Meconium-stained amniotic fluid-associated infectious morbidity: a randomized, double-blind trial of ampicillin-sulbactam prophylaxis

Meconium-stained amniotic fluid

Green-stained amniotic fluid, often referred to as meconium-stained amniotic fluid, is present in 5% to 20% of patients in labor and is considered an obstetric hazard. The condition has been attributed to the passage of fetal colonic content (meconium), intraamniotic bleeding with the presence of heme catabolic products, or both. The frequency of green-stained amniotic fluid increases as a function of gestational age, reaching approximately 27% in post-term gestation. Green-stained amniotic fluid during labor has been associated with fetal acidemia (umbilical artery pH <7.00), neonatal respiratory distress, and seizures as well as cerebral palsy. Hypoxia is widely considered a mechanism responsible for fetal defecation and meconium-stained amniotic fluid; however, most fetuses with meconium-stained amniotic fluid do not have fetal acidemia. Intraamniotic infection/inflammation has emerged as an important factor in meconium-stained amniotic fluid in term and preterm gestations, as patients with these conditions have a higher rate of clinical chorioamnionitis and neonatal sepsis. The precise mechanisms linking intraamniotic inflammation to green-stained amniotic fluid have not been determined, but the effects of oxidative stress in heme catabolism have been implicated. Two randomized clinical trials suggest that antibiotic administration decreases the rate of clinical chorioamnionitis in patients with meconium-stained amniotic fluid. A serious complication of meconium-stained amniotic fluid is meconium aspiration syndrome. This condition develops in 5% of cases presenting with meconium-stained amniotic fluid and is a severe complication typical of term newborns. Meconium aspiration syndrome is attributed to the mechanical and chemical effects of aspirated meconium coupled with local and systemic fetal inflammation. Routine naso/oropharyngeal suctioning and tracheal intubation in cases of meconium-stained amniotic fluid have not been shown to be beneficial and are no longer recommended in obstetrical practice. A systematic review of randomized controlled trials suggested that amnioinfusion may decrease the rate of meconium aspiration syndrome. Histologic examination of the fetal membranes for meconium has been invoked in medical legal litigation to time the occurrence of fetal injury. However, inferences have been largely based on the results of in vitro experiments, and extrapolation of such findings to the clinical setting warrants caution. Fetal defecation throughout gestation appears to be a physiologic phenomenon based on ultrasound as well as in observations in animals.

Antibiotics for neonates born through meconium-stained amniotic fluid

BACKGROUND

Approximately 1 in 10 pregnancies is affected by meconium passage at delivery, which can result in meconium aspiration syndrome (MAS). MAS can cause respiratory complications and, very rarely, death. Antibiotics have been prescribed for neonates exposed to meconium in amniotic fluid, with the intention of preventing infection due to potential bacterial contaminants.

OBJECTIVES

We conducted this review to assess the efficacy and safety of antibiotics for:1. prevention of infection, morbidity, and mortality among infants born through meconium-stained amniotic fluid (MSAF) who are asymptomatic at birth; and2. prevention of infection, morbidity, and mortality among infants born through MSAF who have signs and symptoms compatible with meconium aspiration syndrome (MAS).

SEARCH METHODS

We performed a literature search using the following databases: MEDLINE (1966 to July 2016); Embase (1980 to July 2016); the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to July 2016); and the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 7) in the Cochrane Library. We also searched clinical trials databases, conference proceedings, and reference lists of retrieved articles.

SELECTION CRITERIA

We included randomised and quasi-randomised controlled trials that compared antibiotics administered via any route versus placebo or no treatment for prevention of infection among neonates exposed to MSAF, or who developed MAS. We excluded cohort, case control, and any other non-randomised studies and applied no language restrictions. We included studies of term and preterm infants, and we included studies examining use of any antibacterial antibiotics. We included studies that reported on any outcomes of interest.

