Home Are bacteria, fungi, and archaea present in the midtrimester amniotic fluid?
Article Open Access

Are bacteria, fungi, and archaea present in the midtrimester amniotic fluid?

  • Roberto Romero EMAIL logo , Maria Teresa Gervasi , Daniel B. DiGiulio , Eunjung Jung , Manaphat Suksai , Jezid Miranda , Kevin R. Theis , Francesca Gotsch and David A. Relman
Published/Copyright: May 17, 2023
Download Article (PDF)
Journal of Perinatal Medicine
From the journal Journal of Perinatal Medicine Volume 51 Issue 7

Abstract

Objectives

This study was conducted to determine whether bacteria, fungi, or archaea are detected in the amniotic fluid of patients who underwent midtrimester amniocentesis for clinical indications.

Methods

Amniotic fluid samples from 692 pregnancies were tested by using a combination of culture and end-point polymerase chain reaction (PCR) techniques. Intra-amniotic inflammation was defined as an interleukin-6 concentration >2,935 pg/mL.

Results

Microorganisms were detected in 0.3% (2/692) of cases based on cultivation, 1.73% (12/692) based on broad-range end-point PCR, and 2% (14/692) based on the combination of both methods. However, most (13/14) of these cases did not have evidence of intra-amniotic inflammation and delivered at term. Therefore, a positive culture or end-point PCR in most patients appears to have no apparent clinical significance.

Conclusions

Amniotic fluid in the midtrimester of pregnancy generally does not contain bacteria, fungi, or archaea. Interpretation of amniotic fluid culture and molecular microbiologic results is aided by the assessment of the inflammatory state of the amniotic cavity. The presence of microorganisms, as determined by culture or a microbial signal in the absence of intra-amniotic inflammation, appears to be a benign condition.

Keywords: chorioamnionitis; contamination; inflammation; microbial survey; sterile womb hypothesis

Introduction

The amniotic cavity is thought to be sterile, a concept consistent with the “sterile womb hypothesis,” which posits that under normal circumstances microbial colonization occurs after birth [1], [2], [3]. Some investigators have reported the presence of microorganisms when using DNA sequencing techniques and proposed that human amniotic fluid contains evidence of a microbiome [4], [5], [6], [7], [8], [9], [10], [11], even in clinical states of health. These findings contrast with those of others who used either cultivation or molecular microbiologic techniques, or a combination of both, and did not find evidence of a microbiome [12], [13], [14], [15], [16], [17], [18]. The present study was conducted to determine whether bacteria, fungi, or archaea could be found in the amniotic fluid of patients who underwent midtrimester amniocentesis for clinical indications (see Table 1).

Table 1:

Clinical characteristics, socio-demographics, and perinatal outcomes of the study population.

Characteristics n=692
n, or median (IQR)
Maternal age, years 37 (35–39)
Maternal race
 Caucasian 683 (98.7)
 Black 3 (0.43)
 Hispanic 3 (0.43)
 Asian 3 (0.43)
Nulliparity 278 (40.2)
History of spontaneous preterm delivery 22 (3.2)
Gestational age at amniocentesis, weeks 16.3 (15.9–16.7)
Indication for amniocentesis
 Advanced maternal age 560 (80.9)
 Abnormal 1st or 2nd trimester screening 63 (9.1)
 Maternal request 49 (7.1)
 Suspected fetal anomaly at ultrasound 11 (1.6)
 Others 9 (1.3)
Gestational age at delivery 39.6 (38.6–40.6)
Preterm birth (<37 weeks) 56 (8.1)
 Late spontaneous preterm delivery (≥32 weeks) 37 (5.3)
 Early spontaneous preterm delivery (<32 weeks) 4 (0.6)
 Indicated preterm delivery 15 (2.16)
Delivery route
 Vaginal 524 (75.7)
 Cesarean 168 (24.3)
Gender
 Male 338 (49.2)
 Female 349 (50.8)
Birthweight, grams 3335 (3041–3600)
Birthweight percentile 43 (27.6–63.9)
Small for gestational age 42 (6.1)

  1. IQR, Interquartile range. Missing data: Gender (5).

Materials and methods

This retrospective cohort study included 692 asymptomatic women with a singleton pregnancy who underwent midtrimester amniocentesis for clinical indications between 14 and 26 weeks of gestation (Table 1). Amniotic fluid was cultured for both aerobic and anaerobic bacteria as well as for genital mycoplasmas. Broad-range end-point polymerase chain reaction (PCR) assays were performed to amplify and characterize the ribosomal DNA (rDNA) of bacteria, fungi, and archaea, using a method previously described in detail [19]. In seven cases, quantitative PCR [19] was performed to assess microbial burden. Amniotic fluid concentrations of interleukin (IL)-6 were measured and validated with specific enzyme-linked immunosorbent assays. Intra-amniotic inflammation was diagnosed when the amniotic fluid IL-6 concentration was >2,935 pg/mL. White blood cell count, glucose concentration, and Gram stain of amniotic fluid were also performed. Microbial invasion of the amniotic cavity was defined by the presence of a positive culture or of microbial sequences by broad-range PCR.

