Meconium-stained amniotic fluid: a risk factor for postpartum hemorrhage

Meconium-stained amniotic fluid

Green-stained amniotic fluid, often referred to as meconium-stained amniotic fluid, is present in 5% to 20% of patients in labor and is considered an obstetric hazard. The condition has been attributed to the passage of fetal colonic content (meconium), intraamniotic bleeding with the presence of heme catabolic products, or both. The frequency of green-stained amniotic fluid increases as a function of gestational age, reaching approximately 27% in post-term gestation. Green-stained amniotic fluid during labor has been associated with fetal acidemia (umbilical artery pH <7.00), neonatal respiratory distress, and seizures as well as cerebral palsy. Hypoxia is widely considered a mechanism responsible for fetal defecation and meconium-stained amniotic fluid; however, most fetuses with meconium-stained amniotic fluid do not have fetal acidemia. Intraamniotic infection/inflammation has emerged as an important factor in meconium-stained amniotic fluid in term and preterm gestations, as patients with these conditions have a higher rate of clinical chorioamnionitis and neonatal sepsis. The precise mechanisms linking intraamniotic inflammation to green-stained amniotic fluid have not been determined, but the effects of oxidative stress in heme catabolism have been implicated. Two randomized clinical trials suggest that antibiotic administration decreases the rate of clinical chorioamnionitis in patients with meconium-stained amniotic fluid. A serious complication of meconium-stained amniotic fluid is meconium aspiration syndrome. This condition develops in 5% of cases presenting with meconium-stained amniotic fluid and is a severe complication typical of term newborns. Meconium aspiration syndrome is attributed to the mechanical and chemical effects of aspirated meconium coupled with local and systemic fetal inflammation. Routine naso/oropharyngeal suctioning and tracheal intubation in cases of meconium-stained amniotic fluid have not been shown to be beneficial and are no longer recommended in obstetrical practice. A systematic review of randomized controlled trials suggested that amnioinfusion may decrease the rate of meconium aspiration syndrome. Histologic examination of the fetal membranes for meconium has been invoked in medical legal litigation to time the occurrence of fetal injury. However, inferences have been largely based on the results of in vitro experiments, and extrapolation of such findings to the clinical setting warrants caution. Fetal defecation throughout gestation appears to be a physiologic phenomenon based on ultrasound as well as in observations in animals.

Once We Find Grade III Meconium Stained Amniotic Fluid, Must We Act as Early as Possible?

Background

Grade III meconium stained amniotic fluid (MSAF) is a common obstetric disease, and has the greatest impact on poor maternal and neonatal outcomes.

Question or Hypothesis or Aim

There is no consensus on treatment, especially on the timing of delivery.

Methods

We collected the medical records of 345 women who gave birth with grade III MSAF and analyzed the difference in baseline characteristics and maternal and neonatal outcomes relative to different labor stage, observation times in the first stage of labor, and the presence or absence of abnormal fetal heart rate (FHR) or thick amniotic fluid.

Findings

Higher rate of cesarean section was observed when grade III MSAF was found in active labor. Intervention occurred at an observation time of 90-120 min, but there were no significant differences in maternal or neonatal outcomes shown when the observation time was greater than 3 or 4 hours. However, a higher rate of admission to the neonatal intensive care unit was demonstrated in cases with grade III MSAF with abnormal FHR either in the first or second stage of labor or in cases with thick MSAF in the second stage of labor.

Discussion

Higher rate of composite adverse neonatal outcomes was found when secondary MSAF (a transition from clear AF to MSAF) was diagnosed >3 h before delivery.

Conclusion

In the first stage of labor, an observation time of greater than 4 hours might be possible after grade III MSAF is found if the labor has progressed and is without abnormal FHR.

Is it safe to perform amnioinfusion in the presence of suspected intraamniotic infection?

OBJECTIVE

To study the effect of amnioinfusion in the presence of suspected intra-amniotic infections (SII) on maternal outcomes among women delivering at term.

METHODS

A retrospective cohort study was conducted at a tertiary medical center. All consecutive singleton term deliveries with SII during 2011-2019 were included. Cases where amnioinfusion was performed after the diagnosis of SII were compared to cases without amnioinfusion, matched by cervical dilation at diagnosis of SII. Maternal and obstetric adverse outcomes were compared.

RESULTS

After matching for cervical dilation at diagnosis of SII, the study cohort included 786 women: 62 (7.9%) women in the amnioinfusion group and 724 (92.1%) in the control group. A composite of adverse maternal outcomes occurred in 106 (13.5%) deliveries. There were no significant differences in the rates of maternal adverse outcomes between the amnioinfusion and control groups (11.0% vs 13.7%, respectively; P=0.59), including postpartum endometritis (5.0% vs 3.3%, respectively; P=0.46) and febrile morbidity (10.0% vs 6.5%, respectively; P=0.42). Neonatal blood gas outcomes and Apgar scores did not differ between groups.

CONCLUSION

The use of amnioinfusion for alleviating non-reassuring fetal heart rate in the presence of SII is safe and does not increase the rate of maternal adverse outcome.