Amniotic Sludge and Prematurity: Systematic Review and Meta-analysis

OBJECTIVE

 To perform a systematic review and meta-analysis of studies on maternal, fetal, and neonatal outcomes of women with singleton pregnancies, after spontaneous conception, and with the diagnosis of amniotic sludge before 37 weeks of gestational age.

DATA SOURCES

 We conducted a search on the PubMed, Cochrane, Bireme, and Theses databases until June 2022.

SELECTION OF STUDIES

 Using the keywords intra-amniotic sludge or fluid sludge or echogenic particles, we found 263 articles, 132 of which were duplicates, and 70 were discarded because they did not meet the inclusion criteria.

DATA COLLECTION

 The articles retrieved were analyzed by 2 reviewers; 61 were selected for full-text analysis, 18 were included for a qualitative analysis, and 14, for a quantitative analysis.

DATA SYNTHESIS

 Among the maternal outcomes analyzed, there was an increased risk of preterm labor (95% confidence interval [95%CI]: 1.45-2.03), premature rupture of ovular membranes (95%CI: 1.99-3.79), and clinical (95%CI: 1.41-6.19) and histological chorioamnionitis (95%CI: 1.75-3.12). Regarding the fetal outcomes, there was a significant increase in the risk of morbidity (95%CI: 1.80-3.17), mortality (95%CI: 1.14-18.57), admission to the Neonatal Intensive Care Unit (NICU; 95%CI: 1.17-1.95), and neonatal sepsis (95%CI: 2.29-7.55).

CONCLUSION

 The results of the present study indicate that the presence of amniotic sludge is a risk marker for preterm delivery. Despite the heterogeneity of the studies analyzed, even in patients with other risk factors for prematurity, such as short cervix and previous preterm delivery, the presence of amniotic sludge increases the risk of premature labor. Moreover, antibiotic therapy seems to be a treatment for amniotic sludge, and it may prolong pregnancy.

Characterization of amniotic fluid sludge in preterm and term gestations

OBJECTIVE

To describe the characteristics of amniotic fluid sludge obtained from patients in term and preterm gestations.

METHODS

This cross-sectional study included patients with dense aggregates of particulate matter detected in amniotic fluid, observed with transvaginal sonography. All patients were in labor and had an impending delivery, either preterm or at term. Echogenic material contained within amniotic fluid was retrieved transvaginally by needle amniotomy under direct visualization. The amniotic fluid analysis consisted of a Gram stain, cultures for aerobic/anaerobic bacteria and genital mycoplasmas, and a white blood cell count.

RESULTS

Twenty-five patients ranging from 18 to 41 weeks of gestation were included in the study. We observed the following: (1) the appearance of amniotic fluid was consistent with pus-like material, vernix, or meconium by naked eye examination; (2) samples collected before 33 weeks of gestation (n = 13) had a pus-like appearance; however, after this gestational age, most of the samples [83% (10/12)] appeared to be consistent with vernix; (3) amniotic fluid cultures were positive for microorganisms in 13 patients, of which 10 were preterm gestations before 33 weeks; (4) the most frequent microorganisms retrieved by culture were genital mycoplasmas (Ureaplasma urealyticum [46% (6/13)]), followed by Mycoplasma hominis [31% (4/13)] and Candida albicans [15% (2/13)]; and (5) patients with sonographic particulate matter in preterm gestations frequently presented acute histologic chorioamnionitis and funisitis, but these conditions were rare in patients at term.

CONCLUSION

The nature of amniotic fluid particulate material varies as a function of gestational age. The material obtained in preterm gestations is frequently related to an inflammatory process, while that obtained at term is often consistent with vernix and appears to represent a maturational process.

