Markers of acute and chronic asphyxia in infants with meconium-stained amniotic fluid

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.

Meconium-stained amniotic fluid and histologic signs of fetal distress in stillbirths

OBJECTIVE

Stillbirth is one of the most devastating adverse pregnancy outcome, but it is often associated with a missing post-mortem histological examination. We aimed at evaluating whether the staining of amniotic fluid reflects the fetal conditions surrounding the death and if it correlates with any histologic sign of fetal distress.

STUDY DESIGN

Terminal gasping (represented by the massive presence of intra-alveolar squamous cells), thymic and adrenal cortex modifications were evaluated as histologic signs of fetal distress in stillbirths, and stratified according to the degree of staining of the amniotic fluid.

RESULTS

The presence of meconium-stained amniotic fluid did not correlate with the presence of gasping and/or thymic and/or adrenal cortex changes. Clear amniotic fluid was not associated with the absence of histologic signs of distress.

CONCLUSIONS

The evaluation of the staining of the amniotic fluid fails to identify distressed fetuses. A histologic evaluation of fetal organs provides detailed information, irrespective of the presence/absence of meconium-stained amniotic fluid.

Pregnancy-induced hypertension is an independent risk factor for meconium aspiration syndrome: A retrospective population based cohort study

OBJECTIVE

Meconium aspiration syndrome (MAS), possibly resulting from fetal hypoxia, is a respiratory distress disorder in the infant. Pregnancy-induced hypertension (PIH) can cause placental dysfunction and lead to fetal hypoxia, which may induce the development of MAS. Therefore, the aim of this study was to determine the association between PIH and MAS and to identify the predictive risk factors.

MATERIALS AND METHODS

This was a retrospective cohort study. We selected patients with newly diagnosed PIH and a matched cohort group from the Taiwan National Health Insurance Research Database (NHIRD), from January 1, 2000 till December 31, 2013. For each patient in the PIH cohort, 4 subjects without PIH, matched for age and year of delivery, were randomly selected as the comparison cohort. The incidence of meconium aspiration syndrome was assessed in both groups.

RESULTS

Among the 23.3 million individuals registered in the NHIRD, 29,013 patients with PIH and 116,052 matched controls were identified. Patients who experienced PIH had a higher incidence of MAS than did those without PIH. According to a multivariate analysis, PIH (odds ratio [OR] = 1.70, 95% confidence interval [CI] = 1.49-1.93, p < 0.0001) was independently associated with increased risk of MAS. Additionally, age ≥30 years (OR = 1.26, 95% CI = 1.12-1.42, p = 0.0001), nulliparity (OR = 1.13, 95% CI = 1.01-1.27, p = 0.0367) and patients with diabetes mellitus (OR = 3.09, 95% CI = 1.35-7.09, p = 0.0078) were also independent risk factors of MAS.

CONCLUSION

Patients with PIH obtained higher subsequent risk for the development of MAS than those without PIH. Besides, age ≥30 years, nulliparity and patients with diabetes mellitus are the independent risk factors of developing MAS.

Robust increases in erythropoietin production by the hypoxic fetus is a response to protect the brain and other vital organs

Fetal erythropoietin (EPO), in addition to regulating erythropoiesis, has also tissue-protective properties based on its anti-inflammatory, anti-apoptotic, antioxidant, and neurotrophic effects. Notably, EPO concentrations needed for tissue protection are 100-1000 times higher than concentrations needed for regulating erythropoiesis. This dual effect of EPO is based on EPO-receptor (EPO-R) isoforms, which differ structurally and functionally. We hypothesize in this Integrated Mechanism Review that during severe fetal hypoxia the observed, but poorly understood, marked increases of fetal plasma EPO concentrations occur to protect the brain, heart, and other vital fetal organs. We further hypothesize that the concurrent marked increases of EPO in the amniotic fluid during fetal hypoxia, occur to protect newborn infants from necrotizing enterocolitis. This review presents experimental and clinical evidence in support of these hypotheses and points out unknown or poorly understood functions of EPO in the fetus. If these novel hypotheses are correct, the importance of fetal EPO as an antenatal hypoxia biomarker will become apparent. It will also likely point the way to important diagnostic and therapeutic fetal and neonatal interventions.

Should fetal scalp blood sampling be performed in the case of meconium-stained amniotic fluid?

OBJECTIVE

To investigate the effect of using fetal scalp blood sampling on the risk of neonatal respiratory distress syndrome (NRDS) with meconium-stained amniotic fluid (MSAF).

METHODS

Prospective data collection with regard to MSAF during labor for low-risk term cephalic singleton live birth from 2012 to 2014. Maternal, obstetric and neonatal data were compared according to the occurrence of respiratory distress syndrome (RDS group) or not (no RDS group).

RESULTS

Of 515 newborns born through MSAF, 46 experienced RDS and from them 10 experienced meconium aspiration syndrome. No difference was observed according to maternal characteristic, abnormal fetal heart rate tracing pattern irrespective of its category and cesarean rate. Apgar at one minute was lower in the group RDS (7.6 versus 8.5, p < 0.05). The mean umbilical artery pH values did not differ between the two groups. Significant difference between newborns with and without RDS in terms of fetal scalp lactate sampling during the labor (71.1% versus 55.1%, p < 0.05), and neonatal care unit (NCU) admissions (22.8% versus 10.8%, p < 0.05). Secondary rather than primary meconium was associated with RDS when performing fetal scalp blood assessment (p < 0.05). A significant correlation between RDS, fetal scalp blood assessment and MSAF diagnosed during the first stage of labor (after spontaneous rupture of membranes or at amniotomy) was found.

CONCLUSION

In case of MSAF, fetal scalp blood sampling did not reduce the risk of RDS.

Interpreting category II fetal heart rate tracings: does meconium matter?

OBJECTIVE

Category II fetal heart rate (FHR) tracings are considered indeterminate; thus, improved risk stratification of category II FHR tracings is needed. We estimated whether the presence of meconium increased the risk of adverse neonatal outcomes.

