They also urged parents of young children to ensure their offspring get the vaccine, to combat the impact of the disease which is far more dangerous to young people, especially those with underlying conditions, than seasonal flu.
"I tell every pregnant woman I talk to, that getting the vaccine is the best way to protect yourself and your baby," said Anne Schuchat, Assistant Surgeon General of the US Public Health Service.
"I would get it when it is available, because I think that the risk is substantial," she said at a White House briefing.
"As a doctor, and a public health expert, and a flu expert, if I were pregnant or my sister was pregnant, I would get the vaccine."
Clinical trials for pregnant women tested with the vaccine are expected to be complete by the end of October, while first doses of the drug are due to be available in the first week of the month.
But Health and Human Services Secretary Kathleen Sebelius said trials were taking place due to an abundance of caution, and that years of data on seasonal flu vaccines suggested there was little elevated risk from the dosage.
"When I was pregnant, I was totally reluctant to take anything at any time," said Sebelius.
But she added that there was a imbalance between the risk for pregnant women of getting vaccinated and getting a complication versus the chances of getting (A) H1N1 flu itself.
Studies show that pregnant women are among the highest risk groups in terms of complications of (A)H1N1 flu as they are more likely to face immunity deficiencies or respiratory problems.
Figures show that pregnant women account for six percent of confirmed deaths from the new flu strain, while making up only one percent of the population.
The officials also urged parents of young children, another high-risk group to get vaccinated.
"It is serious, people can die, and the people who are going to be ill and die are much more likely to be children and young adults, not the frail and elderly," Sebelius said.
"Taking a risk, getting sick is probably not a wise role of the dice. The vaccine particularly, for vulnerable populations is the best defense against it."
The US government expects to have six or seven million doses of the vaccine available in the first week of October and production will be quickly ramped up after that. A total of 250 million doses will be eventually available