The collection of samples and clinical data was approved by the Institutional Review Board of the Azienda Ospedaliera Treviso, Azienda Ospedale/Universita’ Padova, Veneto Region, Italy. This institution has a Federal Wide Assurance with the United States Department of Health and Human Services. This study is based on a subset of samples previously investigated in intra-amniotic inflammation [12].

Categorical data are presented as n (%) and continuous data as mean [standard deviation (±SD)] or median [interquartile range (IQR)] according to their distribution. The Kruskal-Wallis test, followed by the Mann-Whitney-Wilcoxon test for post-hoc analysis, was performed to compare continuous variables among and between groups. Comparisons of proportions were performed with Chi-square or Fisher’s exact tests. Statistical analysis was performed by using R language and environment for statistical computing (www.r-project.org). For all analyses, a two-tailed p-value<0.05 was considered significant.

Results

Bacteria were detected in 0.3% (2/692) of cases based on cultivation, 1.73% (12/692) based on broad-range end-point PCR, and 2% (14/692) based on the combination of culture and end-point PCR results (Table 2). Collectively, eight bacterial taxa, one fungal species (Candida albicans), and no archaea were identified. Two bacterial taxa (Staphylococcus aureus and Pseudomonas aeruginosa) were detected by culture only and six bacterial taxa (Ureaplasma, Acinetobacter, Mycoplasma hominis, Streptococcus agalactiae, Streptococcus, and Sneathia) were detected by PCR only. There was no concordance between the results of microbial culture and molecular microbiology. Importantly, quantitative PCR did not yield a signal above the limit of detection of the assay in five of the seven cases tested (Table 2).

Table 2:

Amniotic fluid markers of inflammation and pregnancy outcomes in patients with a positive amniotic fluid culture or an end-point PCR for microorganisms during the midtrimester.

Case number Microorganism identified by culture Microorganism identified by end-point PCR Microbial burden 16S rRNA gene copy number AF WBC, cells/mm3 AF glucose, mg/dL AF IL-6, ng/mL GA at delivery, weeks
1 Negative Ureaplasma 13,003 30 34 8.43 28.6
2 Negative Acinetobacter 745 12 35 0.40 34.7
3 Negative S. agalactiae NI 1 51 0.58 41.3
4 Negative M. hominis NI 2 44 0.43 41
5 Negative Streptococcus Below limit of detection 5 45 0.60 41.4
6 Negative Sneathia NI 5 50 0.17 40.9
7 Negative Sneathia NI 2 44 0.48 39.1
8 Negative Candida Below limit of detection 7 54 0.20 41.1
9 Negative Candida NI 2 45 0.10 39.4
10 Negative Candida Below limit of detection 11 46 0.06 39.3
11 Negative Candida NI 1 55 0.41 38
12 Negative Candida NI 2 50 0.3 37
13 Staphylococcus aureus Negative Below limit of detection 2 50 0.87 40.1
14 Pseudomonas aeruginosa Negative Below limit of detection 3 37 1.09 39.0

  1. AF, amniotic fluid; IL-6, interleukin-6; GA, gestational age; NI, no information; PCR, polymerase chain reaction; WBC, white blood cell count.

The prevalence of spontaneous preterm birth (<37 weeks of gestation) was 5.78% (40/692) whereas that of spontaneous early preterm birth (<32 weeks of gestation) was 1.15% (8/692). Sterile intra-amniotic inflammation (IL-6>2,935 pg/mL and an absence of detectable microorganisms) was found in 6.1% (42/692) of patients in the midtrimester of pregnancy. Patients whose amniotic fluid samples had microorganisms but not inflammation had a similar perinatal outcome to that of women without detectable microorganisms. None of the patients with a positive amniotic fluid culture had intra-amniotic inflammation, and all delivered at term. A positive PCR result was associated with intra-amniotic inflammation in only one case (Case #1 in Table 2), specifically a patient with a high amniotic fluid microbial burden of Ureaplasma (13,003 16S rRNA gene copies) detected only by PCR but not by cultivation. The patient delivered at 28.6 weeks of gestation.

Discussion

Our findings indicate that most asymptomatic patients in the midtrimester of pregnancy do not have bacteria, fungi, or archaea detectable in amniotic fluid and these observations are consistent with previous reports [12], [13], [14], [15].

