneous abortion. However, some researchers argue that this relationship is compromised by variables such as pre-existing mental illness and lifestyle factors.

A Danish study of over 100,000 pregnancies found that SSRI exposure before or during pregnancy was associated with the increased probability of first-trimester, but not second-trimester, spontaneous abortion.

However, this probability was not associated with SSRI use in women without diagnoses of anxiety or depressive disorders. Women diagnosed with these disorders, but not taking SSRIs, were more likely to experience first-trimester miscarriage. SSRI use was also accompanied by other factors such as reduced mental health and less healthy lifestyles. In other words, these additional factors may have an equal chance of being responsible for the increased risk of miscarriage as the use of SSRIs.

Invasive tests or procedures: Tests that involve taking a tissue sample from the foetus or womb during pregnancy have often been linked to the increased risk of miscarriage. These may include amniocentesis, in which a sample of the amniotic fluid is taken, or choronic villus sampling (CVS), in which some cells of the placenta are removed for analysis. A review of data on over 42,000 cases of amniocentesis and over 8800 cases of CVS was conducted. This concluded that the rate of spontaneous abortion before 24 weeks was 2.2% for the CVS group and 0.8% for the amniocentesis group, compared to 1.8% and 0.7% respectively for matched control data from women who did not undergo any procedure.

Genetic factors: Variations in certain genes have been found to be associated with an increased risk of early termination.

Mutations in part of the HLA-G gene were found to be associated with an increased risk in a recent study of 100 women who had experienced multiple unexplained miscarraiges. This study found two discrete mutations, which were associated with a 4.3- and 3.5-fold increase in this risk respectively.

Other forms of genetic disorder resulting in miscarriage may include chromosomal abnormalities. Chromosomes are large molecular structures, the subunits of which are genes. 

The human genome (or total content of genetic material) is contained in 22 chromosomes, plus the X or Y chromosome (which determine gender). In some cases, a foetus may have one or more copies of the same chromosome in its cells, which results in spontaneous abortion.

Airline-based Occupations: Some research indicates a link between the increased risk of early-term miscarriage and working on board airline vehicles (e.g. as a flight attendant). A recent study investigated the rate of spontaneous abortion among over 2000 airline attendants compared to that among 387 female teachers. This resulted in indications that the increased probability of spontaneous abortion in the first nine to thirteen weeks may be associated with increased exposure to cosmic radiation. In addition, there was a slightly increased risk of first-trimester abortion with fifteen hours or more on board during 'normal' sleeping hours and with increased physical demand at work. However, overall rates of miscarriage in flight attendants were similar to those in teachers.

Foetal tumours: Abnormal cellular growths in utero are a relatively recently proposed factor in miscarriage. A study of 2,786 second-trimester miscarriages and stillbirths reported an incidence of tumour development of approximately one in 200, or about fifty times the incidence in live births. This paper proposes that screening for tumours in spontaneously aborted infants is carried out in the future to validate these findings.

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