Meconium below the vocal cords at delivery: correlation with intrapartum events

[The evolution of approach in the resuscitation of neonates born with meconium-stained amniotic fluid: a tale of two countries, China and U.S.A., in the past 60 years]

Neonates born through meconium-stained amniotic fluid (MSAF) may develop complications including meconium aspiration syndrome, persistent pulmonary hypertension of newborn and death. The approach to the resuscitation of these neonates has significantly evolved for the past few decades. Initially, under direct visualization technique, neonates with MSAF were commonly suctioned below the vocal cords soon after delivery. Since 2015, Neonatal Resuscitation Program (NRP^®) of the American Academy of Pediatrics has recommended against "routine" endotracheal suctioning of non-vigorous neonates with MSAF but favored immediate resuscitation with positive pressure ventilation via face-mask bagging. However, the China neonatal resuscitation 2021 guidelines continue to recommend routine endotracheal suctioning of non-vigorous neonates born with MSAF at birth. This review article discusses the differences and the rationales in the approach in the resuscitation of neonates with MSAF between Chinese and American NRP^® guidelines over the past 60 years.

Impact of the Revised NRP Meconium Aspiration Guidelines on Term Infant Outcomes

OBJECTIVES

To evaluate the association of the Neonatal Resuscitation Program, Seventh Edition changes on term infants born with meconium-stained amniotic fluid (MSAF).

STUDY DESIGN

We evaluated the effect of no longer routinely intubating nonvigorous term infants born with MSAF in 14 322 infants seen by the resuscitation team from January 1, 2014 to June 30, 2017 in a large, urban, academic hospital.

RESULTS

Delivery room intubations of term infants with MSAF fell from 19% to 3% after the change in guidelines (P = <.0001). The rate of all other delivery room intubations also decreased by 3%. After the implementation of the Seventh Edition guidelines, 1-minute Apgar scores were significantly more likely to be >3 (P = .009) and significantly less likely to be <7 (P = .011). The need for continued respiratory support after the first day of life also decreased. Admission rates to the NICU, length of stay, and the need for respiratory support on admission were unchanged.

CONCLUSIONS

Implementation of the Neonatal Resuscitation Program, Seventh Edition recommendations against routine suctioning nonvigorous infants born with MSAF was temporally associated with an improvement in 1-minute Apgar scores and decreased the need for respiratory support after the first day of life. There was also a significant decrease in total intubations performed in the delivery room. This has long-term implications on intubation experience among frontline providers.

A Population-Based Study of Meconium Aspiration Syndrome in Neonates Born between 37 and 43 Weeks of Gestation

The epidemiology of meconium aspiration syndrome (MAS) in term neonates is described in a population-based retrospective study of data recorded for all births from 2000 to 2007 in a French region (Burgundy). Of the 132 884 eligible term newborns, the rate of meconium-stained amniotic fluid (MSAF) was 7.93%. The prevalence of severe MAS was 0.067% in the overall population. MAS rate was 0.11% at 37-38 weeks of gestation (WG), 0.20% at 39–41 WG, and 0.49% at 42-43 WG. Factors independently associated with severe MAS were identified by a case-control study, that is, thick meconium amniotic fluid, fetal tachycardia, Apgar score ≤3 at 1 minute, and birth in a level III facility. Our results confirm the high prevalence of MSAF after 37 WG but also show the low frequency of severe MAS in a period corresponding to the new international recommendations on the management of birth with MSAF.

The pros and cons of suctioning at the perineum (intrapartum) and post-delivery with and without meconium

Routine oronasopharyngeal suctioning (ONPS) of the infant at delivery is a common practice in the delivery room. ONPS is performed to remove lung fluid, meconium, or other secretions from the airway, thereby improving oxygenation and/or preventing aspiration. However, there are controversies regarding this practice, as it seems to be associated with complications. In the presence of clear amniotic fluid, routine ONPS in infants born vaginally and by cesarean section is associated with bradycardia, apnea, and delays in achieving normal oxygen saturations, with no benefit. Intrapartum ONPS and post-natal endotracheal suctioning of vigorous infants born through meconium-stained amniotic fluid (MSAF) does not prevent meconium aspiration syndrome (MAS). Although depressed infants born through MSAF are at risk of developing MAS, there is no evidence that endotracheal suctioning of these infants reduces MAS.

