Princess Cruises Diamond Princess Sydney Harbour
However, almost all cruise lines have limitations about carrying pregnant women. A review of the policies I did shows that you will need to be less than 24 weeks pregnant by time the cruise ends before you will be accepted. As requirements can change, you should always check with your agent or the line before booking.
Many cruise lines will ask for a medical certificate from your doctor confirming that both mother and baby are in good health, that it is not a high-risk pregnancy and confirm the expected date of delivery which has been calculated from the Last Menstrual Period and ultrasound.
They all seem to retain the right for the Captain to refuse to embark and carry any pregnant woman if they decide that it is not going to be safe to do so.
So if you are pregnant and want to take that cruise carefully review your options. I recommend using a cruise agent who will be able to do the checking and advise you. Of course, also think about which itinerary you select and avoid those with many sea days that take you far from medical facilities, and perhaps even consider a river cruise where you will always be close to land and expert medical assistance in the unlikely case you need it