Evolving cervical imaging technologies to predict preterm birth

Preterm birth, defined as delivery at less than 37 weeks' gestation, increases maternal-fetal morbidity and mortality and places heavy financial and emotional burdens on families and society. Although premature cervical remodeling is a major factor in many preterm deliveries, how and why this occurs is poorly understood. This review describes existing and emerging imaging techniques and their advantages and disadvantages in assessing cervical remodeling. Brightness mode (B-mode) ultrasound is used to measure the cervical length, currently the gold standard for determining risk of preterm birth. Several new B-mode ultrasound techniques are being developed, including measuring attenuation, cervical gland area, and the cervical consistency index. Shear wave speed can differentiate between soft (ripe) and firm (unripe) cervices by measuring the speed of ultrasound through a tissue. Elastography provides qualitative information regarding cervical stiffness by compressing the tissue with the ultrasound probe. Raman spectroscopy uses a fiber optic probe to assess the biochemical composition of the cervix throughout pregnancy. Second harmonic generation microscopy uses light to quantify changes in collagen fiber structure and size during cervical maturation. Finally, photoacoustic endoscopy records light-induced sound to determine optical characteristics of cervical tissue. In the long term, a combination of several imaging approaches, combined with consideration of clinical epidemiologic characteristics, will likely be required to accurately predict preterm birth.

Presence of amniotic fluid sludge and pregnancy outcomes: A systematic review

INTRODUCTION

Several studies acknowledge that the presence of amniotic fluid sludge (AFS) is an independent predictive factor for preterm birth. In the present systematic review, we summarize research that focuses on the comparison of pregnancy outcomes among women with and without AFS.

MATERIAL AND METHODS

Medline, Scopus, Clinicaltrials.gov, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), and Google Scholar databases were systematically searched from inception. Both observational and randomized controlled studies were considered eligible provided that they reported data on pregnancy outcomes among women with and without AFS. Outcomes were not meta-analyzed because of the high heterogeneity in terms of selected population and outcome reporting.

RESULTS

Seventeen studies of 2432 women were included in this review. Six studies evaluated women at high risk for preterm birth. Pregnancies complicated by AFS had a lower gestational age at delivery and increased incidence of preterm delivery at <37 weeks. Neonatal death rates and admission to the Neonatal Intensive Care Unit were also increased. Evidence in low-risk women, those with signs of preterm labor, in those carrying twins, and in women with cervical cerclage or Arabin pessary was extremely limited.

CONCLUSIONS

Women with AFS seem to deliver at an earlier gestational age, and preterm birth rates are also increased. Limited data seem to point to neonatal morbidity and mortality being increased. However, the presence of a direct association should not be assumed because the evidence is not adjusted for the presence of confounders.

The role of noninvasive diagnostic imaging in monitoring pregnancy and detecting patients at risk for preterm birth: a review of quantitative approaches

Preterm birth (PTB) is the leading cause of neonatal morbidity and mortality worldwide. The ability to predict patients at risk for preterm birth remains a major health challenge. The currently available clinical diagnostics such as cervical length and fetal fibronectin may detect only up to 30% of patients who eventually experience a spontaneous preterm birth. This paper reviews ongoing efforts to improve the ability to conduct a risk assessment for preterm birth. In particular, this work focuses on quantitative methods of imaging using ultrasound-based techniques, magnetic resonance imaging, and optical imaging modalities. While ultrasound imaging is the major modality for preterm birth risk assessment, a summary of efforts to adopt other imaging modalities is also discussed to identify the technical and diagnostic limits associated with adopting them in clinical settings. We conclude the review by proposing a new approach using combined photoacoustic, ultrasound, and elastography as a potential means to better assess cervical tissue remodeling, and thus improve the detection of patients at-risk of PTB.

Effect of Antibiotic Treatment of Amniotic Fluid Sludge

BACKGROUND

Amniotic fluid sludge refers to the sonographic presence of echogenic, free-floating aggregates of debris located within the amniotic cavity near the internal cervical os of women with intact membranes. Clinically, it is independently associated with increased obstetric, infectious, and neonatal morbidity, including: short cervix, chorioamnionitis, and an increased risk of preterm birth. It is thought to be infectious in nature and has been described as an intrauterine bacterial biofilm. There is little evidence on the impact of treatment with antibiotics on outcome.

OBJECTIVE

To determine whether outpatient antibiotics administered to women with amniotic fluid sludge would reduce preterm birth risk compared to no antibiotic treatment.

