As per Family Purity guidelines, after menstruation, husband and wife abstain from marital relations until the woman goes to a mikvah. This brings G‑d into a marriage. By following G‑d's commandments – and not simply "doing what comes naturally" whenever and however – the husband and wife elevate their physical relationship so that it becomes holy and spiritual.

Going to the mikvah is predicated on two givens:

1. The woman is married.

2. The woman has menstruated, and then made the proper preparations for going to the mikvah.

So, a woman who is not married does not go to the mikvah. And a woman who no longer menstruates doesn't go to the mikvah—as long as she immersed in a mikvah after the last time that she menstruated.

However, if she did not immerse that last time – or even if she had never immersed in a mikvah before – then even though it has been many years since she menstruated, it is very important that she go to the mikvah at least one time. This one-time immersion sanctifies the rest of her marriage, and is retroactively spiritually beneficial for her marriage and her children.

Since a woman doesn't just jump into a mikvah – she must prepare properly before going – it is advisable to consult with someone knowledgeable in the laws of Family Purity. Your local rebbetzin (rabbi's wife) is the best bet for this.

Read Confessions of a Mikvah-Goer for a heart-warming firsthand account of a post-menopausal woman's first mikvah experience.

Chaya Sarah Silberberg,
Chabad.org