Infection and preterm birth

Endocrinology of labour

Preterm labour, defined as delivery before 37 weeks of completed pregnancy, continues to present a major problem in clinical obstetrics and remains the major contributory factor to the perinatal mortality and morbidity statistics. While it is now possible, with recent advances in neonatal care, to take infants delivered very prematurely and provide them with the lifelines that will ensure their ultimate discharge from the neonatal intensive care nursery, the cost of this form of management – in terms both of health care funds and of emotion – is extraordinarily high. Hence there remains a strong rationale for attempting to understand the underlying biochemistry and physiology of labour in order to develop methods of recognizing the patient in true preterm labour, and of developing better strategies to prevent or to manage this condition. In the best of our neonatal intensive care settings, survival of the infant born at 28–30 weeks’ gestation, or greater than 1500 grams, may be greater than 90%. Thus, the clinical management strategy may be directed more towards sustaining intrauterine life for 4–6 weeks in those patients presenting in preterm labour before this time in order to gain time for intrauterine maturation of these fetuses before they are delivered to the tertiary care NICU setting.

Recombinant human lactoferrin has preventive effects on lipopolysaccharide-induced preterm delivery and production of inflammatory cytokines in mice

OBJECTIVE

The following animal studies have been conducted to investigate whether recombinant human lactoferrin (rh-LF) has the same effect as bovine lactoferrin (b-LF) in the prevention of preterm delivery.

STUDY DESIGN

Female C3H/HeNCrj mice were pair-mated with male Crj:B6D2F1 mice. On day 15 of gestation, as a model of preterm delivery, a 50 microg/kg intraperitoneal injection of lipopolysaccharide (LPS) was administered twice with a 3-h interval between injections (2:00 and 5:00 PM). One hour prior to each LPS injection (1:00 and 4:00 PM), an intraperitoneal injection of saline, b-LF, or rh-LF (1 mg/body) was administered. In non-LPS-treated controls, an intraperitoneal injection of saline was administered 4 times (1:00, 2:00, 4:00 and 5:00 PM). Body weights and delivery times were recorded. To compare plasma levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) between experimental and other pregnant mice, prepared as above, were sacrificed 6 h after the second LPS injection, and then blood samples were obtained and analyzed.

RESULTS

Preterm delivery occurred (16.2+/-0.4 days of gestation) in all LPS-treated mice that were not administered LF. LF significantly prolonged gestation of LPS-treated mice: b-LF+LPS, 17.8+/-0.3 days; rh-LF+LPS, 18.0+/-0.8 days (P<0.05). LF (1 mg/body) significantly suppressed plasma IL-6 in LPS-treated mice:b-LF+LPS, 1060+/-154; rh-LF+ LPSF, 244+/-59; LPS without LF, 1628+/-115 pg/mL (P<0.05). As well, LF (1 mg/body) significantly suppressed plasma TNF-alpha in LPS-treated mice: b-LF+LPS, 88+/-36; rh-LF+LPS, 37+/-30; LPS without LF, 114+/-49 pg/mL (P<0.05).

CONCLUSIONS

Rh-LF may prolong gestation in LPS-induced preterm delivery in mice, by suppressing LPS-induced plasma IL-6 and TNF-alpha augmentation.

Preventive effect of recombinant human lactoferrin in a rabbit preterm delivery model

OBJECTIVE

Lactoferrin, an iron-binding glycoprotein found in cervical mucus and amniotic fluid, plays a defensive role against mucosal infections. This study examined the effect of recombinant human lactoferrin on preterm delivery in a rabbit model.

STUDY DESIGN

Anesthetized rabbits were randomly assigned to receive either inoculation with Escherichia coli or saline solution and to receive treatment with or without recombinant human lactoferrin inserted into the cervix 2 hours before bacterial inoculation (condition A: saline + saline; condition B: E coli + saline; condition C: E coli + recombinant human lactoferrin). E coli , saline solution, and recombinant human lactoferrin were inserted into the cervix using a hysteroscope and a sterile polyethylene cannula. Fetus survival rate and days to delivery after inoculation were monitored and tumor necrosis factor-alpha concentrations were measured in maternal serum and amniotic fluid.

RESULTS

Fetus survival for conditions A, B, and C were 95.7%, 0%, and 32.6%, respectively, whereas pregnancy continuation was 7.00 +/- 0 days, 3.25 +/- 0.43 days, and 4.85 +/- 1.77 days, respectively.

CONCLUSION

Cervical recombinant human lactoferrin administration increased fetal survival and extended pregnancy. Lactoferrin has an anti-inflammatory action as well as an antibacterial action, suggesting that recombinant human lactoferrin has the potential to prevent preterm delivery originating from cervical infection in the clinical setting.

Preventive effect of recombinant human lactoferrin on lipopolysaccharide-induced preterm delivery in mice

BACKGROUND

In order to investigate whether recombinant human lactoferrin (rh-LF) has the same effect as bovine LF (b-LF) for the prevention of preterm delivery, we conducted the following animal studies.

METHODS

Female C3H/HeNCrj mice were pair-mated with male Crj:B6D2F1 mice. As a model of preterm delivery, on day 15 of gestation, a 50 microg/kg intraperitoneal injection of lipopolysaccharide (LPS) was administered twice with a 3-hr interval between injections (14:00 and 17:00 hours). At 1 hr prior to each LPS injection (13:00 and 16:00 hours), an intraperitoneal injection of saline, b-LF, or rh-LF (1 mg/body) was administered. In non-LPS-treated controls, an intraperitoneal injection of saline was administered four times (13:00, 14:00, 16:00, and 17:00 hours). We measured body weight and recorded delivery time. To measure plasma levels of interleukin-6 (IL-6), other pregnant mice, in which the same preparation as mentioned above had been done, were killed 6 h after the second LPS injection and blood samples were obtained.