The standard diagnosis of amniotic fluid infection depends upon the identification of microorganisms in amniotic fluid obtained in a manner that minimizes the risk of contamination of the specimen (transabdominal amniocentesis vs. intrauterine pressure catheter) [20]. Cultures of aerobic and anaerobic bacteria have been the gold standard. Molecular microbiologic techniques, using PCR with primers designed to target the conserved regions of microbial genomes or primers for specific microorganisms, have emerged as complementary methods to cultures for microbial detection [21], [22], [23], [24], [25], [26], [27], [28]. The individual and combined use of these methods for the diagnosis of intra-amniotic infection has been the subject of previous publications [19, 21, 23], [24], [25], [26, 29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39]. In general, molecular microbiologic techniques are more sensitive than cultivation techniques [40], [41], [42], [43]. Cultivation assays are also prone to false positive results due to contamination of a specimen either at the bedside or in the laboratory [44], [45], [46].

In the current study, two cases of positive amniotic fluid cultures were identified. Neither patient showed clinical evidence of intra-amniotic inflammation (white blood cell count and concentrations of glucose and IL-6), and both had a negative PCR result for microorganisms and subsequently delivered at term. These findings suggest that the positive cultures in these cases represented contamination of the specimens. We have previously reported that a positive amniotic fluid culture in the absence of intra-amniotic inflammation is a benign condition associated with term delivery and normal outcome [47].

Herein, 12 patients had a positive end-point PCR result for microorganisms but only one showed evidence of intra-amniotic inflammation (Case #1 in Table 2). This patient had a preterm delivery at 28 weeks of gestation with histologic evidence of acute chorioamnionitis (a maternal inflammatory response) and funisitis (a fetal inflammatory response). These observations suggest that the patient had a true positive PCR test even though the amniotic fluid culture was negative. Of interest, the microbial burden was high with quantitative real-time PCR. Previous reports suggested that the microbial burden in amniotic fluid may be helpful in the differential diagnosis of a true positive vs. a false positive result of molecular microbiologic tests [25].

Quantification of the microbial burden with real-time PCR for bacterial 16S rDNA was performed in seven cases of which five were positive for the end-point PCR and two were positive by culture. In most cases, real-time PCR did not detect microbial nucleic acids. In one case, the microbial burden was high (13,003 16S rRNA gene copies), and this patient is described in the previous paragraph. In the second case, Acinetobacter was identified by end-point PCR but there were only 745 16S rRNA gene copies. This patient had no evidence of intra-amniotic inflammation (Case #2 in Table 2) and delivered at 34 weeks of gestation; the placenta showed no evidence of acute histologic chorioamnionitis or funisitis.

We conclude that amniotic fluid in the midtrimester of pregnancy of clinically asymptomatic patients generally does not contain bacteria, fungi, or archaea. Interpretation of amniotic fluid culture and molecular microbiologic results is aided by assessment of the inflammatory state of the amniotic cavity, and by the quantification of microbial sequences. The presence of microorganisms by culture or a microbial signature by end-point PCR in the absence of intra-amniotic inflammation appears to be a benign condition.

Corresponding authors: Roberto Romero, MD, DMedSci, Pregnancy Research Branch, Division of Obstetrics and Maternal-Fetal Medicine, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, United States Department of Health and Human Services (NICHD/NIH/DHHS), Bethesda, MD, and Detroit, MI, USA; Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI, USA; and Department of Epidemiology and Biostatistics, Michigan State University, East Lansing, MI, USA, E-mail: ; and David A. Relman, Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA; Infectious Diseases Section, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, USA; and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA,
The study was conducted at the Perinatology Research Branch, NICHD/NIH/DHHS, in Detroit, Michigan; the Branch has since been renamed as the Pregnancy Research Branch, NICHD/NIH/DHHS.

Funding source: Eunice Kennedy Shriver National Institute of Child Health and Human Development

Award Identifier / Grant number: Contract No. HHSN275201300006C

Funding source: Wayne State University

Award Identifier / Grant number: Unassigned

Acknowledgments

The authors thank Maureen McGerty (Wayne State University) for her critical reading of the manuscript and editorial support.

  1. Research funding: This research was supported, in part, by the Perinatology Research Branch, Division of Obstetrics and Maternal-Fetal Medicine, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, U.S. Department of Health and Human Services (NICHD/NIH/DHHS); and, in part, with Federal funds from NICHD/NIH/DHHS under Contract No. HHSN275201300006C. It was also supported by the Thomas C. and Joan M. Merigan Endowment at Stanford University (Dr. Relman). Dr. Romero has contributed to this work as part of his official duties as an employee of the United States Federal Government.

  2. Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.

