Well, interesting question, because the answer to this is that yes, abortion is definitely a theme, but I would argue it is linked to the far bigger theme of how the partner subtly forces Jig to get the abortion.
What is interesting about this story is that although the abortion hangs over this couple, nowhere is the word actually used. Reference is only made to the "awfully simple operation" that is "not really an operation at all" and is "just to let the air in." It is a topic that is avoided head-on by the couple, especially Jig, who, while her partner gives her his medical opinion about abortion first pointedly "looks at the ground" and then "says nothing."
What is clear as you read the story carefully is that Jig does not want the abortion, but the unnamed partner does. Jig has to choose between saving the baby and saving her relationship, which, to be honest, doesn't look that good anyway. The partner shows incredible lack of empathy and understanding. From his point of view her unwanted pregnancy is "the only thing that bothers us" and he promises that everything will be "alright" and "nice again" once she has had the operation performed. What is particularly sinister is the way that the partner keeps on repeating, again and again, the phrase "But I don't want you to do it if you don't really want to." The fact that he keeps on bringing up the topic and keeps on saying this, even when Jig is desperate to change the topic and not talk about it even more, indicates that he will make sure Jig has the abortion but he wants to come across as reasonable and not pressuring her:
"All right. But you've got to realise--"
"I realise," the girl said. "Can't we maybe stop talking?"
They sat down at the table and the girl looked across at the hills on the day saide of the valley and the man looked at her and at the table.
"You've got to realise," he said, "that I don't want you to do it if you don't want to. I'm perfectly willing to go through with it if it means anything to you."
As we read the story it becomes clear to both the reader and Jig that the partner will have this abortion one way or another and the imposition of his will against Jig reveals his dominance and brutality. The irony of the story is that it ends with Jig saying she is "fine" when it is obviously a lie.