Here's an example:
The RSV was unfairly maligned for its rendering of Isa. 7:14, using the word "young woman" rather than "virgin." Shrill cries that the RSV translators were undermining the doctrine of the virgin birth. No one thought about the fact that in Mat. 1:23 the word "virgin" was used. No one investigated why the RSV translators did what they did.
In Hebrew, in Isa. 7:14, the word used is almah, a phrase that could be quite legitimately translated as a young woman, irrespective of her virginity. The focus of the term is her age, not her sexual experience, or lack thereof. Observe the context of the verse in Isa. 7:14 - it's about how Assyria and Samaria, who were confronting Judah, would fall within the lifetime of Isaiah's son, Maher-shalal-hash-baz. He was the initial fulfillment of that prophecy in an all-too-usual non-virgin birth. The "young woman" conceived.
The secondary fulfillment, the one implied in the name Immanuel, is the one that the Septuigent and Matthew caught on - the word the LXX, and thus Matthew, uses to translate almah from the Hebrew to the Greek is parqenoV (parthenos), a word that can only mean "virgin." (The LXX was translated around 200-150 BC.)
The RSV is the only major translation to reflect this nuance; and they were sorely castigated for it. The only modern translation that reflects it that I am aware of is the NET Bible, but it has copious notes to explain its every translation decision.
One of the LXX was St. Symeon (as Jude24 notes, the work was done around 200-150 BC). This translation of the original Hebrew into Greek has special meaning for those of us who are Orthodox because God would not allow St. Symeon to die until he received Christ into the temple.
St. Symeon's prayer is said near the end of every Orthodox vespers service (evening)), (Lk 2:29-32)
Lord, now lettest thou thy servant depart in peace, according to thy word: 2:30 For mine eyes have seen thy salvation, 2:31 Which thou hast prepared before the face of all people; 2:32 A light to lighten the Gentiles, and the glory of thy people Israel.