"Overall, seven (11 percent) of the mothers and seven (12 percent) of the babies died and although a mortality of 11 percent seems low when compared to usual outcomes of respiratory failure in intensive care, a maternal morality of 11 percent is high when compared with any other obstetric condition. Forty-four (68.7 percent) of the women had to be put on ventilators to assist with breathing and of these, nine women (14.1 percent) needed further assistance to help oxygen reach their heart and lungs.

"It is of great concern that none of the women in the study had been immunised against seasonal flu despite widespread recommendations that they should be immunised against swine flu.

"With strong predictions that swine flu will re-surface and amount for up to 75 percent of flu cases in 2010, we cannot stress enough how important it is for pregnant women to be immunised.

"The Australian flu season officially starts in May and we are encouraging expectant mothers to be prepared."