STUDY DESIGN

This study was conducted within a prospective cohort of 5000 women with singleton pregnancies who were admitted in labor at term. Pregnancies with category II FHR in the 60 minutes before delivery were included. FHR data were extracted by trained nurses who were blinded to clinical outcome. The exposure was the presence of meconium. The primary outcome was a composite neonatal morbidity defined as ≥1 of the following: neonatal death, neurologic morbidity, respiratory morbidity, hypotension that required treatment, and sepsis. Secondary outcomes were nursery admission, cord pH, 5-minute Apgar score, and components of the composite. Logistic regression was used to adjust for confounders.

RESULTS

Of the 3257 women with category II FHR tracings, 693 women (21.3%) had meconium, and 2564 women (78.7%) did not. Meconium was associated with higher risk of the composite morbidity (adjusted odds ratio, 2.49; 95% confidence interval, 1.78-3.48) and increased risks of the secondary outcomes. The associations remained significant when infants with meconium aspiration syndrome were excluded. Thick meconium was associated significantly with the composite morbidity.

CONCLUSION

The presence of meconium is associated with an increased risk of neonatal morbidity in women with category II FHR pattern. This clinical factor may assist clinicians in managing category II FHR patterns in labor.

The aetiology of meconium-stained amniotic fluid: pathologic hypoxia or physiologic foetal ripening? (Review)

INTRODUCTION

Despite the many efforts to study the (patho)physiology of meconium release before delivery, it still remains an indistinct subject. Some studies have reported a relationship between hypoxia and MSAF, whilst others have not. The most common association found however, is between MSAF and the term of gestation.

METHODS

MEDLINE, EMBASE and the Cochrane library were electronically searched. Papers about the (patho)physiology of meconium-stained amniotic fluid in English were included. Papers about management strategies were excluded (see elsewhere this issue).

RESULTS

Different theories have been proposed including acute or chronic hypoxia, physiologic foetal ripening and peripartum infection.

CONCLUSION

We suggest that meconium-stained amniotic fluid should be regarded as a symptom rather than a syndrome becoming more prevalent with increasing term and which might be associated with higher levels of infection or asphyxia.

Consequences of meconium stained amniotic fluid: what does the evidence tell us?

BACKGROUND

Meconium stained amniotic fluid (MSAF) is common and associated with meconium aspiration syndrome (MAS). Other consequences of meconium passage before birth are less well understood.

METHODS

We reviewed the literature for original papers reporting on outcomes associated with MSAF.

FINDINGS

Among preterm infants MSAF is more prevalent than previously believed and is associated with higher neonatal morbidity. Intrauterine exposure to meconium is associated with inflammation of tissues of the lung, chorionic plate and umbilical vessels and through various mechanisms may contribute to neonatal morbidity, independent of MAS. No compelling evidence supported an association between MSAF and increased neurological impairment, including early seizure activity.

Bacteria and endotoxin in meconium-stained amniotic fluid at term: could intra-amniotic infection cause meconium passage?

BACKGROUND

Meconium-stained amniotic fluid (MSAF) is a common occurrence among women in spontaneous labor at term, and has been associated with adverse outcomes in both mother and neonate. MSAF is a risk factor for microbial invasion of the amniotic cavity (MIAC) and preterm birth among women with preterm labor and intact membranes. We now report the frequency of MIAC and the presence of bacterial endotoxin in the amniotic fluid of patients with MSAF at term.

MATERIALS AND METHODS

We conducted a cross-sectional study including women in presumed preterm labor because of uncertain dates who underwent amniocentesis, and were later determined to be at term (n = 108). Patients were allocated into two groups: (1) MSAF (n = 66) and (2) clear amniotic fluid (n = 42). The presence of bacteria was determined by microbiologic techniques, and endotoxin was detected using the Limulus amebocyte lysate (LAL) gel clot assay. Statistical analyses were performed to test for normality and bivariate comparisons.

RESULTS

Bacteria were more frequently present in patients with MSAF compared to those with clear amniotic fluid [19.6% (13/66) versus 4.7% (2/42); p < 0.05]. The microorganisms were Gram-negative rods (n = 7), Ureaplasma urealyticum (n = 4), Gram-positive rods (n = 2) and Mycoplasma hominis (n = 1). The LAL gel clot assay was positive in 46.9% (31/66) of patients with MSAF, and in 4.7% (2/42) of those with clear amniotic fluid (p < 0.001). After heat treatment, the frequency of a positive LAL gel clot assay remained higher in the MSAF group [18.1% (12/66) versus 2.3% (1/42), p < 0.05]. Median amniotic fluid IL-6 concentration (ng/mL) was higher [1.3 (0.7-1.9) versus 0.6 (0.3-1.2), p = 0.04], and median amniotic fluid glucose concentration (mg/dL) was lower [6 (0-8.9) versus 9 (7.4-12.6), p < 0.001] in the MSAF group, than in those with clear amniotic fluid.

CONCLUSION

MSAF at term was associated with an increased incidence of MIAC. The index of suspicion for an infection-related process in postpartum women and their neonates should be increased in the presence of MSAF.

The role of growth factors in intestinal regeneration and repair in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal disease resulting in major neonatal morbidity and mortality. The pathology is poorly understood, and the means of preventing and treating NEC are limited. Several endogenous growth factors have been identified as having important roles in intestinal growth as well as aiding intestinal repair from injury or inflammation. In this review, we will discuss several growth factors as mediators of intestinal regeneration and repair as well as potential therapeutic agents for NEC.

Hepcidin and erythropoietin measurements in the cord blood of neonates with meconium-stained amniotic fluid

AIM

To compare hepcidin and erythropoietin levels in the cord blood of neonates with meconium-stained amniotic fluid (MSAF) to levels obtained from age-, body mass index- and gravidity-matched neonates with clear amniotic fluid.

METHODS

A cross-sectional controlled study was conducted in secondary and tertiary care centers. Cord blood samples of 40 neonates following term gestations (≥37 weeks' gestation) with MSAF and 40 maternal age-, body mass index- and gravidity-matched controls with clear amniotic fluid were analyzed in this study. Demographic data, delivery outcomes and laboratory evaluations were recorded.

RESULTS

Cord blood pH levels were lower in fetuses with MSAF when compared to those with clear amniotic fluid (P=0.0001). Fetuses with MSAF had higher cord blood erythropoietin levels in comparison to those with clear amniotic fluid (P=0.0001). Delivery outcomes and hepcidin measurements were similar in both groups.