Developing a systems approach to prevent meconium aspiration syndrome: lessons learned from multinational studies

Passage of fetal bowel movement (meconium) is common (in about one out of six births), and in some the staining of the amniotic fluid is a sign of fetal distress. Inhalation of meconium (aspiration syndrome, in upto one out of five to eight such births) just before or at birth may be preventable by a coordinated approach by well-trained and informed birth attendants. Respiratory failure secondary to meconium aspiration syndrome (MAS) remains a major cause of morbidity and mortality in the neonatal population. Infants with hypoxemic respiratory failure because of MAS, persistent pulmonary hypertension of the newborn and pneumonia/sepsis have an increased survival with extracorporeal membrane oxygenation (ECMO). Other treatment options earlier limited to inotropic support, continuous airway pressure (CPAP), conventional ventilatory management, respiratory alkalosis, paralysis and intravenous vasodilators have been replaced by synchronized intermittent mandatory ventilation (SIMV), high-frequency oscillatory ventilation (HFOV), surfactant and inhaled nitric oxide (iNO). HFOV has been advocated for use to improve lung inflation while potentially decreasing lung injury through volutrauma. Other reports describe the enhanced efficacy of HFOV when combined with iNO. Subsequent to studies reporting that surfactant deficiency or inactivation may contribute to neonatal respiratory failure, exogenous surfactant therapy has been implemented with apparent success. Recent studies have shown that iNO therapy in the neonate with hypoxemic respiratory failure can result in improved oxygenation and decreased need for ECMO. However, these innovative interventions are costly, require a sophisticated infrastructure and are not universally accessible. In this paper, a context of systems-approach for prenatal, natal and postnatal management of babies delivered through meconium stained amniotic fluid (MSAF) so that adverse outcomes are minimized and the least number of babies require innovative ventilatory support is described. Previously reported data from a single urban perinatal center (Philadelphia, PA, USA), over a 6-year period (1995-2000), demonstrated that 14.5% (3370/23175 of live births babies were delivered with MSAF. These data also showed that 4.6% of babies (155/3370) with MSAF sustained MAS. Overall, 26% of babies (40/155) with MAS needed ventilatory support (or 0.17% of all live births); of these, only 20% (8/40 or 0.035% of live births) needed innovative ventilatory support. None died or needed ECMO. These data describe the components for a systems approach to prevent and manage adverse outcomes related to MSAF at the regional level II or III perinatal center. Replication of a similar strategy may be more relevant to cost containment and be a safer approach for neonates at risk for MAS-related respiratory failure. This paper assess the evidence for pivotal steps needed to prevent MAS and ensuing neonatal death and disease in the context of diverse perinatal health services.

Meconium aspiration syndrome requiring assisted ventilation: perspective in a setting with limited resources

To determine characteristics, management, complications and outcome of neonates with meconium aspiration syndrome (MAS) requiring mechanical ventilation (MV). A retrospective review of clinical data of neonates with MAS who were admitted to a public hospital for MV between January 2004 and December 2006. Eighty-eight neonates were ventilated for MAS. Thirty-one percent were postdates and 51% had no electronic fetal monitoring. Postnatal suctioning of meconium was not performed according to protocol in 47% of nonvigorous infants. High-frequency ventilation and surfactant were used in 32 and 14% of cases, respectively. Persistent pulmonary hypertension of the newborn (PPHN) and pneumothorax occurred in 57 and 24% of cases, respectively. Overall mortality rate was 33%. Neonates suffering from MAS with PPHN had higher mortality rate of 48% compared with 13% in those suffering from MAS without PPHN. Factors associated with mortality were peak inspiratory pressure (P<0.001), pneumothorax (P<0.001) and PPHN (P=0.001). Postdates, inadequate intrapartum monitoring and limited use of adjunct respiratory therapies were common. Severe MAS is associated with adverse outcome.