  3. Competing interests: Authors state no conflicts of interest.

  4. Informed consent: Informed consent was obtained from all individuals included in this study.

  5. Ethical approval: Research involving human subjects complied with all relevant national regulations and institutional policies; is in accordance with the tenets of the Helsinki Declaration (as revised in 2013); and has been approved by the Institutional Review Board of Azienda Ospedaliera Treviso, Azienda Ospedale/Universita’ Padova, Veneto Region, Italy.

References

1. Perez-Muñoz, ME, Arrieta, MC, Ramer-Tait, AE, Walter, J. A critical assessment of the “sterile womb” and “in utero colonization” hypotheses: implications for research on the pioneer infant microbiome. Microbiome 2017;5:48. https://doi.org/10.1186/s40168-017-0268-4.Search in Google Scholar PubMed PubMed Central

2. Blaser, MJ, Devkota, S, McCoy, KD, Relman, DA, Yassour, M, Young, VB. Lessons learned from the prenatal microbiome controversy. Microbiome 2021;9:8. https://doi.org/10.1186/s40168-020-00946-2.Search in Google Scholar PubMed PubMed Central

3. Carino, R3rd, Takayasu, L, Suda, W, Masuoka, H, Hirayama, K, Konishi, S, et al.. The search for aliens within us: a review of evidence and theory regarding the foetal microbiome. Crit Rev Microbiol 2022;48:611–23. https://doi.org/10.1080/1040841x.2021.1999903.Search in Google Scholar PubMed

4. Rautava, S, Collado, MC, Salminen, S, Isolauri, E. Probiotics modulate host-microbe interaction in the placenta and fetal gut: a randomized, double-blind, placebo-controlled trial. Neonatology 2012;102:178–84. https://doi.org/10.1159/000339182.Search in Google Scholar PubMed

5. Chu, D, Stewart, C, Seferovic, M, Suter, M, Cox, J, Vidaeff, A, et al.. 26: profiling of microbiota in second trimester amniotic fluid reveals a distinctive community present in the mid trimester and predictive of the placental microbiome at parturition. Am J Obstet Gynecol 2017;216:S18–9. https://doi.org/10.1016/j.ajog.2016.11.917.Search in Google Scholar

6. Collado, MC, Rautava, S, Aakko, J, Isolauri, E, Salminen, S. Human gut colonisation may be initiated in utero by distinct microbial communities in the placenta and amniotic fluid. Sci Rep 2016;6: 23129. https://doi.org/10.1038/srep23129.Search in Google Scholar PubMed PubMed Central

7. Zhu, L, Luo, F, Hu, W, Han, Y, Wang, Y, Zheng, H, et al.. Bacterial communities in the womb during healthy pregnancy. Front Microbiol 2018;9:2163. https://doi.org/10.3389/fmicb.2018.02163.Search in Google Scholar PubMed PubMed Central

8. Stinson, LF, Boyce, MC, Payne, MS, Keelan, JA. The not-so-sterile womb: evidence that the human fetus is exposed to bacteria prior to birth. Front Microbiol 2019;10:1124. https://doi.org/10.3389/fmicb.2019.01124.Search in Google Scholar PubMed PubMed Central

9. Stinson, L, Hallingstrom, M, Barman, M, Viklund, F, Keelan, J, Kacerovsky, M, et al.. Comparison of bacterial DNA profiles in mid-trimester amniotic fluid samples from preterm and term deliveries. Front Microbiol 2020;11:415. https://doi.org/10.3389/fmicb.2020.00415.Search in Google Scholar PubMed PubMed Central

10. Campisciano, G, Quadrifoglio, M, Comar, M, De Seta, F, Zanotta, N, Ottaviani, C, et al.. Evidence of bacterial DNA presence in chorionic villi and amniotic fluid in the first and second trimester of pregnancy. Future Microbiol 2021;16:801–10. https://doi.org/10.2217/fmb-2020-0243.Search in Google Scholar PubMed

11. Wu, S, Yu, F, Ma, L, Zhao, Y, Zheng, X, Li, X, et al.. Do maternal microbes shape newborn oral microbes? Indian J Microbiol 2021;61:16–23. https://doi.org/10.1007/s12088-020-00901-7.Search in Google Scholar PubMed PubMed Central

12. Gervasi, MT, Romero, R, Bracalente, G, Erez, O, Dong, Z, Hassan, SS, et al.. Midtrimester amniotic fluid concentrations of interleukin-6 and interferon-gamma-inducible protein-10: evidence for heterogeneity of intra-amniotic inflammation and associations with spontaneous early (<32 weeks) and late (>32 weeks) preterm delivery. J Perinat Med 2012;40:329–43. https://doi.org/10.1515/jpm-2012-0034.Search in Google Scholar PubMed PubMed Central

