In the second aliyah Pharaoh calls the midwives and asks why they didn't follow his orders about killing the male children. They answer that the Hebrew women are able to deliver without midwives, therefore the midwives did not get a chance to follow Pharaoh's orders.
Rashi says that on Moshe Rabeinu's birthday, Pharaoh's astrologers predict that the deliverer of the Jewish people is being born that day, and they further predict that this deliverer's end will be water. Therefore, Pharaoh commands that all male children should be cast in the river, even Egyptians.
Moshe is born, and his mother puts him into the river in an ark. Moshe's sister Miriam follows and observes what happens to the ark. Pharaoh's daughter comes down to bathe, and takes the child.