Neonatal outcome after caesarean birth for fetal distress and/or meconium staining in a South African rural setting

The aim was to evaluate the effect of caesarean delivery on the neonatal outcome after labour with fetal distress and/or meconium staining (MS). We audited 199 caesarean sections performed for non-reassuring fetal condition (NRFC) and/or MS in a rural regional hospital. The 1 and 5 min Apgar scores were compared with those of 33 vaginal births after labour with MS. There were five neonates out of 232 (2.2%) with an Apgar score <7 at 5 min; one died early, neonatally. In the caesarean section group for NRFC, there were two fresh stillbirths and one early neonatal death, a perinatal mortality of 15.1/1,000 births. The 5 min Apgar score was not statistically significantly affected by the mode of delivery. Caesarean delivery does not improve the neonatal outcome when the amniotic fluid is meconium stained.

Intrapartum and postdelivery management of infants born to mothers with meconium-stained amniotic fluid: evidence-based recommendations

The article reviews and critically evaluates the available evidence to determine whether the current recommendations for the management of infants born through meconium stained amniotic fluid (MSAF) should be maintained. Authors provide evidence-based recommendations regarding the benefits of amnioinfusion prior to delivery, oral suctioning of the newborn prior to delivery of the shoulder, and the practice of routine endotracheal suctioning of the newborn born through MSAF in preventing meconium aspiration syndrome (MAS). Authors also discuss the gaps in knowledge in all the above interventions to prevent MAS.

Pitfalls in neonatal resuscitation

Ten percent of all newborns require resuscitation at birth. The Neonatal Resuscitation Program establishes the authoritative technique of newborn resuscitation. Errors continue to occur that are related to the use of unskilled resuscitators; intubation; inadequate suctioning of meconium; and the postresuscitation problems of hypoglycemia, hypocarbia, and hypotension. Specific recommendations are offered to avoid these pitfalls of neonatal resuscitation.

Albumin mixed with meconium attenuates pulmonary dysfunction in a newborn piglet model with meconium aspiration

We hypothesized that lipids and bile acids in meconium may induce pulmonary insufficiency in newborns. Because albumin may bind these components we studied the effect of albumin on meconium-induced lung injury in piglets. We measured concentration of FFA in the meconium (110 mg dry weight/mL) and added albumin to provide a molar FFA to albumin ratio of 1:1. Newborn piglets, 0-2 d of age, artificially ventilated and exposed to hypoxemia by ventilation with 8% O2, were randomized to group A receiving meconium (n = 12) or group B receiving meconium + albumin (n = 12), 3 mL/kg intratracheally. The animals were reoxygenated for 8 h. Reoxygenation was started when mean blood pressure was <20 mm Hg or base excess was <-20 mM. Pulmonary function was assessed in parallel with pulmonary hemodynamics. From the start of reoxygenation and the next 8 h we found a significant difference (by ANOVA) between the two groups in oxygenation index (p = 0.005), with an increase from 1.6 +/- 0.2 to 6.1 +/- 6.8 (p = 0.04) in the meconium group and from 1.8 +/- 0.3 to 3.1 +/- 3.1 (NS) in meconium + albumin group. There were also significant differences (by ANOVA) between the groups in favor of the treatment group concerning need of inspired fraction of O2, mean airway pressure, dynamic compliance of the respiratory system, time constant, ventilation index, and pulmonary vascular resistance. In conclusion, albumin given concurrently with meconium significantly reduced detrimental effects of meconium aspiration in the lungs of newborn piglets.

Severe meconium aspiration syndrome is not caused by aspiration of meconium

Meconium aspiration syndrome can present clinically with different degrees of severity, ranging from a mild form of respiratory compromise to severe forms that may result in perinatal death despite mechanical ventilation or extracorporeal membrane oxygenation. However, advances in our knowledge concerning meconium aspiration syndrome have revealed that most cases of severe meconium aspiration syndrome are not in fact causally related to the aspiration of meconium but rather are caused by other pathologic processes occurring in utero, primarily chronic asphyxia and infection. Proper understanding of the causative processes underlying fetal or neonatal compromise in these cases is essential to direct future research into preventive or therapeutic treatments and for counseling of the parents of an affected child.

