October 2000
ATLANTA - Pregnant women usually have more access to health care than at other times in their lives. This access enables interventions that help keep her and her newborn healthy.
However, perinatal disease prevention does have challenges. "One challenge is that the populations that we're interested in - pregnant women and their newborns - are two of the most vulnerable populations. Therefore, people don't usually want to include them in clinical trials. A second challenge is that once an effective intervention has been recognized, implementation can be complicated because there are so many different players involved," said Stephanie Schrag, MD, at the International Conference on Emerging Diseases 2000.
Two infection prevention efforts which have been pretty successful are recommendations to prevent HIV and group B streptococcus (GBS).
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Before the 076 protocol that
calls for giving zidovudine (AZT, Retrovir, Glaxo Wellcome) to a pregnant woman
to prevent transmission of HIV to her infant, there was "a fairly steady
increase in the incidence of perinatally acquired HIV in the United States.
This pretty much parallels the incidence of HIV/AIDS among women of
childbearing age in the United States," Schrag said.
The regimen calls for giving AZT prenatally and during childbirth to pregnant women who are HIV positive, and then giving an AZT regimen to the newborns. This regimen has reduced the risk of transmission from 25% to 8% of infants.
"This was a huge breakthrough in the HIV epidemic," said Schrag, an epidemic intelligence officer with the Respiratory Disease Branch at the Centers for Disease Control and Prevention.
Immediately following the successful clinical trials for this protocol in 1994, the Public Health Service released guidelines for the use of AZT to prevent perinatal HIV disease. The following year the guidelines were expanded to recommend universal prenatal counseling and voluntary HIV testing of all pregnant women in the United States. "So, there was a rapid public health response, and this coincided with a striking decline in the incidence of perinatal HIV, and over an 80% decline by 1999," she explained.
GBS emerged in the United States in the 1970s as a leading cause of neonatal morbidity and mortality. By the early 1980s, clinical trials had demonstrated that giving antibiotics during labor was a highly effective intervention at preventing newborn disease. However, guidelines for using this intervention took 15 years to be released.
"In contrast to the situation we saw with perinatal HIV, and despite this recognition of an effective intervention, the medical community was quite slow to incorporate this into routine practice," she said.
Active surveillance for GBS was initiated in the late 1980s, and several studies looked at cost-effectiveness of intervention. Finally in 1996, the Consensus Guidelines for the Prevention of Perinatal Group B Streptococcus Disease were released.
In the early 1990s, the GBS incidence was between 1.5 and 2 cases per 1,000 live births. By 1999, there was a 70% decline in the incidence of early-onset disease. "That coincides with some of the prevention activities," Schrag said.
"So, we've made really great strides in both perinatal HIV and group B strep prevention," said Schrag, but she admitted that the efforts need to be monitored to fully appreciate the effects.
When it comes to monitoring compliance, Schrag recommends auditing a random sample of labor and delivery records for a given geographic area. "This can give you, retrospectively, a good picture of the general population delivering and what sort of prenatal prevention measures they were exposed to," she explained.
Schrag showed data from one such audit of Connecticut conducted in 1996. The researchers checked to see if women received prenatal screening according to recommendations. They found that screening for syphilis, rubella and hepatitis B was close to 100%. However, only 25% of women were screened for HIV and only 33% were screened for GBS.
Missed opportunities can be assessed by reviewing any cases born after the recommendations. This is being done by enhanced surveillance for HIV in seven states. Data collected from 1995 to 1997 from these states show that 14% of women who had an infant with perinatal HIV still had no prenatal care, and 8% had one or two visits only.
"Not all women who were in prenatal care were actually getting prenatal HIV testing at the recommended time. About one-quarter of the women had their first HIV test at or after delivery, which is a little bit late to try to get the full benefit of the AZT intervention. Also not all women who were known to be HIV positive were actually prescribed AZT," Schrag added.
And there was a group of prevention failures. In this case, 29% of women received prenatal care, had a prenatal HIV test and received AZT, but still had a positive infant. There have been some strides to reduce the number of women and infants who fall in this group by using combination therapies that reduce viral load or recommending elective Cesarean section.
Schrag is conducting a similar enhanced surveillance for missed opportunities for perinatal GBS. She looked at women in eight states from 1998 and 1999 who had infants with early-onset disease. Sixty-five percent did not receive prenatal GBS testing; 56% had no intrapartum risk factor.
Additionally, more than half of women who actually had an indication for intrapartum antibiotics never received them. And there was a group who did receive intervention, but still had a child with GBS. "They could be considered prevention failures, and we're hoping we can reduce some of the women who fall in this category for GBS by trying to encourage earlier administration of antibiotics during labor," she said.
Another important challenge when monitoring the success of prevention is to consider the adverse effects of the intervention. Does resistance develop for AZT or the antibiotics? Are there potential toxicities to perinatal and neonatal exposures to these drugs? Most of the agents, especially the HIV drugs, were not tested in pregnant women or newborns, Schrag admitted, "so we still don't fully know what the long-term effects will be."
For more information:
- Schrag SJ. Reducing the burden of perinatal diseases: The success of perinatal group B streptococcal disease and HIV prevention efforts. Session 70. Presented at the International Conference on Emerging Infectious Diseases 2000. July 16-19, 2000. Atlanta.
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