CONCLUSIONS

We demonstrated a significant relationship between erythropoietin levels and meconium passage, but failed to show the existence of a relationship between hepcidin levels and meconium passage.

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.

Meconium-stained amniotic fluid in term pregnancies-a clinical view

The objective of this study was to explore details of the clinical relationship between meconium-stained amniotic fluid (MSAF) in labour, abnormal fetal heart pattern and meconium aspiration (MA). This was a prospective study carried out in Princess Badeea Teaching hospital during a 6-month period from March to September 1997. During the study period 344 (8.5%) of the deliveries had MSAF (344 women). Continuous fetal heart monitoring was routinely used and 36 women with MSAF (10.5%) needed to be delivered by caesarean section because of fetal distress (diagnosed by abnormal fetal heart pattern) in early labour, compared with 0.95% in those with clear amniotic fluid (CAF), (P <0.00001). Many infants in the MSAF group had a low Apgar score and required ventilation at birth. Nineteen infants (5.5%) developed MA, three of whom (15.8%) died. We conclude that there is an association between MSAF, abnormal fetal heart pattern in labour and a low Apgar score and that it should be considered a high risk situation. MA a problem that occurs with particulate meconium was significantly related to abnormal fetal heart pattern and longer length of labour.

Localization and gestation-dependent pattern of corticotrophin-releasing factor receptor subtypes in ovine fetal distal colon

Meconium passage is frequently observed in association with feto-maternal stress factors such as hypoxia and infection, but the triggering mechanism is unknown. We hypothesize that differential regulation of corticotrophin-releasing factor (CRF) receptors during gestation play an important role in determining the susceptibilities of the fetus to stress-induced in utero meconium passage at term. We examined the innervation patterns of CRF-receptor type 1 (CRF-R1), a stimulator of gastrointestinal motility and CRF-receptor type II (CRF-R2), an inhibitor of gastrointestinal motility in ovine fetal distal colonic segments from very preterm to term gestation. Both CRF-R1 and CRF-R2 receptors were present in muscularis mucosa as well as in longitudinal and circular smooth muscle layers in fetal distal colonic segments at all gestational ages. Quantitative image analysis indicated a 42% increase in CRF-R1 receptor immunoreactivity in muscularis mucosa and a 30% in longitudinal smooth muscle layers from very preterm to term. In contrast, CRF-R2 receptor immunoreactivity in muscularis mucosa as well as in longitudinal and circular smooth muscle layers decreased by 38%, 55% and 51%, respectively, at term. The percentage of enteric ganglia and the number of enteric neurons expressing CRF-R1 receptors were high at term. Western blot analysis identified 235 and 50 kDa molecular species of CRF-R1 receptors and 37 and 28 kDa molecular species of CRF-R2 receptors. In summary, we speculate that downregulation of CRF-R2 receptor abundance with concurrent increases in CRF-R1 receptor levels in myenteric-smooth muscle unit with advancing gestation sensitizes the colonic motility responses to stressors.

Mechanism(s) of in utero meconium passage

To use sheep and rat models and demonstrate that stressors activate fetal glucocorticoid (GC) system, corticotrophin-releasing factor (CRF) system and cholinergic neurotransmitter system (ChNS) leading to propulsive colonic motility and in utero meconium passage. Immunohistochemical studies (IHS) were performed to localize GC-Receptors, CRF-receptors and key molecules of ChNS in sheep fetal distal colon. CRF expression in placenta and enteric endocrine cells in fetal rat system were examined and the effects of acute hypoxia on in utero meconium passage was tested. IHS confirmed localization and gestation dependent changes in GC-Rs, CRF-Rs and cholinergic markers in sheep fetal colon. Rat placenta and enteric endocrine cells express CRF and gastrointestinal tract express CRF-Rs. Hypoxia is a potent inducer of meconium passage in term fetal rats. Stress is a risk factor for in utero meconium passage and laboratory animal models can be used to develop pharmacotherapy to prevent stress-induced in utero meconium passage.

Increased fetal plasma and amniotic fluid erythropoietin concentrations: markers of intrauterine hypoxia

Tissue hypoxia is the major stimulus of erythropoietin (EPO) synthesis in fetuses and adults. Since EPO does not cross the placenta and is not stored, fetal plasma and amniotic fluid levels indicate EPO synthesis and elimination. Acutely, the rate and magnitude of the increase in plasma EPO levels correlate with the intensity of hypoxia. Amniotic fluid EPO levels correlate with cord plasma levels in normal and abnormal pregnancies, with fetal plasma EPO levels in humans averaging 2.6 times higher than the corresponding amniotic fluid EPO levels. Recent experimental and clinical studies demonstrate that EPO has neuroprotective effects related to its anti-apoptotic and vascular growth-promoting properties. Although under basal conditions the fetal kidneys are the main site of EPO production, during hypoxia recent experimental data indicate an important role of the placenta. Amniotic fluid EPO levels have been shown to increase exponentially during fetal hypoxia in preeclamptic, diabetic and Rh-immunized pregnancies, to correlate inversely with cord blood pH, pO(2) and base excess and to predict neonatal morbidities and NICU admission. As an indicator of chronic intrauterine hypoxia, fetal EPO measurements have increased our knowledge about the pathogenesis and importance of intrauterine growth restriction, macrosomia, diabetic pregnancy, prolonged pregnancy, meconium staining, fetal hemorrhage, fetal anemia, maternal smoking and alcohol consumption, abnormal fetal heart rate and abnormal Doppler flow patterns. While the clinical utility of fetal amniotic fluid and plasma EPO measurements in the management of high-risk pregnancies and their offspring is promising, adequately powered clinical trials are urgently needed.

A long-standing incomprehensible matter of obstetrics: meconium-stained amniotic fluid, a new approach to reason

OBJECTIVE

We sought to determine whether meconium-stained amniotic fluid is based on chronic hypoxia or not? In case of chronic hypoxia, higher red blood cell (Rbc) count and/or total hemoglobin levels (Hgb) and/or higher fetal hemoglobin (HbF) and/or lower adult hemoglobin (HbA) levels were expected when compared with controls.

DESIGN

Case-control study.

SETTING

Obstetric unit of a tertiary ministry of health hospital.

