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Miscarriages can occur for many reasons, not all of which can be identified.
First trimester
Most miscarriages (more than three-quarters) occur during the first trimester.
Chromosomal abnormalities are found in more than half of embryos miscarried in the first 13 weeks. A pregnancy with a genetic problem has a 95% chance of ending in miscarriage. Most chromosomal problems happen by chance, have nothing to do with the parents, and are unlikely to recur. Genetic problems are more likely to occur with older parents; this may account for the higher miscarriage rates observed in older women.
Another cause of early miscarriage may be progesterone deficiency. Women diagnosed with low progesterone levels in the second half of their menstrual cycle (luteal phase) may be prescribed progesterone supplements, to be taken for the first trimester of pregnancy.
Second trimester
Up to 15% of pregnancy losses in the second trimester may be due to uterine malformation, growths in the uterus (fibroids), or cervical problems. These conditions may also contribute to premature birth.
One study found that 19% of second trimester losses were caused by problems with the umbilical cord. Problems with the placenta may also account for a significant number of later-term miscarriages.
General risk factors
Pregnancies involving more than one fetus are at increased risk of miscarriage.
Uncontrolled diabetes greatly increases the risk of miscarriage. Women with controlled diabetes are not at higher risk of miscarriage. Because diabetes may develop during pregnancy (gestational diabetes), an important part of prenatal care is to monitor for signs of the disease. High blood pressure and certain illnesses (such as rubella and chlamydia) increase the risk of miscarriage.
Tobacco (cigarette) smokers have an increased risk of miscarriage. An increase in miscarriage is also associated with the father being a cigarette smoker. The husband study observed a 4% increased risk for husbands who smoke less than 20 cigarettes/day, and an 81% increased risk for husbands who smoke 20 or more cigarettes/day.
Severe cases of hypothyroidism increase the risk of miscarriage. The effect of milder cases of hypothyroidism on miscarriage rates has not been established. Certain immune conditions such as autoimmune diseases greatly increase the risk of miscarriage.
Cocaine use increases miscarriage rates.
Physical trauma, exposure to certain chemicals, obesity, high caffeine intake (> 300 mg/day), high levels of alcohol consumption, and use of NSAIDs have also been linked to increased risk of miscarriage.
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Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
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