13. Rowlands, S, Danielewski, JA, Tabrizi, SN, Walker, SP, Garland, SM. Microbial invasion of the amniotic cavity in midtrimester pregnancies using molecular microbiology. Am J Obstet Gynecol 2017;217:71.e1–5. https://doi.org/10.1016/j.ajog.2017.02.051.Search in Google Scholar PubMed

14. Lim, ES, Rodriguez, C, Holtz, LR. Amniotic fluid from healthy term pregnancies does not harbor a detectable microbial community. Microbiome 2018;6:87. https://doi.org/10.1186/s40168-018-0475-7.Search in Google Scholar PubMed PubMed Central

15. Rehbinder, EM, Lodrup Carlsen, KC, Staff, AC, Angell, IL, Landro, L, Hilde, K, et al.. Is amniotic fluid of women with uncomplicated term pregnancies free of bacteria? Am J Obstet Gynecol 2018;219:289.e1–12. https://doi.org/10.1016/j.ajog.2018.05.028.Search in Google Scholar PubMed

16. Burnham, P, Gomez-Lopez, N, Heyang, M, Cheng, AP, Lenz, JS, Dadhania, DM, et al.. Separating the signal from the noise in metagenomic cell-free DNA sequencing. Microbiome 2020;8:18. https://doi.org/10.1186/s40168-020-0793-4.Search in Google Scholar PubMed PubMed Central

17. Liu, Y, Li, X, Zhu, B, Zhao, H, Ai, Q, Tong, Y, et al.. Midtrimester amniotic fluid from healthy pregnancies has no microorganisms using multiple methods of microbiologic inquiry. Am J Obstet Gynecol 2020;223:248.e1–21. https://doi.org/10.1016/j.ajog.2020.01.056.Search in Google Scholar PubMed

18. Wang, H, Yang, GX, Hu, Y, Lam, P, Sangha, K, Siciliano, D, et al.. Comprehensive human amniotic fluid metagenomics supports the sterile womb hypothesis. Sci Rep 2022;12:6875. https://doi.org/10.1038/s41598-022-10869-7.Search in Google Scholar PubMed PubMed Central

19. DiGiulio, DB, Romero, R, Amogan, HP, Kusanovic, JP, Bik, EM, Gotsch, F, et al.. Microbial prevalence, diversity and abundance in amniotic fluid during preterm labor: a molecular and culture-based investigation. PLoS One 2008;3:e3056. https://doi.org/10.1371/journal.pone.0003056.Search in Google Scholar PubMed PubMed Central

20. Gibbs, RS, Blanco, JD, St Clair, PJ, Castaneda, YS. Quantitative bacteriology of amniotic fluid from women with clinical intraamniotic infection at term. J Infect Dis 1982;145:1–8. https://doi.org/10.1093/infdis/145.1.1.Search in Google Scholar PubMed

21. Yoon, BH, Romero, R, Kim, M, Kim, EC, Kim, T, Park, JS, et al.. Clinical implications of detection of Ureaplasma urealyticum in the amniotic cavity with the polymerase chain reaction. Am J Obstet Gynecol 2000;183:1130–7. https://doi.org/10.1067/mob.2000.109036.Search in Google Scholar PubMed

22. DiGiulio, DB, Romero, R, Kusanovic, JP, Gomez, R, Kim, CJ, Seok, KS, et al.. Prevalence and diversity of microbes in the amniotic fluid, the fetal inflammatory response, and pregnancy outcome in women with preterm pre-labor rupture of membranes. Am J Reprod Immunol 2010;64:38–57. https://doi.org/10.1111/j.1600-0897.2010.00830.x.Search in Google Scholar PubMed PubMed Central

23. DiGiulio, DB, Gervasi, M, Romero, R, Mazaki-Tovi, S, Vaisbuch, E, Kusanovic, JP, et al.. Microbial invasion of the amniotic cavity in preeclampsia as assessed by cultivation and sequence-based methods. J Perinat Med 2010;38:503–13. https://doi.org/10.1515/jpm.2010.078.Search in Google Scholar PubMed PubMed Central

24. DiGiulio, DB, Gervasi, MT, Romero, R, Vaisbuch, E, Mazaki-Tovi, S, Kusanovic, JP, et al.. Microbial invasion of the amniotic cavity in pregnancies with small-for-gestational-age fetuses. J Perinat Med 2010;38:495–502. https://doi.org/10.1515/jpm.2010.076.Search in Google Scholar PubMed PubMed Central

