UPDATE ON INFECTIOUS DISEASE

Dr. Tita reports receiving research support from the NIH. Dr. Subramaniam and Dr. Andrews report no financial relationships relevant to this article.

Despite continuing advances in obstetric and neonatal care, including the use of antimicrobials, infection remains a major cause of maternal and perinatal morbidity and death. Indeed, infection is among the top five causes of maternal death in the United States, with 10% to 15% of deaths directly linked to it. Maternal and fetal infections are also a common cause of perinatal death. Clearly, interventions to prevent infection or minimize its effect during pregnancy and postpartum are a priority.

This article focuses on three notable developments of the past year:

• release of revised guidelines on the prevention of perinatal group B streptococcal disease (GBS)
• publication of surveillance data on 2009 influenza A(H1N1) among pregnant women, which reveals the life-threatening nature of the flu in this population
• publication of a Committee Opinion from ACOG on the timing of antimicrobial prophylaxis for cesarean delivery, in which administration within 60 minutes of the start of the procedure is recommended.

There’s room for improvement in GBS screening and prophylaxis,
says CDC

Verani JR, McGee L, Schrag SJ, National Center for Immunization and Respiratory Diseases. Prevention of perinatal group B streptococcal disease. Revised guidelines from CDC, 2010. MMWR Recomm Rep. 2010;59(RR-10):1–36. http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5910a1.htm.

The latest revision of CDC guidelines on screening and prophylaxis for perinatal group B streptococcal disease were developed by a multidisciplinary working group representing several professional organizations, including ACOG. Information that has come to light since the most recent guidelines were released in 2002 was incorporated, and areas that have seen suboptimal implementation or interpretation were addressed here as well.

Although the use of prophylactic antibiotics during labor reduces the incidence of invasive GBS during the first week of life, GBS remains a leading cause of neonatal morbidity and death in the United States and elsewhere. Universal screening and intrapartum antibiotic prophylaxis for women who test positive for GBS remain the cornerstone of prevention of early-onset neonatal GBS disease. Penicillin G is still the agent of choice, and ampicillin is an acceptable alternative. When prophylaxis is warranted, intravenous antibiotic administration at least 4 hours before delivery is recommended.

Other recommendations from the CDC include:

• Women who have GBS bacteriuria (≥10⁴ colony-forming units/mL) any time during pregnancy, and women who had a previous infant with invasive GBS disease, should receive intrapartum antibiotic prophylaxis. In these cases, third-trimester screening for GBS is unnecessary.
• All other women should be screened at 35 to 37 weeks’ gestation for rectovaginal GBS colonization.
• At the onset of labor or rupture of membranes, antibiotic prophylaxis should be given to all women who tested positive for GBS—with the exception of women who are undergoing cesarean delivery, at any gestational age, with intact membranes.
• If GBS status is unknown, intrapartum prophylaxis should be given for gestational ages below 37 weeks, membrane rupture lasting 18 hours or longer, or temperature of 100.4°F (38.0°C) or above.
• Health-care providers should inform women of their GBS screening results and the recommended interventions.

Some updates to the guidelines clarify areas in which there was some confusion. For example, the guidelines delineate that women who have preterm labor or preterm premature rupture of the membranes (PPROM) should be screened for GBS and started on prophylaxis immediately, unless they have received a negative screen within the preceding 5 weeks. Antibiotics should be discontinued if a woman who has intact membranes is found not to be in true labor or if the GBS culture is negative.

For the woman who has PPROM, antibiotics to prolong latency are sufficient, provided they include adequate GBS coverage; otherwise, GBS prophylaxis is warranted for as long as 48 hours.

In addition:

• Women who are allergic to penicillin and who have no history of anaphylaxis, angioedema, respiratory distress, or urticaria in response to penicillin or a cephalosporin, should be given cefazolin for GBS prophylaxis. Women at risk of anaphylaxis should undergo antimicrobial susceptibility testing. For these women, clindamycin is acceptable if the GBS isolate is susceptible to both clindamycin and erythromycin or resistant to erythromycin with negative inducible clindamycin resistance. Otherwise, vancomycin is recommended. Erythromycin is not acceptable because of a high prevalence of resistance.
• The dosage of penicillin is 5 million U initially, followed by 2.5 million to 3 million U every 4 hours.
• If a laboratory providing nucleic acid amplification testing (NAAT) is available, intrapartum testing for women who have unknown GBS status and no intrapartum risk factors (i.e., gestational age <37 weeks, membrane rupture for 18 hours or longer, or temperature ≥100.4°F) is an option.