SAMPLE

Fifty singleton pregnancies with meconium-stained amniotic fluid and 50 singleton pregnancies with clear amniotic fluid at all stages of labor.

METHODS

Umbilical cord blood samples were collected for determination of total blood parameters and hemoglobin electrophoresis.

MAIN OUTCOME MEASURES

Red blood cell count, total hemoglobin, fetal and adult hemoglobin contents (HbF and HbA).

RESULTS

Red blood cell count, total hemoglobin, fetal hemoglobin (HbF) and adult hemoglobin (HbA) contents were not different between meconium stained and clear amniotic fluid groups.

CONCLUSION

These results suggest that meconium passage may not be associated with chronic fetal hypoxia as demonstrated by similar red blood cell count, total hemoglobin values and fetal hemoglobin (HbF) and adult hemoglobin (HbA) contents.

Elevated plasma corticotrophin release factor levels and in utero meconium passage

Intrauterine meconium (MEC) passage and aspiration may result in significant newborn morbidity, though there is little understanding of the physiologic mechanisms for MEC passage. We hypothesized that stress induces fetal MEC passage via corticotrophin releasing factor (CRF), a known mediator of colonic motility in adult rats. Pregnant rats at e22 were subjected to acute hypoxia or normoxia for 35 min, after which rats were anesthetized and fetuses operatively delivered. Amniotic fluid bilirubin and intestinal alkaline phosphatase were measured as markers for MEC passage, and fetal and maternal plasma CRF and corticosterone levels determined. Hypoxic stress induced defecation in all dams and provoked visible MEC passage in all fetuses. Amniotic fluid bilirubin content was significantly higher in hypoxic fetuses versus controls (1.064 +/- 0.101 versus 0.103 +/- 0.003 O.D. at 410 nm) and intestinal alkaline phosphatase was consistently elevated in MEC stained amniotic fluid. Hypoxia significantly increased plasma CRF (maternal, 82 +/- 5 to 196 +/- 14 pg/mL; fetal, 284 +/- 15 to 1523 +/- 185 pg/mL) and corticosterone (maternal, 417 +/- 50 to 1150 +/- 50 ng/mL; fetal, 96 +/- 5 to 182 +/- 10 ng/mL) compared with controls. In view of the known action of CRF in adult colonic motility, these results suggest that hypoxic stress-mediated MEC passage in term fetal rats is mediated by a CRF dependent pathway.

Meconium-stained amniotic fluid--perinatal outcome and obstetrical management in a low-risk suburban population

OBJECTIVE

To determine whether amniotic fluid (MSAF) affects obstetrical interventions and immediate perinatal outcome in a low-risk suburban population.

STUDY DESIGN

A retrospective cohort study examined 11,226 deliveries at Tübingen University Hospital (1998-2003). Thousand one hundred and twenty-three women (10%) had MSAF during labor. A control group of matched pairs was created, assigning to each patient the next woman that gave birth without MSAF. Exclusion criteria were: gestational age less than 37+0 weeks, primary Cesarean (C-)section, multiple gestation, severe maternal disease, preeclampsia and fetal malformations.

RESULTS

Only small differences were noted between the meconium and non-meconium groups with regard to arterial pH and Apgar scores: mean arterial-pH was 7.26 (+/-0.7) for both. Five minutes Apgar scores <6 occurred in 0.9% versus 0.4%. Obstetrical interventions were more common in the meconium group: C-section rates were 17.4% versus 9.6%, vaginal operative delivery rates 13.9% versus 6.2% and scalp pH rates 9.5% versus 3.7%, respectively.

CONCLUSIONS

In a low-risk suburban population the effect of MSAF on the newborn during the immediate postpartum period was small. However, obstetrical management was significantly effected by the presence of MSAF, possibly reflecting a combination of more difficult labor and a lower threshold for obstetric intervention.

Lactate: creatinine ratio in babies with thin meconium staining of amniotic fluid

BACKGROUND

ACOG states meconium stained amniotic fluid (MSAF) as one of the historical indicators of perinatal asphyxia. Thick meconium along with other indicators is used to identify babies with severe intrapartum asphyxia. Lactate creatinine ratio (L:C ratio) of 0.64 or higher in first passed urine of babies suffering severe intrapartum asphyxia has been shown to predict Hypoxic Ischaemic Encephalopathy (HIE). Literature review shows that meconium is passed in distress and thin meconium results from mixing and dilution over time, which may be hours to days. Thin meconium may thus be used as an indicator of antepartum asphyxia. We tested L:C ratios in a group of babies born through thin and thick meconium, and for comparison, in a group of babies without meconium at birth.

METHODS

86 consecutive newborns, 36 to 42 weeks of gestation, with meconium staining of liquor, were recruited for the study. 52 voided urine within 6 hours of birth; of these 27 had thick meconium and 25 had thin meconium at birth. 42 others, who did not have meconium or any other signs of asphyxia at birth provided controls. Lactate and creatinine levels in urine were tested by standard enzymatic methods in the three groups.

RESULTS

Lactate values are highest in the thin MSAF group followed by the thick MSAF and controls. Creatinine was lowest in the thin MSAF, followed by thick MSAF and controls. Normal babies had an average L:C ratio of 0.13 (+/- 0.09). L:C ratio was more among thin MSAF babies (4.3 +/- 11.94) than thick MSAF babies (0.35 +/- 0.35). Median L:C ratio was also higher in the thin MSAF group. Variation in the values of these parameters is observed to be high in the thin MSAF group as compared to other groups. L:C ratio was above the cutoff of 0.64 of Huang et al in 40% of those with thin meconium. 2 of these developed signs of HIE with convulsions (HIE Sarnat and Sarnat Stage II) during hospital stay. One had L:C Ratio of 93 and the other of 58.6. A smaller proportion (20%) of those with thick meconium had levels above the cutoff and 2 developed HIE and convulsions with L:C ratio of 1.25 and 1.1 respectively.

CONCLUSION

In evolving a cutoff of L:C ratios that would be highly sensitive and specific (0.64), Huang et al studied it in a series of babies with severe intrapartum asphyxia. Our study shows that the specificity may not be as good if babies born through thin meconium are also included. L:C ratios are much higher in babies with thin meconium. It may be that meconium alone is not a good indicator of asphyxia and the risk of HIE. However, if the presence of meconium implies asphyxia then perhaps a higher cut-off than 0.64 is needed. L:C ratios should be tested in a larger sample that includes babies with thin meconium, before L:C ratios can be applied universally.

