How many pregnancies result from assault rape?

Let's look, using the figure of 200,000 rapes each year—and that’s a high figure (figure for 2004-2005 was around 64,000). 

• Of the 200,000 women who were forcibly raped, one-third were either too old or too young to get pregnant. That leaves 133,000 at risk for pregnancy.
• A woman is capable of being fertilized only 3 days (perhaps 5) out of a 30-day month. Multiply our figure of 133,000 by three tenths. Three days out of 30 is one out of ten, divide 133 by ten and we have 13,300 women remaining. If we use five days out of 30 it is one out of six. Divide one hundred and thirty three thousand by six and we have 22,166 remaining.
• One-fourth of all women in the United States of childbearing age have been sterilized, so the remaining three-fourths come out to 10,000 (or 15,000).
• Only half of assailants penetrate her body and/or deposit sperm in her vagina,¹ so let's cut the remaining figures in half. This gives us numbers of 5,000 (or 7,500).
• Fifteen percent of men are sterile, that drops that figure to 4,250 (or 6,375).
• Fifteen percent of non-surgically sterilized women are naturally sterile. That reduces the number to 3,600 (or 5,400).
• Another fifteen percent are on the pill and/or already pregnant. That reduces the number to 3,070 (or 4,600).
• Now factor in the fact that it takes 5-10 months for the average couple to achieve a pregnancy. Use the smaller figure of 5 months to be conservative and divide the above figures by 5. The number drops to 600 (or 920).
• In an average population, the miscarriage rate is about 15 percent. In this case we have incredible emotional trauma. Her body is upset. Even if she conceives, the miscarriage rate will be higher than in a more normal pregnancy. If 20 percent of raped women miscarry, the figure drops to 450 (or 740).

Now, then, many women who become pregnant through assault rape choose not to compound the crime by killing the baby, and they don’t abort.

http://www.christianliferesources.com/article/rape-pregnancies-are-rare-461

http://blogs.scientificamerican.com/context-and-variation/2012/08/20/here-is-some-legitimate-science-on-pregnancy-and-rape/