Abortion is the spontaneous or induced (therapeutic) expulsion of the products of conception from the uterus before 20 weeks gestation (fetal weight less than 500 g [17½2 oz]). Up to 15% of all pregnancies and about 30% of all first pregnancies end in spontaneous abortion (miscarriage). At least 75% of miscarriages occur during the first trimester.


Spontaneous abortion may result from fetal, placental, or maternal factors. (See Types of spontaneous abortion.) Fetal factors usually cause abortions before the 12th week of gestation and include:

  • defective embryologic development resulting from abnormal chromosome division (most common cause of fetal death)

  • faulty implantation of the fertilized ovum

  • failure of the endometrium to accept the fertilized ovum.

Placental factors usually cause abortion around the 14th week of gestation, when the placenta takes over the hormone production necessary to maintain the pregnancy. These factors include:

  • premature separation of the normally implanted placenta

  • abnormal placental implantation.

Maternal factors usually cause abortion during the second trimester and include:

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Jun 16, 2016 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Abortion

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