DATA COLLECTION AND ANALYSIS

We assessed the methodological quality of included trials by reviewing information provided in study reports and obtained by personal communication with study authors. We extracted data on relevant outcomes, estimated effect size, and reported values as risk ratios (RRs), risk differences (RDs), and mean differences (MDs), as appropriate. We conducted subgroup analyses for treatment of MAS and for prophylaxis (asymptomatic neonates exposed to meconium).

MAIN RESULTS

Four randomised controlled studies including a total of 695 participants were eligible for inclusion. Three studies evaluated neonates with MAS, and one study assessed asymptomatic neonates exposed to meconium in amniotic fluid. These studies exhibited varying degrees of methodological rigour: Two studies were at low risk of bias, and two were at unclear risk. We graded evidence derived from these studies as low quality. We downgraded overall evidence owing to the large number of participants lost to follow-up in one trial, the small sample sizes of all trials, and unclear methodological details provided for two trials.The primary outcome was risk of early- and late-onset neonatal sepsis. Antibiotics did not decrease the risk of sepsis in neonates with a diagnosis of MAS (RR 1.54, 95% confidence interval (CI) 0.27 to 8.96; RD 0.00, 95% CI -0.02 to 0.03; 445 participants, three studies; I² = 0%) nor in asymptomatic neonates exposed to meconium in amniotic fluid (RR 0.76, 95% CI 0.25 to 2.34; RD -0.01, 95% CI -0.07 to 0.04; 250 participants, one study; I² = 0%). Results show no significant differences in mortality or duration of stay in hospital between groups given antibiotics and control groups of symptomatic and asymptomatic neonates. One study in asymptomatic neonates reported a significant reduction in duration of mechanical ventilation for the control group compared with the antibiotic group (MD 0.26, 95% CI 0.15 to 0.37; 250 participants, one study; I² = 0%).

AUTHORS' CONCLUSIONS

Upon review of available evidence, we found no differences in infection rates following antibiotic treatment among neonates born through meconium-stained fluid and those with meconium aspiration syndrome. The overall quality of evidence is low owing to the small number of included studies. Well-controlled studies of adequate power are needed.

Infants at risk of cerebral palsy: a systematic review of outcomes used in Cochrane studies of pregnancy, childbirth and neonatology

OBJECTIVE

To systematically review meta-analyses (MAs) and randomised controlled trials (RCTs) of interventions for infants at risk of cerebral palsy (CP), to determine if consensus exists in study end-points.

METHODS

MAs within the "Neonatal" and "Pregnancy and Childbirth" Review Groups in Cochrane Database of Systematic Reviews (to June 2011) were included if they contained risk factors for CP as a study end-point, and were either published in 2010 or 2011 or cited >20 times in Sciverse Scopus. Up to 20 RCTs from each MA were included. Outcome measures, definitions and cut-points for ordinal groupings were extracted from MAs and RCTs and frequencies calculated.

RESULTS

Twenty-two MAs and 165 RCTs were appraised. High consistency existed in types of outcome domains listed as important in MAs. For 10/16 most frequently cited outcome domains, <50% of RCTs contributed data for meta-analyses. Low consistency in outcome definitions, measures, cut-points in RCTs and long-term follow-up prohibited data aggregation.

CONCLUSIONS

Variation in outcome measurement and long-term follow up has hampered the ability of RCTs to contribute data on important outcomes for CP, resulting in lost opportunities to measure the impact of maternal and neonatal interventions. There is an urgent need for and long-term follow up of these interventions and an agreed set of standardised and clinically relevant common data elements for study end-points.

Antibiotics for meconium-stained amniotic fluid in labour for preventing maternal and neonatal infections

BACKGROUND

Chorioamnionitis is more likely to occur when meconium-stained amniotic fluid (MSAF) is present. Meconium may enhance the growth of bacteria in amniotic fluid by serving as a growth factor, inhibiting bacteriostatic properties of amniotic fluid. Many adverse neonatal outcomes related to MSAF result from meconium aspiration syndrome (MAS). MSAF is associated with both maternal and newborn infections. Antibiotics may be an effective option to reduce such morbidity.

