How high are the chances of pregnancy when the male does not ejaculate in the vagina and pulls out before he does do so?

See below. Any nonprotected sex always has the chance to get somebody pregnant. Take a Plan B contraception. Always have protected sex (condom) to avoid pregnancy if you are not ready, as well as stds.
High. 'pull ou' or coitus unterruptus isn't a method of birth control it's like playing russian roulette. There can be a total lack of sensation when pre-cum escapes. Pre-cum often contains live sperm ; escapes from a male's penis before ejaculation. Thus also like closing barn door after horse has escaped. You need real contraception if having sex without desire for pregnancy.
High. Withdrawal or coitus interuptus is only as good as your own restraint, meaning not even ejaculating the slightest bit into the woman's vagina. The risk of pregnancy in the first year of use are more than 25% which are not good odds if trying to prevent pregnancy. Try condoms, which are the only method as well of preventing std's.