Also known as spontaneous abortion, miscarriage refers to to the natural and sudden termination of a pregnancy during a stage where the fetus or embryo is still incapable of survival outside the womb, usually on the first 5 months or 13-20 weeks of fetal development.

This condition is the most known type of failed pregnancy, as mentioned by the American College of Obstetricians and Gynecologists. According to studies, 10 to 25% of pregnancies reported to clinics and hospitals will terminate by miscarriage. Chemical pregnancy, where pregnancy ends immediately after the implantation and results to bleeding during the time of the woman's expected menstruation, answers for 50 to 75% of all lost pregnancies.

The causes of miscarriage varies, and most doctors cannot point out the cause. Miscarriages that happen on the first three months of pregnancy or first trimester are usually attributed to chromosomal abnormality. This means that something was wrong with the chromosomes of the baby because of a deficient sperm or egg cell or a problem occurred during zygote division. There are also several more known factors, such as lifestyle (smoking, caffeine intake, drug usage, etc.), infections, hormonal problems, age, and other health problems.

The chance that a woman in her fertile or child-bearing age will experience miscarriage ranges from 10 to 25%. Also, as the woman ages, the chance of experiencing miscarriage is increased. Particularly, women above 45 have the highest probability of miscarriage, with a 50% chance that they will lose their baby.

Some of the warning symptoms of miscarriage are mild to extreme back pain, whitish-pink mucus, painful contractions, brown or red bleeding which may be accompanied by cramps, and weight loss.