Quran.com has a few different translations:
http://quran.com/65/4Sahih International
And those who no longer expect menstruation among your women - if you doubt, then their period is three months, and [also for] those who have not menstruated. And for those who are pregnant, their term is until they give birth. And whoever fears Allah - He will make for him of his matter ease.
Muhsin Khan
And those of your women as have passed the age of monthly courses, for them the 'Iddah (prescribed period), if you have doubts (about their periods), is three months, and for
those who have no courses [(i.e. they are still immature) their 'Iddah (prescribed period) is three months likewise, except in case of death]. And for those who are pregnant (whether they are divorced or their husbands are dead), their 'Iddah (prescribed period) is until they deliver (their burdens), and whosoever fears Allah and keeps his duty to Him, He will make his matter easy for him.
Pickthall
And for such of your women as despair of menstruation, if ye doubt, their period (of waiting) shall be three months, along with those who have it not. And for those with child, their period shall be till they bring forth their burden. And whosoever keepeth his duty to Allah, He maketh his course easy for him.
Yusuf Ali
Such of your women as have passed the age of monthly courses, for them the prescribed period, if ye have any doubts, is three months, and for those who have no courses (it is the same): for those who carry (life within their wombs), their period is until they deliver their burdens: and for those who fear Allah, He will make their path easy.
Shakir
And (as for) those of your women who have despaired of menstruation, if you have a doubt, their prescribed time shall be three months, and of
those too who have not had their courses; and (as for) the pregnant women, their prescribed time is that they lay down their burden; and whoever is careful of (his duty to) Allah He will make easy for him his affair.
Dr. Ghali
And as for those of your women who have despaired of menstruation, in case you have any suspicion, then their (fixed) spell shall be three months, (along) with
those who have not menstruated (as yet). And (as for) those with burden, (i.e., those who are pregnant) their term is when they bring forth their burden; and whoever is pious to Allah, He will make for him, of His Command, easiness.
The highlighted translations seem to be talking about underage/pre-pubescent girls. The others are more vague. Arabic speakers, would love to hear your opinions.