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Intrauterine Infection (Chorioamnionitis) – A Patient‑Friendly Medical Guide

Overview

Intrauterine infection, most commonly referred to as chorioamnionitis, is an infection of the fetal membranes (the chorion and amnion) and the amniotic fluid surrounding the developing baby. It usually occurs during the third trimester or during labor, but it can develop earlier.

Who it affects

• Pregnant women of any age, race, or socioeconomic status.
• Most cases happen at term (≥37 weeks) or near‑term, but preterm chorioamnionitis accounts for a large portion of preterm births.

Prevalence

• Clinically diagnosed chorioamnionitis occurs in 1–5 % of all deliveries in high‑income countries.<sup>1</sup>
• When laboratory criteria are added, the rate rises to **8–10 %** of term births and up to **30 %** of preterm births before 34 weeks.<sup>2</sup>
• It is a leading cause of early‑onset neonatal sepsis, responsible for roughly **10–20 %** of such cases worldwide.<sup>3</sup>

Because the condition can progress quickly, early recognition and treatment are critical to protect both mother and baby.

Symptoms

Symptoms can be subtle, especially in early stages, but most women develop a recognizable pattern during labor. Common signs include:

Maternal Signs

• Fever – temperature ≥ 38 °C (100.4 °F) sustained for > 30 minutes, often the first clue.
Uterine tenderness – pain when the abdomen is gently pressed.
• Foul‑smelling amniotic fluid – described as “rotten egg” or “putrid” odor.
• Maternal tachycardia – heart rate > 100 bpm.
• Leukocytosis – white‑blood‑cell count > 15,000 cells/mm³ (detected on labs).
• Maternal chills, shivering, or rigors.
• Abnormal vaginal discharge – increased volume, watery or mucopurulent.

Fetal/Neonatal Signs

• Fetal tachycardia (heart rate > 160 bpm) detected on fetal monitoring.
• Decreased fetal movements reported by the mother.
• Pre‑term labor or premature rupture of membranes (PROM).
• Newborn signs after delivery: respiratory distress, temperature instability, lethargy, or purulent drainage from the umbilical cord stump.

It is important to note that not all women will have every symptom; some may present with only fever and fetal tachycardia.

Causes and Risk Factors

How the infection occurs

Chorioamnionitis is most often caused by bacteria ascending from the vagina and cervix into the uterine cavity. The infection can be polymicrobial, with common organisms including:

• Group B Streptococcus (GBS)
• Escherichia coli
• Ureaplasma urealyticum and Mycoplasma hominis
• Gram‑negative rods (e.g., Klebsiella, Pseudomonas)
• Anaerobes (e.g., Bacteroides)

Key risk factors

• **Prolonged rupture of membranes (PROM)** – especially > 18 hours.
• **Pre‑term labor** or delivery before 37 weeks.
• **Multiple vaginal examinations** during labor (each exam increases bacterial exposure).
• **Maternal colonization** with GBS or other pathogens.
• **Intra‑uterine procedures** (amniocentesis, intra‑uterine device placement).
• **Maternal infections** such as urinary tract infection, bacterial vaginosis, or sexually transmitted infections.
• **Smoking, illicit drug use, or poor oral hygiene** – associated with altered vaginal flora.
• **Pre‑existing medical conditions** – diabetes, immunosuppression, obesity.

Diagnosis

Because the condition can evolve quickly, clinicians use a combination of clinical signs, laboratory tests, and sometimes imaging.

Clinical criteria (CDC/ACOG)

A diagnosis is often made when at least two of the following are present:

• Maternal fever ≥ 38 °C.
• Maternal leukocytosis (> 15,000 cells/mm³) without another cause.
• Fetal tachycardia (> 160 bpm) lasting ≥ 10 minutes.
• Purulent or foul‑smelling amniotic fluid.
• Maternal uterine tenderness.

Laboratory tests

• Complete blood count (CBC) – looks for leukocytosis.
• C‑reactive protein (CRP) and procalcitonin – inflammatory markers that rise early.
• Blood cultures – taken before antibiotics to identify bacteremia.
• Amniotic fluid analysis (when feasible):
• Gram stain, culture, or nucleic‑acid amplification tests (NAAT) for specific pathogens.
• Glucose level – low glucose (< 14 mg/dL) suggests infection.
• Leukocyte count – > 50 cells/mm³ is concerning.

Imaging (rarely needed)

• Ultrasound may be used to assess for intra‑uterine fluid collections or to confirm PROM.

Treatment Options

Prompt antimicrobial therapy is the cornerstone of care, combined with obstetric management to minimize risks to the fetus.