OBJECTIVES

The objective of this review is to assess the efficacy and side effects of prophylactic antibiotics for MSAF during labour in preventing maternal and neonatal infections.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2014). 

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing prophylactic antibiotics with placebo or no treatment during labour for women with MSAF.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy.

MAIN RESULTS

We included two studies with 362 pregnant women. Both studies compared ampicillin-sulbactam (N = 183) versus normal saline (N = 179) in pregnant women with MSAF. Prophylactic antibiotics appeared to have no statistically significant reduction in the incidence of neonatal sepsis (risk ratio (RR) 1.00, 95% CI 0.21 to 4.76), neonatal intensive care unit (NICU) admission (RR 0.83, 95% CI 0.39 to 1.78) and postpartum endometritis (RR 0.50, 95% CI 0.18 to 1.38). However, there was a significant decrease in the risk of chorioamnionitis (RR 0.36, 95% CI 0.21 to 0.62). No serious adverse effects were reported. Drug resistance, duration of mechanical ventilation and duration of admission to NICU/hospital were not reported. Most of the domains for risk of bias were at low risk of bias for one study and at unclear risk of bias for the other study. The quality of the evidence using GRADE was low for neonatal sepsis, postpartum endometritis, and neonatal mortality and morbidity prior to discharge (Neonatal intensive care admissions) and of moderate quality for chorioamnionitis.

AUTHORS' CONCLUSIONS

Current evidence indicates that compared to placebo, antibiotics for MSAF in labour may reduce chorioamnionitis. There was no evidence that antibiotics could reduce postpartum endometritis, neonatal sepsis and NICU admission. This systematic review identifies the need for more well-designed, adequately powered RCTs to assess the effect of prophylactic antibiotics in the incidence of maternal and neonatal complications.

Consequences of meconium stained amniotic fluid: what does the evidence tell us?

BACKGROUND

Meconium stained amniotic fluid (MSAF) is common and associated with meconium aspiration syndrome (MAS). Other consequences of meconium passage before birth are less well understood.

METHODS

We reviewed the literature for original papers reporting on outcomes associated with MSAF.

FINDINGS

Among preterm infants MSAF is more prevalent than previously believed and is associated with higher neonatal morbidity. Intrauterine exposure to meconium is associated with inflammation of tissues of the lung, chorionic plate and umbilical vessels and through various mechanisms may contribute to neonatal morbidity, independent of MAS. No compelling evidence supported an association between MSAF and increased neurological impairment, including early seizure activity.

Bacteria and endotoxin in meconium-stained amniotic fluid at term: could intra-amniotic infection cause meconium passage?

BACKGROUND

Meconium-stained amniotic fluid (MSAF) is a common occurrence among women in spontaneous labor at term, and has been associated with adverse outcomes in both mother and neonate. MSAF is a risk factor for microbial invasion of the amniotic cavity (MIAC) and preterm birth among women with preterm labor and intact membranes. We now report the frequency of MIAC and the presence of bacterial endotoxin in the amniotic fluid of patients with MSAF at term.

MATERIALS AND METHODS

We conducted a cross-sectional study including women in presumed preterm labor because of uncertain dates who underwent amniocentesis, and were later determined to be at term (n = 108). Patients were allocated into two groups: (1) MSAF (n = 66) and (2) clear amniotic fluid (n = 42). The presence of bacteria was determined by microbiologic techniques, and endotoxin was detected using the Limulus amebocyte lysate (LAL) gel clot assay. Statistical analyses were performed to test for normality and bivariate comparisons.