MATERIALS AND METHODS

This was a retrospective cohort study of all patients diagnosed with amniotic fluid sludge by transvaginal sonography between 15 and 25 weeks' gestation in the outpatient ultrasound unit at a single academic center between 2010 and 2017. Patients were segregated according to whether they were treated with oral antibiotics at the time of diagnosis. Women with multiple gestation, fetal anomalies, preterm rupture of membranes prior to initial diagnosis of amniotic fluid sludge, and active preterm labor placenta previa and/or suspected accreta were excluded from analysis. Primary outcome of preterm birth at less than 37 weeks' gestation was compared by univariate and regression analysis to control for potential co-linear and/or confounding variables. Additional outcomes were compared by univariate analysis.

RESULTS

A total of 181 patients were initially identified, and 97 patients met inclusion criteria. Of these patients, 51 were treated with oral antibiotics (46 azithromycin and 5 moxifloxacin), and 46 were not treated. The overall incidence of preterm birth at <37 weeks was 49.4 % (48 of 97) and preterm birth <28 weeks was 22.7% (22 of 97). There was no significant difference in preterm birth, either at <37 weeks (P = .47) or <28 weeks (P = .83) between the treated and untreated women. After adjusting for race, body mass index, tobacco use, cervical length, and preterm birth history, antibiotic treatment did not reduce the risk of preterm birth (adjusted odds ratio, 1.3; confidence interval, 0.77-1.9). No differences were seen in the incidence of preterm premature rupture of membranes (P = .94) or median latency from diagnosis to delivery (P = .47). Birthweight (P = .99), sepsis (P = .53), intraventricular hemorrhage (P = .95), and neonatal intensive care unit (NICU) admission (P = .08) were not affected by antibiotic treatment. Antibiotic treatment did not affect the incidence of either clinical or histologic chorioamnionitis (P = .92 and .14, respectively) or histologic stage 2-3 maternal or fetal inflammation (P = .94 and 0.58, respectively). Sonographic resolution of amniotic fluid sludge on first subsequent scan was seen in 34% of antibiotic-treated women and 43% of untreated women (P = .42). There was no difference in latency from diagnosis to delivery or mean gestational age at delivery according to whether sludge resolved or persisted at the first subsequent scan (P = .14 for each).

CONCLUSION

Antibiotic treatment of amniotic fluid sludge is not associated with a reduction in premature birth. Likewise, antibiotic treatment of amniotic fluid sludge was not associated with improvement in other obstetric, neonatal, or pathologic variables. These findings suggest that the presumed infectious nature of sludge and subsequent adverse outcomes are not treated or improved by administration of azithromycin following midtrimester sonographic diagnosis.

Association of amniotic fluid sludge with preterm labor and histologic chorioamnionitis in pregnant Japanese women with intact membranes: A retrospective study

AIM

The presence of amniotic fluid sludge has been identified as a risk factor for preterm birth. We sought to validate the clinical characteristics of amniotic fluid sludge in Japanese pregnant women with preterm labor and intact membranes.

METHODS

This was a retrospective study of 54 patients. The presence of amniotic fluid sludge was confirmed using transvaginal ultrasonography data during pregnancy. The following data were collected: gestational age, the presence of histologic chorioamnionitis, time from the diagnosis of threatened premature labor to delivery, oncofetal fibronectin (onfFN) levels, C-reactive protein peak value levels, cervical length at the time of onset of threatened premature labor and types of neonatal complications.

RESULTS

Significant differences (P = 0.03) were observed in the age at delivery in relation to the presence of amniotic sludge: delivery occurred at 28.3 ± 4.5 weeks and 31.7 ± 4.3 weeks in sludge positive patients and sludge-negative patients, respectively. Presence of sludge in patients diagnosed with histological chorioamnionitis at <37 weeks of gestation differed significantly (P = 0.01): sludge-positive, 81.8%; sludge-negative, 20.9%. Among the sludge-positive patients, 100% were positive for serum onfFN (≥50 ng/mL), whereas only 54% of sludge-negative patients were positive for serum onfFN (P = 0.03). Presence of amniotic fluid sludge did not significantly affect neonatal complications.

CONCLUSION

Our results confirmed previous findings that amniotic fluid sludge is a self-determining risk factor for preterm birth and chorioamnionitis in pregnant Japanese women.

