Objective
We sought to determine the influence of microbial invasion of the amniotic cavity (MIAC) and acute histologic chorioamnionitis (HCA) on the intensity of the intraamniotic inflammatory response and neonatal morbidity in preterm prelabor rupture of membranes (PPROM) between 34-37 weeks.
Study Design
This study included 99 women with singleton pregnancies complicated by PPROM between the gestational ages of 34-37 weeks. Amniocenteses were performed at the time of admission, and MIAC and amniotic fluid interleukin-6 concentrations were determined. After delivery, the placenta was evaluated for the presence of HCA.
Results
Women with both MIAC and HCA had the highest intraamniotic inflammatory response, which was mediated by interleukin-6 concentrations (both MIAC and HCA: median 2164.0 pg/mL; HCA alone: median 654.8 pg/mL; MIAC alone: median 784.1 pg/mL; neither MIAC nor HCA: median 383.0 pg/mL; P < .0001) and the highest incidence of newborns with early-onset sepsis ( P = .02).
Conclusion
Both MIAC and HCA affect the intensity of the intraamniotic inflammatory response and the incidence of early-onset sepsis following PPROM between 34-37 weeks. The intensity of the intraamniotic inflammatory response should be considered in the clinical management of PPROM between 34-37 weeks.
Preterm prelabor rupture of membranes (PPROM) is defined as the leakage of amniotic fluid <37 gestational weeks, which precedes the onset of regular uterine activity. PPROM accounts for approximately 30-40% of all preterm deliveries.
A substantial proportion of PPROM cases (40-60%) occur between 34-37 weeks. Although newborns of mothers with PPROM between 34-37 weeks are often incorrectly considered nearly physiologically mature, they represent a high-risk group with an increased rate of morbidities and a higher rate of hospital readmission in the first month of life when compared to full-term infants.
Recent studies have evaluated the differences between expectant and active management of women with PPROM between 34-37 weeks with respect to short-term neonatal morbidity, especially for early-onset sepsis. Although these studies were well designed, they did not shed light on this problem, as they revealed no difference in the rate of early-onset sepsis between active and expectant management of pregnancies with PPROM between 34-37 weeks. Therefore, the optimal management of PPROM between 34-37 weeks remains a clinical dilemma because there is lack of evidence to justify either expectant or active management. This is in contrast to PPROM <34 weeks, a condition for which expectant management is recommended.
Strong evidence indicates that in addition to gestational age (GA), the intraamniotic inflammatory response is one of the most important determinants of the adverse neonatal outcomes associated with PPROM. Our group recently showed that not only intraamniotic but also fetal inflammatory responses in PPROM between 24-37 gestational weeks are highest when both microbial invasion of the amniotic cavity (MIAC) and acute histologic chorioamnionitis (HCA) are present. Therefore, we hypothesize that PPROM pregnancies between 34-37 weeks complicated by these conditions may have a higher intraamniotic inflammatory response, resulting in worse short-term neonatal morbidity when compared to PPROM between 34-37 weeks without MIAC and HCA. Furthermore, this topic is of particular clinical relevance, as it may result in the optimization of the clinical management of PPROM between 34-37 weeks.
Therefore, the purpose of this study was to evaluate the intensity of the intraamniotic inflammatory response, as characterized by amniotic fluid interleukin (IL)-6 concentrations, and subsequent neonatal morbidity based on the presence of MIAC and HCA in PPROM pregnancies between 34-37 weeks.
Materials and Methods
Sample collection
From May 2008 through March 2013, a prospective cohort study was conducted on pregnant women at GA between 34+0 and 36+6 weeks who were admitted to the Department of Obstetrics and Gynecology, University Hospital in Hradec Kralove, Czech Republic. Pregnant women with singleton pregnancies, PPROM, and maternal age >18 years were invited to participate in the study. Exclusion criteria included women with gestational hypertension, preeclampsia, fetuses with an estimated weight <10th percentile, the presence of either congenital or chromosomal fetal abnormalities, gestational or pregestational diabetes, and signs of fetal hypoxia. The primary outcome of this study was the intensity of the intraamniotic inflammatory response, characterized by IL-6 concentrations in the amniotic fluid. The secondary outcome was neonatal morbidity.
GA were established by first-trimester fetal biometry. In our department, PPROM pregnancies between 34-37 weeks are actively managed. Induction of labor is initiated or a cesarean section is performed within 24 hours after membrane rupture depending on the fetal status, the maternal serum concentration of C-reactive protein, and cervicovaginal streptococcus beta colonization. All these women receive antibiotics after hospital admission and amniocentesis.
PPROM was diagnosed visually using a sterile speculum examination to confirm the pooling of amniotic fluid in the vagina and confirmed by a positive test for the presence of insulin-like growth factor–binding protein-1 (ACTIM PROM test; Medix Biochemica, Kauniainen, Finland) in the vaginal fluid when necessary.