Meconium passage in utero: mechanisms, consequences, and management

Meconium passage in newborn infants is a developmentally programmed event normally occurring within the first 24 to 48 hours after birth. Intrauterine meconium passage in near-term or term fetuses has been associated with fetomaternal stress factors and/or infection, whereas meconium passage in postterm pregnancies has been attributed to gastrointestinal maturation. Despite these clinical impressions, little information is available on the mechanism(s) underlying the normal meconium passage that occurs immediately after birth or during the intrauterine period of fetal development. Birth itself is a stressful process and it is possible that fetal stress-mediated biochemical events may regulate the meconium passage occurring either during labor or after birth. Aspiration of meconium during intrauterine life may result in or contribute to meconium aspiration syndrome (MAS), representing a continued leading cause of perinatal death. This article reviews aspects of meconium passage in utero, its consequences, and management.

Prognostic Value of Change in Amniotic Fluid Color during Labor

OBJECTIVE

Evidence of meconium-stained amniotic fluid (AF) during labor suggests implementation of close monitoring of fetal well-being. We have investigated whether the presence of meconium in the AF on admission for labor is as important a predictor of neonatal outcome as a change in AF color during labor.

METHODS

AF characteristics on admission for labor at term (37-42 weeks) and their changes during labor were recorded in all singleton pregnancies during an 8-year period (1992-1999). Excluded were stillbirths on admission, congenital anomalies, and elective cesarean sections. The presence of meconium and its consistency (light or thick) were documented on admission by inspection with transcervical amnioscopy in women with intact membranes or in the vaginal pool in those with ruptured membranes. Changes in AF color or consistency during labor were recorded and correlated with the obstetric and neonatal outcome. Statistical analysis utilized chi(2) for trend, with p < 0.05 considered significant.

RESULTS

19,090 women were admitted in labor at term during the study period and fulfilled the study inclusion criteria and had amniotic fluid evaluation available. The appearance of meconium or worsening in thickness of meconium during labor was associated with higher rates of Apgar scores <7 at 5 min (clear AF on admission and at delivery 0.6%; light or thick meconium on admission and no change at delivery 0.8%; clear AF on admission and light or thick meconium at delivery 3.2%, and light meconium on admission and thick meconium at delivery 2.5%; p < 0.001) and umbilical artery pH <7.10 (the respective rates in the four groups were 1.7, 1.8, 3.6, and 3.8%; p < 0.001).

CONCLUSION

The appearance or thickening of meconium during labor has a greater predictive ability for depressed neonates than the presence of meconium on admission.

Amniotic fluid and cord plasma erythropoietin levels in pregnancies complicated by preeclampsia, pregnancy-induced hypertension and chronic hypertension

AIMS

The purpose of the present study was to compare fetal and neonatal outcomes with amniotic fluid erythropoietin (EPO) levels obtained in the antepartum period in pregnancies complicated by preeclampsia, pregnancy-induced hypertension or chronic hypertension.

METHODS

Erythropoietin concentrations were measured in amniotic fluid within 2 days before delivery and in cord blood at birth in 75 hypertensive women and in 23 healthy controls delivered by cesarean section before labor contractions. Erythropoietin levels did not influence clinical decisions.

RESULTS

Amniotic fluid erythropoietin levels correlated highly significantly with cord plasma EPO levels and were significantly higher in pregnancies complicated by hypertension than in control pregnancies. Umbilical arterial pH, acid-base and blood gas values at birth were not different from controls. Both cord plasma and amniotic fluid erythropoietin levels correlated with cord blood pH, acid-base and blood gas values at birth in the study group. Newborn infants admitted to the newborn intensive care unit had significantly higher fetal erythropoietin levels and were more acidotic, hypoxemic and hypoglycemic than infants admitted to the normal care nursery.

CONCLUSIONS

Our findings suggest that elevated amniotic fluid erythropoietin levels are markers of chronic or subchronic fetal hypoxia and are associated with neonatal morbidity in pregnancies complicated by hypertension.

Endogenous and recombinant erythropoietin levels decline in human amniotic fluid and fetal plasma in vitro at 37 degrees C

OBJECTIVE

To determine the in vitro stability of endogenous and recombinant erythropoietin (EPO) incubated at 37 degrees C in amniotic fluid (AF) and fetal plasma.

STUDY DESIGN

Endogenous and recombinant EPO in AF, fetal plasma and phosphate buffer were incubated in vitro for 21 days at 37 degrees C. Serial aliquots were analyzed for EPO and the rates of EPO decline were compared within and between groups.

RESULTS

Endogenous and recombinant EPO declined significantly in plasma and AF at 37 degrees C. Endogenous EPO displayed a similar linear rate of decline in AF and plasma, with nearly 70% of the initial hormone concentration remaining at 21 days. Recombinant EPO incubated in buffer did not change.

CONCLUSIONS

Using the rate of decline in endogenous EPO we observed, EPO levels measured in AF or plasma within 21 days of fetal demise can be extrapolated back to the level likely present at fetal death.

Meconium and fetal hypoxia: some experimental observations and clinical relevance

In an experimental study, chemically sympathectomised near term fetal sheep and a control group were subjected to repeated episodes of acute hypoxia. Despite severe hypotension and metabolic acidosis, no animal in the control group had meconium-stained amniotic fluid, whereas every animal in the sympathectomised group had heavily meconium-stained amniotic fluid at the end of the experiments. These data and the available literature do not support a direct association between acute hypoxia and meconium-stained amniotic fluid but suggest that a reduction in sympathetic neural tone must be a component of meconium passage. Clinical and experimental data on the occurrence of meconium-stained amniotic fluid are reviewed.

