1.5 Infectious Diseases in Inpatient Obstetrics
Key Takeaways
- Universal rectovaginal Group B Streptococcus (GBS) screening is performed at 36 0/7 to 37 6/7 weeks of gestation; intrapartum antibiotic prophylaxis (IAP) is indicated for positive GBS screen, GBS bacteriuria in current pregnancy, prior infant with invasive GBS disease, or unknown status with risk factors (<37 weeks, ROM ≥18 hr, temp ≥100.4°F/38.0°C).
- First-line IAP for GBS is IV Penicillin G (5 million units load, then 2.5-3.0 million units q4h) or IV Ampicillin (2 g load, then 1 g q4h) administered for ≥4 hours prior to delivery; for penicillin-allergic patients at high anaphylaxis risk, Clindamycin is used ONLY with verified susceptibility and negative D-test, otherwise weight-based Vancomycin (20 mg/kg q8h, max 2 g) is required.
- Maternal syphilis at any stage is treated exclusively with Benzathine Penicillin G (2.4 million units IM single dose for primary/secondary/early latent; 2.4 million units IM weekly x 3 doses for late latent); pregnant patients with penicillin allergy MUST undergo inpatient desensitization and penicillin therapy. The Jarisch-Herxheimer reaction can induce transient fetal late decelerations within 24 hours of initiation.
- Active genital Herpes Simplex Virus (HSV) lesions or prodromal symptoms at the time of labor or membrane rupture are an absolute indication for cesarean delivery to prevent neonatal disseminated infection; oral suppressive antiviral therapy (Acyclovir 400 mg TID or Valacyclovir 500 mg BID) begins at 36 0/7 weeks for all patients with a history of genital HSV.
- Pregnant patients with HIV and a viral load >1,000 copies/mL (or unknown) at ≥36 weeks require scheduled cesarean delivery at 38 0/7 weeks with continuous IV Zidovudine (AZT) infusion (2 mg/kg load over 1 hr, then 1 mg/kg/hr) initiated 3 hours pre-operatively; avoid invasive intrapartum procedures including fetal scalp electrodes, vacuum, and artificial rupture of membranes.
Last updated: August 2026
Group B Streptococcus (GBS) Screening and Intrapartum Antibiotic Prophylaxis
Streptococcus agalactiae (Group B Streptococcus [GBS]) is a gram-positive diplococcus that asymptomatically colonizes the gastrointestinal and genitourinary tracts of 15% to 30% of pregnant women. Vertical transmission during labor or following membrane rupture is the leading cause of neonatal early-onset GBS disease (sepsis, pneumonia, and meningitis presenting within the first 7 days of life).
Universal Screening Protocol
In accordance with ACOG and CDC guidelines, all pregnant women must undergo universal culture-based rectovaginal screening at 36 0/7 to 37 6/7 weeks of gestation (swabbing the lower vagina followed by the rectum through the anal sphincter without a speculum). If GBS culture results are negative, they remain clinically valid for 5 weeks; if the patient delivers beyond 5 weeks from testing and has not yet delivered, repeat screening is indicated.
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| GBS INTRAPARTUM ANTIBIOTIC PROPHYLAXIS (IAP) ALGORITHM |
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[ Assess GBS Indications at Admission ]
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[ IAP DEFINITIVELY INDICATED ] [ IAP NOT INDICATED ]
- Positive GBS rectovaginal screen at 36-37 wk - Negative GBS screen at 36-37 wk
- GBS Bacteriuria at any concentration during current pregnancy (unless obstetric risk factors develop)
- History of a previous infant with invasive GBS disease - Planned Cesarean Delivery prior to
- Unknown GBS Status AT PRESENTATION WITH ANY RISK FACTOR: onset of labor AND with intact membranes
* Preterm Labor (<37 0/7 weeks gestation) (regardless of GBS culture status)
* Prolonged Rupture of Membranes (ROM ≥18 hours)
* Intrapartum Maternal Fever (Temperature ≥100.4°F [38.0°C])
* Intrapartum NAAT/PCR positive for GBS
Antibiotic Selection and Penicillin Allergy Decision Tree
Intrapartum antibiotic prophylaxis (IAP) is designed to achieve bactericidal levels in the fetal circulation and amniotic fluid; adequate IAP requires administration of IV antibiotics for at least 4 hours prior to birth.
