A Review of the Literature: Amniotic Fluid "Sludge"-Clinical Significance and Perinatal Outcomes

Introduction: This paper seeks to report and emphasize the most important aspects from the scientific literature about the diagnostic accuracy of the amniotic fluid "sludge" (AFS), its characterization, its treatment, and its association with premature birth. AFS is defined as a floating freely hyperechogenic material within the amniotic cavity in the proximity of the internal os. Materials and Methods: We conducted a search on Pubmed and Google Scholar for relevant articles on the subject of amniotic fluid "sludge" published until January 2024. Searches were focused on articles about diagnosis, treatment, maternal and neonatal outcomes, risk of preterm birth, and case reports. The full-text reading stage resulted in the inclusion of 51 studies. Results: AFS is independently associated with chorioamnionitis, preterm delivery, short cervix, increased risk of neonatal morbidity, and cervical insufficiency. This hyperechogenic free-floating material is linked with preterm birth before 32 weeks of gestation, especially when it is associated with short cervical length. Discussion: Present studies identify some controversial benefits of antibiotics in reducing the incidence of preterm birth in women with AFS. Nevertheless, in this review, we can conclude that the presence of AFS in pregnancy is a marker for the microbial invasion of the amniotic cavity, as it is associated with preterm birth. Further studies on a larger group of patients are necessary to clarify and exactly define the terms of managing these cases.

Antibiotic therapy in patients with amniotic fluid sludge and risk of preterm birth: a meta-analysis

PURPOSE

Amniotic Fluid Sludge (AFS) has been theorized to be sonographic evidence of an underlying infection/inflammation and studies have concluded that approximately 10% of the patients who show signs of preterm labor with intact membranes have an underlying intraamniotic infection, mostly subclinical, carrying an increased risk for preterm birth with its subsequent neonatal and maternal complications. The purpose of the present systematic review is to evaluate the impact of antibiotic therapy on preterm birth rates of women diagnosed with AFS.

METHODS

We searched Medline, Scopus, the Cochrane Central Register of Controlled Trials CENTRAL, Google Scholar, and Clinicaltrials.gov databases for relevant articles published until the 30th of September 2022. Observational studies (prospective and retrospective) that evaluated the impact of antibiotics on preterm delivery rates of patients with AFS were considered eligible for inclusion. Statistical meta-analysis was performed with RStudio and we calculated pooled risk ratios (OR) and 95% confidence intervals (CI). To evaluate the information size, we performed trial sequential analysis (TSA) and the methodological quality of the included studies was assessed using RoBINS tools.

RESULTS

Overall, four retrospective cohort studies were included in the present systematic review and 369 women were enrolled. We demonstrated that preterm delivery prior to 34, 32 and 28 weeks of gestational age was comparable among the groups of women that had antibiotics and those that did not (OR: 0.34, 95% CI 0.05, 2.14, 0.40 [0.09, 1.66], 0.35 [0.08, 1.58], respectively) but the statistical heterogenicity of the studies included was high for every gestational period that was examined.

CONCLUSIONS

According to our study, we cannot conclude that the use of antibiotics in women with amniotic fluid sludge benefit the prognostic risk to deliver prematurely. It is quite clear that data from larger sample sizes and more well adjusted and designed studies are needed.

Antenatal azithromycin to prevent preterm birth in pregnant women with vaginal cerclage: A randomized clinical trial

Objective

To assess whether antenatal azithromycin given to pregnant women with vaginal cerclage can reduce preterm birth or not.

Materials and Methods

We randomized 50 pregnant ladies who underwent cerclage at Ain Shams University Maternity Hospital in group A (receiving 500 mg Azithromycin oral tablets (Zithrokan^®, Hikma, Egypt) one tablet orally twice daily for three days in 3 courses at 14^th, 24^th and 32^nd week, plus usual antenatal care) and an identical group B (receiving usual antenatal care). Our primary outcome was gestational age at delivery, and secondary outcomes were birthweight, mode of delivery, and maternal, and perinatal complications. This study was registered on ClinicalTrials.gov with number: NCT04278937.

