I understand why it is common to praise mothers for giving their children the gift of life. I am a mother of four; it's hard work. From pregnancy to parenting, child-rearing is plain tough. A mother, particularly, gives so much of herself, including her own body, in her child's life. It seems as though this deep and all-encompassing giving is a gift. It's not.
A gift is something given freely, something undeserved; that is, a gift is unrelated to deserving. In our culture, obviously, we misuse the word gift all the time. I cringe every time I hear a "thank you" followed by "oh, you deserve it" or "it couldn't 've happened to more deserving people." You've seen the shows, game shows, home renovation shows, where the network takes half of the episode to prove the receivers are good, deserving people. This is not entirely invalid -- seeking to reward goodness -- but it does encourage a distorted view of mercy and duty.
I cannot gift you something I owe you. At Christmastime, for instance, we say "gift" when we mean something closer to "payment." Why should it bother me if someone gives me a Christmas gift and I have nothing to give in return? Why do I worry so much about how much I'm expected to spend on each gift for each person? Why must gift-giving be an exact trade?
I understand why it is common to praise mothers for giving their children the gift of life.
I'll answer my own question. Worth. Giving one person more than another, or less than they* give you, seems as though you're saying one person has more value than another. My children claim foul along these lines almost daily some weeks. If I give a gift to one, those who received no gift or a lesser gift, contend they were cheated. They weren't cheated. You see, neither the one who received the gift nor the ones who didn't receive anything deserve a gift. It feels unfair, but it's not. This is untrue with a non-gift such as proper food, appropriate clothing, learning opportunities, and all of the other near-infinite things children naturally require of their parents. A child who has not received something he needs from his parents has indeed been treated unfairly.
Continued life is one of those non-gifts. As far as it depends on us, birth is a non-gift. It is a necessity like food; it is deserved. I do not "give" life as though it is something I can rightfully choose to give or withhold, as a gift. I am the mother; life-giving is my responsibility.
*Over the past year I have tried to adopt the now-common usage of the plural pronouns in place of the singular (he or she and variants such as s/he) when gender is unknown or neutral.