Miscarriage, also called spontaneous abortion, is the accidental or natural ending of a pregnancy before a baby can live outside its mother’s body. Studies indicate that 15 to 20 percent of all diagnosed pregnancies end in miscarriage. But the risk of miscarriage is highest during the first two weeks following conception (fertilization), a time at which most women do not even know they are pregnant. Thus, many physicians believe the overall rate of miscarriage, including undiagnosed pregnancies, may actually be as high as 50 percent.
Up to 60 percent of all miscarriages occur because of defects in the embryo’s chromosomes. Chromosomes are tiny, threadlike structures that carry genes. In most miscarriages involving defective chromosomes, the embryo cannot develop normally. A miscarriage may also occur if progesterone, a hormone necessary to maintain pregnancy, is not present in sufficient amounts. Some women miscarry because the uterus, the organ in which the offspring develops, cannot withstand the pressures of the growing fetus. Some chronic (long-term) diseases, such as diabetes and kidney disease, also are linked to miscarriages. Pregnant women with such diseases require close medical attention.
