Q. I am four months pregnant and very concerned about this new type of swine flu. I have family visiting from San Diego next month. Should I ask them not to come?  The swine flu virus was only recently identified as a unique variant and it is being studied very aggressively. It is not yet known if there are certain populations, such as pregnant women who are at greater risks for complications if infected.

But there is historical evidence that pregnant women are at higher risk for complications of the seasonal flu variants, and that is why the Centers for Disease Control and Prevention recommends vaccination for all pregnant women with the annually created vaccine for a season's strain. Currently there is no vaccine for this variant of swine flu.

During the pandemics of 1918-1919 and 1957-1958 there did appear to be increased risks of spontaneous miscarriage and pre-term labor among pregnant women who contracted the flu, especially if they developed pneumonia.

But it is not clear if this risk is any greater than that of other significant viral and bacterial illnesses that cause pneumonia. Certainly infection during late pregnancy and labor is to be avoided, as there may not be time enough to create maternal antibodies that can cross the placenta and partially protect the newborn.

Pregnant women who contract swine flu (or any flu strain) would likely have typical symptoms -- cough, sore throat and fever. But in some, the symptoms could progress aggressively and possibly become complicated by additional bacterial infections that occur because of the individual's weakened condition. In late pregnancy, fetal distress could occur because of maternal stresses of fever, dehydration and viremia -- just as with any significant viral or bacterial infection.

Any woman who suspects she may have contracted this flu should be tested by her physician and the swabs sent to the state public health authority for confirmation. This virus is sensitive to Tamiflu and other antivirals. Pregnant women who meet the criteria for confirmed, probably or suspected swine flu should receive prophylactic antiviral treatment. This should occur as soon as possible after the onset of symptoms, with the greatest benefit being within the first 48 hours.

Preventative dosing should be for 10 days and actual treatment dosing for five days. The safety of these antivirals in pregnancy has not been studied directly; no clinical studies have been conducted. They should be used in pregnancy only when exposure or infection is strongly suspected and their benefit will then outweigh the risk. This should be discussed with your obstetrician if indication arises.

With regard to your family in California, it must be recognized that the incubation period of this virus can be 10 days, and that unknowingly exposed and infected individuals can shed this virus before they become symptomatic. Simple precautions, such as hand washing, avoiding those with coughs and sneezes and staying healthy otherwise remain excellent and adequate strategies for prevention.