H1N1 and Pregnancy: Special Issues

H1N1 flu is similar to the seasonal flu. There is a vaccine for the seasonal flu available every fall and this year is no different. There is an extra vaccine for the H1N1 flu.

Thimerosal Issues. We are partial to a thimerosal free vaccine for the seasonal flu (individual dose versus a multi-dose vial vaccine that contains thimerosal). Thimerosal is a mercury containing component used in the multi-dose seasonal flu vaccine as a preservative. The level of mercury in one vaccine is about the same as a helping of tuna. The risk should be negligible due to this but giving pregnant women a mercury-containing vaccine seems potentially problematic. Regarding other risks and benefits of the seasonal flu vaccine (and likely H1N1), please review our handout detailing the seasonal flu vaccine and pregnancy. The H1N1 vaccine is made the same way as the seasonal vaccine.

There may or may not be thimerosal in the H1N1 flu vaccine. Recent reports indicate that only one shot may be needed for adults rather than the expected two. This is good from a thimerosal point of view. Pregnant women may still need two, however. Therefore, a pregnant woman who receives both vaccines has the potential to receive three doses of thimerosal. No one can say this is OK except to point out the comparison to tuna as noted above.

Are pregnant women at a higher risk of death if they contract H1N1 flu? The answer is YES, but let’s look at details.

Data released in July of 2009 indicated that of the 266 deaths with information available, 15 were pregnant women (6%). Most of these pregnant women were in the third trimester and the fatal event was a lung and or heart problem (pneumonia). Pregnant women had a 4X increased risk of needing to be hospitalized. The reports indicate that patients and doctors waited too long to start treatment (Tamiflu or Relenza). These medicines fight the virus and should be started within 2 days of symptoms. Their risk in pregnancy should be very minimal but data is limited.

What are the symptoms of the true “flu”? They include fever(97%), cough(94%), runny nose(59%), sore throat(50%), headache(47%), shortness of breath(41%), body aches(35%), vomiting(18%), and diarrhea(12%). Generally sudden onset. The most common are fever and dry cough. The “stomach flu” which is not the true flu consists of mostly diarrhea and nausea.

Why are pregnant women at greater risk of death? There are two theories both of which may play a role. The first has to do with the pregnant uterus pushing up on the diaphragm making the lungs more vulnerable. The second has to do with decreased immunity to viruses. This is why some pregnant women have a growth of warts (HPV virus). Of course there is no way to alter these two issues.

Pregnant women are also at risk of preterm labor and delivery, possibly stillbirth, and possibly miscarriage/birth defects if they contract H1N1 during pregnancy. The stress of the infection explains the first two issues. If a women is in the ICU on a ventilator for example but survives, the risk to the baby will be significant and gestational age dependent. It is well known that maternal fever in the first trimester can cause birth defects and this may account for a higher miscarriage rate.

Take home lessons:

Use all precautions possible to prevent getting the flu. Frequent hand washing. Cough etiquette. Limiting exposures. Etc.

Consider the H1N1 flu vaccine. It is ultimately up to you to decide on the vaccine. Safety data is limited. Long-term effects are unknown but should not be different from the seasonal vaccine which are minimal. The vaccine stimulates antibodies after 10 days which is good. If as the H1N1 flu spreads it is obvious pregnant women are really at high risk even with prompt treatment, you can still get the vaccine if you initially choose not to. If you are exposed to a high risk population/kids (teacher, day care center, health care, retail, etc), you may want to strongly consider the H1N1 vaccine. As the season unfolds we will be able to predict better. You can still get the flu even if you receive both vaccines.

If you have symptoms of the flu or have a close exposure, start treatment with an anti-viral immediately (recommended within 2 days). If you have symptoms, we would give treatment doses (Tamiflu 75mg twice daily for 5 days). If you are exposed, we would give prevention doses (Tamiflu 75mg once a day for at least 10 days; start within 2 days of exposure).

Breastfeeding will help protect newborns. The vaccine and anti-virals would have no greater risk while breastfeeding than being pregnant. The vaccine would stimulate antibodies which would protect the baby. Infants less than 6 months cannot receive the vaccine, therefore this transfer of antibodies could be crucial.

Newborn babies will benefit from breastfeeding as outlined above. Infants less than 6 months are at higher risk if they contract the flu. It is recommended that care givers of these kids receive the H1N1 vaccine as well as siblings(who themselves are in a high risk group). Therefore, even if not breastfeeding, a pregnant or postpartum woman should consider the H1N1 vaccine.

Ultimately it is up to you to decide whether to vaccinate yourself for the seasonal flu and H1N1 flu. It seems the benefits outweigh the risks for most people.

Click Here To Read About Seasonal Influenza Vaccine in Pregnancy

Websites:

www.cdc.gov/flu

www.FluFacts.com