DEAR ABBY: Here’s one for the books on parental stupidity. When my daughter, “Marissa,” began to reach her teen years, her father – in an attempt to be funny – advised her that she could keep from becoming pregnant by putting an aspirin between her knees and keeping it there.

My stupidity was assuming that sex education and pregnancy prevention were taught in her school. I never broached the subject with her.

Marissa became pregnant at 15. The young man she was seeing told her she couldn’t get pregnant in a swimming pool because the chlorine would kill the sperm. Have you heard that before? Needless to say, the inevitable result was a baby.

I love my grandson dearly. God did not make a mistake even though we adults were all dummies in the advice department. Please tell parents, children and adults to educate themselves and learn all the facts and fictions about teen pregnancy and prevention. – STUPID MOM WITH NO EXCUSE IN NEW JERSEY

DEAR MOM: Your letter underscores the importance of parents taking the initiative and discussing sex and values with their children before hormones kick in and peers fill their heads with misinformation about birth control.

Some popular misconceptions include the idea that jumping up and down after sex prevents pregnancy, that douching with Coca-Cola is an effective contraceptive, that you can’t get pregnant during your menstrual cycle, that “withdrawal” prevents pregnancy, and that you won’t get pregnant if it’s your first time or if your breasts aren’t developed.

It is vitally important that parents talk to their children about sex because many schools offer only abstinence-based sex education – which has not slowed the spread of STDs. According to the April 2005 issue of Journal of Adolescent Health, teens who pledge to remain virgins until marriage are more likely to take chances with other kinds of sex that increase the risk of STDs.

For parents who have difficulty discussing sex and values, I offer my booklet, “What Every Teen Should Know,” that explains not only sex and contraception, but also the important topics of sexually transmitted diseases and date rape. My booklet has been distributed in doctors’ offices and used to promote discussion by educators and religious leaders. It can be ordered by sending a business-size, self- addressed envelope, plus check or money order for $6 (U.S. funds) to Dear Abby, Teen Booklet, P.O. Box 447, Mount Morris, IL 61054-0447. Shipping and handling are included in the price.

DEAR ABBY: I was married last June. I wrote my thank-you notes for our wedding gifts a week after returning from our honeymoon. I thought they had been mailed.

It is now 11 months later, and I found the cards in the trunk of my husband’s car. What do I do? – CATHI IN STOCKTON, CALIF.

DEAR CATHI: You should mail them now. A late thank-you is far better than none at all.

Dear Abby is written by Abigail Van Buren, also known as Jeanne Phillips, and was founded by her mother, Pauline Phillips. Write Dear Abby at www.DearAbby.com or P.O. Box 69440, Los Angeles, CA 90069.