Original: The risk of spontaneous abortion decreases sharply after the 10th week from the last menstrual period ( LMP ) . One study of 232 pregnant women showed '' virtually complete ( pregnancy loss ) by the end of the embryonic period '' ( 10 weeks LMP ) with a pregnancy loss rate of only 2 percent after 8.5 weeks LMP .
Simplified: The risk of spontaneous abortion decreases sharply after the 10th week of pregnancy , with a loss rate between 8.5 weeks LMP and birth of about two percent ; pregnancy loss is â virtually complete by the end of the embryonic period . ''