Unlike women who have an unquestioned right to have or not have a child after becoming pregnant, men have no choice. However, men can choose to take steps to prevent pregnancy. The use of a condom is the first line of defense. However, accidents happen including damaged condoms. Consequently a more secure approach is desirable.
The most secure method is a vasectomy. This requires a surgical intervention. Unfortunately, there are complications. For example, Wikipedia reports (http://en.wikipedia.org/wiki/Vasectomy#Vasectomy_reversal) that Post-vasectomy pain syndrome (PVPS) is a chronic and sometimes debilitating condition that may develop immediately or several years after vasectomy. ne survey cites studies that estimate incidence at one case every ten to thirty vasectomies. The pain can be constant, or it can be pain that occurs only at particular times such as with intercourse, ejaculation, or physical exertion. It is possible to have a vasectomy reversed in some cases, should a return to potency be desired at some point in time. Again this is not an assured procedure. Wikipedia reports that Vasectomy reversal is effective at achieving pregnancy in only 50%-70% of cases, and it is costly, with total out-of-pocket costs in the United States often upwards of $10,000. Some men opt for cryostorage of sperm before sterilization but again costs of artificial insemination can be prohibitive.
Another possibility that has revealed itself is the use of anabolic steroids. According to .Stanton C. Honig M.D. (firstname.lastname@example.org) in a recent newsletter from Men’s Health Network (www.menshealthnetwork.org),
“When a man is taking anabolic steroids, it is virtually impossible for him to get his partner pregnant.” So this could be interpreted as saying there is a male contraceptive. Of course anabolic steroids are regulated drugs and it might be difficult to obtain a legal prescription for the this application. Furthermore, Dr. Honig points out that anabolic steroids can cause health problems that sometimes can be irreversible: “These include aggressive behavior, acne, baldness, prominent breasts, liver disease, high blood pressure, heart attack and stroke. In adolescents, it may result in stunted growth and accelerated puberty changes. [Performance Enhancing Drugs] can also cause sexual dysfunction. When the anabolic steroids are stopped, the “sexual rush” is gone and this will cause testosterone levels to crash to virtually zero. This may cause symptoms such as tiredness, loss of energy and loss of sex drive. Testosterone production may return in a few months, however, in certain situations, it may be a permanent problem. Luckily, there is medical treatment for this problem to raise testosterone levels back to the normal range.
Hence, it is possible to mitigate the possibility of an undesired child birth by pro-active steps, but the reliability and full consequences must be weighed carefully.
Having said all the above, remember if your partner does get pregnant by another man you can still be held responsible if you are married to her or if you have assumed any parental role toward the child (which can be interpreted as living in the same residence). Even if the mother fraudulently fails to let you know the child is not yours, she faces no punishment and you receive no alleviation of your support penalty.
Ex-fathers recommends that you should not rely to any extent on the generalized information given here, but seek competent legal and/or medical advice as applicable if you are in any such situations.