Erythropoietin in human milk: physiology and role in infant health

Human milk contains substantial concentrations of erythropoietin, a hormone best known for its role in the regulation of erythropoiesis. Recent studies show that erythropoietin receptors are widely distributed in human tissues, including the gastrointestinal tract, endothelial cells, spinal cord, and brain, suggesting that erythropoietin plays a wider role in infant development. Mammary epithelial cells contribute to the production of erythropoietin in human milk, and erythropoietin concentrations appear to rise slowly in human milk during the first few months of lactation. Current data suggest that erythropoietin in human milk may play a pleiomorphic role in erythropoiesis, neurodevelopment, maturation of the gut, apoptosis, and immunity in the infant.

Amniotic fluid erythropoietin concentrations differentiate between acute and chronic causes of fetal death

BACKGROUND

Increased fetal plasma erythropoietin concentration is an indicator of chronic fetal hypoxia. Amniotic fluid erythropoietin levels correlate highly significantly with fetal erythropoietin levels before labor. We studied AF erythropoietin levels after fetal death in order to determine whether this could differentiate between stillbirths from acute or chronic causes.

METHODS

Amniotic fluid was obtained after fetal death for erythropoietin measurement following fetal death in 21 pregnancies. Two of the pregnancies had twins, of which one infant was born alive. All 22 stillborn fetuses had an autopsy. None had malformations. Without prior knowledge of the results of the erythropoietin analyzes, the causes of fetal death were divided into acute, chronic or unknown groups.

RESULTS

Eight pregnancies had an acute cause of fetal death (e.g. cord complication or placental abruption), eight pregnancies had a chronic cause (intrauterine growth restriction or erythroblastosis) and in five pregnancies the cause of fetal death could not be determined. In all eight pregnancies with an acute cause of fetal death, AF erythropoietin levels were normal (< 20 mU/mL). In contrast, six of the eight pregnancies with a chronic cause had AF erythropoietin levels above normal (range from 49.9 mU/mL to 391 mU/mL). In the five pregnancies with an unknown cause of fetal death, AF erythropoietin levels were normal in three and elevated in two.

CONCLUSIONS

Elevated AF erythropoietin levels, identified after fetal death, suggest that the fetus died from a chronic hypoxic event, whereas normal AF erythropoietin levels suggest that the fetus died from an acute event.

Erythropoietin acts as a trophic factor in neonatal rat intestine

BACKGROUND

Erythropoietin (Epo) receptors are present on enterocytes of fetal and neonatal small bowel but the role of Epo in the bowel is not known.

AIMS

We tested the following hypotheses: (1) enterally dosed Epo is absorbed from the intestines of neonatal rats, (2) Epo acts as a trophic factor in developing small bowel, and (3) the trophic effects of Epo are dependent on the route of administration.

METHODS

The dose dependent effects of enterally dosed recombinant human erythropoietin (rEpo 0--1000 U/kg/day) were studied in artificially raised rat pups and compared with dam raised controls and dam raised pups given rEpo in rat milk. After one week, reticulocyte counts, haematocrits, and plasma Epo concentrations were measured, and calibrated morphometric measurements of villi were performed. The effects of route of rEpo administration (enteral v parenteral) on erythropoiesis, bowel growth, and disaccharidase activity were studied in nursing pups treated for one and two weeks.

RESULTS

Serum Epo concentrations ranged from undetectable (<0.6 mU/ml) to 8.4 mU/ml in control and enterally dosed pups (median 1.8 mU/ml), and from 4.9 to 82.3 mU/ml (median 20.4 mU/ml) in parenterally dosed animals. No increase in haematocrit or reticulocyte count was noted in enterally treated pups compared with controls after up to two weeks of treatment. Small bowel length was greater in rEpo treated pups, and a dose dependent increase in villus surface area which was independent of the route of dosing and associated with increased BrdU uptake was found.

CONCLUSIONS

rEpo is not enterally absorbed in an intact and functional form from the intestines of neonatal rat pups. Thus enterally dosed rEpo has no erythropoietic effects. However, rEpo acts as a trophic factor in developing rat small bowel whether given enterally or parenterally.

Significance of meconium-stained amniotic fluid in the preterm population

OBJECTIVE

Numerous studies have assessed the significance of meconium-stained amniotic fluid (MSAF) at term. However, to date, there has been very little documentation on the incidence and significance of meconium in the preterm population. Our objective was to define the incidence of MSAF in patients delivering prematurely (<37 weeks) and examine its association with underlying fetal acidosis, Apgars and admission to the neonatal intensive care unit (NICU).

METHOD

All patients delivering at a single tertiary care center between June 1994 and September 1997 were reviewed for the presence of meconium and gestational age <37 weeks at delivery. Maternal demographics and birth outcomes including cord gases, Apgar scores and admission to the NICU were collected. Exclusion criteria included multiple gestations, breech presentations, fetal anomalies and patients not in labor.

RESULTS

Out of a total of 9570 patients there were 506 (5.3%) preterm births meeting the inclusion criteria, of whom 24 (4.8%) had MSAF noted either during labor or at delivery. Comparing the preterm group with and without meconium, there were no differences in maternal age, gravidity, rate of Cesarean section, or gestational age at delivery. Cord pH (7.27 meconium vs. 7.29 no meconium) and base excess (-5.1 meconium vs. -4.0 no meconium) were similar in both groups. There were no clinically significant differences in mean Apgar scores at 1 and 5 minutes. However, an increased number of NICU admissions were noted in the group with meconium (75% vs. 53%, p=0.04).

CONCLUSION

The incidence of meconium staining of the amniotic fluid in labor in the preterm population is less than 5% and by itself is not a significant marker of fetal acidosis.

Risk factors for meconium aspiration syndrome in infants born through thick meconium

OBJECTIVE

To determine risk factors for meconium aspiration syndrome (MAS).

METHOD

A cohort study was conducted of 70 consecutive singleton pregnancies complicated with thick meconium-stained amniotic fluid delivered at > or = 37 weeks' gestation. Cases were randomized either for elective abdominal delivery or spontaneous vaginal delivery after 20 min of external fetal heart rate (FHR) monitoring. Risk estimation analysis for MAS was performed calculating relative risks (RR) and odds ratios (OR).

