The outcome of miscarriage is usually the expulsion of the fetus (viable or not), less often the dead fetus remains in the uterus. A non-developing pregnancy in such cases is classified as a failed miscarriage or failed birth. In modern obstetrics, the following division of pregnancy loss according to the timing of the episode (according to the WHO classification) is accepted:
• Spontaneous abortion (miscarriage). Interruption of the gestation process up to 21 completed weeks. In Russia, early (up to 12 full weeks) miscarriage and late - from the thirteenth week are distinguished.
• Premature birth. Interruption from the 22nd to the full 37th week (with a fetal weight of 500 grams), including very early (at 22-27 weeks) and early (at 28-33 weeks) preterm birth. In Russia, pregnancy loss before the full 27th week does not apply to preterm birth, and perinatal mortality is counted from the 28th week.