This text simply says that God knew Jeremiah as a fertilised zygote, his unformed substance, and was involved in Jeremiah's growth in the womb, recording every event and every day as he was being formed. That is how God knew Jeremiah before he was formed in the womb. And God had a plan in mind for Jeremiah proclaim God's messages to the nations. There does not appear to me to be any need to add to this text some extraneous foreign idea of God knowing and choosing Jeremiah from before the creation of the world.