Enviado por " CONSULTORIO MÉDICO JAVIER FLORES BUISSON " MÁNCORA- PERÚ...
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Miscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving, generally defined in humans at prior to 24 weeks of gestation. Miscarriage is the most common complication of early pregnancy.Miscarriages can occur for many reasons, not all of which can be identified. Some of these causes include genetic, uterine or hormonal abnormalities, reproductive tract infections, and tissue rejection.
First trimester: A complete spontaneous abortion at about six weeks from conception, i.e. eight weeks from the last menstrual period (LMP)Most clinically apparent miscarriages (two thirds to three-quarters in various studies) occur during the first trimester.
Chromosomal abnormalities are found in more than half of embryos miscarried in the first 13 weeks. A pregnancy with a genetic problem has a 95% probability of ending in miscarriage. Most chromosomal problems happen by chance, have nothing to do with the parents, and are unlikely to recur. Chromosomal problems due to a parent's genes is, however, a possibility. This is more likely to have been the cause in the case of repeated miscarriages, or if one of the parents has a child or other relatives with birth defects.Genetic problems are more likely to occur with older parents; this may account for the higher miscarriage rates observed in older women.
Another cause of early miscarriage may be progesterone deficiency. Women diagnosed with low progesterone levels in the second half of their menstrual cycle (luteal phase) may be prescribed progesterone supplements, to be taken for the first trimester of pregnancy. However, no study has shown that general first-trimester progesterone supplements reduce the risk of miscarriage,and even the identification of problems with the luteal phase as contributing to miscarriage has been questioned.
Second trimester: Up to 15% of pregnancy losses in the second trimester may be due to uterine malformation, growths in the uterus (fibroids), or cervical problems.These conditions may also contribute to premature birth.
One study found that 19% of second trimester losses were caused by problems with the umbilical cord. Problems with the placenta may also account for a significant number of later-term miscarriages.