Antibiotic regimens

Regimen	Typical Use
Penicillin G + Gentamicin	Broad‑spectrum coverage for GBS, Gram‑negative rods, and anaerobes; classic first‑line when susceptibility is unknown.
Ampicillin + Gentamicin	Alternative for patients allergic to penicillin (if not severe IgE‑mediated).
Cefazolin + Azithromycin	Used in many U.S. hospitals for intra‑uterine infection when GBS prophylaxis is already given.
Clindamycin + Gentamicin + Ampicillin	For severe cases or when anaerobic coverage is a priority.

Antibiotics are given intravenously until delivery, then usually switched to oral therapy for an additional 5–7 days, depending on maternal and neonatal status.

Obstetric management

• Labor induction or augmentation – to shorten the interval between infection onset and delivery.
• Cesarean delivery – may be indicated for fetal distress, failure to progress, or when vaginal delivery is deemed unsafe.
• Tocolysis – typically avoided because prolonging pregnancy in the presence of infection can worsen outcomes.

Supportive care

• IV fluids to maintain maternal hemodynamics.
• Antipyretics (acetaminophen) for fever control.
• Continuous fetal monitoring to detect distress.
• Neonatal resuscitation team present at delivery.

Lifestyle & adjunct measures

• Good hand hygiene for staff and visitors.
• Limiting the number of vaginal examinations during labor.
• Prompt treatment of maternal urinary or genital infections during pregnancy.

Living with Intrauterine Infection (Chorioamnionitis)

While the acute phase requires hospital care, many women wonder how to manage recovery and future pregnancies.

Post‑delivery recovery

• Continue the full course of antibiotics as prescribed, even if you feel better.
• Monitor for fever, worsening abdominal pain, or foul lochia (vaginal discharge) that persists beyond 2 weeks.
• Maintain good perineal hygiene; use sit‑z baths if recommended.
• Schedule a follow‑up visit within 1–2 weeks to assess healing and discuss contraception or future pregnancy plans.

Emotional wellbeing

• It’s common to feel anxiety about the baby’s health—talk to a counselor or support group.
• Ask your obstetrician about postpartum depression screening.

Future pregnancies

• Discuss prophylactic GBS screening and intrapartum antibiotics in the next pregnancy.
• Consider a pre‑conception visit to optimize chronic conditions (diabetes, hypertension).

Prevention

Many cases are preventable with timely prenatal care and attention to risk factors.

Key preventive strategies

• Early and regular prenatal visits – enable screening for GBS, urinary tract infections, and bacterial vaginosis.
• GBS screening at 35‑37 weeks – 10‑30 % of pregnant women carry GBS; intrapartum penicillin reduces neonatal infection risk by up to 80 %.<sup>4</sup>
• Prompt treatment of maternal infections – UTIs, bacterial vaginosis, and STIs should be fully treated before delivery.
• Limit vaginal examinations – each exam introduces bacteria; use a sterile technique and document necessity.
• Manage PROM quickly – if membranes rupture > 18 hours before delivery, consider induction and antibiotics per hospital protocol.
• Smoking cessation and substance‑use counseling – reduces colonization with pathogenic bacteria.
• Good oral hygiene – periodontal disease is linked with higher rates of intra‑uterine infection.

Complications

If left untreated or inadequately managed, chorioamnionitis can lead to serious maternal, fetal, and neonatal problems.

Maternal complications

• Sepsis and septic shock.
• Post‑partum endometritis (uterine infection) – occurs in up to 5 % of women after chorioamnionitis.<sup>5</sup>
• Pelvic abscess or peritonitis.
• Increased risk of postpartum hemorrhage.

Fetal and neonatal complications

• Pre‑term birth and its cascade of complications (respiratory distress syndrome, intraventricular hemorrhage, necrotizing enterocolitis).
• Early‑onset neonatal sepsis – the leading cause of neonatal mortality in low‑resource settings.<sup>3</sup>
• Neonatal pneumonia, meningitis, or urinary tract infection.
• Long‑term neurologic sequelae (cerebral palsy, developmental delay) associated with severe intra‑uterine inflammation.

When to Seek Emergency Care

References

1. Mayo Clinic. Chorioamnionitis. Updated 2023. https://www.mayoclinic.org
2. Cleveland Clinic. Intrauterine Infection (Chorioamnionitis). 2022. https://my.clevelandclinic.org
3. World Health Organization. Neonatal sepsis. Fact sheet, 2021. https://www.who.int
4. CDC. Guidelines for Prevention of Perinatal Group B Streptococcal Disease. 2020 revision. https://www.cdc.gov
5. American College of Obstetricians and Gynecologists (ACOG). Infection in Pregnancy. Practice Bulletin No. 222, 2021.

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