Board Exam Corner

Zika virus in pregnancy


 

Editor’s Note: This is the second installment of a six-part series that will review key concepts and articles that ob.gyns. can use to prepare for the American Board of Obstetrics and Gynecology Maintenance of Certification examination. The series is adapted from Ob/Gyn Board Master (obgynboardmaster.com), an online board review course created by Erudyte Inc. The series will cover issues in reproductive endocrinology and infertility, maternal-fetal medicine, gynecologic oncology, and female pelvic medicine, as well as general test-taking and study tips. This month’s edition of the Board Corner focuses on Zika virus.

In 2016, The American Board of Obstetricians and Gynecologists assigned four maintenance of certification (MOC) articles dealing with Zika virus:

Zika Virus and Pregnancy: What Obstetric Health Care Providers Need to Know1

Dr. Sam Siddighi

Dr. Sam Siddighi

Estimating Contraceptive Needs and Increasing Access to Contraception in Response to the Zika Virus Disease Outbreak – Puerto Rico, 20162

Update: Interim Guidance for Health Care Providers Caring for Women of Reproductive Age with Possible Zika Virus Exposure – United States, 20163

Interim Guidelines for Pregnant Women During a Zika Virus Outbreak – United States, 20164

The diagnosis and management of Zika virus in pregnancy is a hot topic that should be reviewed before any Obstetrics and Gynecology board exam. This month’s Board Corner will review the key elements for ob.gyns.

Let’s begin with a possible medical board question: Which of the following is LEAST LIKELY to be associated with congenital Zika virus infection?

A. Omphalocele

B. Microcephaly

C. Ventriculomegaly

D. Cataract

E. Intracranial calcifications

The correct answer is A.

Omphalocele has not been observed to be associated with Zika virus infection. Answers B-E are incorrect because reported fetal and neonatal abnormalities associated with Zika virus include microcephaly, ventriculomegaly, intracranial calcifications, brain atrophy, and cataracts.

Key points

The key points to remember are:

Transmission of Zika virus to humans most commonly occurs from the bite of an infected mosquito. Other modes of transmission have been reported, such as sexual transmission, maternal-fetal transmission, and transmission through blood transfusion.

Infection with Zika virus and maternal-fetal transmission have been documented in all trimesters of pregnancy. Reported fetal and neonatal sequelae include microcephaly, ventriculomegaly, intracranial calcifications, brain atrophy, and cataracts.

Immunoglobulin M (IgM) can also be detected as early as 4 days after the onset of illness. For those women who have laboratory-confirmed Zika virus infection during pregnancy, amniocentesis should be offered after 15 weeks gestation.

Literature summary

Zika virus is a mosquito-borne virus that is most commonly transmitted by the Aedes aegypti mosquito. This species of mosquito is also known to transmit dengue, yellow fever, and chikungunya viruses. Initial data suggest that the incubation period for Zika virus is a few days up to 2 weeks. Acute onset of fever, maculopapular rash, conjunctivitis, and arthralgia are the most common symptoms of Zika infection. Symptoms generally only last up to 7 days and are typically mild. Only about 20% of people infected with the virus become ill. There is currently no specific antiviral treatment available for Zika virus disease.

Testing for Zika virus can include detection of viral RNA, Zika antigen, or antibodies. Reverse transcription–polymerase chain reaction (RT-PCR) can be performed on serum, amniotic fluid, and tissue (such as placenta). It is recommended that RT-PCR testing of serum be performed within 7 days of the onset of symptoms. Immunoglobulin M (IgM) can also be detected as early as 4 days after the onset of illness.

Though fetal microcephaly can be detected ultrasonographically at 18-20 weeks gestation, the diagnosis can be challenging because there is no standard definition of fetal microcephaly. Because other intracranial abnormalities have been detected in association with congenital Zika infection, a complete ultrasound examination should be performed to assess the fetal neuroanatomy.

For those women who have laboratory-confirmed Zika virus infection during pregnancy, amniocentesis should be offered after 15 weeks gestation. RT-PCR can be used to test for the presence of Zika virus RNA in the amniotic fluid. Patients should be referred to a maternal-fetal medicine specialist for serial ultrasounds to assess fetal anatomy and monitor fetal growth every 3-4 weeks.

References

1. Obstet Gynecol. 2016 Apr;127(4):642-8.

2. Morb Mortal Wkly Rep. 2016;65:311-4.

3. Morb Mortal Wkly Rep. 2016;65:315-22.

4. Morb Mortal Wkly Rep. 2016;65:30-3.

Dr. Siddighi is editor-in-chief of the Ob/Gyn Board Master and director of female pelvic medicine and reconstructive surgery and director of grand rounds at Loma Linda University Health in California. Ob.Gyn. News and Ob/Gyn Board Master are owned by the same parent company, Frontline Medical Communications.

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