Results

Pregnancy was more prolonged in the Azithromycin group (delivery at 36.8 weeks vs 34.1 weeks; p=0.017). Also, a higher birthweight was observed in the Azithromycin group (2932.6 gm vs 2401.8 gm; p=0.006). No significant difference was found between the two groups as regards to other outcomes (miscarriage, stillbirth, neonatal intensive care unit admission, antepartum hemorrhage, postpartum pyrexia, need for blood transfusion).

Conclusion

Adding antenatal azithromycin to women undergoing cerclage prolongs pregnancy and reduces the risk of preterm birth, with a slight increase in birthweight.

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.

Preterm labor with intact membranes: a simple noninvasive method to identify patients at risk for intra-amniotic infection and/or inflammation

OBJECTIVE

To develop a noninvasive scoring system to identify patients at high risk for intra-amniotic infection and/or inflammation, which would reduce the need for amniocentesis.

METHODS

This prospective cohort study comprised patients admitted with preterm labor and intact membranes (20-34 weeks of gestation) who underwent a transabdominal amniocentesis and for whom concentrations of quantitative cervical fetal fibronectin and of maternal serum C-reactive protein (CRP) were determined. Intra-amniotic infection was defined as a positive amniotic fluid culture for microorganisms. Intra-amniotic inflammation was defined as an amniotic fluid matrix metalloproteinase-8 concentration >23 ng/mL. Multivariate logistic regression analysis was performed to identify intra-amniotic infection/inflammtion with noninvasive parameters that had a significant relationship with univariate analysis. With four parameters identified by multivariate analysis, we generated a noninvasive risk scoring system.

RESULTS

Of the study population consisting of 138 singleton pregnant women, (1) the overall rate of intra-amniotic infection/inflammation was 28.3% (39/138); (2) four parameters were used to develop a noninvasive risk scoring system [i.e. cervical fetal fibronectin concentration (score 0-2), maternal serum CRP concentration (score 0-2), cervical dilatation (score 0-2), and gestational age at presentation (score 0-1)]; the total score ranges from 0 to 7; 3) the area under the curve of the risk score was 0.96 (95% confidence interval (CI), 0.92-0.99), significantly higher than that of each predictor in the identification of intra-amniotic infection/inflammation (p < .001, for all); 4) the risk score with a cutoff of 4 had a sensitivity of 94.9% (37/39), a specificity of 90.9% (90/99), a positive predictive value of 80.4% (37/46), a negative predictive value of 97.8% (90/92), a positive likelihood ratio of 10.4 (95% CI, 5.6-19.5), and a negative likelihood ratio of 0.06 (95% CI, 0.15-0.22) in the identification of intra-amniotic infection/inflammation.

CONCLUSIONS

(1) The combination of four parameters (concentrations of cervical fetal fibronectin and maternal serum CRP, cervical dilatation, and gestational age) was independently associated with intra-amniotic infection and/or inflammation; and (2) the risk scoring system comprised of the combination of 4 noninvasive parameters was sensitive and specific to identify the patients at risk for intra-amniotic infection and/or inflammation.

Relationship of Amniotic Fluid Sludge and Short Cervix With a High Rate of Preterm Birth in Women After Cervical Cerclage

OBJECTIVE

We aims to determine the relationship of amniotic fluid sludge (AFS) and/or short cervical length (CL, ≤25 mm) with a high rate of preterm birth in women after cervical cerclage.

METHODS

A retrospective cohort study was conducted among singleton pregnancies after cervical cerclage between January 2018 and December 2021. A total of 296 patients who underwent transvaginal ultrasound to evaluate CL and the presence of AFS within 2 weeks after cerclage were included. Pregnancy outcome after cerclage was analyzed in accordance with the presence of AFS and CL ≤25 mm.

RESULTS

In patients with cerclage, AFS was an independent risk factor for preterm birth at <28 and <36 weeks but not for preterm birth at <32 weeks, and CL ≤25 mm was an independent risk factor for preterm birth at <28, <32, and <36 weeks. The Kaplan-Meier analysis showed that the association between the presence of AFS and short gestational age at delivery was statistically significant in women with CL ≤25 mm (log rank test, P = .000). The Cox regression analysis showed that these results remained significant after adjusting for confounding factors (P = .000). The negative linear relationships between AFS and CL (R = -0.454, P < .001) also explained the outcome.