RESULTS

Bacteria were more frequently present in patients with MSAF compared to those with clear amniotic fluid [19.6% (13/66) versus 4.7% (2/42); p < 0.05]. The microorganisms were Gram-negative rods (n = 7), Ureaplasma urealyticum (n = 4), Gram-positive rods (n = 2) and Mycoplasma hominis (n = 1). The LAL gel clot assay was positive in 46.9% (31/66) of patients with MSAF, and in 4.7% (2/42) of those with clear amniotic fluid (p < 0.001). After heat treatment, the frequency of a positive LAL gel clot assay remained higher in the MSAF group [18.1% (12/66) versus 2.3% (1/42), p < 0.05]. Median amniotic fluid IL-6 concentration (ng/mL) was higher [1.3 (0.7-1.9) versus 0.6 (0.3-1.2), p = 0.04], and median amniotic fluid glucose concentration (mg/dL) was lower [6 (0-8.9) versus 9 (7.4-12.6), p < 0.001] in the MSAF group, than in those with clear amniotic fluid.

CONCLUSION

MSAF at term was associated with an increased incidence of MIAC. The index of suspicion for an infection-related process in postpartum women and their neonates should be increased in the presence of MSAF.

The utility of amnioinfusion in the prophylaxis of meconium-stained amniotic fluid infectious morbidity

Objectives: To evaluate the utility of intrapartum amnioinfusion (AI) in reducing the infectious morbidity of patients with meconium-stained fluid (MSF). Previous studies have shown increased intraamniotic infection (IAI) and postpartum endometritis (PPE) rates in patients with MSF. Intraamniotic infection has been reduced with the prophylactic administration of ampicillin–sulbactam in MSF. Intraamniotic infection and PPE have been reduced with the use of AI in patients with clear fluid. No investigators have specifically examined the efficacy of AI in reducing meconium-stained, amniotic-fluid-associated infectious morbidity.

Methods: A retrospective cohort study of all cases of MSF was conducted and included patients who delivered at Louisiana State University Medical Center–Shreveport during the one-year period from January to December 1996. Patients were identified from the perinatal database by the diagnosis code of MSF. The medical records were reviewed to determine the consistency of MSF and the presence or absence of infectious morbidity. Patient demographics, labor characteristics, and various risk factors for infection were sought. The main outcome measures were the occurrence of clinical IAI or PPE. Statistical analysis included two-tailed unpaired t-test, X², ANOVA, and Fisher exact test when appropriate.

Results: Two hundred seventy-three medical records of patients with MSF were studied. One hundred twenty nine patients received AI, and 144 did not receive AI. No significant differences in demographics, labor characteristics, or outcome variables were noted between the two groups. The incidences of IAI were 18.6% and 24.3%, P = 0.13, in the AI and non-AI groups, respectively. Postpartum endometritis occurred in 22.5% of AI patients and 21.5% of non-AI patients, P = 0.97.

Conclusions: The use of AI confers no benefit for the reduction of infectious morbidity in patients with MSF.

Antibiotics for meconium-stained amniotic fluid in labour for preventing maternal and neonatal infections

BACKGROUND

Chorioamnionitis is more likely to occur when meconium-stained amniotic fluid (MSAF) is present. Meconium may enhance the growth of bacteria in amniotic fluid by serving as a growth factor, inhibiting bacteriostatic properties of amniotic fluid. Many adverse neonatal outcomes related to MSAF result from Meconium Aspiration Syndrome (MAS). MSAF is associated with both maternal and newborn infections. Antibiotics may be an effective option to reduce such morbidity.

OBJECTIVES

The objective of this review is to assess the efficacy and side effects of prophylactic antibiotics for MSAF during labour in preventing maternal and neonatal infections.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2010). 

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing prophylactic antibiotics with placebo or no treatment during labour for women with MSAF.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the results of the only available trial and extracted data on maternal and neonatal outcomes.

MAIN RESULTS

We included one study with 120 pregnant women. It compared ampicillin-salbactam (N = 60) versus normal saline (N = 60) in pregnant women with MSAF. Prophylactic antibiotics appeared to have no statistically significant reduction in the incidence of neonatal sepsis (risk ratio (RR) 1.00, 95% CI 0.21 to 4.76), neonatal intensive care unit (NICU) admission (RR 0.83, 95% CI 0.39 to 1.78) and postpartum endometritis (RR 0.50, 95% CI 0.18 to 1.38). However, significant decrease in the risk of chorioamnionitis (RR 0.29, 95% CI 0.10 to 0.82). No serious adverse effects were reported.