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| STANDARDIZED ANTIBIOTIC SELECTION PROTOCOL FOR GBS IAP |
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Patient Allergy Status Recommended Regimen & Dosing
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NO PENICILLIN ALLERGY ★ PENICILLIN G (Gold Standard):
5.0 million units IV loading dose, then 2.5 to 3.0 million units IV every 4 hr until delivery
★ AMPICILLIN (Alternative):
2.0 g IV loading dose, then 1.0 g IV every 4 hr until delivery
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PENICILLIN ALLERGIC: ★ CEFAZOLIN (Ancef):
Low Risk of Anaphylaxis 2.0 g IV loading dose, then 1.0 g IV every 8 hr until delivery
(Mild rash, maculopapular, no hives)
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PENICILLIN ALLERGIC: ★ Check Lab for GBS Antibiogram and D-Zone Test:
High Risk of Anaphylaxis - IF SUSCEPTIBLE TO CLINDAMYCIN AND D-TEST NEGATIVE:
(Anaphylaxis, angioedema, hives, CLINDAMYCIN 900 mg IV every 8 hr until delivery
bronchospasm, Stevens-Johnson) - IF RESISTANT TO CLINDAMYCIN, D-TEST POSITIVE, OR SUSCEPTIBILITY UNKNOWN:
VANCOMYCIN 20 mg/kg IV (max single dose 2 g) every 8 hr until delivery
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Sexually Transmitted Infections in Inpatient Obstetrics
1. Syphilis (Treponema pallidum)
- Maternal Stages:
- Primary: Painless, indurated ulcer (chancre) at the site of inoculation.
- Secondary: Diffuse maculopapular rash involving the palms and soles, condyloma lata (flat, moist, highly contagious genital plaques), lymphadenopathy, fever.
- Early Latent (<1 year duration): Asymptomatic with reactive serology.
- Late Latent (>1 year or unknown duration): Asymptomatic; unknown timing of infection.
- Tertiary: Neurosyphilis, cardiovascular aortitis, gummatous lesions.
- Diagnostic Serology: Screen with non-treponemal test (RPR or VDRL); confirm reactive screens with treponemal-specific test (FTA-ABS, TP-PA, or automated treponemal immunoassay).
- Mandatory Treatment Protocol: Benzathine Penicillin G (Bicillin L-A) is the ONLY proven effective antibiotic for treating maternal syphilis and preventing congenital syphilis. No alternative antibiotic crosses the placenta reliably.
- Primary, Secondary, or Early Latent: Benzathine Penicillin G 2.4 million units IM single dose.
- Late Latent or Unknown Duration: Benzathine Penicillin G 2.4 million units IM once weekly for 3 consecutive weeks (total dose 7.2 million units). If a dose is missed by >7 to 9 days, the entire 3-week series must be restarted.
- Penicillin Allergy in Pregnancy: Pregnant patients with a documented penicillin allergy MUST BE ADMITTED FOR INPATIENT PENICILLIN DESENSITIZATION followed immediately by treatment with Benzathine Penicillin G.
- Jarisch-Herxheimer Reaction: An acute systemic inflammatory response caused by massive endotoxin and cytokine release following treponemal lysis. Occurs in up to 40% of treated pregnant gravidas, usually within 2 to 24 hours after the first penicillin injection. Symptoms include maternal fever, chills, tachycardia, uterine contractions, and transient Category II fetal heart rate decelerations. Treatment is supportive with antipyretics and intrauterine resuscitation; it is not an allergic reaction and does not warrant discontinuing therapy.