Maternal Supplementation of Low Dose Fluoride Alleviates Adverse Perinatal Outcomes Following Exposure to Intrauterine Inflammation

Maternal periodontal disease has been linked to adverse pregnancy sequelae, including preterm birth (PTB); yet, root planing and scaling in pregnancy has not been associated with improved perinatal outcomes. Fluoride, a cariostatic agent, has been added to drinking water and dental products to prevent caries and improve dental health. The objective of this study was to explore the effects of fluoride supplementation using a mouse model of preterm birth and perinatal sequalae. Pregnant mice were fed low dose fluoride (LF^-) or high dose fluoride (HF^-) and given intrauterine injections of lipopolysaccharide (LPS) or phosphate-buffered saline (PBS). We found that LPS + LF^- significantly increased livebirths, pup survival, and litter size compared to LPS alone. Moreover, offspring from the LPS + LF^- group exhibited significantly improved neuromotor performance and more neurons compared to those from the LPS group. Additionally, LF^- treatment on human umbilical vein endothelial cells (HUVECs) increased cell viability and decreased oxidative stress after treatment with LPS. Collectively, our data demonstrates that maternal LF^- supplementation during pregnancy postpones the onset of PTB, acts to increase the liveborn rate and survival time of newborns, and reduces perinatal brain injury in cases of intrauterine inflammation.

The presence of amniotic fluid sludge in pregnant women with a short cervix: an independent risk of preterm delivery

Objective: To examine whether the presence of amniotic fluid sludge (AFS) could increase the risk of preterm delivery in women with a cervical length (CL) of less than 25 mm.Materials and methods: This is a retrospective cohort study of 110 women who were 14-30 weeks pregnant with a singleton gestation and a CL of less than 25 mm. The primary outcomes were defined as preterm delivery before 34 weeks and preterm delivery before 37 weeks. The secondary outcome was defined as preterm premature rupture of membranes (PPROM) prior to preterm delivery. Risk factors for preterm delivery were defined as AFS, subchorionic hematoma (SCH), history of preterm delivery, CL of less than 20 mm, and CL of less than 15 mm. A univariate analysis was performed to assess the primary and secondary outcomes according to the presence or absence of each risk factor. A multiple logistic regression analysis was performed to evaluate the parameters, using a significance of p < .05 on the univariate analysis to examine whether they were independent risk factors.Results: A significantly increased risk of preterm delivery was found in the group of women with AFS who actually did deliver prior to 34 weeks (p < .001; odds ratio [OR] 6.44; 95% confidence interval [CI] 2.51-16.5), prior to 37 weeks (p = .001; OR 4.46; 95% CI 1.76-11.3), and who had PPROM (p < .001; OR 4.96; 95% CI 2.00-12.3). A multivariate logistic regression analysis was performed in the women with AFS who experienced preterm delivery before 34 weeks, in the women with a CL less than 20 mm, and in the women with a CL less than 15 mm. The results showed that AFS was an independent risk factor for preterm delivery before 34 weeks (p = .001; OR 5.86; 95% CI 2.11-16.3).Conclusion: The presence of AFS was an independent risk factor for preterm delivery before 34 weeks in women with a CL less than 25 mm.

Transabdominal collection of amniotic fluid "sludge" and identification of Candida albicans intra-amniotic infection

A G3P2 patient who conceived while using an intrauterine contraceptive device (IUD) presented at 20 weeks of gestation with mild irregular uterine contractions and vaginal bleeding. Sonographic examination at admission showed the presence of dense amniotic fluid "sludge" and a long sonographic uterine cervix (42 mm). To assess the microbiologic significance of amniotic fluid "sludge", we performed a transabdominal amniocentesis. The procedure was performed under real-time ultrasound, and fluid resembling pus at gross examination was noted. Rapid amniotic fluid analysis showed the presence of a high white blood cell count and structures resembling hyphae. Amniotic fluid cultures were positive for Candida albicans. Treatment was begun with broad-spectrum antibiotics, including Fluconazole, upon the visualization of pus in the "sludge" material because of the presence of hyphae in the Gram stain. Despite treatment, the patient went into spontaneous preterm labor and delivered five days after admission. Placental examination revealed acute fungal histologic chorioamnionitis and funisitis. This represents the first report of transabdominal collection and analysis of amniotic fluid "sludge" and the microbiologic detection of Candida albicans in this material. This report provides evidence that transabdominal retrieval of "sludge" is possible and may be of significant value for patient management and selection of antimicrobial agents.

