Preterm prelabour amniorrhexis

HISTOLOGICAL CHORIOAMNIONITIS: CURRENT CONCEPTS OF DIAGNOSIS, CLASSIFICATION AND CLINICAL SIGNIFICANCE

Interest in the clinical associations between maternal intrapartum fever and adverse neonatal outcome has been longstanding, with publications of a relationship between maternal fever and cerebral palsy dating from the 1950s. Further recognition of the associations between either clinically or histologically characterised chorioamnionitis, ascending infection and neonatal wellbeing followed, with numerous reports in the 1960s and 70s, particularly as the neonatal significance of group B streptococcal infections became apparent. Similarly, with the systematic introduction of diagnostic light microscopy into clinical medicine, chorioamnionitis (inflammation of the placental membranes) and funisitis (inflammation of the umbilical cord) were recognised as distinct histological entities, with increasing recognition that the aetiology was likely to be infective. There are numerous texts discussing in detail the pathogenesis and histological features of chorioamnionitis and funisitis. The aim of this review is to provide an overview of the salient associated issues for clinical practitioners and to highlight areas of ongoing uncertainty and recent developments in understanding.

Preterm prelabour amniorrhexis

Preterm delivery occurs in less than 10% of pregnancies but accounts for more than 60% of all neonatal deaths. Approximately one third of preterm deliveries are associated with preterm prelabour amniorrhexis and in a high proportion of such cases the underlying cause may be ascending infection from the lower genital tract. The causes of neonatal death in pregnancies with amniorrhexis are prematurity, pulmonary hypoplasia and sepsis. In the management of pregnancies with preterm prelabour amniorrhexis it is essential to distinguish between those with and without intrauterine infection. If there is no infection at presentation it is unlikely that this will develop and in such cases there is no benefit from hospitalisation, bed rest, prophylactic tocolytics or antibiotics. The group with evidence of intrauterine infection go into spontaneous labour within a few days of amniorrhexis; in this group the main determinant for the appropriate management is the gestation at amniorrhexis.

A randomized controlled trial of adjunctive erythromycin in women with idiopathic preterm labor

OBJECTIVE

Our purpose was to determine the effects of erythromycin among hospitalized women with idiopathic preterm labor who were treated with tocolytics.

METHODS

This prospective randomized trial was conducted in patients with preterm labor of no clinically identifiable cause between 26 and 34 weeks of gestation, who were receiving magnesium sulfate. A total of 136 patients were screened. Of these, 80 eligible, consenting patients were randomized to receive either 400 mg erythromycin or placebo orally every 6 hours for 10 days. Necessary statistical comparisons were preformed using unpaired two-tailed Student's t-test and Chi-square analysis.

RESULTS

In comparing the 38 erythromycin and 42 placebo patients there was improvement in the treatment-to-delivery interval (33.33 +/- 18.36 versus 26.88 +/- 13.9 days, respectively), mean gestational age at delivery (36.11 +/- 2.33 versus 34.36 +/- 2.33 weeks, respectively), mean birth weight (2722.31 +/- 511.65 versus 2419.41 +/- 513.54 g, respectively), and reduced neonatal admission to NICU (36.8% versus 60.19%) in the erythromycin group.

CONCLUSION

In patients with idiopathic preterm labor the adjunctive use of erythromycin therapy appeared safe and well tolerated and resulted in a statistically significant delay from admission to delivery and improved gestational age at delivery, mean birth weight and neonatal outcome.

Ex vivo evaluation of human fetal membrane closure

BACKGROUND AND OBJECTIVE

This study compares stress and leak point pressure of human fetal membranes following closure with suture, laser welding, or a new tissue sealant, SynthaSeal.

STUDY DESIGN/MATERIALS AND METHODS

Samples of fetal membrane were bisected and repaired with suture, laser welding with albumin solders, or a tissue sealant. Representative tissue samples were assessed by histology. Anastomotic strength was evaluated by tensiometry. Additionally, leak pressure was measured after membrane samples were placed onto an infusion pump/pressure transducer, incised, and repaired as above.

RESULTS

Membrane stress was strongest (P<0.001) for the tissue sealant group. Sutured samples were stronger than laser-welded samples. Membrane leak pressure was greatest for the tissue sealant group. The suture group demonstrated a higher leak pressure than the laser-welded group.