Newborn piglets with meconium aspiration resuscitated with room air or 100% oxygen

We investigated whether newborn piglets exposed to hypoxemia and severe meconium aspiration could be reoxygenated with room air as efficiently as with 100% O(2). Twenty-one 2- to 5-d-old piglets were randomly divided into three groups: 1) the room air group: hypoxemia, meconium aspiration, and reoxygenation with room air (n = 8); 2) the O(2) group: hypoxemia, meconium aspiration, and reoxygenation with 100% O(2) (n = 8); and 3) the control group: meconium aspiration, and reoxygenation with room air (n = 5). Hypoxemia was induced by ventilation with 8% O(2) until the mean blood pressure reached <20 mm Hg or the base excess reached <-20 mM. At this point, reoxygenation was started with either room air or 100% O(2). Three milliliters per kilogram of meconium 110 mg/mL was instilled into the trachea immediately before the start of reoxygenation. The O(2) tension in arterial blood was significantly lower in the room air group; at 5 min of reoxygenation it was 9.1 +/- 0.5 kPa versus 43.5 +/- 6 kPa in the O(2) group (p < 0.05). At 5 min of reoxygenation the tidal volume per kilogram was 12.1 +/- 0.7 mL/kg in the room air group and 13.1 +/- 0.9 mL/kg in the O(2) group (NS). There were no significant differences between the room air and the O(2) groups during 120 min of reoxygenation in mean arterial blood pressure, pulmonary arterial pressure, cardiac index, base excess, or plasma hypoxanthine. In conclusion, hypoxic newborn piglets with meconium aspiration were found to be reoxygenated as efficiently with room air as with 100% O(2).

Variables associated with meconium aspiration syndrome in labors with thick meconium

OBJECTIVE

To examine the possible maternal and fetal variables associated with meconium aspiration syndrome in labors with thick meconium.

STUDY DESIGN

The fetal heart rate tracings, cord pH, Apgar scores and maternal risk factors were evaluated in singleton pregnancies with vertex presentation and thick meconium in labor. The study included 33 consecutive fetuses which developed a moderate or severe meconium aspiration syndrome and 104 consecutive fetuses which had a favorable outcome.

RESULTS

Significant differences between fetuses with meconium aspiration syndrome and healthy fetuses were found in the following parameters: baseline FHR (154+/-17 vs. 136+/-10, P<0.0001), small accelerations/30 min (1.47+/-1.52 vs. 3.04+/-1.2, P<0.0001), large accelerations/30 min (1.46+/-1.96 vs. 3.5+/-2.31, P<0.0003), decelerations/30 min (4.9+/-3.9 vs. 2.4+/-2.1, P<0.0034), number of fetuses with reduced beat-to-beat variability (9/33 vs. 0/104, P<0.0001), cord pH (7.21+/-0.09 vs. 7.33+/-0.08, P<0.0013) and Apgar scores at 1 min (5+/-2 vs. 8+/-1, P<0.0001) and Apgar scores at 5 min (8+/-2 vs. 9.7+/-0.6, P<0.0001). Maternal risk factors were found in two of 33 sick infants and in 13 of 104 healthy infants.

CONCLUSION

Thick meconium by itself is not associated with adverse fetal outcome. However, the incidence of meconium aspiration syndrome increases in cases of a non-reassuring FHR.

Fetal distress

The term 'fetal distress' should be replaced by 'suspected fetal compromise' because the diagnosis of 'fetal distress' is often unproven. Cardiotocography remains the cornerstone of making the diagnosis, but as a test it is renowned for its high sensitivity and low specificity. It has reduced intrapartum fetal mortality but not long-term neonatal morbidity or the incidence of cerebral palsy. There is no doubt that when obvious signs of fetal compromise, such as late decelerations in the presence of intrauterine growth retardation and oligohydramnios, are present, the diagnosis of fetal compromise is relatively simple. Often, however, the subtle signs of fetal compromise are missed; these are a change in the grade of meconium in the amniotic fluid, a rising base-line fetal heart rate, the absence of accelerations, the presence of 'atypical' variable decelerations or a combination of the above. To date, there is no test available to replace the cardiotocograph, although fetal pulse oximetry is the most promising adjunctive test. Above all, no test result obtained in isolation must detract from the whole clinical picture.

