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Chou R, Smits AK, Huffman LH, et al. Screening for Human Immunodeficiency Virus in Pregnant Women [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2005 Jul. (Evidence Syntheses, No. 39.)

  • This publication is provided for historical reference only and the information may be out of date.

This publication is provided for historical reference only and the information may be out of date.

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Screening for Human Immunodeficiency Virus in Pregnant Women [Internet].

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4Discussion

Summary of Evidence

There is no direct evidence on benefits of screening for HIV infection in pregnant women. Other evidence obtained for the systematic review is summarized in Table 15. It indicates the study design and the quality of evidence for each key question. Briefly, universal screening identifies significantly more HIV-infected pregnant women than targeted screening. HIV tests are extremely accurate and recommended interventions markedly reduce the risk of mother-to-child transmission of HIV infection. Currently recommended interventions appear to be associated with high benefit-to-harm ratios.

Table 15. Summary of Findings of Systematic Evidence Review of HIV Screening for Pregnant Women.

Table 15

Summary of Findings of Systematic Evidence Review of HIV Screening for Pregnant Women.

Outcomes Table

Table 16 estimates the outcomes from screening prior to the third trimester in three hypothetical cohorts (0.15% prevalence, 0.30% prevalence, and high risk) of 10,000 pregnant women, using the highest quality and most applicable available evidence. We did not include areas in this table in which reliable data to estimate the clinical magnitude of benefit or harm were not available, such as harms from screening (anxiety, labeling, violence, suicide, partnership dissolution) or decreased horizontal transmission from counseling. We focused on the benefits of receipt of combination antiretroviral regimens on the risk of mother-to-child transmission, as this intervention has the greatest impact on transmission rates, and there were insufficient or limited data on other clinical outcomes (such as long-term maternal outcomes or horizontal transmission rates) or benefits associated with other interventions such as prophylaxis for opportunistic infections, counseling on risky behaviors, immunizations, routine monitoring and follow-up, or additional benefits from elective cesarean section in women receiving HAART. For harms of interventions, we focused on the rate of postpartum complications from elective cesarean section, as studies have not shown clear evidence of long-term infant adverse events from exposure to antiretrovirals, and there are insufficient data regarding the risks of antiretroviral exposure on long-term maternal outcomes. We calculated numbers needed to screen and treat to prevent one case of maternal-to-child transmission and cause one postpartum complication (postpartum fever, endometritis, hemorrhage, or urinary tract infection) from elective cesarean section (Appendix E).

Table 16. Outcome Table of Screening for HIV Infection in 10,000 Asymptomatic Pregnant Women.

Table 16

Outcome Table of Screening for HIV Infection in 10,000 Asymptomatic Pregnant Women.

To estimate the benefits of counseling and screening for HIV infection in pregnant women, we made several assumptions. We used recent estimates of rates of combination antiretroviral regimens (60%-90%)37, 134137 and elective cesarean section (37%-50%) utilization by HIV-infected pregnant women in the U.S.134, 137, 138 Our estimates of the effectiveness of interventions were conservative and did not include potential benefits from elective cesarean section or avoidance of breastfeeding in women receiving combination therapy.48 We also did not include potential benefits from screening on long-term maternal outcomes.

Numbers needed to screen to prevent one case of infant HIV infection ranged from 3,500 to 12,170 in the low-risk population to 105 to 365 in high-risk women. The number needed to treat with interventions to prevent one case of infant HIV infection was 4.3–9.9. The number needed to screen to cause one postpartum complication from elective cesarean section ranged from 4,280 to 31,640 in the low-risk population to 130 to 940 in the high-risk population. The number needed to treat to cause one postpartum complication from elective cesarean section was about 6 (95% CI, 2.9 to 15.9).