RESULTS

The presence of meconium below the vocal cords (RR=7.3, 95% CI=2.6-20.3), non-reassuring FHR tracings (RR=3.0, 95% CI=1.2-7.5), Apgar score < or = 6 at 5 min (RR=3.8, 95% CI=1.7-8.4) and an umbilical cord plasma erythropoietin (UCPer) level > 50 mlU/ml (RR=5.0, 95% CI=2.1-12.0) were found to be significant risk factors for MAS. The presence of meconium below the vocal cords (OR=33.4, 95% CI=3.6-303.7) and non-reassuring FHR tracings (OR=12.2, 95% CI=1.3-111.7) remained as significant risk factors at the end of the multivariate analysis.

CONCLUSION

Non-reassuring FHR tracings and the presence of meconium below vocal cords are associated with an increased risk for MAS in infants born through thick meconium.

Nucleated red blood cells as a marker in acute and chronic fetal asphyxia

OBJECTIVE

To investigate the variations of nucleated red blood cell (NRBC) counts in acute and chronic fetal hypoxia and to examine if it could be possible to establish a cutoff value for the number of NRBCs for prediction of fetal acidosis.

METHOD

We prospectively studied 77 pregnant women. Patients were grouped as acute (n=11) and chronic fetal distress (n=21) and controls (n=45). At delivery the umbilical cord was double clamped and blood samples were collected.

RESULTS

The mean NRBC counts in chronic fetal distress group was higher than acute fetal distress. NRBC counts were found to be correlated with umbilical cord pH (r=-0.57; P<0.001). The cutoff value predicting fetal acidosis was determined as 14/100 leukocytes (sensitivity 87%, specificity 81%) by using ROC analysis.

CONCLUSION

The duration and the severity of fetal asphyxia may be predicted by the number of NRBCs per leukocyte.

Origin and fate of erythropoietin in human milk

Erythropoietin (Epo) is a normal constituent of human milk, but the origin and fate of this cytokine in milk are not known. Regarding its origin, we hypothesized that cells of the mammary gland secrete Epo into milk actively and, therefore, that concentrations in milk do not correlate with concentrations in serum. Regarding its fate, we hypothesized that Epo concentrations in milk change with time postpartum and that Epo in milk is protected from digestion in the neonatal gastrointestinal tract. To address these issues, we measured Epo concentrations in 103 milk samples (ELISA), 55 of which were paired with serum. Mammary duct epithelial cells were evaluated as a source of Epo by breast tissue immunohistochemistry and by cell culture. Circulating and milk Epo were compared by Western analysis to detect size differences, possibly reflecting differences in processing. Epo stability in simulated conditions of digestion was evaluated. We observed that milk Epo concentrations increase as a function of duration of breast-feeding and have a negative correlation with serum Epo or milk protein concentration. Mammary duct epithelial cells from breast biopsies of lactating women had marked immunoreactivity to Epo, but such activity was minimal to absent in nonlactating breast tissue. Further evidence that mammary duct epithelia produce Epo was obtained by observing Epo mRNA and protein expression in cultured human mammary epithelial cells. The molecular size of Epo in milk and serum is identical. Recombinant Epo added to human milk or commercial infant formulas was relatively stable in conditions that simulate gastric and small intestinal conditions of newborn infants; however, recombinant Epo added to D(5)W was not protected from digestion. We conclude that Epo concentrations in milk increase as a function of the duration of breast feeding, that Epo is actively secreted into human milk by mammary duct epithelia, and that the Epo within milk is largely protected from digestion.

Fetal erythropoietin levels in pregnancies complicated by meconium passage: does meconium suggest fetal hypoxia?

OBJECTIVE

We sought to determine whether umbilical cord plasma erythropoietin levels were different in deliveries complicated by meconium passage and to determine whether this response is influenced by gestational age.

STUDY DESIGN

Fetal erythropoietin levels were measured in 203 appropriately grown neonates at 37 to 43 weeks of gestation; among those, 70 had passed meconium.

RESULTS

Meconium passage in the entire population was associated with elevated fetal erythropoietin levels (68 vs 31 mIU/mL; P <.001). Cord blood gases, pH, base deficit, and PO (2), as well as the 1- and 5-minute Apgar scores, were not different between the meconium and no-meconium groups. Gestational age and birth weights were significantly higher in the meconium group. Stepwise multiple regression analysis with meconium and gestational age used as the independent variables showed both meconium and gestational age to be independently associated with fetal erythropoietin levels (r = 0.356, F = 14.5; meconium, P <.001; gestational age, P <.01).

CONCLUSIONS

These results suggest that meconium passage can be associated with chronic fetal hypoxia as demonstrated by elevated fetal erythropoietin levels, independent of gestational age.

Nucleated red blood cell count at birth as an index of perinatal brain damage

OBJECTIVE

The prognostic value of the nucleated red blood cell count at birth with respect to perinatal brain damage and neonatal outcome was assessed in infants at high risk of having neurologic damage.

STUDY DESIGN

The nucleated red blood cell count at birth, pulsed Doppler ultrasonography in the cerebral arteries, cranial fontanelle sonograms, and neurodevelopmental status were evaluated in 337 newborn infants.

RESULTS

The nucleated red blood cell count at birth was significantly higher (1) in neonates with abnormal Doppler ultrasonographic parameters for the cerebral arteries at 48 to 72 hours after birth than in healthy neonates, (2) in 6-month-old infants with sequelae of hypoxic-ischemic encephalopathy than in healthy infants, and (3) in 3-year-old children with abnormal developmental status than in those with no abnormalities at follow-up. Significant correlations were observed between the nucleated red blood cell count and gestational age, Apgar score at 1 and 5 minutes, pH, base deficit, fraction of inspired oxygen, blood oxygen content, and birth weight.

CONCLUSIONS

The nucleated red blood cell count at birth not only reflects a response of the infant to perinatal hypoxia but is also a reliable index of perinatal brain damage.

Nucleated red blood cells as a marker of acidemia in term neonates

OBJECTIVES

Nucleated red blood cells are produced in increased numbers under hypoxic conditions. We sought to examine the relationship between nucleated red blood cell count in the circulations of term neonates and other possible markers of fetal hypoxia.

STUDY DESIGN

We prospectively collected umbilical blood from all live-born neonates delivered at our institution. Arterial blood was analyzed for pH and blood gas values. Venous blood was analyzed for nucleated red blood cell count. We reviewed the medical records for maternal data and neonatal outcomes of gestations of >/=37 weeks' duration.

