Pregnant women and Zika virus: What we know, what we don’t know

by Mayo Clinic Staff

Although the Zika virus was first discovered in 1947, it has been in the last two years that physicians and researchers have identified a link between the Zika virus and birth defects. Zika is transmitted primarily by mosquitoes. When mosquitoes bite an infected person, they transfer the virus to an unaffected person through an additional bite. At this time, the Aedes species of mosquito passes the virus, although new reports may demonstrate that all types of mosquitoes can pass the virus. The Zika virus also can be passed from mother to fetus, through sexual contact and through blood transfusions. To date, no reports are present that show Zika is spread through breast milk.

Usually, symptoms of Zika are mild, and many patients do not know they have the virus. The most common symptoms are fever, rash, joint pain and red eyes. These symptoms appear to be the same in pregnant women.

Currently, there has been no local transmission of Zika virus in the United States.

Risks to pregnant women

What is the risk in pregnancy? The risk still is largely unknown. Brazil is one of the largest affected countries from the Zika virus, and has documented cases of microcephaly and mental retardation. Microcephaly is an abnormally small head, due to a decrease or stopping in brain growth. Microcephaly also can occur due to malnutrition, other infections, certain drugs and toxins. The severity of microcephaly can vary. Usually, a diagnosis can be made from an ultrasound; however, the severity is determined after delivery. There is no known cure or treatment for microcephaly or mental retardation.

As of late January, Zika has been identified in at least three Minnesotans and at least one who is pregnant. All people had traveled or lived outside of the United States in areas of high transmission. As of late February, there have been no reports of Zika in Wisconsin.

Zika virus prevention

How should pregnant women protect themselves?

• Avoid traveling to infected countries, including Mexico, Brazil and most Caribbean countries.
• Avoid sex, or use condoms to if you have concerns that your partner may have Zika or is at high risk for Zika.
• Wear long-sleeved shirts and long pants.
• Use Environmental Protection Agency (EPA)-registered insect repellents, which according to the Centers for Disease Control (CDC), are safe and effective in pregnancy.
• Be sure your repellents include one of these ingredients: DEET, picaridin, IR3535, oil of lemon eucalyptus, or para-menthane-diol.
• Visit your health care provider immediately if you develop symptoms and have traveled to infected area or have concerns about a mosquito bite.

At this time, there are many unknowns about the virus. Researchers are unsure if there is a safe time to travel to an infected area during pregnancy or if you are bitten by an infected mosquito, how likely you are to contract the Zika virus. Also, if a pregnant woman has Zika, it is unknown what the likelihood is of transmitting the virus with birth defects to her fetus. At this time, no cure or vaccine exists — there only are prevention methods to reduce transfer of the virus.

As more research continues to be discovered, the Centers for Disease Control (CDC) and your health care provider are two resources for more information.

Emily Linklater, D.O., is a physician at Mayo Clinic Health System in Red Wing and specializes in women’s health. She is certified by the American Board of Obstetricians and Gynecologists.