To prevent miscarriage, some women are treated with the progesterone, a hormone which is needed for implantation in the uterus. Research is mixed on the effectiveness of this, and researchers believe it should only be done it tests show that the body products too little of that hormone in the early weeks of pregnancy.
Most women who have miscarriages have subsequent normal pregnancies and births. But about one percent of pregnant women have repeated (three or more) miscarriages, usually without a history of any normal births. Some researchers believe that this is an autoimmune disorder.
Early (before age 11) or late (after 16) menarche--the start of menstruation -- is associated with multiple miscarriages as are ovaries with many cysts. Women who have repeated miscarriages are four times more likely to have multiple ovarian cysts. Another link to repeated miscarriages is an "allergy" to the mate's sperm. Some women go on to have normal pregnancies and births after they change partners.
An ectopic pregnancy is one located outside the uterus, usually in one of the fallopian tubes. If a tube is damaged in any way, the fertilized egg may never complete its journey to the uterus. Ectopic pregnancies rarely last past eight weeks.