Causes and misconceptions of miscarriage
Assistant Professor, Department of Pharmacy, Life Science Faculty, BSMRSTU, Gopalganj-8100, Bangladesh.
Miscarriage is a common consequence of pregnancy. In most cases, 12 to 15per cent of miscarriages occur within 20 weeks of conception. However, determining the total miscarriage rate in one country is very challenging because it is higher when the pregnancies are medically recognized. Moreover, there is an unclear conception among people about the difference between miscarriage and stillbirth. The miscarriage rate is also affected by the competing risk of induced abortion.
The causes of most miscarriages are a complex interplay between parental age, genetic, hormonal, immunological, and environmental factors. Maternal age is the strongest known risk factor. The risk of miscarriage is slightly elevated in the youngest mothers and then rises sharply in older mothers. A survey of 421201 pregnant women in Norway between 2009-13 suggests that the risk of miscarriage is lower in women aged 25-29 (10per cent), then rose rapidly after age 30, reaching 53per cent in women aged 45 and over. Genetic factors, including parental chromosomal rearrangements and abnormal embryonic genotypes or karyotypes, could underlie more than half of recurrent miscarriages. Miscarriage may adversely affects the future pregnancy outcomes and complications.
About 75per cent miscarriages happen during the first trimester of pregnancy; infection around the baby and its mother's health condition affect greatly in this stage. In this trimester, miscarriages are often caused by problems with the chromosomes of the fetus. The mother's placenta supplies blood to her baby's body; any problem in this organ may lead to miscarriage. Moreover, obesity, smoking behavior, certain drugs (e.g., misoprostol, retinoids, methotrexate, ibuprofen), caffeine at high dose (>200 mg/kg/day), herbal tea (>4 cups/day) and alcohol drinking also increase the risk of miscarriage among the pregnant women.
Several long-term (chronic) health conditions also increase the risk of miscarriage in the second trimester, including diabetes, (if left uncontrolled or poorly-controlled), severe hypertension, lupus, kidney disease, thyroid gland's under or over activity, anti-phospholipid syndrome, problems and abnormalities in womb (e.g., fibroids and shape abnormality), weakened cervix or cervical incompetence, and polycystic ovary syndrome (also causes infertility, lowers the production of eggs). Many infections may increase the risk of miscarriage, such as rubella (german measles), cytomegalovirus, bacterial vaginosis, human immunodeficiency viruses, chlamydia, gonorrhoea, syphilis, malaria, etc. The severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2) induced placental infections also have been reported for newborns with fetal distress and stillbirth after maternal contraction of the virus during the third trimester. Food containing poisonous substances, such as listeriosis, toxoplasmosis and salmonella etc. Therefore, a pregnant woman should avoid mould-ripened soft cheeses, unpasteurised milk and milk products, raw or undercooked meat, liver and liver products, all types of pâté, game meats such as goose, partridge or pheasant, raw or partially cooked eggs, some fishes like - swordfish, marlin, shark and raw shellfish, and high-dose multivitamin supplements.
However, there are lots of misconceptions about miscarriage, including the emotional state of the woman, having a shock or fright, exercise, lifting or straining, working, having sex, travelling by air and eating spicy food during pregnancy; as these are not the risk factors in miscarriage (if no one cross the limit). Many women having a miscarriage for the first time may have another. But most miscarriages are a one-off event. About 0.01per cent women experience recurrent miscarriages and many of them go on to have a successful pregnancy.