AUTHORS' CONCLUSIONS

Current evidence indicates that compared to placebo, antibiotics for MSAF in labour may reduce chorioamnionitis. There was no evidence that antibiotics could reduce postpartum endometritis, neonatal sepsis and NICU admission. This systematic review identifies the need for more well-designed, adequately powered RCTs to assess the effect of prophylactic antibiotics in the incidence of maternal and neonatal complications.

Diagnosis and management of clinical chorioamnionitis

Chorioamnionitis is a common complication of pregnancy associated with significant maternal, perinatal, and long-term adverse outcomes. Adverse maternal outcomes include postpartum infections and sepsis whereas adverse infant outcomes include stillbirth, premature birth, neonatal sepsis, chronic lung disease, and brain injury leading to cerebral palsy and other neurodevelopmental disabilities. Research in the past 2 decades has expanded understanding of the mechanistic links between intra-amniotic infection and preterm delivery as well as morbidities of preterm and term infants. Recent and ongoing clinical research into better methods for diagnosing, treating, and preventing chorioamnionitis is likely to have a substantial impact on short and long-term outcomes in the neonate.

Meconium-stained amniotic fluid is associated with puerperal infections

OBJECTIVE

The purpose of this study was to determine whether meconium-stained amniotic fluid is associated with puerperal infection and whether the quality of the meconium is further associated with this risk.

STUDY DESIGN

We designed a retrospective cohort study of all deliveries beyond 37 weeks gestational age from 1992 to 2002 at a single community hospital. Data were collected on rates of chorioamnionitis, endomyometritis, quality of amniotic fluid, and length of labor and analyzed with bivariate and multivariate analyses.

RESULTS

We found that, among the 43,200 women who were delivered at term, 18.9% of the women had meconium staining (8.8% thin, 5.5% moderate, 4.6% thick). Compared with deliveries with clear amniotic fluid, those with meconium-stained amniotic fluid had higher rates of chorioamnionitis (2.3% vs 4.1%, P<.001) and endomyometritis (1.0% vs 1.7%, P<.001). Further, the severity of meconium staining was associated with increased rates of infection.

CONCLUSION

We found that the presence and severity of meconium-stained amniotic fluid is associated with puerperal infection even when being controlled for confounders.

Severe meconium aspiration syndrome is not caused by aspiration of meconium

Meconium aspiration syndrome can present clinically with different degrees of severity, ranging from a mild form of respiratory compromise to severe forms that may result in perinatal death despite mechanical ventilation or extracorporeal membrane oxygenation. However, advances in our knowledge concerning meconium aspiration syndrome have revealed that most cases of severe meconium aspiration syndrome are not in fact causally related to the aspiration of meconium but rather are caused by other pathologic processes occurring in utero, primarily chronic asphyxia and infection. Proper understanding of the causative processes underlying fetal or neonatal compromise in these cases is essential to direct future research into preventive or therapeutic treatments and for counseling of the parents of an affected child.

Amnioinfusion for meconium-stained liquor

Amnioinfusion reduces the risk of meconium aspiration by the infants of women with thick meconium staining of the amniotic fluid. The benefits are clear in facilities with high baseline rates of meconium aspiration, and are therefore likely to outweigh the risk of uncommon but serious maternal side-effects. Larger randomized trials are needed to determine more precisely the relative risks and benefits in facilities with low baseline rates of meconium aspiration. The addition of antibiotics to the infusate has not been shown to reduce the risk of sepsis related to meconium.

Maternal and neonatal infection rates with three different protocols for prevention of group B streptococcal disease

OBJECTIVES

We compared maternal and neonatal infection rates under 3 different group B streptococcal prevention strategies and also evaluated reasons for each protocol's failures in preventing neonatal disease.

