if you bought your ticket directly from JAL website....
Go to the JAL website (link) and click on "Manage Booking", then either login or enter ticket information to access the booking details.
Scroll down to the bottom of the page with your booking details, and you will see the "Penalties".
cancellations
before departure
charge AUD xxx for cancel/refund.

You can cancel online, and if the ticket is refundable, the ticket original amount minus the penalty amount will be refunded to your original payment card. If the ticket is nonrefundable, you may chose to change it to an earlier date where you both can fly before the pregnancy effects become too severe, or cancel it for zero refund. The change fee is also in the "Penalties" section.

However, if you bought your ticket from an online travel agent (Expedia or what not), you need to call your travel agent to confirm the exact amount of penalties, whether the ticket is refundable, and how to process the cancellation.