流产包括人工流产（堕胎）和自然流产。怀孕期在满28周之前就终止通称流产，俗称「小产」。流产的婴胎无法自活。在医学上，人类流产的定义是在胎儿发育至能够存活前因任何方式而终止妊娠。胎儿发育自能够存活的时间约是怀孕母体最后一前月经来的第一天算起28周。

自然流产在怀孕前三个月很常见，有时候母亲自己都不知道怀了孕，所以有时流产只包括第4到6个月内失去婴胎。到了28周，婴儿可以活命，至妊娠足月（37周）前胎儿离开母体，则称为早产。

自然流产对母亲身体影响很大。流产时可能会大量失血，对心灵打击沉重，尤其觉得自己太不小心以至流产的人。

Miscarriage, also known as spontaneous abortion and pregnancy loss, is the natural death of an embryo or fetus before it is able to survive independently. Some use the cutoff of 20 weeks of gestation after which fetal death is known as a stillbirth. The most common symptoms of a miscarriage is vaginal bleeding with or without pain. Sadness, anxiety, and guilt may occur. Tissue or clot like material may also come out of the vagina.