Miscarriage is most commonly caused by problems with the unborn baby, particularly chromosomal abnormalities. About half to two-thirds of miscarriages in the first trimester are linked to extra or missing chromosomes, which prevent proper development of the embryo or fetus
. These chromosomal issues may result in conditions such as anembryonic pregnancy (no embryo forms) or intrauterine fetal demise (embryo stops developing). Other causes and risk factors include:
- Maternal health conditions: Uncontrolled diabetes, thyroid disorders, blood clotting problems (e.g., antiphospholipid syndrome), and infections can increase miscarriage risk
- Uterine or cervical problems: Structural abnormalities of the uterus or cervical insufficiency (weak cervix that opens too early) can lead to miscarriage, especially later in pregnancy
- Infections: Certain infections like rubella (German measles), listeria food poisoning, and some sexually transmitted infections may cause miscarriage
- Lifestyle factors: Smoking, heavy alcohol use, excessive caffeine, and illicit drug use (e.g., cocaine) raise miscarriage risk
- Age of parents: Advanced maternal or paternal age increases the likelihood of chromosomal abnormalities and miscarriage
- Other causes: Trauma (serious injury), hormonal imbalances, and sometimes unknown reasons contribute to miscarriage
Most miscarriages are random events not caused by anything the pregnant person did or did not do. Activities such as working, exercising, sex, or previous use of birth control pills do not cause miscarriage
. In summary, miscarriage is primarily caused by chromosomal abnormalities in the fetus, with additional contributions from maternal health, uterine conditions, infections, lifestyle factors, and parental age. Often, the exact cause remains unidentified
