Pregnancy is divided into three equal lengths: the first, second and third trimesters. Miscarriage in the second trimester occurs during the period from the 13th to the 27th week of pregnancy. It is a rare event. Loss of pregnancy up to and including the 22nd week is defined as a miscarriage, while after the 22nd week it is considered a stillbirth.
How common is miscarriage?
Most miscarriages occur in the first trimester and the risk decreases throughout pregnancy. A total of 10–20% of all verified pregnancies and 30–40% of all verified and unverified pregnancies end in miscarriage. About 1-5% of pregnancies are lost in weeks 13 to 19, while stillbirth / miscarriage occurs in 0.3% of pregnancies in weeks 20 to 27, which corresponds to the proportion of stillbirths in the third trimester.
It is difficult to determine the cause in each case, but damage to the fetus due to genetic, chromosome abnormalities or other reasons are important causes. All in all, it is estimated that the cause of a miscarriage remains unexplained in up to half of the cases.
In the first trimester, chromosome failure is the cause of at least half of the miscarriage. It is likely that the relationship between the mother or the interaction between mother and child is more important later in pregnancy.
Risk factors in the mother are approximately the same throughout pregnancy. These include changes in the uterus, hormonal changes, immunological factors, infections, disorders of the body’s coagulation system, poorly controlled chronic diseases such as diabetes and high blood pressure, and severe acute illness. During the last trimester, conditions surrounding the pregnancy itself, such as the present placenta and premature discharge of the placenta, come into play.
The main causes of miscarriage / stillbirth in the second trimester
This is an important explanation for miscarriage in the second trimester. About 1/4 of all miscarriages / stillbirths in the second trimester and just over 10% in the third trimester are due to chromosome changes. These changes are the same as those found in live births – the most common being trisomy 13, 18 and 21 (Down syndrome), Turner’s syndrome and sex-linked changes.
Anatomical conditions in mother and child.
Several conditions in the fetus / child cause bodily (anatomical) changes, such as neural tube defects, which predispose to miscarriage.
In the woman, changes in the uterus – constrictions, muscle knots, connective tissue bands that divide the uterus in several rooms – are important causes of miscarriage in the second trimester. The utility of surgical correction of such changes is debated, but surgery is the only possible treatment for major errors. However, research shows that surgical correction of the uterine muscle (myoma) does not improve the outcome in subsequent pregnancies.
Impaired cervix is associated with miscarriage in the second trimester. The cervix should be closed throughout pregnancy, that is, it should not open before the normal delivery. Some women, however, have errors in the “closure mechanism” of the cervix, so that when the weight of pregnancy reaches a certain level, the cervix succumbs, opens, the fetal membranes burst and it becomes a premature birth. In women who have had repeated episodes of insufficient cervix with subsequent miscarriage or stillbirth, the obstetrician can sew the cervix together (hoping to prevent the cervix opening). It has been shown that cerclage can prevent new miscarriage / stillbirth in women with previous miscarriage.
Thrombophilia – predisposition to thrombosis
Initial failures after 20-24 weeks of pregnancy are in some cases due to errors in the mother’s coagulation system. A condition known in the professional language as thrombophilia. A distinction is made between several subtypes: For women with miscarriage after the 20th week of pregnancy, blood tests are recommended. For women with miscarriage before the 20th week, there is insufficient evidence to recommend such an investigation.
If thrombophilia is diagnosed, treatment with blood thinners (heparin and acetylsalicylic acid) will be given at the next pregnancy.
Infection is reported to contribute to 10–25% of all miscarriages in the second trimester. The significance of infection is still uncertain. One type of vaginal catarrh, bacterial vaginosis, has been associated with miscarriage in the second trimester, but not in the first trimester. Treatment of bacterial vaginosis is considered to prevent premature birth in women with previously premature births.
How are women who have had miscarriages in the second trimester investigated?
After a miscarriage in the second trimester, a thorough investigation should be done to look for factors that may predispose to future miscarriages.
While reviewing the history of illness, the doctor will emphasize the following:
- What are the signs and symptoms you experienced before the miscarriage?
- Do you have a chronic illness that can affect the outcome of your pregnancy?
- Have others in the family experienced something similar? Can this be hereditary?
- Do you use medicines regularly? Could a drug have caused the event, or is the disease that you are using medicine for, significant?
- Have you been exposed to environmental / environmental impacts? Toxic substances?
- Do you use drugs?
- Were you exposed to injuries during pregnancy? Is your partner violent?
- How have any previous births gone?
The physician will reassess the observations made during the maternal care checks. He or she will look closely at weight gain, increase in abdominal volume, possible ultrasound findings and blood test results.
What treatment options are available?
Detailed investigation and assessment of many of the factors linked to the mother require referral to obstetricians. Any treatment options depend on what the doctor believes is the cause of your problems.
- If you suffer from a chronic disease such as diabetes, thyroid disease or high blood pressure, it is important to ensure that the treatment of the disease is as accurate as possible.
- Make sure you start with folic acid supplements when planning to become pregnant, as it will reduce the risk of neural tube defects in the baby.
- Do not smoke, do not use alcohol or drugs during pregnancy, although the significance of these factors is unclear in case of miscarriage.
- In some cases, genetic investigation and counseling may be necessary.