Respiratory problems of newborn calves

Cardiopulmonary development of fetus is a timely event that proceeds to the point that birth can take place. Calves may be born premature, and because of surfactant deficiency, develop the respiratory distress syndrome. More research needs to be done on fetal lung development in calves to determine the age when maturity has been reached for compatibility with extrauterine life. Also, more specific therapy regimens need to be developed that will enhance lung development. The birthing process is a major event that must proceed in a timely fashion. Any delay in delivery will compromise further the already hypoxic fetus. Practitioners need to recognize the severely hypoxic/ asphyxiated calf and be prepared to therapeutically support the cardiopulmonary systems.

Fatal meconium aspiration in spite of appropriate perinatal airway management: pulmonary and placental evidence of prenatal disease

OBJECTIVE

Our purpose was to summarize eight cases of fatal meconium aspiration syndrome where pathologic review showed evidence of chronic prenatal disease and to compare these findings with those of a group of control infants and fetuses who died of other causes.

STUDY DESIGN

A 15-year retrospective chart review identified the infants who died of meconium aspiration within 48 hours of life and who also had autopsies performed. Neonatal pulmonary and available placental pathologic findings are described from these study infants and are compared with published norms and with autopsy results from a group of control infants and fetuses.

RESULTS

Seven of the eight study infants underwent suctioning of the trachea immediately after birth. In all eight cases the neonatal lungs demonstrated histologic evidence of significant hypoxic changes of a chronic nature with onset before birth. The available placentas showed variable but significant abnormalities that support a case for subacute or chronic in utero compromise.

CONCLUSIONS

As in other reports, there is evidence that meconium aspiration may be a prenatal rather than a postnatal disease. However, this is the first study that presents evidence on the basis of both pulmonary and placental pathologic findings and reinforces the importance of placental examinations in complicated pregnancies.

Meconium aspiration syndrome--prevention and treatment

Meconium aspiration syndrome (MAS) is a common neonatal problem and, sadly, results in acute and chronic respiratory morbidity. Although meconium aspiration can occur prior to delivery even in the absence of labour, in many infants this condition could be prevented by appropriate suctioning at birth. More accurate prediction of high risk patients and greater use of amnioinfusion may further reduce the occurrence of MAS. In infants with severe respiratory failure both high frequency ventilation and extracorporeal membrane oxygenation have a role. The place for either steroid or exogenous surfactant therapy in MAS remains to be defined.

Perinatal asphyxia: assessing its causal role and timing

Perinatal asphyxia, whether prenatal, intrapartum, or neonatal is thought to be a significant contributor to newborn morbidity and mortality as well as long-term neurological deficits. Development of an intrapartum tool/test that can reliably identify and discriminate between varying degrees of fetal acidemia and suggest whether it is respiratory or metabolic in nature would be highly desirable. This article critically reviews the available experience with the currently available monitoring techniques and the significance of abnormalities of fetal and intrapartum measurements with respect to the predictive value of the observations available to the clinician.

The epidemiology of neonatal respiratory disease

The epidemiology of many conditions affecting the newborn infant is influenced by the health of the mother, prematurity and the effects of medical and obstetric management. In this review we have considered the role of each of these factors in seven respiratory conditions presenting in the newborn infant.

Poor glycemic control and antepartum obstetric complications in women with insulin-dependent diabetes

OBJECTIVE

The purpose of this study was to test the hypothesis that the rate of complications of pregnancy in women with insulin-dependent diabetes is higher than in nondiabetic women and is associated with poor glycemic control and microvascular disease.

METHOD

Women who enrolled in a multidisciplinary program of diabetes in pregnancy prior to 20 weeks' gestation were included in the study and matched 1:2 by age, race and parity to a control group of nondiabetic women. Complications of pregnancy were retrospectively analyzed and compared between groups. The association of complications with glycemic control and microvascular disease was analyzed within the diabetic group.