2. Genital Herpes Simplex Virus (HSV-1 / HSV-2)
- Neonatal Risk: Disseminated neonatal herpes, encephalitis, or local skin/eye/mouth (SEM) disease. Neonatal mortality exceeds 60% if untreated. Transmission risk is 30% to 50% during a primary maternal infection near delivery, compared to <1% to 3% during recurrent episodes.
- Antenatal Suppression: All pregnant women with a history of genital HSV must be initiated on daily oral suppressive therapy at 36 0/7 weeks of gestation (Acyclovir 400 mg TID or Valacyclovir 500 mg BID) to reduce viral shedding and clinical recurrences at delivery.
- Intrapartum Decision-Making:
- On admission in labor or with ruptured membranes, perform a careful visual inspection of the perineum, vulva, vagina, and cervix under bright illumination.
- Indication for Cesarean Delivery: Presence of active genital lesions (vesicles, ulcers) OR prodromal symptoms (vulvar burning, pain, paresthesias) at the time of labor or membrane rupture.
- Vaginal Delivery Permitted: If there are NO active genital lesions and NO prodromal symptoms (even if history is positive or non-genital lesions are present [e.g., thigh or buttocks lesions, which can be covered with an occlusive dressing]).
- Intrapartum Precautions: Avoid invasive fetal monitoring (fetal scalp electrodes, fetal scalp blood sampling, intrauterine pressure catheters) and artificial rupture of membranes in HSV-positive patients due to microtrauma facilitating viral inoculation.
3. Human Immunodeficiency Virus (HIV)
- Antenatal and Intrapartum Protocol: All patients must continue their combination antiretroviral therapy (cART) schedule throughout the intrapartum period.
- Viral Load Stratification and Mode of Delivery (ACOG Guidelines):
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| INTRAPARTUM MANAGEMENT OF HIV BASED ON VIRAL LOAD AT ≥36 WEEKS |
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Maternal HIV Viral Load Recommended Mode of Delivery Intrapartum IV Zidovudine (AZT) Protocol
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Viral Load ≤1,000 copies/mL Vaginal Delivery is Appropriate IV Zidovudine is NOT required (continue oral cART)
(or undetectable) (Deliver according to OB indications) (Option to infuse if clinical compliance uncertain)
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Viral Load >1,000 copies/mL SCHEDULED CESAREAN DELIVERY ★ ADMINISTER CONTINUOUS IV ZIDOVUDINE:
(or Unknown Viral Load) AT 38 0/7 WEEKS OF GESTATION - IV Loading Dose: 2.0 mg/kg over 1 hour
(Prior to onset of labor and - Continuous Maintenance: 1.0 mg/kg/hour
prior to membrane rupture) - Initiate IV 3 hours prior to surgical incision
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- Inpatient Intrapartum Nursing Precautions:
- STRICTLY AVOID ALL INVASIVE PROCEDURES: No fetal scalp electrodes (FSE), no fetal scalp blood sampling, no intrauterine pressure catheters (IUPC), no artificial rupture of membranes (AROM), and avoid operative vaginal delivery (forceps or vacuum extractor).
- Neonatal Care: Bathe the newborn immediately with soap and water prior to any injections or skin punctures (e.g., Vitamin K, Hepatitis B vaccine) to eliminate maternal blood/secretions from the skin surface.
- Lactation: In high-resource settings where safe formula and potable water are universally accessible, breastfeeding is historically avoided in HIV-positive mothers, although shared decision-making is supported if the mother maintains full viral suppression on cART.
