Myometrial contractile strain at uteroplacental separation during parturition

The frequency and clinical significance of intra-amniotic inflammation in twin pregnancies with preterm labor and intact membranes

OBJECTIVE

The objective of this study is to evaluate the frequency and clinical significance of intra-amniotic inflammation in twin pregnancies with preterm labor and intact membranes.

STUDY DESIGN

Amniotic fluid (AF) was retrieved from both sacs in 90 twin gestations with preterm labor and intact membranes (gestational age between 20 and 34 6/7 weeks). Preterm labor was defined as the presence of painful regular uterine contractions, with a frequency of at least 2 every 10 min, requiring hospitalization. Fluid was cultured and assayed for matrix metalloproteinase-8. Intra-amniotic inflammation was defined as an AF matrix metalloproteinase-8 concentration >23 ng/mL.

RESULTS

The prevalence of intra-amniotic inflammation for at least 1 amniotic sac was 39% (35/90), while that of proven intra-amniotic infection for at least one amniotic sac was 10% (9/90). Intra-amniotic inflammation without proven microbial invasion of the amniotic cavity was found in 29% (26/90) of the cases. Intra-amniotic inflammation was present in both amniotic sacs for 22 cases, in the presenting amniotic sac for 12 cases, and in the non-presenting amniotic sac for one case. Women with intra-amniotic inflammation observed in at least one amniotic sac and a negative AF culture for microorganisms had a significantly higher rate of adverse pregnancy outcome than those with a negative AF culture and without intra-amniotic inflammation (lower gestational age at birth, shorter amniocentesis-to-delivery interval, and significant neonatal morbidity). Importantly, there was no significant difference in pregnancy outcome between women with intra-amniotic inflammation and a negative AF culture and those with a positive AF culture.

CONCLUSION

Intra-amniotic inflammation is present in 39% of twin pregnancies with preterm labor and intact membranes and is a risk factor for impending preterm delivery and adverse outcome, regardless of the presence or absence of bacteria detected using cultivation techniques.

Simulation of the uterine contractions and foetus expulsion using a chemo-mechanical constitutive model

During vaginal delivery women sustain stretching of their pelvic floor, risking tissue injury and adverse outcomes. Since studies in pregnant women are limited with ethical constraints, computational models have become an interesting alternative to elucidate the pregnancy mechanisms. This research investigates the uterine contractions during foetus expulsion without an imposed trajectory. Such physical process is captured by means of a chemo-mechanical constitutive model, where the uterine contractions are triggered by chemical stimuli. The foetus descent, which includes both pushing and resting stages, has a descent rate within the physiological range. Moreover, the behaviour of the foetus and the uterus stretch agree well with clinical data presented in the literature. The follow-up of this study will be to obtain a complete childbirth simulation, considering also the pelvic floor muscles and its supporting structures. The simulation of a realistic rate of descent, including the pushing and resting stages, is of significant importance to study the pelvic floor muscles due to their viscoelastic nature.

Dynamic Changes in the Myometrium during the Third Stage of Labor, Evaluated Using Two-Dimensional Ultrasound, in Women with Normal and Abnormal Third Stage of Labor and in Women with Obstetric Complications

OBJECTIVE

To investigate dynamic changes in myometrial thickness during the third stage of labor.

METHODS

Myometrial thickness was measured using ultrasound at one-minute time intervals during the third stage of labor in the mid-region of the upper and lower uterine segments in 151 patients including: women with a long third stage of labor (n = 30), postpartum hemorrhage (n = 4), preterm delivery (n = 7) and clinical chorioamnionitis (n = 4). Differences between myometrial thickness of the uterine segments and as a function of time were evaluated.

RESULTS

There was a significant linear increase in the mean myometrial thickness of the upper uterine segments, as well as a significant linear decrease in the mean myometrial thickness of the lower uterine segments until the expulsion of the placenta (p < 0.001). The ratio of the measurements of the upper to the lower uterine segments increased significantly as a function of time (p < 0.0001). In women with postpartum hemorrhage, preterm delivery, and clinical chorioamnionitis, an uncoordinated pattern among the uterine segments was observed.

CONCLUSION

A well-coordinated activity between the upper and lower uterine segments is demonstrated in normal placental delivery. In some clinical conditions this pattern is not observed, increasing the time for placental delivery and the risk of postpartum hemorrhage.

