I'm wondering if washing immediately and throughly after intercourse helps prevent pregnancy.
Dear Wondering woman,
Washing immediately after sex may give you a squeaky clean feeling, but it will not help prevent pregnancy. Showering or bathing after sex can help clear the vulva of semen. Douching (which is not recommended by women's health care providers for many reasons) may even clear some semen out of the vagina. However neither of these can flush out sperm that have already entered the uterus through the cervix. This is a myth that may have grown out of the (common 19th century) idea that douching could help remove semen. However, studies have shown that douching is not an effective contraception. See What is douching? for more information.
There are many other (water not required) ways to prevent pregnancy including male and female condoms, the birth control pill, and IUDs to name a few. Also, if you're seeking a post-sex birth control solution, you can use emergency contraception to help to prevent pregnancy up to 120 hours after sex that occurs when a method of birth control was not used or failed. Speaking with a health care provider about these options might be a good idea. You can check out Planned Parenthood for more information on birth control options.
Hopefully this satisfies your wondering mind.Alice!