RESULTS

Delivery occurred in preterm (16.2 +/- 0.4 days of gestation) in all LPS-treated mice not administered LF. LF significantly prolonged gestation of LPS-treated mice: LPS + b-LF, 17.8 +/- 0.3 days; LPS + rh-LF, 18.2 +/- 1.3 days (p < 0.05). LF (1 mg/body) significantly suppressed plasma IL-6 in LPS-treated mice: LPS + b-LF, 1060 +/- 154; LPS + rh-LF, 244.2 +/- 59.4; and LPS without LF, 1628 +/- 115 pg/ml (p < 0.05).

CONCLUSIONS

rh-LF has an effect of prolongation of gestation in LPS-induced preterm delivery in mice, suppressing LPS-induced plasma IL-6 augmentation.

Lipoteichoic acid induces preterm delivery in mice

The purpose of this study was to determine whether or not lipoteichoic acid (LTA) could induce preterm delivery in mice. On days 15 and 17 of pregnancy, female C3H/HeN mice impregnated by male B6D2F1 mice were given intraperitoneal injections of LTA (12.5-75 mg/kg, single dose or repeated doses at a 3-h interval). We examined the changes in cervix, placental trophoblasts, and plasma and amniotic fluid concentrations of interleukin-1alpha (IL-1alpha), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) after dosing with LTA. In addition, the effect of LTA on the contraction of isolated uterine muscle from pregnant mice was also measured. The incidence of preterm delivery was highest (100%), when the pregnant animals were treated with 75 mg/kg LTA twice on day 15 of pregnancy or with 25 mg/kg LTA twice on day 17 of pregnancy. LTA-accelerated cervical ripening and placental abruption preceding the onset of preterm delivery, as well as increased plasma and amniotic fluid concentrations of IL-1alpha, IL-6, and TNF-alpha. Also, LTA increased contraction of uterine muscle strips. In conclusion, LTA induced preterm delivery in mice in the same manner as lipopolysaccharide (LPS), but the effective dose of LTA was larger than that of LPS.

The relationship between bacterial vaginosis and preterm birth. A review

Bacterial vaginosis is currently the most prevalent form of vaginal infection of reproductive age women. The etiology of bacterial vaginosis has not yet been defined. However, clear criteria for diagnosis and treatment have been established in the absence as well as in presence of pregnancy. Recent data show an association between bacterial vaginosis and preterm labor and delivery. This review outlines the role of bacterial vaginosis in preterm birth and other pregnancy complications.

Streptococci and the genital tract

Streptococci of Lancefield Group B (GBS) are known to cause maternal sepsis and neonatal infection, whereas streptococci Lancefield Group A (GAS) cause vulvo-vaginitis in both children and adults. Prevalence of SGB colonization of the lower genital tract of normal women is between 4-18%, with higher rates found in hospital personnel and delivery rooms. Such high carriage rates may be a significant factor in nosocomial transmission of GBS to neonates. Symptomatic infection is uncommon and usually secondary to other pathological states. Amnionitis is a complication of vaginal carriage of GBS and there is now evidence that chorioamnionitis is associated with pre-term labour and its attendant problems. GBS infection of the male genitalia has also been described. Intrapartum chemoprophylaxis has been shown to prevent early onset GBS disease of the neonate. Prevalence of GAS in the genital tract is lower than that for GBS, but is more likely to be symptomatic. The response to penicillin is usually prompt. Optimal drug regimens need to be determined, particularly for use in pregnancy.

Placental morphology and concentrations of glutathione (GSH and GSSG) and lipid peroxides (LPO) in two models of disturbed pregnancy of Uje:WIST rats

Treatment of pregnant rats with heat-denaturated bacterial material (endotoxin-model) or exposure to chronic restraint of prenatally lithium-treated pregnant dams (stress-model) were used as two models of disturbed pregnancy, both causing decreased fetal body mass. The quotient of fetal/placental mass was lowered in the endotoxin-group only. Placental mass and protein content were not changed significantly in both experimental groups, although a tendency to smaller placentae was noticed in the stress-group. Placental histology of the stress-group did not differ from untreated controls. In the endotoxin-group an altered structure of the placental barrier was observed. Small decreases of GSH and GSSG in the endotoxin-group and of GSSG in the stress-group without significant changes of the GSH/GSSG relationship were measured in homogenates of the placental labyrinth. Moderate enhancement of LPO concentration occurred in the endotoxin-group and more distinctly in two litters of the stress-group, the latter being connected with high GSSG concentrations and low fetal/placental mass-quotients.

A contemporary view of the human placenta

Our current knowledge of the human placenta is briefly reviewed. Particular stress is placed upon the considerable functional reserve capacity of the placenta, the unimportance of most visible abnormalities of the placenta, the lack of any evidence that the placenta ages during gestation and the lack of significance of placental weight. The effects on the placenta of infection and of maternal cigarette smoking are considered and the concept of placental insufficiency critically discussed. It is concluded that most cases of 'placental insufficiency' are, in reality, examples of maternal vascular insufficiency resulting from inadequate placentation during the early stages of pregnancy.