RESULT

Women with diabetes had significantly higher rates of pregnancy-induced hypertension (PIH), polyhydramnios, pyelonephritis, preterm delivery and meconium-stained amniotic fluid. Poor glycemic control, particularly during the first and second trimesters of pregnancy, was associated with all complications, except pyelonephritis. Microvascular disease was associated with PIH and preterm delivery prior to 34 weeks.

CONCLUSION

Women with insulin-dependent diabetes are at high risk for complications of pregnancy. Glycemic control during the first and second trimesters may affect events later in pregnancy.

Meconium staining and the meconium aspiration syndrome. Unresolved issues

Meconium staining of the amniotic fluid and the meconium aspiration syndrome will likely remain common occurrences faced by health care providers. Unfortunately, our understanding of these entities is incomplete. There are a number of issues which need to be adequately evaluated regarding the pathophysiology of MAS, the delivery room management of the meconium-stained infant, and the neonatal intensive care unit management of MAS. Currently, there is much dogma in various hospitals throughout this country regarding these issues, dogma which has yet to be substantiated by quality scientific investigations.

Prediction of the severity of meconium aspiration syndrome

OBJECTIVE

Meconium aspiration syndrome is associated with increased neonatal morbidity and mortality. We sought to determine whether the need for neonatal mechanical ventilation or prolonged ventilation (> or = 3 days) was predictable from antepartum, intrapartum, and immediate neonatal events.

STUDY DESIGN

Between 1987 and 1989, 8003 of 43,906 (18%) live infants had meconium-stained amniotic fluid; 82 of these infants had clinical and radiographic evidence of meconium aspiration, and of these 82, 39 (48%) required mechanical ventilation. Predictors of ventilation or prolonged ventilation were determined by means of stepwise logistic regression.

RESULTS

Predictors of neonatal ventilation included fetal tachycardia, interval from meconium detection to delivery, low 5-minute Apgar score, respiratory distress necessitating intubation in the delivery suite, and delivery by cesarean section. Sensitivity was 72%, and specificity was 64%; the model was incorrect in 32% of the cases. Predictors of prolonged ventilation were ominous fetal heart rate tracing, umbilical arterial pH < 7.20, birth weight > 90th percentile, nulliparity, and Apgar score > 4 at 1 minute and < or = 6 at 5 minutes. Sensitivity was 67%, and specificity was 91%; prolonged ventilation was incorrectly predicted in 17% of the cases.

CONCLUSIONS

Use of these models to determine the need for mechanical ventilation or prolonged ventilatory assistance will enhance identification of infants at risk of severe meconium aspiration and will lead to early transfer to the neonatal intensive care unit for intense observation and management.

Does DeLee suction at the perineum prevent meconium aspiration syndrome?

OBJECTIVE

We attempted to determine the impact of "early" (before delivery of the chest) oronasopharyngeal DeLee suctioning at the perineum in the prevention of meconium aspiration syndrome and to confirm that meconium aspiration syndrome is a postnatal event.

STUDY DESIGN

We compared infants with meconium-stained fluid who underwent "early" oronasopharyngeal DeLee suctioning with a similar group of infants whose airways were suctioned "late" (after chest delivery). Practicing obstetricians did not know the study was being conducted by the pediatric staff, and an independent observer documented whether obstetricians performed "early" or "late" oronasopharyngeal DeLee suctioning. Immediate postnatal tracheal suctioning was performed in both groups. The study was conducted in a private tertiary care center averaging 5800 deliveries annually. A consecutive sample of 438 infants with meconium-stained fluid was analyzed. Of these infants, 221 received "early" oronasopharyngeal DeLee suctioning, while 217 infants were suctioned "late".

RESULTS

Of the 438 infants with meconium-stained fluid, meconium aspiration syndrome developed in 38 (9%). These infants had higher rates of fetal distress (i.e., abnormal fetal heart rates) and lower Apgar scores (< or = 6) than infants without meconium aspiration syndrome (58% vs 17% and 65% vs 13%, respectively; p < 0.001). Forty-five percent of the infants with meconium aspiration syndrome had renal failure during the first 20 hours of life. In spite of "early" oronasopharyngeal DeLee suctioning, 53% of the infants in this group had meconium below the vocal cords and meconium aspiration syndrome developed in 7%. The time of oronasopharyngeal DeLee suctioning did not affect the rate of meconium aspiration syndrome or the presence of meconium below the vocal cords.

