Contraception why not?

Birth control/regulation is allowed by the Catholic Church. The Church simply wants the best method which is effective and will not hurt a women's well being.

The best method from both a medical and psychological standpoint is Napro Technology which has an effectiveness of 99.5 percent and a use effectiveness of 96.8 percent. These figures are as good or better than the effectiveness of any contraceptive drug or device on the market. Napro is not the rhythm method.

Happier marriages: Over 96% of couples who use Napro technology remain married and have better relationships than couples who use other methods.

More intimate relationships with Napro. Even couples who are not seeking to bring about new life can still experience the wonder of how they are made and see fertility as a powerful gift which needs to be used responsibly.

Sterilization hurts this intimacy because it basically views the other's most intimate gift (fertility) as a threat which needs to be cut off. Or as a disease in which a drug needs to be taken to fight it. Napro not only avoids a negative view of the other spouse but deepens the perception of seeing the other as a gift.

This leads to a better emotional, spiritual and physical relationship. Or to put in in other words a better sex life. John Paul II thinks sex is a means to holiness in marriage.

Physical side effects from artificial birth control can lower a women's sex drive.

The Catholic Church is for natural regulation of births. John Paul II does ask that a couple be generous but only they can determine this. The Church rejects unnatural birth control because of it's potential to harm a women or a couple.

Higher failure rate with contraception leads to unwanted pregnancy which can put a strain on marriages and lead to abortion.

The physical risks to women are not acceptable:

Cancer

The subgroup of women who are young, childless and users of the pill for a number of years, is 40% to 1000% more likely to develop breast cancer at a younger age and in a more aggressive variety[37] than non-users of the pill. Even more startling is the finding that the low-dose pill's tendency to protect women from uterine and ovarian cancer is negated by the increased incidence of cervical cancer, thought to be associated with the human papilloma virus, from which the pill offers no protection [38].

The negative side effects also go against the dignity of women:

Depression

Lower Sex drive

Nausea, fluid retention, cyclic weight gain, cervical ectopia, rising cholesterol concentration in gallbladder bile, growth of fibroid tumors of the uterus, and the pill's promotion of red "spider veins." [40] Other unpleasant side-effects include headache, hypertension, breast tenderness, carbohydrate intolerance, depression, fatigue and tiredness [41],Link: http://www.catholiceducation.org/articles/sexuality/se0002.html