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Questions
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West
Nile Virus, Pregnancy and Breast-feeding
Q.
What risk does WNV illness
during pregnancy present to a fetus?
A. Based on the limited number
of cases studied so far, it is not yet possible to determine what
percentage of WNV infections during pregnancy result in infection
of the fetus or medical problems in newborns.
In
2002, one case of transplacental (mother-to-child) transmission
of WNV was reported to CDC. In this case, the infant was born
with WNV infection and severe medical problems. It is unclear,
however, whether WNV infection caused these problems or whether
they were due to other causes (see
MMWR
Dec 20, 2002).
After
the report of this case, CDC and state and local health departments
formed a registry to follow birth outcomes among women with WNV
illness in pregnancy. Three additional pregnancies in which the
expectant mother became infected with WNV were detected and evaluated
in 2002; none of these 3 resulted in fetal infection. In one additional
case it remains unclear whether the fetus was infected; appropriate
testing was not done.
In 2003, the registry identified
74 women who acquired WNV illness while pregnant. Preliminary
findings regarding outcomes of these pregnancies were first presented
at the Fifth
Annual National West Nile Virus Conference in Denver CO on February
2, 2004.
As
of May 10, 2004, 62 of these women had delivered live infants,
2 had had elective abortions, 5 miscarried in the first trimester
and 5 had not yet delivered.
In
2004, CDC is continuing to gather clinical and laboratory information
on outcomes of pregnancies of women with WNV illness during pregnancy.
Pregnant women who think they may have become infected with WNV
should contact their private health care providers. Clinicians
who are aware of WNV infections of pregnant women are encouraged
to report such cases by calling their state or local health departments,
or by contacting CDC, telephone 970-221-6400. For more information
see the section on Clinical
Guidance.
Because of ongoing concerns that
mother-to-child WNV
transmission can occur with possible adverse health effects, pregnant
women should take precautions to reduce their risk for WNV and
other mosquito-borne infections by avoiding mosquitoes, using
protective clothing, and using repellents containing DEET. Repellents
with DEET are safe for pregnant women, and there are other options
as well such as a soybean oil based repellent that provides good,
though quite limited, protection, as judged by a study published
in the new England Journal of Medicine. (See
Using Repellent Safely.)
Pregnant
women who become ill should see their health care provider, and
those who have an illness consistent with acute WNV infection
should undergo appropriate diagnostic testing.
Additional
clinical information on intrauterine WNV can be found in these
recent publications:
- Hayes
EB and O'Leary DR. West Nile virus infection: a pediatric perspective.
Pediatrics. 5 May 2004; 113(5): 1375-1381.
- Alpert
SG, Fergerson J, Noel LP. Intrauterine West Nile virus: ocular
and systemic findings. Am J Ophthalmol. 2003 Oct;136(4):733-5.
- Chapa
et al. West Nile Virus Encephalitis During Pregnancy. Obstetrics
and Gynocology. 2003 Aug; 102(2):229-231.
Q.
Where can I get more detailed clinical information about WNV in
pregnancy?
A. More
information on issues that may be helpful to clinicians working
with WNV can be found on the Clinical
Guidance page.
Q.
Are infants at higher risk than other groups for illness with
West Nile virus?
A. No. West Nile virus illnesses in children younger than
1 year old are infrequent. During 1999-2001, no cases in children
younger than one year of age were reported to CDC. In 2002, 2,500
total West Nile Virus disease cases were reported to CDC, and
only six occurred in children less than one year of age. The number
of children infected with WNV during 2003 will be updated when
data are finalized.
Breastfeeding
Q.
Can West Nile virus be transmitted through breast milk?
A. Based on a 2002 case in Michigan, it appears that West
Nile virus can be transmitted through breast milk. A new mother
in Michigan contracted West Nile virus from a blood transfusion
shortly after giving birth. Laboratory analysis showed evidence
of West Nile virus in her breast milk. She breastfed her infant,
and three weeks later, her baby's blood tested positive for West
Nile virus. Because of the infant's minimal outdoor exposure,
it is unlikely that infection was acquired from a mosquito. The
infant was most likely infected through breast milk. The child
is healthy, and does not have symptoms of West Nile virus infection.
Q.
If I am pregnant or breast-feeding, should I use insect repellent
containing DEET?
A. Yes. Insect repellents help people reduce their exposure
to mosquito bites that may carry potentially serious viruses such
as West Nile virus, and allow them to continue to play and work
outdoors. There are no reported adverse events following use of
repellents containing DEET in pregnant or breast-feeding women.
Click here for more information about using
repellents safely.
Q.
Should I continue breast-feeding if I am symptomatic for West
Nile virus?
A. Because the health benefits of breast-feeding
are well established, and the risk for West Nile virus transmission
through breast-feeding is unknown, the new findings do not suggest
a change in breast-feeding recommendations.
Lactating
women who are ill or who are having difficulty breast-feeding
for any reason should, as
always,consult
their physicians.
Q.
Should I continue breast-feeding if I live in an area of WNV transmission?
A. Yes. Because the health benefits of breast-feeding
are well established, and the risk for West Nile virus transmission
through breast-feeding is unknown, the new findings do not suggest
a change in breast-feeding recommendations.
Q.
If I am breast-feeding, should I be tested for West Nile virus?
A. No. There is no need to be tested just because
you are breast-feeding.
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