CONCLUSIONS

We concluded that "early" oronasopharyngeal DeLee suctioning at the perineum does not affect the rate of meconium aspiration syndrome. We speculate that meconium aspiration syndrome is predominantly an intrauterine event associated with fetal distress and that meconium in the airways is merely a "marker" of previous fetal hypoxia.

Disparate black and white neonatal mortality rates among infants of normal birth weight in Chicago: a population study

To determine the extent to which disparities in risk status and access to tertiary care affect racial differences in neonatal mortality rates among normal birth weight infants, we conducted a vital records study concerning normal weight black (N = 44,399) and white (N = 48,146) singleton births in Chicago. Neonatal mortality rate among black infants was twice that among white infants (3.3 deaths per 1000 births vs 1.5 deaths per 1000 births); the unadjusted black relative risk equaled 2.2 (95% confidence interval, 1.7 to 2.9). Because prematurity, growth retardation, congenital anomalies, low Apgar scores at 5 minutes, teenage mothers, and poverty were more common among black infants, multivariate analyses were performed. The disparity in mortality rate was greatest between black and white infants with none of these risk factors; relative risk for black infants equaled 3.6 (95% confidence interval, 2.0 to 6.7). Approximately 30% of all deaths of black infants were attributable to birth in nontertiary hospitals. When the confounding variables, including hospital of birth, were put into a multivariate logistic-regression model, the adjusted relative risk estimate (odds ratio) for black infants equaled 1.5 (95% confidence interval, 1.1 to 2.0). Traditional risk factors fail to explain the racial disparity in neonatal mortality rate among normal birth weight infants. Level of perinatal care available, or some factor closely related to this level, is an important determinant of neonatal chance of survival for normal birth weight urban black infants.

Pulmonary inflammation associated with aspirated meconium and epithelial cells in calves

"Meconium aspiration syndrome" is a condition resulting in respiratory distress and the occasional death of newborn human beings. A retrospective study was conducted on 52 calves that were submitted for postmortem examination to the Atlantic Veterinary College, Charlottetown, Prince Edward Island, Canada. These calves died of infectious and noninfectious diseases within the first 2 weeks of life due to a variety of causes. The most common cause of death was infectious enteric disease. Histologic examination of lungs revealed that 42.5% of calves had evidence of meconium, squamous cells, or keratin in the lung. There was considerable variation in the magnitude of histologic changes in lungs containing aspirated material. Typically, affected lungs had only a few inconspicuous pieces of meconium, keratin, and squamous cells within bronchoalveolar spaces. Sporadically, the entire lumen of airways was obliterated by aspirated material. Lungs with aspirated material had a mild but diffuse alveolitis characterized by exudation of a few neutrophils, macrophages, and occasional multinucleated giant cells. Obstruction of small airways and focal atelectasis were also observed. Similar lesions have been reported in human meconium aspiration syndrome. It is concluded that histologic changes similar to those of human meconium aspiration syndrome occur commonly in calves that die within 2 weeks of birth. Further studies involving healthy age-matched calves are required to evaluate the clinicopathologic significance of meconium aspiration in this species.

Meconium aspiration syndrome: the role of resuscitation and tracheal suction in prevention

We reviewed our experience of meconium staining of liquor and meconium aspiration syndrome over a 33 month period. The clinical and radiological severity of disease was assessed in comparison with tracheal suction and resuscitation. Sixty (27%) of newborns with meconium stained liquor subsequently developed MAS. No association was found between the thickness of meconium or its presence on tracheal aspiration with subsequent severity of respiratory disease. However, the presence of meconium in the trachea was strongly associated with radiological abnormality. The severity of meconium aspiration syndrome and mortality were also related to the clinical stability of the infants at presentation. Our results indicate that intrauterine aspiration and pulmonary maladaptation may play a significant role in meconium aspiration syndrome rather than resuscitative events at delivery.