Ultrasound-guided transabdominal amniocentesis was performed upon admission, prior to the administration of antibiotics. The amniotic fluid samples were immediately divided into 3 polypropylene tubes. The first and second tubes containing noncentrifuged samples were immediately transported to the microbiology laboratory, where the first tube was used for polymerase chain reaction (PCR) testing for Ureaplasma species, Mycoplasma hominis , and Chlamydia trachomatis , and the second tube was used for aerobic and anaerobic bacterial culture. The third tube was centrifuged for 15 minutes at 2000 g to remove cells and debris, divided into aliquots and stored at –70°C until analysis.
After delivery, the placentas were fixed in formalin, and tissue samples from the placenta, umbilical cord, and placental membranes were routinely processed and embedded in paraffin. Tissue sections were stained with hematoxylin-eosin for standard histologic examination.
The study was approved by the institutional review board committee (March 19, 2008; no. 200804 SO1P). Written informed consent was obtained from all participants. All women self-identified as Caucasian. Forty-three women in the study group were examined in one of our previous reports on the intraamniotic inflammatory response in women with PPROM throughout the whole range of preterm delivery.
Diagnosis of MIAC
MIAC was defined as a positive PCR for genital mycoplasmas ( Ureaplasma parvum , Ureaplasma urealyticum , and Mycoplasma hominis ) and/or Chlamydia trachomatis and/or as the growth of any bacteria in the amniotic fluid except for coagulase-negative Staphylococcus epidermidis , which was considered a skin contaminant.
Diagnosis of HCA
The degree of neutrophil infiltration was evaluated separately in the free membranes (amnion and chorion-decidua), in the chorionic plate, and in the umbilical cord based on the criteria provided by Salafia et al. A diagnosis of HCA was made based on histologic grades of 3-4 for the chorion-decidua (multiple or confluent foci of at least 5-20 neutrophils), 3-4 for the chorionic plate (at least a few neutrophils present in the connective tissue or chorionic plate), 1-4 for the umbilical cord (any neutrophils present in the umbilical cord), and/or 1-4 for the amnion (at least 1 focus of at least 5 neutrophils). Histologic grades of 1-4 for the umbilical cord were considered to indicate the presence of funisitis. Histopathological examinations were performed by a single pathologist who was blinded to the clinical status of the patient.
Measurement of intraamniotic inflammatory response
The intensity of the intraamniotic inflammatory response was measured by determining the IL-6 concentration in the amniotic fluid. IL-6 concentrations were assessed by the human IL-6 Quantikine enzyme-linked immunosorbent assay (R&D Systems Inc, Minneapolis, MN). Amniotic fluid samples were diluted 10-fold. The sensitivity of the test was <0.70 pg/mL, and the interassay and intraassay coefficients were <10%.
Diagnosis of severe neonatal morbidity
Maternal and perinatal medical records were reviewed by 2 investigators (M.K. and I.M.). Data regarding morbidity and mortality were reviewed for all newborns. For the current study, we defined “severe neonatal morbidity” as follows: the need for tracheal intubation, respiratory distress syndrome (defined by the presence of ≥2 of the following criteria: evidence of respiratory compromise, a persistent oxygen requirement for >24 hours, administration of exogenous surfactant, and radiographic evidence of hyaline membrane disease), transient tachypnea (any oxygen supplement requirement during the first 6 hours that does not increase during the subsequent 18 hours as clinical conditions improve within 3-6 hours, and chest radiographs either normal or indicating reduced translucency, infiltrates, and hyperinsufflation of the lungs), intraventricular hemorrhage (diagnosed by cranial ultrasound examinations based on the criteria defined by Papile et al ), necrotizing enterocolitis (defined as the radiologic finding of either intramural gas or free intraabdominal gas), retinopathy of prematurity (identified using retinoscopy), early- and late-onset sepsis (defined as any systemic bacterial infection documented by a positive blood culture during the first 72 hours of life and the presence of symptoms of or strong clinical suspicion of sepsis [presence of symptoms and elevated C-reactive protein and/or affected white blood cell count] between 4-120 days of life), bronchopulmonary dysplasia (defined by the infant’s oxygen requirement at 28 days of life), pneumonia (diagnosed by abnormal findings on chest x-rays), and neonatal death prior to hospital discharge.