CONCLUSIONS

AFS and short cervix have a direct effect on pregnancies after cerclage. Mid-trimester AFS can become a supplementary ultrasound index for detecting preterm birth after cerclage in pregnant women with a short cervix.

Prognosis and Prognostic Factors of Patients with Emergent Cerclage: A Japanese Single-Center Study

Objectives

The aims of this study were to clarify the following: (1) how often does prolonged pregnancy ≥34 weeks occur in patients with emergent cerclage without progesterone and (2) the risk factors preventing such pregnancy continuation.

Materials and Methods

This retrospective observational study was performed using medical records of patients for whom emergent cerclage had been performed between April 2006 and December 2018 in our institute.

Results

Emergent cerclage was performed in 123 patients (median age: 34, interquartile range: 31–36). Primiparous patients numbered 44 (36%). A history of spontaneous preterm birth (SPTB) was present in 30 (24%). The median presurgical cervical length (CL) was 16 (8–21) mm at surgery. Of the 123, 20 (16%) were delivered at 33 + 6 weeks or less (<34 weeks). We conducted logistic regression analysis of the risk factors of SPTBs <34 weeks after cerclage. Three risk factors were identified that increased the risk of SPTB <34 weeks: presurgical CL 0 mm (odds ratio (OR): 5.30; 95% confidence interval (CI): 1.58–17.7), a history of SPTB (OR: 4.65; 95% CI: 1.38–15.7), and the presence of sludge (OR: 4.14; 95% CI: 1.20–14.3).

Conclusion

Three risk factors predicted SPTB <34 weeks after emergency cerclage without progesterone administration: unmeasurable CL (CL 0 mm), a history of SPTB, and the presence of sludge on ultrasound. SPTB <34 weeks occurred after emergency cerclage in 16% of patients, being comparable with the recent data with progesterone.

Does amniotic fluid sludge result in preterm labor in pregnancies after assisted reproduction technology? A nested Case - Control study

OBJECTIVE

to investigate the relationship between the Amniotic fluid Sludge exposure during pregnancy and the Preterm Labor (PTL) in pregnant women who had undergone Assisted Reproductive Technology procedures (ART) in Royan institute.

MATERIALS AND METHODS

It was a nested case-control study that was conducted on 110 eligible pregnant women who had undergone IVF procedure in Royan institute, Tehran, Iran. The final sample size was 63 subjects with Amniotic fluid Sludge and 67 subjects with normal Amniotic fluid. Delivery before 37 of gestation was considered as PTL.The study was approved by the ethics committee of the Royan institute and the written consent form was filled by participants. Data was entered to the SPSS (version 21, SPSS, Inc.). The baseline characteristics of the participants were described as absolute (n) and relative (%) frequencies for the covariates. Man Whitney and T-Test were used to compare the mean of covariates and the P-value lower than 0.05 was considered significant. The prevalence of the PTL was compared between two groups.

RESULTS

The mean Gestational Age at delivery in case and control group were 36.46 ± 3.45 and 38.03 ± 1.61, respectively which was significant (p = .01). The prevalence of PTL in case and control group were 23.8% and 10.4% respectively which was significant (p = .04). The percentage of cases with cervical length less than 30 (mm) in case and control group were 28.6% and 10.4%, respectively (p = .008) and the percentage of cerclage in case and control group were 33.3% and 7.5% respectively, (p = .00) which were significant statistically.

CONCLUSION

The amniotic fluid sludge has a direct effect on the cervical length of pregnancies after ART. In such cases, PTB will be probable in the presence of sludge in spite of preventive treatments such as cerclage.

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.

Amniotic immune biomarkers as risk factors in women with different symptoms of threatened late miscarriage

PROBLEM

To investigate risk factors that can help identify the possibility of pregnancy loss in threatened late miscarriage (TLM) patients with and without spontaneous uterine contractions.

