Causes of Spontaneous Abortion

Chromosomal and Genetic Abnormalities

Fetal chromosomal abnormalities account for the majority of early pregnancy losses, with advanced maternal age (≥35 years) significantly increasing this risk through age-related aneuploidy, according to the Centers for Disease Control and Prevention 1
Genetic testing through chorionic villus sampling or amniocentesis can identify these abnormalities, though the procedure itself carries a 0.25-0.50% miscarriage risk, as reported by the Centers for Disease Control and Prevention 1

Elevated glucose levels during embryogenesis directly increase spontaneous abortion rates; achieving HbA1c <7% preconceptionally (ideally <6%) reduces this risk to levels comparable with non-diabetic pregnancies, as recommended by the American Diabetes Association 2
Thyroid dysfunction affects 5-10% of women with recurrent losses, particularly those with autoimmune conditions, making TSH testing essential, according to the American Thyroid Association 2
Hormonal imbalances require optimization before conception to reduce pregnancy loss risk, as stated by the Endocrine Society 2

Women with blood lead levels 5-9 µg/dL have an odds ratio of 2.3 for spontaneous abortion; this increases to 5.4 at 10-14 µg/dL and 12.2 at >15 µg/dL compared to <5 µg/dL, as reported by the National Institute of Environmental Health Sciences 3
Each 1 µg/dL increase in blood lead across the range of 1.4-29 µg/dL confers an OR of 1.13 (95% CI, 1.01-1.30) for spontaneous abortion before 21 weeks, according to the National Institute of Environmental Health Sciences 3
Occupational exposure to cytotoxic drugs carries an odds ratio of 2.30 for spontaneous abortion in exposed nurses, as reported by the Occupational Safety and Health Administration 4

Approximately 40% of pregnant women ≥35 years underwent prenatal diagnostic testing in 1990 due to age-related aneuploidy risk, as reported by the American College of Obstetricians and Gynecologists 1
Smoking and alcohol consumption directly increase miscarriage risk and require complete abstinence, as recommended by the American College of Obstetricians and Gynecologists 2
Both underweight and overweight/obesity status increase pregnancy complications including loss, according to the American College of Obstetricians and Gynecologists 2

Folic acid supplementation (minimum 400 mcg daily) started before conception prevents birth defects and reduces pregnancy loss, as recommended by the Centers for Disease Control and Prevention 2
Discontinue teratogenic medications immediately when planning pregnancy, as stated by the American College of Obstetricians and Gynecologists 2
Use effective contraception until all metabolic targets are achieved, according to the American College of Obstetricians and Gynecologists 2
Establish multidisciplinary care for high-risk patients, as recommended by the American College of Obstetricians and Gynecologists 2