Conclusions

There are no published trials directly linking screening for HIV in pregnant women with clinical outcomes. In developed countries, the rate of mother-to-child transmission from untreated HIV-infected women ranges from 14% to 25%. Targeted screening of pregnant women with risk factor assessment would miss a significant proportion of infected persons. Standard office-based testing is highly (>99%) sensitive and specific, and initial studies of rapid HIV tests in labor and delivery settings found similar diagnostic accuracy. HIV testing rates during pregnancy continue to vary widely in the U.S. and appear to be higher in states using ‘opt-out’ testing policies. Recommended interventions (antiretroviral prophylaxis, elective cesarean section in selected patients, and avoidance of breastfeeding) are associated with transmission rates of 1%-2% in clinical trials and large observational studies. Shorter regimens are less effective, but also decrease the rate of transmission. The estimated benefits from combination antiretroviral regimens appear to greatly outweigh the risk of short-term complications, but long-term follow-up is not yet available. Elective cesarean section is associated with an increased risk of mostly short-term maternal adverse events. There are insufficient data to estimate the effects of interventions during pregnancy on long-term maternal disease progression or other outcomes (such as horizontal transmission).

Limitations of the Literature

In assessing the balance of benefits and harms from screening for HIV infection in pregnant women, we highlight several areas of key uncertainties.

Population Screened

Studies that have assessed the usefulness of risk factor assessment to guide screening were mostly performed before the CDC recommended universal counseling and voluntary prenatal HIV testing, but indicated that targeted screening missed a significant proportion of HIV-positive women. Even with universal counseling and voluntary testing policies, a significant minority of women remains untested. Studies evaluating programs to increase uptake rates in target groups such as adolescent minority women are lacking.

Currently recommended HIV counseling prior to testing and subsequent follow-up require substantial resources. More abbreviated or streamlined counseling methods (including opt-out testing policies) might encourage more providers to offer screening and patients to accept it, but could also result in less informed choices by women, and require further study. There are also insufficient data regarding the usefulness of repeat screening in the third trimester in high- or low-risk women who tested negative earlier.

Screening Methods

Rapid serum testing of women with unknown HIV status presenting in labor appears to be an accurate and feasible method for quickly determining eligibility for urgent interventions. The effect of other sampling or testing methods (home-based sampling, urine or oral specimens, or on-site testing) on acceptance of testing and rates of patient notification of results have not been evaluated in pregnant women, but could be effective in women who receive limited or no prenatal care or who do not undergo standard office-based testing for other reasons.

Harms from Screening

Anecdotal reports of violence, suicide, partnership dissolution, and other adverse effects from screening are concerning, but data to estimate the magnitude of these harms are limited. Pregnant women may be particularly vulnerable to these adverse effects. Good-quality studies on methods to minimize the risk of these harmful outcomes are lacking.

Interventions

The combination of antiretroviral prophylaxis, elective cesarean section, and avoidance of breastfeeding is highly effective in reducing rates of mother-to-child transmission of HIV infection. Studies on long-term maternal and infant risks and benefits associated with different combination regimens, however, are not yet available. Further studies are needed to determine the optimal antiretroviral regimen, and whether elective cesarean section has an additive effect in women receiving HAART. The long-term effects of transient antiretroviral exposure or less-intense antiretroviral regimens during pregnancy on resistance rates and future response to therapy also need to be studied further. There are insufficient data regarding the effectiveness of counseling on rates of vertical or horizontal transmission, or on the effect that knowledge of HIV status has on future reproductive choices.

Future Research

Studies evaluating short and long-term effects of different antiretroviral regimens, particularly in women who do not otherwise meet criteria for initiation of HAART, are being conducted and will help clarify the optimal antiretroviral regimen choice during pregnancy. Longer-term follow-up studies of women and infants who received antiretrovirals are also being conducted and remain a priority. Particular attention should be paid to long-term outcomes in women who discontinued antiretrovirals after delivery to determine whether brief exposure affects future response rates or the choice of subsequent antiretroviral regimens. Children exposed to antiretrovirals in utero should continue to be followed to help identify unexpected or emerging long-term harms from combination regimens.

Most studies of HIV-infected pregnant women have focused on benefits from reductions in mother-to-child transmission rates. Studies evaluating the effects of HIV diagnosis and counseling on future reproductive choices, high-risk behaviors, horizontal transmission rates, and other non-pregnancy-related outcomes could help to further strengthen the case for universal screening, particularly in low-risk populations.

Further studies of rapid tests and other new sampling and testing methods in office-based and outreach settings will help clarify their role in improving prenatal testing and notification rates. Studies evaluating methods to resolve barriers to testing remain a priority and include further evaluation on the impact of policy choices (such as opt-out testing or mandatory newborn screening) and different (such as streamlined or targeted) counseling methods on testing rates.

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