25. Romero, R, Miranda, J, Chaiworapongsa, T, Chaemsaithong, P, Gotsch, F, Dong, Z, et al.. A novel molecular microbiologic technique for the rapid diagnosis of microbial invasion of the amniotic cavity and intra-amniotic infection in preterm labor with intact membranes. Am J Reprod Immunol 2014;71:330–58. https://doi.org/10.1111/aji.12189.Search in Google Scholar PubMed PubMed Central

26. Romero, R, Miranda, J, Kusanovic, JP, Chaiworapongsa, T, Chaemsaithong, P, Martinez, A, et al.. Clinical chorioamnionitis at term I: microbiology of the amniotic cavity using cultivation and molecular techniques. J Perinat Med 2015;43:19–36. https://doi.org/10.1515/jpm-2014-0249.Search in Google Scholar PubMed PubMed Central

27. Romero, R, Gomez-Lopez, N, Winters, AD, Jung, E, Shaman, M, Bieda, J, et al.. Evidence that intra-amniotic infections are often the result of an ascending invasion - a molecular microbiological study. J Perinat Med 2019;47:915–31. https://doi.org/10.1515/jpm-2019-0297.Search in Google Scholar PubMed PubMed Central

28. Winters, AD, Romero, R, Graffice, E, Gomez-Lopez, N, Jung, E, Kanninen, T, et al.. Optimization and validation of two multiplex qPCR assays for the rapid detection of microorganisms commonly invading the amniotic cavity. J Reprod Immunol 2022;149:103460. https://doi.org/10.1016/j.jri.2021.103460.Search in Google Scholar PubMed PubMed Central

29. Romero, R, Emamian, M, Quintero, R, Wan, M, Hobbins, JC, Mazor, M, et al.. The value and limitations of the Gram stain examination in the diagnosis of intraamniotic infection. Am J Obstet Gynecol 1988;159:114–9. https://doi.org/10.1016/0002-9378(88)90503-0.Search in Google Scholar PubMed

30. Goldstein, I, Zimmer, EZ, Merzbach, D, Peretz, BA, Paldi, E. Intraamniotic infection in the very early phase of the second trimester. Am J Obstet Gynecol 1990;163:1261–3. https://doi.org/10.1016/0002-9378(90)90703-a.Search in Google Scholar PubMed

31. Watts, DH, Krohn, MA, Hillier, SL, Eschenbach, DA. The association of occult amniotic fluid infection with gestational age and neonatal outcome among women in preterm labor. Obstet Gynecol 1992;79:351–7. https://doi.org/10.1097/00006250-199203000-00005.Search in Google Scholar PubMed

32. Mandar, R, Li, K, Ehrenberg, A, Smidt, I, Raukas, E, Kask, V, et al.. Amniotic fluid microflora in asymptomatic women at mid-gestation. Scand J Infect Dis 2001;33:60–2. https://doi.org/10.1080/003655401750064095.Search in Google Scholar PubMed

33. Markenson, GR, Adams, LA, Hoffman, DE, Reece, MT. Prevalence of Mycoplasma bacteria in amniotic fluid at the time of genetic amniocentesis using the polymerase chain reaction. J Reprod Med 2003;48:775–9.Search in Google Scholar

34. Perni, SC, Vardhana, S, Korneeva, I, Tuttle, SL, Paraskevas, LR, Chasen, ST, et al.. Mycoplasma hominis and Ureaplasma urealyticum in midtrimester amniotic fluid: association with amniotic fluid cytokine levels and pregnancy outcome. Am J Obstet Gynecol 2004;191:1382–6. https://doi.org/10.1016/j.ajog.2004.05.070.Search in Google Scholar PubMed

35. DiGiulio, DB, Romero, R, Kusanovic, JP, Gómez, R, Kim, CJ, Seok, KS, et al.. Prevalence and diversity of microbes in the amniotic fluid, the fetal inflammatory response, and pregnancy outcome in women with preterm pre-labor rupture of membranes. Am J Reprod Immunol 2010;64:38–57. https://doi.org/10.1111/j.1600-0897.2010.00830.x.Search in Google Scholar PubMed PubMed Central

36. Payne, MS, Feng, Z, Li, S, Doherty, DA, Xu, B, Li, J, et al.. Second trimester amniotic fluid cytokine concentrations, Ureaplasma sp. colonisation status and sexual activity as predictors of preterm birth in Chinese and Australian women. BMC Pregn Childbirth 2014;14:340. https://doi.org/10.1186/1471-2393-14-340.Search in Google Scholar PubMed PubMed Central

37. Romero, R, Miranda, J, Chaemsaithong, P, Chaiworapongsa, T, Kusanovic, JP, Dong, Z, et al.. Sterile and microbial-associated intra-amniotic inflammation in preterm prelabor rupture of membranes. J Matern Fetal Neonatal Med 2015;28:1394–409. https://doi.org/10.3109/14767058.2014.958463.Search in Google Scholar PubMed PubMed Central

