Contraception in Contemporary Orthodox Judaism

In summation, Rabbenu Tam certainly held that there is no debate
between Rabbi Meir and the Sages about whether or not a moch is
permitted. The moch before intercourse may be prohibited, though
the problem may be related to spilled seed or it may be merely a delay
of procreation. Then again, there may be no problem with a moch
before intercourse at all. After intercourse, there is certainly no
problem at all, for either the man or the woman, according to both
Rabbi Meir and the Sages.
Rambam
The most noticeable feature of the Rambam’s view of the moch issue
is that he did not mention it at all in the entire Mishna Torah. He
explicitly forbade spilling seed, though it is not clear what the nature
of the prohibition is 22 . One looks in vain for a problem associated
with the moch. The simplest explanation for this glaring omission is
that Rambam agreed with Rabbenu Tam that there is no prohibition
whatsoever, only a recommendation by Rabbi Meir to use the moch
under certain situations. The Sages disagreed, so there is nothing to
write.
However, the situation is a little more complicated than that. First,
Rambam does write that one of the implications of the prohibition of
spilled seed is that a man should not marry a minor who is not
capable of bearing children. In paragraph 26 of the same chapter, he
wrote that a man should not marry any other infertile woman.
Complicating matters, he wrote elsewhere (Hilchos Ishus 15:7) that a
man should not marry a woman incapable of bearing children unless
he has already fulfilled the mitzvah of procreation or has another wife
through whom he could fulfill the mitzvah. At first glance, there
seems to be a blatant contradiction – if marrying an infertile woman
22Hilchos Issurei Biyah 21:18