Umbilical vein injection of misoprostol versus normal saline for the treatment of retained placenta: intrapartum placebo-controlled trial

BACKGROUND

The third stage of labour may be complicated by retained placenta, which should be managed promptly because it may cause severe bleeding and infection, with a potentially fatal outcome. This study evaluated the effectiveness of umbilical vein injection of misoprostol for the treatment of retained placenta in a hospital setting.

METHODS

This hospital-based placebo-controlled trial was conducted at the Maternity Teaching Hospital, Erbil City, Kurdistan region, Northern Iraq from April 2011 to February 2012. The inclusion criteria were: gestational age of at least 28 weeks, vaginal delivery, and failure of the placenta to separate within 30 minutes after delivery of the infant despite active management of the third stage of labour. Forty-six women with retained placentas were eligible for inclusion. After informed consent was obtained, the women were alternately allocated to receive umbilical vein injection of either 800 mcg misoprostol dissolved in 20 mL of normal saline (misoprostol group) or 20 mL of normal saline only (saline group). The women were blinded to the group allocation, but the investigator who administered the injection was not. The trial was registered by the Research Ethics Committee of Hawler Medical University.

RESULTS

After umbilical vein injection, delivery of the placenta occurred in 91.3% of women in the misoprostol group and 69.5% of women in the saline group, which was not a significant difference between the two groups. The median vaginal blood loss from the time of injection until delivery of the placenta was significantly less in the misoprostol group (100 mL) than in the saline group (210 mL) (p value < 0.001).

CONCLUSION

Umbilical vein injection of misoprostol is an effective treatment for retained placenta, and reduces the volume of vaginal blood loss with few adverse effects.

CLINICAL TRIAL REGISTRATION

Current Controlled Trial HMU: N252.1.2011.

The retained placenta

The retained placenta is a significant cause of maternal mortality and morbidity throughout the developing world. It complicates 2% of all deliveries and has a case mortality rate of nearly 10% in rural areas. Ultrasound studies have provided fresh insights into the mechanism of the third stage of labour and the aetiology of the retained placenta. Following delivery of the baby, the retro-placental myometrium is initially relaxed. It is only when it contracts that the placenta shears away from the placental bed and is detached. This leads to its spontaneous expulsion. Retained placenta occurs when the retro-placental myometrium fails to contract. There is evidence that this may also occur during labour leading to dysfunctional labour. It is likely that this is caused by the persistence of one of the placental inhibitory factors that are normally reduced prior to the onset of labour, possibly progesterone or nitric oxide. Presently, the only effective treatment is manual removal of placenta (MROP) under anaesthetic. This needs to be carried out within a few hours of delivery to avoid haemorrhage. For women in rural Africa, facilities for MROP are scarce, leading to high mortality rates. Injection of oxytocin into the umbilical vein has been suggested as an alternative. This method relies on the injected oxytocin passing through the placenta to contract the retro-placental myometrium and cause its detachment. Despite several placebo controlled trials of this technique, no firm conclusion have been reached regarding its efficacy. This may be due to inadequate delivery of the oxytocin to the placenta. Further trials are in progress to assess the optimal dose of oxytocin as well as the efficacy of a new technique designed to improve delivery of the oxytocin to the placental bed.

Down-up sequential separation of the placenta

OBJECTIVE

To characterize the patterns of placental separation during the third stage of labor.

METHODS

Continuous real-time ultrasound was performed during the third stage of labor in 101 normal deliveries. The sequence of placental separation was recorded for determining whether the process was multiphasic, the site from which separation commenced and the mode of its progression.

RESULTS

Separation in 97 cases was multiphasic. Monophasic separation in which all parts of the placenta appeared to separate simultaneously occurred in two cases only. Pathological prolongation of the third stage precluded determination of separation in two cases. Ninety-two cases had a uterine wall placenta (anterior or posterior); the separation commenced at one pole and progressed sequentially towards the opposite side in 89 of them. The process started at the lower pole (down-up separation) in 83/92 cases (90.2%) and began from the upper pole (up-down separation) in only 6/92 cases (6.5%). Nine cases had a fundal placenta; of these the separation was also multiphasic but began sequentially from either the anterior or posterior pole, or simultaneously from both, in 8 (88.9%) cases so that the fundal part was separated last (bipolar separation).

CONCLUSIONS

Placental separation is usually an orderly multiphasic phenomenon that begins mostly from the lower pole of the placenta and propagates sequentially upwards. Fundal placentae, however, separate first at their poles with the fundal part being separated last. Recognition of the sequence of events and understanding of the mechanism of placental separation may aid in detecting cases prone to third-stage complications and in managing pathological ones.