All it does is start an arms race between Leah and Rachel. Both servants bear kids. But Rachel is still barren.
A bit later, Reuben comes in from the fields with mandrakes, which were believed to be an aphrodisiac, which would assist in getting pregnant. Rachel, desperately wanting children, sees them; she wants them. So, she gives away a night with Jacob to Leah in hopes of a long-term gain: pregnancy.
What happens next is interesting. Leah, who gave away the mandrakes, get pregnant. Not once, but three times! So much for the effectiveness of the aphrodisiac!
I think there's something theological going on here, don't you? God's trying to teach Rachel that you can't manipulate him. (Of course, if we learn the lesson, so much the better!) Aphrodisiacs don't work. Prayer does. Not that Rachel really learns; later she steals Laban's idols in another vain attempt to control the future...but that's another story for another day : )
Here's the text in the CEB (chosen because it translates mandrakes as "erotic herbs")
14 During the wheat harvest, Reuben found some erotic herbs in the field and brought them to his mother Leah. Rachel said to Leah, “Give me your son’s erotic herbs.”
15 Leah replied, “Isn’t it enough that you’ve taken my husband? Now you want to take my son’s erotic herbs too?”
Rachel said, “For your son’s erotic herbs, Jacob may sleep with you tonight.”
16 When Jacob came back from the field in the evening, Leah went out to meet him and said, “You must sleep with me because I’ve paid for you with my son’s erotic herbs.” So he slept with her that night.
17 God responded to Leah. She became pregnant and gave birth to a fifth son for Jacob. 18 Leah said, “God gave me what I paid for, what I deserved for giving my servant to my husband.” So she named him Issachar. 19 Leah became pregnant again and gave birth to a sixth son for Jacob, 20 and she said, “God has given me a wonderful gift. Now my husband will honor me since I’ve borne him six sons.” So she named him Zebulun. 21 After this, she gave birth to a daughter and named her Dinah.
22 Then God remembered Rachel, responded to her...