Spontaneous miscarriage in the first trimester is related to Chromosomal defects in the fetus. An estimated 15 to 20 percent of known pregnancies end in miscarriage, the loss of a pregnancy before the 20th week. Upto 70 percent of first-trimester miscarriages, and 20 percent of second-trimester miscarriages, are caused by chromosomal anomalies/abnormalities in the fertilized egg. Most often, it means that the egg or sperm had wrong number of chromosomes, and consequently the fertilized egg can't develop normally.
Your answer would be Grafting.
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Circulatory system because, movement causes circulation and movement is only possible by our muscles.