You forget that in a poor country, children are not a luxury, but a retirement policy. There certainly isn't going to be any social security for a poor Indian woman, so what does she do? Have four or five children, and hope that one of them survives and does well enough to provide for her when she's older. A food shortage means more babies, not fewer.
If that poor Indian woman sits in prison as a consequence for having kids just to make herself a living, she may not end up with as many children and others may be deterred from following her example. A food shortage needn't mean more babies then. That may seem harsh but the alternative is worse: when you extend your example to its inevitable conclusion there will be millions of Indians dying young, when the amount of free food can no longer grow along with the exponentially growing population.