Meconium aspiration syndrome: reflections on a murky subject

Meconium-stained amniotic fluid occurs in approximately 12% of live births. In approximately one third of these infants meconium is present below the vocal cords. However, meconium aspiration syndrome develops in only 2 of every 1000 live-born infants. Ninety-five percent of infants with inhaled meconium clear the lungs spontaneously. Recent investigations have suggested that a reexamination of our assumptions about the etiology of meconium aspiration syndrome is in order. Several authors have provided evidence that support the hypothesis that it is not the inhaled meconium which produces the primary pathologic condition of meconium aspiration syndrome but rather it is fetal asphyxia that is the etiologic agent. Asphyxia in utero produces pulmonary vasospasm and hyperreactivity of the pulmonary vessels. With severe asphyxia the fetal lungs undergo pulmonary vascular damage with pulmonary hypertension. The damaged lungs are then unable to clear the meconium. In the most severe cases there is right-to-left shunting and persistent fetal circulation with subsequent fetal death. The incidence of meconium aspiration may thus be essentially unaffected by current obstetric and pediatric interventions at birth. For the asphyxiated or distressed infant we recommend suctioning at birth and tracheal intubation. In the healthy fetus observation may be sufficient.

Significance of observing no fluid at amniotomy

Thirty patients with oligohydramnios observed at artificial rupture of membranes were studied to determine the significance of this finding. Fifteen were subsequently found to have meconium-stained amniotic fluid and 21 had abnormal fetal heart rate tracings. This clinical observation warrants close intrapartum surveillance and preparation for delivery.

Significance of meconium staining of the amniotic fluid

The study was conducted to determine the significance of meconium staining and more specifically its association with fetal heart rate patterns. Five hundred and one patients in labor were examined, 106 of whom had meconium stained amniotic fluid. A multivariate analysis of the data was performed by logistic regression analysis using meconium staining as the dependent variable. The determinants of meconium in the amniotic fluid were gestational age, base deficit, calcified placenta, late decelerations and placental weight. The following variables had no effect on the occurrence of meconium: maternal age, type of risk, parity, fetal sex, duration of labor, duration of the second stage of labor, entanglement of the umbilical cord, FHR variability, variable decelerations, oxytocin usage, type of anesthesia, maternal smoking and alcohol consumption habits. In conclusion, meconium in the amniotic fluid seems to be associated with placental rather than with umbilical insufficiency.

Meconium aspiration syndrome: intrapartum and neonatal attributes

To identify the fetus and newborn at risk for meconium aspiration syndrome the perinatal characteristics of 238 infants delivered through meconium-stained amniotic fluid were prospectively examined. All infants with meconium-stained amniotic fluid were routinely suctioned with a DeLee apparatus before tracheal intubation and suctioning. The type and presence of meconium in the trachea, neonatal breathing before intubation, and Apgar scores were recorded in the delivery room. Intrapartum fetal monitoring data were collected for 80% (190/238) of the mothers and umbilical artery pH for 74% (177/238) of the newborns. Despite suctioning with a DeLee apparatus and endotracheal suctioning, meconium was present in the trachea in 87/238 (37%) and meconium aspiration syndrome developed in 22 (9.2%). A total of 73% of newborns who had meconium aspiration syndrome were delivered through thick meconium. Thick meconium, the presence of fetal tachycardia, and absence of intrapartum fetal cardiac accelerations identified the fetus at high risk for meconium aspiration syndrome. The presence of these monitoring findings and thick meconium should alert obstetricians to the possibility of a fetus that requires intervention. Low umbilical artery pH, Apgar scores less than 5, and meconium in the trachea further characterized the newborn at high risk for meconium aspiration syndrome. The combination of these findings may best identify the infant delivered through meconium-stained amniotic fluid who requires close observation for meconium aspiration syndrome.

Meconium aspiration syndrome: a 6-year retrospective study

The incidence and outcome of babies suffering from meconium aspiration syndrome (MAS) has been analysed in a 6-year review of 38,395 births at Guy's Hospital and Queen Charlotte's Maternity Hospital. One in 533 births (0.2%) was complicated by MAS, the mortality rate for which was 1 in 12. There was also a number of babies identified as possibly suffering from 'subclinical MAS' but no deaths occurred in this group. Males were more affected than females.