In the words of Tina Johnson of the American College of Nurse-Midwives: "By not getting the flu yourself, you are going to protect your children better."
Dr. Anne Schuchat of the Centers for Disease Control and Prevention said at a briefing Thursday that women of any trimester should get the vaccine.
"There's no benefit to waiting until you're out of the first trimester," added Dr. Laura Riley of Massachusetts General Hospital.
The swine flu, also known as H1N1, first appeared in the spring, and then spread to the southern hemisphere where thousands have been infected. It is expected to return this fall, when the normal flu season arrives in this hemisphere.
Vaccine for the seasonal flu is available in many parts of the country now and testing is under way for the swine flu vaccine, which is expected to be available in October. Experts urge people to get both seasonal and swine flu vaccinations, and not to wait to get them together.
Asked if there will be swine flu vaccines available without the preservative Thimerosal, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Disease, said yes.
Fauci said there is no evidence that Thimerosal poses any medical hazard, but because some people are concerned about it a form of the vaccine without it will be available.