Statistical analysis
Demographic and clinical characteristics were compared using a nonparametric Jonckheere-Terpstra test and the Mann-Whitney U test for continuous variables and presented as medians (range). Categorical variables were compared using the Cochran-Armitage test for trends or Fisher exact test and the results were presented as numbers (%). Receiver operating characteristic curves were used to determine the best cutoff value of IL-6 concentration in the amniotic fluid for the diagnosis of early-onset sepsis in newborns. A Spearman partial correlation was used to adjust the data for GA. Differences were considered statistically significant at P < .05. All P values were determined from 2-sided tests, and all statistical analyses were carried out using SPSS 19.0 for Mac OS X (IBM Corp, Armonk, NY) and GraphPad Prism 5.03 for Mac OS X (GraphPad Software, La Jolla, CA).
Results
A total of 118 women with PPROM occurring at GA between 34-37 weeks were recruited for the study. Of these 118 women, amniocentesis was not possible in 10 (8%) women, and the results of the histopathological assessment of the placenta were not available for 9 (7%) women. The remaining 99 women were included in the study. The overall rate of MIAC was 23% (23/99), and HCA was found in 49% (49/99) of women. Funisitis was identified in 12% (12/99) of women. Both MIAC and HCA were present in 12% (12/99) of women. HCA alone and MIAC alone were present in 37% (37/99) and 11% (11/99) of women, respectively. Almost 40% (39/99) of women exhibited neither MIAC nor HCA. No differences in maternal and clinical characteristics were observed among these subgroups ( Table 1 ). No cases of clinical chorioamnionitis were present in the study population. The most common bacteria was Ureaplasma species, which was identified in 65% (15/23) of women. Polymicrobial findings were found in 9% (2/23) of women ( Ureaplasma species + Mycoplasma hominis and Ureaplasma species + streptococcus alpha hemolytic). Table 2 lists all microorganisms detected in the amniotic fluid.
| Characteristic | Presence of MIAC and HCA (n = 12) | Presence of HCA alone (n = 37) | Presence of MIAC alone (n = 11) | Absence of MIAC and HCA (n = 39) | P value |
|---|---|---|---|---|---|
| Maternal age, y, median (range) | 32 (21–40) | 29 (24–35) | 32 (24–44) | 32 (22–38) | .49 |
| Prepregnancy body mass index, kg/m 2 , median (range) | 24.3 (17.6–34.4) | 23.1 (18.0–36.8) | 22.7 (17.9–29.7) | 21.8 (17.5–38.6) | .17 |
| Smoking, n (%) | 2 (17) | 4 (11) | 3 (27) | 7 (18) | .52 |
| Gestational age at admission, wk, median (range) | 35 (34–37) | 36 (34–37) | 36 (34–37) | 36 (34–37) | .15 |
| Gestational age at delivery, wk, median (range) | 35 (35–37) | 36 (34–37) | 36 (34–37) | 36 (34–37) | .18 |
| Latency from PPROM to amniocentesis, h, median (range) | 6.0 (3.0–20.0) | 5.0 (1.0–22.0) | 4.0 (2.0–23.0) | 6.0 (1.0–23.0) | .78 |
| Latency from PPROM to delivery, h, median (range) | 24.0 (9.0–64.0) | 22.0 (6.0–94.0) | 16.0 (5.0–51.0) | 15.0 (4.0–73.0) | .20 |
| Latency from amniocentesis to delivery, h, median (range) | 14 (3–47) | 11 (1–92) | 12 (2–28) | 9 (1–65) | .64 |
| Amniotic fluid IL-6, pg/mL, median (range) | 2164.0 (226.5–6159.0) | 654.8 (24.3–6072.0) | 784.1 (319.4–3484.0) | 383.0 (35.7–3097.0) | < .0001 a |
| CRP levels at admission, mg/L, median (range) | 5.7 (2.2–14.1) | 8.0 (1.1–82.0) | 5.0 (1.0–13.0) | 5.0 (0.6–71.3) | .06 |
| WBC count at admission, ×10 9 L, median (range) | 11.5 (9.0–14.0) | 11.0 (6.0–17.0) | 11.0 (7.0–19.0) | 11.1 (7.0–18.0) | .97 |
| Administration of antibiotics, no. (%) | 12 (100) | 36 (97) | 11 (100) | 37 (95) | .37 |
| Induction of labor, no. (%) | 6 (50) | 16 (43) | 5 (45) | 12 (31) | .17 |
| Spontaneous vaginal delivery, no. (%) | 8 (67) | 33 (89) | 10 (91) | 33 (85) | .76 |
| Cesarean section, no. (%) | 3 (25) | 4 (11) | 1 (9) | 4 (10) | .35 |
| Forceps delivery, no. (%) | 1 (8) | 0 (0) | 0 (0) | 1 (5) | .72 |
| Birth weight, g, median (range) | 2490 (1810–3870) | 2480 (1860–2870) | 2470 (1820–3310) | 2390 (1790–3390) | .58 |