38. Oh, KJ, Romero, R, Park, JY, Hong, JS, Yoon, BH. The earlier the gestational age, the greater the intensity of the intra-amniotic inflammatory response in women with preterm premature rupture of membranes and amniotic fluid infection by Ureaplasma species. J Perinat Med 2019;47:516–27. https://doi.org/10.1515/jpm-2019-0003.Search in Google Scholar PubMed PubMed Central

39. Tetu, A, Guerby, P, Rallu, F, Duperron, L, Morin, V, Bujold, E. Mid-trimester microbial invasion of the amniotic cavity and the risk of preterm birth. J Matern Fetal Neonatal Med 2022;35:4071–4. https://doi.org/10.1080/14767058.2020.1846704.Search in Google Scholar PubMed

40. Woo, PC, Lau, SK, Teng, JL, Tse, H, Yuen, KY. Then and now: use of 16S rDNA gene sequencing for bacterial identification and discovery of novel bacteria in clinical microbiology laboratories. Clin Microbiol Infect 2008;14:908–34. https://doi.org/10.1111/j.1469-0691.2008.02070.x.Search in Google Scholar PubMed

41. Rhoads, DD, Cox, SB, Rees, EJ, Sun, Y, Wolcott, RD. Clinical identification of bacteria in human chronic wound infections: culturing vs. 16S ribosomal DNA sequencing. BMC Infect Dis 2012;12:321. https://doi.org/10.1186/1471-2334-12-321.Search in Google Scholar PubMed PubMed Central

42. Dickson, RP, Erb-Downward, JR, Prescott, HC, Martinez, FJ, Curtis, JL, Lama, VN, et al.. Analysis of culture-dependent versus culture-independent techniques for identification of bacteria in clinically obtained bronchoalveolar lavage fluid. J Clin Microbiol 2014;52:3605–13. https://doi.org/10.1128/jcm.01028-14.Search in Google Scholar PubMed PubMed Central

43. Gupta, S, Mortensen, MS, Schjørring, S, Trivedi, U, Vestergaard, G, Stokholm, J, et al.. Amplicon sequencing provides more accurate microbiome information in healthy children compared to culturing. Commun Biol 2019;2:291. https://doi.org/10.1038/s42003-019-0540-1.Search in Google Scholar PubMed PubMed Central

44. Dargère, S, Cormier, H, Verdon, R. Contaminants in blood cultures: importance, implications, interpretation and prevention. Clin Microbiol Infect 2018;24:964–9. https://doi.org/10.1016/j.cmi.2018.03.030.Search in Google Scholar PubMed

45. Giuliano, C, Patel, CR, Kale-Pradhan, PB. A guide to bacterial culture identification and results interpretation. P T 2019;44:192–200.Search in Google Scholar

46. Bool, M, Barton, MJ, Zimmerman, PA. Blood culture contamination in the emergency department: an integrative review of strategies to prevent blood culture contamination. Australas Emerg Care 2020;23:157–65. https://doi.org/10.1016/j.auec.2020.02.004.Search in Google Scholar PubMed

47. Jung, E, Romero, R, Yoon, BH, Theis, KR, Gudicha, DW, Tarca, AL, et al.. Bacteria in the amniotic fluid without inflammation: early colonization vs. contamination. J Perinat Med 2021;49:1103–21. https://doi.org/10.1515/jpm-2021-0191.Search in Google Scholar PubMed PubMed Central

Received: 2022-12-12
Accepted: 2023-01-14
Published Online: 2023-05-17
Published in Print: 2023-09-26

© 2023 the author(s), published by De Gruyter, Berlin/Boston

This work is licensed under the Creative Commons Attribution 4.0 International License.