Amniotic fluid sludge as a marker of intra-amniotic infection and histological chorioamnionitis in cervical insufficiency: a report of four cases and literature review

Amniotic fluid sludge (AFS) is defined as the presence of particulate matter in the amniotic fluid in close proximity to the cervix. Although its prevalence is known to correlate with the risk of preterm delivery, initial reports describe a strong association between AFS and microbial invasion of the amniotic cavity (MIAC) and histological chorioamnionitis. However, AFS is also present in uncomplicated pregnancies, and its prevalence appears to increase with gestational age. Recent evidence debates the usefulness of AFS as a marker of early preterm delivery risk. We present four cases with AFS diagnosed by transvaginal ultrasound at admission for cervical insufficiency between 20 and 24 weeks of gestation, with confirmed lower genital tract and intra-amniotic infections by amniocentesis and histological chorioamnionitis and funisitis. Our findings reinforce the presence of AFS as a useful marker of MIAC, chorioamnionitis and funisitis that increase the likelihood of preterm delivery at an extreme gestational age.

Amniotic fluid "sludge" is an independent risk factor for preterm delivery

OBJECTIVE

To determine the prevalence and the clinical significance of amniotic fluid "sludge" (AFS) in asymptomatic patients at low and high risk for spontaneous preterm delivery.

METHOD

A prospective cohort study was conducted on 195 singleton pregnancies at low or high risk for preterm birth (PTB) between the 16th and 26th weeks. Cervical length (CL) <25 mm and the presence of AFS were evaluated. The risk for preterm delivery before 28, 32, 35 and 37 weeks were determined according to the presence of AFS, CL < 25 mm and history of high risk for PTB. Stepwise logistic regression was performed to compare variables.

RESULTS

AFS was an independent risk factor for PTB < 35 weeks (OR: 3.08, 95% CI: 1.13-8.34, p = 0.027) but not for PTB < 28, 32 and 37 weeks. CL < 25 mm was an independent risk factor for PTB < 28, 32 and 35 but not for PTB < 37 weeks. High risk for PTB was not found as an independent risk factor for PTB.

CONCLUSION

AFS is an independent risk factor for PTB before 35 weeks.

Clinical significance of amniotic fluid sludge in twin pregnancies with a short cervical length

OBJECTIVE

The objective of the study was to determine the clinical significance of amniotic fluid (AF) sludge in twin pregnancies with a short cervix.

STUDY DESIGN

We evaluated twin pregnancies with a short cervical length that had an ultrasound between 16 and 26 weeks (n = 78). Pregnancy outcomes in those with sludge (n = 27) and those without (n = 51) were compared. Outcome variables included gestational age at delivery, premature rupture of the membranes, chorioamnionitis, funisitis, composite neonatal morbidity, and perinatal death. For statistical analysis, the first-born (A) and second-born (B) twins were studied separately.

RESULTS

The prevalence of AF sludge was 34.6% (27 of 78). Pregnancies with sludge delivered earlier (27.2 ± 5.6 weeks vs 31.0 ± 4.05 weeks, P < .01) and had a higher rate of extreme prematurity (<26 weeks: 52.2% [12 of 23] vs 15.6% [5 of 32]; P < .01). Both twins had higher rates of histological chorioamnionitis (twin A, 50.0% [13 of 26] vs 12.8% [6 of 47]; P < .01; twin B, 42.3% [11 of 26] vs 13.3% [6 of 45]; P < .01) and neonatal death (twin A, 33.3% [9 of 27] vs 3.9% [2 of 51]; P < .01; twin B, 33.3% [9 of 27] vs 6.0% [3 of 50]; P = .01). Higher rates of funisitis (23.1% [6 of 26] vs 4.3% [2 of 47]; P = .02) and composite neonatal morbidity were observed for twin A only (66.7% [14 of 21] vs 37.5% [18 of 48]; P = .04).

CONCLUSION

The presence of AF sludge in twin pregnancies with a short cervix is a risk factor for extreme prematurity, histological chorioamnionitis, and perinatal death. Twin A had higher rates of funisitis and neonatal morbidity in the presence of AF sludge.