| Funisitis, no. (%) | 5 (42) | 7 (19) | – | – | .14 |
| 5-min Apgar score, median (range) | 9 (9–10) | 9 (8–10) | 9 (8–10) | 9 (7–10) | .63 |
| 10-min Apgar score, median (range) | 10 (9–10) | 10 (8–10) | 10 (9–10) | 10 (7–10) | 1.00 |
| Presence of MIAC and HCA (n = 12) | Presence of MIAC alone (n = 11) |
|---|---|
| Ureaplasma species | Ureaplasma species |
| Ureaplasma species | Ureaplasma species |
| Ureaplasma species | Ureaplasma species |
| Ureaplasma species | Ureaplasma species |
| Ureaplasma species | Ureaplasma species |
| Ureaplasma species | Mycoplasma hominis |
| Ureaplasma species | Mycoplasma hominis |
| Ureaplasma species | Chlamydia trachomatis |
| Haemophilus influenzae | Streptococcus alpha hemolytic |
| Streptococcus alpha hemolyticus | Streptococcus pneumoniae |
| Ureaplasma species; Mycoplasma hominis | Candida albicans |
| Ureaplasma species; Streptococcus alpha hemolytic |
Amniotic fluid IL-6 concentrations
We observed differences in the IL-6 concentrations in the amniotic fluid among the subgroups based on the presence or absence of MIAC and HCA ( P < .0001). Women with both MIAC and HCA exhibited the highest median concentration of IL-6 among the subgroups (both MIAC and HCA: 2164.0 pg/mL; HCA alone: 654.8 pg/mL; MIAC alone: 784.1 pg/mL; and neither MIAC nor HCA: 383.0 pg/mL), and differences were observed in the IL-6 concentrations in the amniotic fluid between women with both MIAC and HCA and other women (MIAC and HCA vs HCA alone: P = .005; MIAC and HCA vs MIAC alone: P = .03; MIAC and HCA vs neither MIAC nor HCA: P < .0001) ( Figure 1 ). Women without MIAC and HCA had lower amniotic fluid IL-6 concentrations than women with HCA alone ( P = .03) and those with MIAC alone ( P = .02), as shown in Figure 2 . No differences in the amniotic fluid IL-6 concentrations were observed between women with HCA alone and those with MIAC alone ( P = .60) ( Figure 2 ).
Neonatal morbidity
Respiratory disorders (respiratory distress syndrome or transient tachypnea of newborns) and the need for tracheal intubation were observed in 14% (14/99) and 3% (3/99) of newborns, respectively. Intraventricular hemorrhages of grades I-II were found in 6% (6/99) of newborns. No intraventricular hemorrhages of grades III or IV were observed. Pneumonia was diagnosed in 2% (2/99) of newborns. Severe neonatal morbidity was observed in 25% (25/99) of newborns. This cohort of women had no evidence of bronchopulmonary dysplasia, retinopathy of prematurity, necrotizing enterocolitis, or late-onset sepsis, and no neonatal death.
Selected neonatal morbidities are presented in Table 3 according to the presence or absence of MIAC and/or HCA. Differences were observed among subgroups in early-onset sepsis ( P = .02), which was observed in 4% (4/99) of newborns, and severe neonatal morbidity ( P = .03). Three cases of early-onset sepsis occurred in the subgroup of women with both MIAC and HCA. One case (culture proven) was in a woman with MIAC alone. Two newborns had culture-proven early-onset sepsis ( Haemophilus influenzae and Streptococcus pneumoniae ). Differences in severe neonatal morbidity ( P = .003) were only observed among the 3 GA subgroups (34-35, 35-36, and 36-37 weeks) ( Table 4 ).
| Characteristic, no. (%) | Presence of MIAC and HCA (n = 12) | Presence of HCA alone (n = 37) | Presence of MIAC alone (n = 11) | Absence of MIAC and HCA (n = 39) | P value for trend |
|---|---|---|---|---|---|
| Tracheal intubation | 1 (8) | 0 (0) | 0 (0) | 2 (5) | .72 |
| Respiratory disorders | 4 (33) | 6 (16) | 2 (18) | 2 (5) | .02 |
| Respiratory distress syndrome | 3 (25) | 3 (8) | 1 (9) | 2 (5) | .11 |
| Transient tachypnea | 1 (8) | 3 (8) | 1 (9) | 0 (0) | .10 |
| Intraventricular hemorrhage grades I-II | 0 (0) | 3 (8) | 0 (0) | 3 (8) | .94 |
| Early-onset sepsis | 3 (25) | 0 (0) | 1 (9) | 0 (0) | .02 a |
| Cultivation-proven early-onset sepsis | 1 (8) | 0 (0) | 1 (9) | 0 (0) | .31 |
| Pneumonia | 0 (0) | 1 (3) | 1 (9) | 0 (0) | .72 |
| Severe neonatal morbidity | 6 (50) | 10 (27) | 3 (27) | 6 (15) | .03 a |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
