What does Genesis 30:17 mean?

Rachel and Leah are two sisters engaged in what amounts to a fertility completion with their mutual husband, Jacob, squarely in the middle. Even though Rachel is the more-loved wife (Genesis 29:31), and the only one Jacob really intended to marry (Genesis 29:18–30), she has only been able to obtain two children by using a proxy mother, her servant Bilhah (Genesis 30:1–8). Leah, despite being unloved, has managed to have four children of her own (Genesis 29:31–35), plus two through her servant Zilpah (Genesis 30:9–13).

When one of Leah's children found mandrakes—thought to enhance fertility—Rachel attempted to acquire some of them. Leah's anger was only abated when Rachel offered to "let" Jacob sleep with her for a night. Apparently, not only is Rachel greatly in control of Jacob, she is also the reason Leah has stopped bearing children of her own (Genesis 29:35). Leah takes her first opportunity to tell Jacob that he's been sold, in essence, and is hers for the night (Genesis 30:14–16).

In spite of this strange trade between Rachel and Leah, we're told in this verse that God listened to Leah. In other words, Leah had been asking God to give her more children with Jacob. Now God has answered her prayer. Despite the efforts of man, Genesis continues to insist that God is ultimately the one who gives children, not husbands or mandrake plants, or—as seen later in this chapter—striped sticks (Genesis 30:37–43).

This fifth natural-born son of Leah will be named Issachar due to the circumstances of his birth. This is Jacob's ninth son in total.