Perinatal Bacterial and Viral Infections
| Pathogen | Clinical Maternal Presentation | Fetal / Neonatal Risk | Inpatient Nursing & Medical Interventions |
|---|---|---|---|
| Chlamydia trachomatis | Asymptomatic (80%), mucopurulent cervicitis, dysuria | Neonatal conjunctivitis (ophthalmia neonatorum), infant afebrile pneumonia (at 4-12 wk) | Azithromycin 1 g PO single dose (or Doxycycline postpartum). Erythromycin 0.5% ophthalmic ointment at birth. |
| Neisseria gonorrhoeae | Green-yellow discharge, dysuria, Bartholin abscess | Severe neonatal ophthalmia neonatorum with rapid corneal perforation and blindness | Ceftriaxone 500 mg IM single dose plus treatment for Chlamydia if not ruled out. Neonatal eye prophylaxis. |
| Acute Pyelonephritis | High fever (>38°C), chills, CVA tenderness, flank pain, nausea | Preterm labor, transient Category II FHR decelerations, maternal septic shock / ARDS | Hospital admission, IV hydration, IV Ceftriaxone (1 g q24h) or Ampicillin + Gentamicin. Monitor for pulmonary edema. |
| Influenza (A & B) | High fever, myalgias, cough, dyspnea; high risk of ARDS | Preterm birth, FGR, severe maternal cardiopulmonary collapse | Immediate initiation of oral Oseltamivir (Tamiflu) 75 mg BID x 5 days (do not wait for swab results). Droplet precautions. |
| COVID-19 | Fever, dry cough, loss of taste/smell, hypoxia, preeclampsia-like syndrome | Preterm birth, stillbirth (histiocytic intervillositis of placenta) | Airborne/droplet precautions, SpO2 monitoring, remdesivir/dexamethasone for severe hypoxemia (SpO2 <94%). |
Summary of High-Yield Pharmacologic Regimens
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| MASTER PHARMACOLOGY REFERENCE: INFECTIONS IN PREGNANCY |
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Infection / Indication First-Line Drug & Route Exact Dosing Protocol & Clinical Notes
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GBS Prophylaxis (No Allergy) Penicillin G IV 5 million units IV load, then 2.5-3.0 million units q4h
GBS (Mild PCN Allergy) Cefazolin IV 2 g IV load, then 1 g IV q8h
GBS (Severe PCN Allergy) Clindamycin IV (if sensitive) 900 mg IV q8h (D-test MUST be negative)
Vancomycin IV (if resistant) 20 mg/kg IV (max 2 g) q8h
Syphilis (All Stages) Benzathine Penicillin G IM 2.4 million units IM (x1 for early; x3 weekly for late)
Genital HSV (Suppression) Acyclovir / Valacyclovir PO Acyclovir 400 mg TID or Valacyclovir 500 mg BID from 36 wk
HIV (Intrapartum VL >1000) Zidovudine (AZT) IV 2 mg/kg IV over 1 hr, then 1 mg/kg/hr until cord clamped
Acute Chlamydia Azithromycin PO 1 g oral single dose
Acute Gonorrhea Ceftriaxone IM 500 mg IM single dose (1 g if weight ≥150 kg)
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Test Your Knowledge
A G2P1 at 39 weeks of gestation is admitted in active labor with ruptured membranes. Her 36-week rectovaginal GBS screen was positive. The patient has a severe penicillin allergy characterized by documented anaphylaxis and throat swelling. The laboratory report indicates that the GBS isolate is resistant to erythromycin and clindamycin. Which intrapartum antibiotic regimen must the nurse prepare to administer?
A
B
C
D
Test Your Knowledge
A primigravida at 38 weeks of gestation with known HIV infection presents for a scheduled delivery. Her most recent viral load drawn at 36 weeks of gestation was 4,200 copies/mL. Which mode of delivery and intrapartum pharmacologic management are indicated?
A
B
C
D
Test Your Knowledge
A 24-year-old multigravida at 37 weeks of gestation with a known history of recurrent genital HSV-2 presents in early active labor. She states she has taken daily acyclovir suppression since 36 weeks. Upon speculum and physical examination under bright lighting, the nurse notes two tender, vesicular ulcerations on the left labia majora. What is the priority obstetric plan of care?
A
B
C
D
Test Your Knowledge
A pregnant patient at 28 weeks of gestation is diagnosed with secondary syphilis (palmar rash and reactive RPR 1:64 confirmed by TP-PA). She has a documented history of severe penicillin anaphylaxis. What is the only acceptable and standard-of-care clinical management for this patient?
A
B
C
D