From Yaakov's descent until the Exodus was 210 years. This seems fairly miraculous. Considering the excitement over Sarah's giving birth at 90, it's surprising that this miracle is completely glossed over. Ramban offers an explanation for the low-key nature of this miracle. Everything is a miracle, as we know.
Natural miracles are the hidden ones.
Sarah's giving birth at 90 wasn't a miracle. Birth-giving is within the realm of nature. The prophecy of the angels that she would have a child is the miracle. Yocheved had no such prophecy, so here the miracle is hidden. Her age when she had Moshe was an odd side of nature, but nature all the same.