METHOD OF STUDY

Amniotic immune biomarkers (IL2β receptor, IL6, IL8, IL10, IL1β, and TNFα) were assayed, and "sludge" was assessed. Patients without intrauterine infections were treated and followed up until delivery, and pregnancy outcomes were recorded. The two groups were compared for the differences in biomarker levels and "sludge," and the independent associations of biomarkers, "sludge," and other maternal factors with late miscarriage were investigated.

RESULTS

The amniotic levels of IL2βR, IL8, and TNFα were higher in the group with contractions (P < .05). When considered alone, each of the six biomarkers was significantly associated with late miscarriage in the no-contractions group and four of these (IL8, IL10, IL1β, and TNFα) in the contractions group (P < .05). Biomarker levels were correlated, and in multivariate Cox regression analysis, there was an independent effect only for IL8 in the no-contractions group (HR = 18.16, 95% CI: 5.75-57.43) and TNFα in the contractions group (HR = 4.11, 95% CI: 1.68-10.08). For patients with contractions, IL10, IL8, and IL1β were different in those with and without "sludge," but no such difference was seen in the no-contractions group.

CONCLUSION

For TLM patients without intrauterine infections, amniotic immune biomarkers differ between patients with different symptoms, not only for their levels but also for the impact of these biomarkers on the risk of late miscarriage. These findings suggest that the symptoms of TLM should be considered in the study of miscarriage risk.

Porphyromonas gingivalis and adverse pregnancy outcomes: a review on its intricate pathogenic mechanisms

Porphyromonas gingivalis (P. gingivalis), a Gram-negative facultative anaerobe of the oral cavity, is associated with the onset of various adverse pregnancy outcomes. P. gingivalis is linked with the development of preeclampsia, preterm labour, spontaneous abortion, gestational diabetes, foetal growth restriction, and misconception. The unique virulence factors, surface adhesions, enzymes of P. gingivalis can directly injure and alter the morphology, microbiome the foetal and maternal tissues. P. gingivalis can even exaggerate the production of cytokines, free radicals and acute-phase proteins in the uterine compartment that increases the risk of myometrial contraction and onset of preterm labour. Although evidence confirms the presence of P. gingivalis in the amniotic fluid and placenta of women with poor pregnancy outcomes, the intricate molecular mechanisms by which P. gingivalis initiates various antenatal and postnatal maternal and foetal complications are not well explained in the literature. Therefore, the present review aims to comprehensively summarise and highlight the recent and unique molecular pathogenic mechanisms of P. gingivalis associated with adverse pregnancy outcomes.

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.

A high concentration of fetal fibronectin in cervical secretions increases the risk of intra-amniotic infection and inflammation in patients with preterm labor and intact membranes

Objective To determine whether the risk of intra-amniotic infection/inflammation and spontaneous preterm delivery (SPTD) varies as a function of the concentration of cervical fetal fibronectin (fFN) in patients with preterm labor and intact membranes. Methods This prospective study included 180 patients with preterm labor and intact membranes who had a sample collected for quantitative fFN measurement and underwent amniocentesis. Amniotic fluid was cultured for aerobic and anaerobic bacteria and genital mycoplasmas. Intra-amniotic inflammation was defined as an amniotic fluid matrix metalloproteinase-8 concentration >23 ng/mL. Results (1) The prevalence of intra-amniotic infection/inflammation and SPTD within 7 days was 32.2% (58/180) and 33.9% (61/178), respectively; (2) The higher the fFN concentration, the greater the risk of intra-amniotic infection/inflammation and SPTD within 7 days (P<0.001, respectively); (3) An fFN concentration 150 ng/mL had a better diagnostic performance than an fFN 50 ng/mL in the identification of intra-amniotic infection/inflammation and SPTD within 7 days; (4) Among the patients with an fFN <50 ng/mL, intra-amniotic infection/inflammation was identified in 7.6% (6/79) of patients and 66.7% (4/6) delivered within 7 days. Conclusion The higher the concentration of fFN, the greater the risk of intra-amniotic infection/inflammation and SPTD in patients with preterm labor and intact membranes.

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.