Maternity Care Calendar and Guidelines: Screening for cytomegalovirus

Literature Search:

Medline was searched using both the MeSH and keywords cytomegalovirus, pregnancy and mass screening, limited to English and human from 1995-2003. Clinical practice guidelines and review articles were selected. The Canadian Task Force on Preventive Health Care, the US Preventive Services Task Force and the US National Guideline Clearinghouse were also reviewed for guidelines on toxoplasmosis and pregnancy.

Summary of Evidence:

Background
CMV is a virus transmitted by infected blood, saliva, urine, breast milk or sexual contact, with an incubation period of 28-60 days. Vertical transmission may occur from transplacental infection, exposure to virus in the birth canal or breastfeeding. Primary CMV is usually asymptomatic in adults. Recurrent infection occurs when the latent virus is reactivated. Estimates of the prevalence in pregnant women vary from 0.7-4% for primary infection and 13.5% for recurrent infection.(1) With primary infection, the risk of vertical transmission is 30-40%. 10% of infected infants are symptomatic at birth, 20-30% of these infants will die and 80% of survivors have severe neurologic sequelae. (1-3) Clinical manifestations of congenital CMV infection include hepatosplenomegaly, thrombocytopenia, jaundice, pneumonitis, growth retardation, microcephaly and cerebral calcifications.(3) Long-term sequelae include cerebral palsy and mental retardation. As well, it is the leading cause of congenital hearing loss.(1, 3, 4) The most severe fetal complications occur after infection in the first trimester, although the risk of vertical transmission is highest in the third trimester. (1)

Vertical transmission rates after reactivation of CMV are between 0.15-2%. Significant sequelae are much less common in recurrent infection.(1) CMV infection acquired in the birth canal or through breastfeeding is usually asymptomatic. (1, 3)

In industrialized nations, approximately half of women are susceptible to CMV infection.(3, 4) In the UK, 1/1000 fetuses are infected with CMV and 3/10,000 infants suffer from long-term complications of infection.(4)

Presently, the best method of confirming maternal primary infection is by detecting seroconversion or a fourfold rise in CMV IgG titres in samples collected 3-4 weeks apart. Fetal CMV infection is usually diagnosed by characteristic ultrasound abnormalities. Amniocentesis (with culture or PCR) is the preferred method of fetal sampling in cases of possible CMV infection, but must be delayed until 6 weeks after maternal infection.(5) However, the usefulness of these tests is limited as not all cases of congenital CMV are detected and the detection of CMV does not accurately predict the fetal complications.(1)

There are no therapies routinely available for the treatment of maternal or fetal CMV infection. (1)Neonates with congenital CMV and neurologic signs at birth are being treated with ganciclovir in some centers. (5, 6)

Screening
In view of the limitations of CMV testing for mothers and fetuses, the lack of available treatment, most authors do not recommend routine screening for CMV in pregnant women at this time. (1-4, 7-10) Neonatal screening is also not currently recommended.(3, 4)

One author compares two theoretical models of CMV screening -1 in the UK where the seroprevalence is 50% and one in Italy where the seroprevalence is 85%. They found that in both scenarios, the likelihood of diagnosing the pregnancies that would have resulted in the birth of a severely damaged infant was low and that in most pregnancies in which a termination was offered, the fetus would be unaffected.(3)

Several authors suggest screening for CMV IgG prior to conception for day-care workers as they are at particularly high risk of seroconversion(6, 10) If they are seronegative prior to pregnancy, counselling about avoiding CMV would be undertaken.

Prevention:
The main source of CMV exposure for women is contact with infected children. In one small study 18/20 women with CMV infection were multiparous or had professional contact with children.(2) 11% of seronegative childcare workers will seroconvert in their first 10 months of work and half of families with young children have at least one family member seroconvert within a year. (1) Measures such as frequent hand-washing (particularly after changing diapers), the use of latex gloves when handling body fluids and avoiding intimate contact with an infected child (kissing, sharing utensils) have been suggested.(9) This would be particularly important for day-care or health-care workers, who more frequently come in contact with body fluids. Currently, the greatest impact maternity care givers can have on preventing CMV infections is by educating patients about these measures. (1) In addition, women should be counselled about avoiding sharing of needles and condom use.

Other factors associated with an increased risk of CMV infection include abnormal cervical cytology, low socioeconomic status, birth outside of North America, first pregnancy younger than 15 years and infection with STD's.(1)

Canadian Task Force on Preventive Health Care (CTFPHC)

The CTFPHC has not completed a review on screening for cytomegalovirus

U.S. Preventive Services Task Force (USPSTF)

The USPSTF has not completed a review on screening for cytomegalovirus

Recommendations of Others:

American College of Obstetricians and Gynecologists (ACOG):(1)
Currently the ACOG does not endorse routine screening for CMV in pregnancy. They do however, recommend that pregnant women are counseled about how to prevent CMV infection in pregnancy. (level C evidence -based primarily on consensus and expert opinion)

Society of Obstetricians and Gynaecologists of Canada (SOGC:) (11)

In the Healthy Beginnings document the authors state that no pregnancy screening is indicated. The potential public health effect of preconception screening remains to be determined because of the possibility of recurrent infection.

Motherisk:
In a recent Motherisk update, the authors recommend that women at risk (mothers of children in daycare and day care workers) should have their antibody status assessed before conception. (6) "The immune status of at-risk patients should be evaluated as the pregnancy progresses." They note that annual seroconversion rate in these women ranges from 12-20%. They suggest that seronegative women adhere to strict hygiene practices, particularly washing hands after contact with urine and saliva.

Conclusions:
The new guideline on the MCC will be as follows:

Reviewer: Colleen Kirkham, MD CCFP January 2003

3/30/2005 9:09:00 PM

1. ACOG Practice Bulletin: Perinatal viral and parasitic infections. 2000.
2. Grangeot-Keros L, Simon B, Audibert F, Vial M. Should we routinely screen for cytomegalovirus antibody during pregnancy? Intervirology 1998;41(4-5):158-62.
3. Peckham C, Tookey P, Logan S, Giaquinto C. Screening options for prevention of congenital cytomegalovirus infection. J Med Screen 2001;8(3):119-24.
4. Antenatal and neonatal screening. second ed: Oxford University Press; 2000.
5. Infection and Pregnancy. In: Royal College of Obstetricians and Gynaecologists.
6. Bar-Oz B BM, Ford-Jones L, Koren G. Motherisk update: congenital cytomegalovirus infection Is there a breakthrough? Canadian Family Physician 2001;47:1179-1181.
7. Hagay ZJ, Biran G, Ornoy A, Reece EA. Congenital cytomegalovirus infection: a long-standing problem still seeking a solution. Am J Obstet Gynecol 1996;174(1 Pt 1):241-5.
8. Daniel Y, Gull I, Peyser MR, Lessing JB. Congenital cytomegalovirus infection. European Journal of Obstetrics, Gynecology, & Reproductive Biology. 1995;63(1):7-16.
9. Kuller JA CN, Cefalo RC. Prenatal Diagnosis & Reproductive Genetics: Mosby; 1996.
10. Gilbert GL. 1: Infections in pregnant women.[comment]. Medical Journal of Australia. 2002;176(5):229-36.
11. SOGC Clinical Practice Guidelines. No 71. Healthy Beginnings: guidelines for care during pregnancy and childbirth. 1998.