Articles in the same Issue

  1. Frontmatter
  2. Reviews
  3. Covid-19 vaccination and pregnancy: a systematic review of maternal and neonatal outcomes
  4. Improvised bubble continuous positive airway pressure ventilation use in neonates in resource-limited settings: a systematic review and meta-analysis
  5. Opinion Papers
  6. Anger: an underappreciated destructive force in healthcare
  7. Severe maternal thrombocytopenia and prenatal invasive procedures: still a grey zone
  8. Commentary
  9. The care of the magic of life before and after its beginning
  10. Original Articles – Obstetrics
  11. The impact of trimester of COVID-19 infection on pregnancy outcomes after recovery
  12. Adverse outcomes and maternal complications in pregnant women with severe-critical COVID-19: a tertiary center experience
  13. Are bacteria, fungi, and archaea present in the midtrimester amniotic fluid?
  14. Bioavailability of the tumor necrosis factor alpha/regulated on activation, normal T cell expressed and secreted (RANTES) biosystem inside the gestational sac during the pre-immune stages of embryo development
  15. The role of the soluble fms-like tyrosine kinase-1/placental growth factor (sFlt-1/PIGF) – ratio in clinical practice in obstetrics: diagnostic and prognostic value
  16. Prenatal diagnosis of non-mosaic sex chromosome abnormalities: a 10-year experience from a tertiary referral center
  17. Prediction of lung maturity through quantitative ultrasound analysis of fetal lung texture in women with diabetes during pregnancy
  18. Evaluation of an artificial intelligent algorithm (Heartassist™) to automatically assess the quality of second trimester cardiac views: a prospective study
  19. Original Article – Fetus
  20. Fetal brain activity and the free energy principle
  21. Predictive value of ultrasound in prenatal diagnosis of hypospadias: hints for accurate diagnosis
  22. The effect of maternal diabetes on the expression of gamma-aminobutyric acid and metabotropic glutamate receptors in male newborn rats’ inferior colliculi
  23. Original Articles – Neonates
  24. Respiratory function monitoring during early resuscitation and prediction of outcomes in prematurely born infants
  25. Quality improvement sustainability to decrease utilization drift for therapeutic hypothermia in the NICU
  26. Short Communication
  27. Use of a pocket-device point-of-care ultrasound to assess cervical dilation in labor: correlation and patient experience
  28. Letters to the Editor
  29. Correspondence on “COVID-19 vaccination and pregnancy”
  30. Response to the letter to the editor regarding “Covid-19 vaccination and pregnancy: a systematic review of maternal and neonatal outcomes”
https://doi.org/10.1515/jpm-2022-0604
Keywords for this article
chorioamnionitis; contamination; inflammation; microbial survey; sterile womb hypothesis
Creative Commons
BY 4.0

Articles in the same Issue

  1. Frontmatter
  2. Reviews
  3. Covid-19 vaccination and pregnancy: a systematic review of maternal and neonatal outcomes
  4. Improvised bubble continuous positive airway pressure ventilation use in neonates in resource-limited settings: a systematic review and meta-analysis
  5. Opinion Papers
  6. Anger: an underappreciated destructive force in healthcare
  7. Severe maternal thrombocytopenia and prenatal invasive procedures: still a grey zone
  8. Commentary
  9. The care of the magic of life before and after its beginning
  10. Original Articles – Obstetrics
  11. The impact of trimester of COVID-19 infection on pregnancy outcomes after recovery
  12. Adverse outcomes and maternal complications in pregnant women with severe-critical COVID-19: a tertiary center experience
  13. Are bacteria, fungi, and archaea present in the midtrimester amniotic fluid?
  14. Bioavailability of the tumor necrosis factor alpha/regulated on activation, normal T cell expressed and secreted (RANTES) biosystem inside the gestational sac during the pre-immune stages of embryo development
  15. The role of the soluble fms-like tyrosine kinase-1/placental growth factor (sFlt-1/PIGF) – ratio in clinical practice in obstetrics: diagnostic and prognostic value
  16. Prenatal diagnosis of non-mosaic sex chromosome abnormalities: a 10-year experience from a tertiary referral center
  17. Prediction of lung maturity through quantitative ultrasound analysis of fetal lung texture in women with diabetes during pregnancy
  18. Evaluation of an artificial intelligent algorithm (Heartassist™) to automatically assess the quality of second trimester cardiac views: a prospective study
  19. Original Article – Fetus
  20. Fetal brain activity and the free energy principle
  21. Predictive value of ultrasound in prenatal diagnosis of hypospadias: hints for accurate diagnosis
  22. The effect of maternal diabetes on the expression of gamma-aminobutyric acid and metabotropic glutamate receptors in male newborn rats’ inferior colliculi
  23. Original Articles – Neonates
  24. Respiratory function monitoring during early resuscitation and prediction of outcomes in prematurely born infants
  25. Quality improvement sustainability to decrease utilization drift for therapeutic hypothermia in the NICU
  26. Short Communication
  27. Use of a pocket-device point-of-care ultrasound to assess cervical dilation in labor: correlation and patient experience
  28. Letters to the Editor
  29. Correspondence on “COVID-19 vaccination and pregnancy”
  30. Response to the letter to the editor regarding “Covid-19 vaccination and pregnancy: a systematic review of maternal and neonatal outcomes”
Sign up now to receive a 20% welcome discount
Institutional Access
How does access work?
Have an idea on how to improve our website?
Please write us.
© 2025 De Gruyter Brill
Downloaded on 23.9.2025 from https://www.degruyterbrill.com/document/doi/10.1515/jpm-2022-0604/html
Scroll to top button