RESULTS

We evaluated 1561 cases. The mean nucleated red blood cell count per 100 white blood cells was 9.2 +/- 18.1 (range, 0-327). Nucleated red blood cell counts were higher in infants with pH <7.20 (P =.001). Both patients with respiratory acidemia and patients with uncompensated metabolic acidemia had elevated nucleated red blood cell counts (P =.013 and P =.014, respectively). As umbilical artery pH and base excess decreased, nucleated red blood cells became more prevalent. Elevated nucleated red blood cell counts were associated with presence of meconium (P =. 020) and neonatal intensive care unit admission (P =.024).

CONCLUSIONS

We found that nucleated red blood cell counts vary widely in the circulation of term neonates. Elevated nucleated red blood cell counts are associated with fetal acidemia, meconium, and neonatal intensive care unit admission.

Meconium stained amniotic fluid in very low risk pregnancies at term gestation

OBJECTIVE

To determine the prevalence and clinical significance of meconium stained amniotic fluid (MSAF) in a low risk population at term gestation and to investigate whether MSAF is a predictor for intrapartum and neonatal morbidity.

METHODS

A very low risk population including 37 085 consecutive deliveries at term composed the study population. A cross-sectional study was conducted and two groups of patients were identified according to the presence (n=6164) or absence (n=30921) of meconium in the amniotic fluid at delivery and the outcomes of the two groups compared.

RESULTS

The prevalence of MSAF was 16.6%. The incidence of cesarean section (5.6% vs 2.3% P<0.01), instrumental deliveries (3.2% vs 1.8% P<0.01), fetal distress (6.5% vs. 2.1% P<0.01), clinical chorioamnionitis (0.2% vs. 0.1% P<0.01), post-partum infection (0.5% vs. 0.2% P<0.01), 1-minute Apgar score <3 (1.9% vs. 1.1% P<0.01), small for gestational age (7.4% vs. 6.4% P<0.01). was significantly higher in the MSAF compared with the clear amniotic fluid group. Intrapartum and neonatal mortality in this low risk population was significantly higher in the MSAF group (1.7/1000) compared with women with clear AF (0.3/1000).

CONCLUSIONS

MSAF in a low risk population at term gestation is a predictor for adverse perinatal outcome and peripartum complications.

Intrapartum fetal hypoxia and biochemical markers: a review

Intrapartum fetal hypoxia is a rare event, although fetal intrapartum surveillance is discussed as a subject of major importance. This is mainly because of consequences of fetal hypoxia that may lead to cerebral palsy. A fetus suffering from hypoxia initially compensates by producing energy through anaerobic metabolism. At some stage, the fetus becomes decompensated and basic cellular functions fail, with risks of permanent morbidity or mortality. How long a fetus can survive on anaerobic metabolism differs because metabolic reserves differ, i.e., growth-restricted fetuses might deteriorate at an earlier stage. An increasing body of evidence has clarified brain-damaging mechanisms. Neuronal loss occurs in two phases: during the primary hypoxic event and later during the reperfusion/reoxygenation phase. Animal studies have suggested the possibility of prophylactic treatment to prevent neuronal loss after the hypoxic event. Intrapartum diagnostic tools should aim for detecting fetal hypoxemia/hypoxia when the fetus is still compensated. This may be achieved by assessment of biochemical data such as pH, lactate, and oxygen saturation, with the aim of prophylactic intervention before the fetus becomes decompensated. The measurement of cord blood levels of oxygen free radicals and excitatory amino acids at the time of birth may prove to be helpful in determining the risk of brain damage and evaluating the effect of prophylactic treatments to prevent or ameliorate brain injury from hypoxia.

Umbilical cord plasma erythropoietin levels in pregnancies complicated by maternal smoking

OBJECTIVE

Our goal was to determine whether maternal smoking was associated with elevated umbilical cord erythropoietin, a marker for chronic hypoxia.

STUDY DESIGN

Plasma erythropoietin levels were measured in umbilical cord plasma of 222 newborns. There were 48 mothers who smoked and 174 nonsmokers.

RESULTS

When all pregnancies were included, mean cord plasma erythropoietin levels were significantly higher in the smokers (78.0 +/- 15.3 mIU/ml) compared with the nonsmoking group (35.2 +/- 4.0 mIU/ml; p < 0.005). Regression analysis showed a significant positive correlation between the number of cigarettes smoked per day and cord plasma erythropoietin levels (r = 0.26, p < 0.0001). Smoking was associated with a significantly elevated risk (relative risk = 2.6, 95% confidence interval 1.7 to 10.9, p < 0.005) of fetal growth restriction. When pregnancies with fetal growth restriction were excluded from the analysis, the difference between the two groups remained significant (smokers 81.3 +/- 18.6, n = 38; nonsmokers 24.3 +/- 1.4, n = 164; p < 0.03).

CONCLUSIONS

These results illustrate that smoking during pregnancy is associated with fetal growth restriction and significantly elevated umbilical cord erythropoietin levels.

Nucleated red blood cells in cord blood of singleton term neonates

OBJECTIVE

This study aims to establish normal values for nucleated red blood cells in term singletons and factors associated with their elevation.

STUDY DESIGN

Cord blood was prospectively collected from term singleton gestations from Feb. 1 to July 31, 1995. Umbilical vein white blood cells and nucleated red blood cells were counted and umbilical arterial pH was determined. Medical records provided maternal and neonatal information.

RESULTS

Cord blood from 1112 cases was obtained and evaluated for nucleated red blood cells per 100 white blood cells. Nine outliers were censored (nucleated red blood cells per 100 white blood cells = 126 to 830); five cases were excluded because of missing data. The mean value of nucleated red blood cells per 100 white blood cells was 8.55, the SD was 10.27, and the range was 0 to 89. The value did not very by maternal tobacco or drug use, anemia, fetal presentation, or mode of delivery. Both maternal diabetes and meconium were associated with elevated values, p < 0.01. Apgar scores and cord pHs showed trends toward inverse proportionality to the number of nucleated red blood cells per 100 white blood cells.

CONCLUSION

The mean number of nucleated red blood cells per 100 white blood cells was 8.55, with a wide range and SD. Elevated values may be associated with markers of intrauterine hypoxia such as meconium, lower Apgar scores, and lower pH values.