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Zika's impact on mother and child

The impact of Zika ranges from benign to devastating: Little to no symptoms for most people and potentially severe birth defects in the unborn children of infected pregnant women.

About four in five people infected by Zika experience no symptoms, and those who do usually recover within a week to 10 days. So it's the risk for pregnant women and women trying to get pregnant that is the most worrisome, in particular those who have traveled to countries where Zika is circulating.

Unlike other mosquito-borne viruses in the same flavivirus family, Zika can cause a severe birth defect – microcephaly – characterized by an abnormally small head and associated with extensive brain damage and mental retardation, says Charles J. Lockwood, MD, senior vice president for USF Health and dean of the Morsani College of Medicine. Babies are often born with developmental problems requiring lifelong care.

"Complicating matters further, pregnant women may retain the virus in their blood for a prolonged period of time because the fetus acts as a reservoir to 'reinfect' the mother, further exacerbating the opportunity for mosquito transmission," adds Dr. Lockwood, a nationally recognized leader in maternal and child health, and a member of the National Academy of Medicine and the March of Dimes National Foundation Board.

"Moreover, there are documented cases of sexual transmission and the virus can persist in semen for up to 10 weeks. That means in endemic areas, pregnant women who meticulously avoid being bitten by Zika-bearing mosquitos may still become infected if their husbands are less scrupulous about avoiding mosquito bites. Thus, in infected areas, male partners of pregnant women should use condoms throughout pregnancy."

Experts are still uncertain of the likelihood of a Zika- infected woman passing the infection to her fetus, or for infected fetuses developing birth defects. Some preliminary findings suggest women infected with the virus later in a pregnancy (third trimester) are more likely to give birth to healthy babies, but transmission of Zika is seen throughout all trimesters, says Lindsay Maggio, MD, a USF Health maternal-fetal medicine physician who cares for women with high-risk pregnancies and has focused research in infectious diseases.

"The risk is real, but not huge," Dr. Maggio says.

Estimates of microcephaly risk are largely based on one retrospective study of the 2013 French Polynesia outbreak, which only included eight babies, says Beata Casañas, DO, associate professor of infectious diseases in the USF Health Morsani College of Medicine.

"It's all we have," she adds. "We take math modeling and extrapolate from that data to estimate that about 1 percent of fetuses born to women exposed to Zika during their first trimester will have microcephaly."

Dr. Maggio and her obstetric colleagues share the latest scientific knowledge and try to calm the anxiety expressed by pregnant patients seeing international news reports about Zika's potentially devastating consequences and the arrival of non-travel related cases in Florida. Pregnant women who test positive or experience symptoms are recommended to have a series of ultrasounds (every three to four weeks across the entire pregnancy) to monitor the fetus. While the technology is good at identifying certain brain abnormalities, it is limited in detecting microcephaly early because unusually small brain size and head circumference do not appear until later in pregnancy.

In keeping with Centers for Disease Control and Prevention guidelines, USF health care providers also advise patients to limit travel to Zika hot spots, including areas in south Florida.

To a much lesser extent than with microcephaly, Zika has been linked to Guillain-Barré syndrome, or GBS, a rare neurological disorder that can cause paralysis or even death. Often preceded by an infection in the days or weeks before symptom onset, GBS is "very likely triggered" by Zika in a small proportion of cases, according to the CDC.

"The risk for GBS in the general population is about one in 100,000," says Clifton Gooch, MD, USF professor and chair of neurology. "French Polynesia's 2013 Zika outbreak shifted that to one in 10,000."

What you need to know: Much is still unknown about Zika's effect on pregnancy, but experts agree the chances of your baby having microcephaly are quite small. Avoid travel to infected areas. Zika is now in Florida, so pregnant women are advised to remain indoors most of the day. Wear repellent, which hasn't been shown to harm fetuses. If you and/or your partner recently visited infected areas, use condoms during sex for at least six months before trying to get pregnant, and for the remainder of the pregnancy if you are already pregnant. Women who get Zika while not pregnant should wait at least eight weeks before trying to conceive, giving their immune system time to fight the virus.