CONCLUSIONS

Human fetal membranes were not suited for repair with laser welding under the conditions tested. A new tissue sealant, SynthaSeal, may provide a simple, effective method for membrane closure following fetoscopy, amniocentesis, and open fetal surgery.

Closure techniques for fetoscopic access sites in the rabbit at mid-gestation

Operative fetoscopy may be limited by its relatively high associated risk of preterm prelabour rupture of membranes. The objective of this study was to study closure techniques of the access site for fetoscopy in the mid-gestational rabbit. A total of 32 does (288 amniotic sacs) at 22 days gestational age (GA; term = 32 days) underwent 14 gauge needle fetoscopy, by puncture through surgically exposed amnion. Entry site was randomly allocated to four closure technique groups: myometrial suture (n = 14), fibrin sealant (n = 15), autologous maternal blood plug (n = 13), collagen plug (n = 14); 16 sacs were left unclosed (positive controls), and the unmanipulated 216 sacs were negative controls. Membrane integrity, presence of amniotic fluid and fetal lung to body weight ratio (FLBWR) were evaluated at 31 days GA. Following fetoscopy without an attempt to close the membranes, amniotic integrity was restored in 41% of cases (amniotic integrity in controls 94%; P = 0.00001). When the access site was surgically closed, the amnion resealed in 20-44% of cases, but none of the tested techniques was significantly better than the others or than positive controls. Permanent amniotic disruption was associated with a significantly lower FLBWR in all groups. In conclusion, the rate of fetoscopy-induced permanent membrane defects in this model did not improve by using any of the closure techniques tested here.

Effect of nimesulide and indomethacin on contractility and the Ca2+ channel current in myometrial smooth muscle from pregnant women

The non-steroidal anti-inflammatory drug (NSAID) indomethacin inhibits both constitutive and inducible forms of cyclo-oxygenase (COX-1 and COX-2, respectively), while nimesulide is a selective COX-2 inhibitor. Uterine COX-2 is upregulated before and during term and pre-term labour, and prostaglandins play a crucial role in parturition. We therefore evaluated the effects of these drugs on myometrial contractility and the voltage-gated Ca2+ channel current in tissue strips and isolated human myometrial smooth muscle cells (HMSMC) from myometrial biopsies taken with informed consent from women undergoing caesarean section at term (not in labour). Nimesulide and indomethacin caused almost complete inhibition of spontaneous myometrial contractions at concentrations of 100 and 300 microM, respectively. The Ca2+ channel current was inhibited in a concentration-dependent manner by both drugs, with a 40% reduction of the current at 100 microM nimesulide and 300 microM indomethacin. Nimesulide also accelerated the decay of the Ca2+ channel current. The inhibition of the Ca2+ channel current by 100 microM nimesulide and 300 microM indomethacin was unaffected by the presence of either PGF2alpha or PGE2 (30 microM), and was of similar magnitude whether 10 mM Ba2+ or 1.5 mM Ca2+ was used as the charge carrier. The concentrations of indomethacin and nimesulide required to suppress spontaneous contractility in human pregnant myometrium were much higher than those necessary to inhibit prostaglandin production. The results suggest that both nimesulide and indomethacin inhibit myometrial contractility via mechanisms independent of cyclo-oxygenase inhibition. Blockade of the Ca2+ current may contribute to this effect.

Fetal membrane closure techniques after hysteroamniotomy in the midgestational rabbit model

OBJECTIVE

We studied closure techniques for amniotic access in midgestational rabbits.

STUDY DESIGN

Twenty-eight rabbits with a total of 313 amniotic sacs were used for this study. In each animal a 1 cm hysteroamniotomy was made in two amniotic sacs at 22 days' gestation (term = 32). For 12 amniotic sacs (group 1) only the myometrium was closed by microsurgical suturing. In group 2 (n = 12), sutures included myometrium and membranes. In group 3 (n = 8), a collagen plug was placed, and in group 4 (n = 12) fibrin glue was used. Twelve sacs were left unclosed (positive controls) and the unmanipulated 257 sacs were negative controls. Eight days later (gestational age 30 days) amniotic sacs were evaluated for the presence of amniotic fluid, membrane integrity, and fetal weight and survival. Statistics were done with two-tailed Fisher's exact test and one-way analysis of variance.

RESULTS

Membrane integrity (p = 0.0036) and amniotic fluid (p = 0.047) were best restored after myometrial closure. Fetal weight and survival rate were not affected by different closure techniques.

CONCLUSION

In this model primary closure of the myometrium only yielded best results.