page_title: Miscarriage
section_title: First Trimester (Weeks 1-12)
hierarchical_section_title: Miscarriage / Causes of Miscarriage / First Trimester (Weeks 1-12)
caption_attribution_description: Approximately 6 weeks from conception, i.e. 8 weeks from LMP. Shot with 105 mm Micro-NIKKOR lens with 2 off camera SB-800's. Specimen is submerged in alcohol. This is a spontaneous (ie. not a termination) abortion. It was extruded intact with the gestational sac surrounded by developing placental tissue and decidual tissue. This was carefully opened to avoid damaging the embryo.
context_page_description: A miscarriage is the natural death of an embryo or fetus in the womb, before it is old enough to live on its own, outside the mother. The medical words for a miscarriage are spontaneous abortion.
  Among women who know they are pregnant, about 15-20% have miscarriages. It is the most common complication that happens in early pregnancy in humans.
context_section_description: Most miscarriages happen during the first trimester.  Some studies say that two-thirds (two out of three) to three-quarters (three out of four) of all miscarriages happen during this trimester. About 30% to 40% (3 to 4 in every 10) of all fertilized eggs miscarry, often before a woman knows she is pregnant.
  In more than half of embryos miscarried in the first 13 weeks of pregnancy, the embryo has chromosomes that are not normal. These chromosomal problems may happen because of problems as the embryo grows and its cells make copies of themselves.  It is also possible for chromosomal problems to happen because of a problem with a parent's genes.  However, this is more likely to happen in women who has had other miscarriages, or if one of the parents has a child or other relatives with birth defects. Genetic problems are more likely to happen with older parents; this may be why miscarriages are more common in older women.
  Another cause may be the mother not having enough progesterone.  If a woman is diagnosed with low progesterone levels in the second half of her menstrual cycle (the luteal phase), she may be prescribed progesterone, to take during the first trimester of her pregnancy.  However, when a woman might already be miscarrying, there is no evidence that first-trimester progesterone pills decrease the risk of having a miscarriage.  Scientists have even questioned whether problems with the luteal phase really can cause miscarriages.
caption: This is what a human embryo looks like about eight weeks after conception
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