Tubal Ligation is a low risk medical procedure, a small incision is made just under a females navel, a small instrument is inserted through a tiny tube to either tie, block or medically staple the tube to prevent passage of the egg and sperm. This procedure is considered permanent birth control, but it can be reversed, though reversal of the procedure is not guaranteed as the tube could have taken damage.
Ultimately the responsibility of birth control is that of the owner of the body who does not wish a pregnancy. It is noble to think that you can make someone else co-responsible for your body (as in a long term relationship or marriage).
Every individual is responsible for their own body, thus if I was to share a bottle of alcohol with my partner, I cannot blame that partner for my headache, drunkedness or hang-over, I willingly and knowingly drank the alcohol being fully aware of the possible consequences.
Females need to understand that they are in control of their bodies, not the state, church, a friend or partner - just as it is a womans choice to have an abortion or not.
So the ultimate responsibility of pregnancy is that of the female, however we live in a society where we have a system of moral obligation and co-responsibility, for instance, I invite a friend over to visit, we have some alcohol, the friend later leaves and has a car accident, someone is injured or killed, I now sit with the moral dilemma of having been a participant in actions that lead to serious consequences, I thus morally make myself co-responsible for knowingly having shared something with someone that I knew could have serious consequences - this decision to be co-responsible is up to me, if I subscribe to the mutual code of morals and ethics that society has developed in order to protect the innocent and to take to task the reckless.
Thus a woman and a man in a committed relationship (here, the commitment makes the difference) as the man has made a moral commitment to the woman, to stand by her, to support her, to be faithful and so on, then pregnancy becomes part of that commitment and that man makes a moral commitment to take co-responsibility for the pregnancy and his child.