Abram and Sarai are renamed by YHWH due to His covenant with them. The LORD then proclaims that Sarai, at age 90, will be with child. The miracle conception of Isaac parallels the immaculate conception of Jesus.  Jesus is the one from Eve’s offspring, to Sarai’s offspring, down to Bathsheba’s offspring who will complete the covenant to Abraham: that his offspring will be a blessing to all the families of the earth. (Gen. 12:3b)