STUDY DESIGN

Women who were delivered at our center from August 1, 1991, through April 30, 1998, were managed by 1 of 3 protocols for prevention of early-onset neonatal group B streptococcal infection: a selective screening protocol, The American College of Obstetricians and Gynecologists protocol, and the Centers for Disease Control and Prevention-recommended universal screening strategy. We compared maternal infection rates and neonatal group B streptococcal infection rates under each protocol. We also compared reasons for each protocol's failures in preventing neonatal infection.

RESULTS

Clinical chorioamnionitis rates were 7.4% with selective screening, 7.7% under The American College of Obstetricians and Gynecologists' protocol, and 5.2% with universal screening (relative risk 0.7, 95% confidence interval 0.6-0.8). Endometritis rates were 4.0% with selective screening, 4.6% with The American College of Obstetricians and Gynecologists protocol, and 2. 8% with universal screening (relative risk 0.7, 95% confidence interval 0.6-0.8). Overall neonatal group B streptococcal infection rates were lower under the 2 more recent strategies, but not significantly so. Despite the ability of universal screening to find more women at risk for group B streptococcal transmission, half of the neonatal infections under this protocol occurred when the mothers were not considered candidates for prophylaxis.

CONCLUSIONS

The Centers for Disease Control and Prevention-endorsed universal screening strategy for group B streptococcal infection prevention was associated with significantly lower rates of clinical chorioamnionitis and endometritis than were the other strategies. We were unable to document statistically significant improvement in neonatal outcome under the universal screening protocol.

Prophylactic cefazolin in amnioinfusions administered for meconium-stained amniotic fluid

OBJECTIVE

To determine if amnioinfusion with an antibiotic solution decreased the rate of clinical chorioamnionitis and puerperal endometritis in patients with meconium-stained amniotic fluid.

METHODS

Patients in labor at 36 weeks of gestation or greater with singleton pregnancies and meconium-stained amniotic fluid were randomized to receive either cefazolin, 1 g/1,000 mL, of normal saline (n = 90) or normal saline (n = 93) amnioinfusion. Rates of clinically diagnosed chorioamnionitis and endometritis and of suspected and culture-proven neonatal infection were determined.

RESULTS

Between the study and control groups, the incidences of clinical chorioamnionitis (7.8% vs. 8.6%), endometritis (2.4% vs. 3.5%), aggregate intrauterine infection (10.0% vs. 11.8%), suspected neonatal infection (17.8% vs. 21.5%), and proven neonatal infection (0.0% vs. 2.2%) were not significantly different.

CONCLUSIONS

Prophylactic use of cefazolin in amnioinfusions did not significantly reduce rates of maternal or neonatal infection in patients with meconium-stained amniotic fluid.

Meconium stained amniotic fluid in very low risk pregnancies at term gestation

OBJECTIVE

To determine the prevalence and clinical significance of meconium stained amniotic fluid (MSAF) in a low risk population at term gestation and to investigate whether MSAF is a predictor for intrapartum and neonatal morbidity.

METHODS

A very low risk population including 37 085 consecutive deliveries at term composed the study population. A cross-sectional study was conducted and two groups of patients were identified according to the presence (n=6164) or absence (n=30921) of meconium in the amniotic fluid at delivery and the outcomes of the two groups compared.

RESULTS

The prevalence of MSAF was 16.6%. The incidence of cesarean section (5.6% vs 2.3% P<0.01), instrumental deliveries (3.2% vs 1.8% P<0.01), fetal distress (6.5% vs. 2.1% P<0.01), clinical chorioamnionitis (0.2% vs. 0.1% P<0.01), post-partum infection (0.5% vs. 0.2% P<0.01), 1-minute Apgar score <3 (1.9% vs. 1.1% P<0.01), small for gestational age (7.4% vs. 6.4% P<0.01). was significantly higher in the MSAF compared with the clear amniotic fluid group. Intrapartum and neonatal mortality in this low risk population was significantly higher in the MSAF group (1.7/1000) compared with women with clear AF (0.3/1000).

CONCLUSIONS

MSAF in a low risk population at term gestation is a predictor for adverse perinatal outcome and peripartum complications.