Colloid osmotic pressure of umbilical cord plasma in healthy and sick newborn infants

Colloid osmotic pressure of umbilical cord plasma was measured in 242 healthy infants, in 34 infants with respiratory distress syndrome (RDS), in 18 infants with asphyxia, in 13 infants who were small for gestational age, in 15 infants born to mothers with diabetes mellitus, and in 18 infants born to mothers with pregnancy-induced hypertension. In healthy infants, colloid osmotic pressure correlated highly significantly with umbilical cord blood total protein level, gestational age, and birth weight. In infants with RDS, no correlation between colloid osmotic pressure and gestational age or birth weight was found. Infants with RDS and gestational age between 36 and 38 weeks had significantly lower colloid osmotic pressure than healthy infants, whereas colloid osmotic pressure of infants with RDS and gestational age between 32 and 35 weeks did not differ from that of healthy infants of corresponding gestational age. Healthy term infants delivered by cesarean section had significantly lower colloid osmotic pressure than infants delivered vaginally. Infants with asphyxia had significantly higher colloid osmotic pressure than healthy infants. Colloid osmotic pressure is related to the lung maturity of the near-term and term neonate. Infants with a colloid osmotic pressure greater than 16 mm Hg are unlikely to develop RDS.     

Low colloid osmotic pressure in very low birthweight infants receiving assisted ventilation

Plasma colloid osmotic pressure (COP) was measured in three groups of very low birthweight infants. Babies in Group 1 ( n = 8) were breathing spontaneously and had no respiratory disease. Those in Group 2 ( n = 9) received assisted ventilation for hyaline membrane disease (HMD), and those in Group 3 ( n = 7) received assisted ventilation for other reasons (five apnoea, two pneumonia).
Both assisted ventilation groups had lower mean COP values than spontaneously breathing infants. Mean values (s.e.m.) for Groups 1,2 and 3, respectively, were: 15.3 (0.6), 11.3 (0.4) and 11.9 mmHg (0.5)( P < 0.001) on Day 1; and 15.2 (0.4), 12.9 (0.4) and 12.8 mmHg (0.3) ( P < 0.001) on Day 2. The Increase from Day 1 to Day 2 was significant for those with HMD ( P < 0.05). Colloid osmotic pressure correlated with mean blood pressure ( r = 0.51; P < 0.001) but not with birthweight, gestation, crystalloid fluid intake or pH.
The role of low COP in the pathogenesis of acute respiratory failure in infants with uncomplicated HMD is unclear, but such low COP may contribute to development of pulmonary oedema as a complication, particularly if the ductus'arteriosus is still patent and the infants are given high volume intravenous fluids.     

Ontogeny of unconjugated estriol in fetal blood and the relation of estriol levels at birth to the development of respiratory distress syndrome

Unconjugated estriol (E3) was quantified in serum of umbilical cord blood of 533 newborn infants, 360 of whom were delivered between 23 and 37 wk of gestation. Serum E3 levels rose (F = 7.71, p less than 0.0001) as a function of gestational age; the mean concentration of E3 at 37.5-42 wk of gestation (105 ng/ml, n = 173) was significantly higher than that in serum of newborns delivered at 23-28 wk of gestation (63 ng/ml, n = 33). Umbilical cord serum levels of E3 were significantly higher among newborns delivered vaginally between 31.5 and 42 wk of gestation than among newborns delivered by cesarean section (p less than 0.005). Although serum E3 levels correlated highly (p less than 0.0001) to newborn weight throughout the entire period of gestation, there was no relationship of newborn weight to umbilical serum E3 levels within a given gestational period. Also, the umbilical serum levels of E3 in male infants were similar to those of female infants at each gestational age. Significant changes in umbilical serum levels of E3 as a function of gestational age were not observed among newborns (n = 90) who developed respiratory distress syndrome (RDS). The mean umbilical serum concentration of E3 in newborns delivered at 34.5-37 wk of gestation who developed RDS were significantly lower (p less than 0.01) than that in similar aged newborns whose lung function was normal.(ABSTRACT TRUNCATED AT 250 WORDS)     

Low colloid osmotic pressure in very low birthweight infants receiving assisted ventilation

Plasma colloid osmotic pressure (COP) was measured in three groups of very low birthweight infants. Babies in Group 1 (n = 8) were breathing spontaneously and had no respiratory disease. Those in Group 2 (n = 9) received assisted ventilation for hyaline membrane disease (HMD), and those in Group 3 (n = 7) received assisted ventilation for other reasons (five apnoea, two pneumonia). Both assisted ventilation groups had lower mean COP values than spontaneously breathing infants. Mean values (s.e.m.) for Groups 1, 2 and 3, respectively, were: 15.3 (0.6), 11.3 (0.4) and 11.9 mmHg (0.5) (P less than 0.001) on Day 1; and 15.2 (0.4), 12.9 (0.4) and 12.8 mmHg (0.3) (P less than 0.001) on Day 2. The increase from Day 1 to Day 2 was significant for those with HMD (P less than 0.05). Colloid osmotic pressure correlated with mean blood pressure (r = 0.51; P less than 0.001) but not with birthweight, gestation, crystalloid fluid intake or pH. The role of low COP in the pathogenesis of acute respiratory failure in infants with uncomplicated HMD is unclear, but such low COP may contribute to development of pulmonary oedema as a complication, particularly if the ductus arteriosus is still patent and the infants are given high volume intravenous fluids.     

晚期早产儿和足月儿呼吸窘迫综合征的临床特点

目的 比较晚期早产儿或足月儿和早产儿呼吸窘迫综合征(respiratory distress syndrome,RDS)的特点,探讨晚期早产儿或足月儿RDS的临床特征和发病机理.方法 2005年5月至2007年5月,在本院住院177例RDS患儿,＜35周为早产组,103例,≥35周为晚期早产儿或足月儿组,74例.结果 早产组开始应用呼吸机时间为8.7 h,持续应用呼吸机时间4.3 d,氧合指数(Oxygenation index,OI)11.9,PaO2/PAO2 0.29,有28例应用表面活性物质(pulmonary surfactant,PS),其中11例应用呼吸机,应用PS前及后2 h、8～12 h、20～24 h OI分别为10.5、5.4、3.4、4.3(P＜0.01).晚期早产儿或足月儿组开始应用呼吸机时间为27.8 h(与早产组比,下同,P＜0.01),持续应用呼吸机时间3.7 d,OI 19.70(P＜0.01),PaO2/PAO20.16(P＜0.01),8例应用PS中有7例应用呼吸机,应用PS前及后2 h,8～12 h、20～24 h OI分别为11.2、7.6、7.5、7.6(其中8～12 h、20～24 h OI与早产组比,P均＜0.05).结论 晚期早产儿或足月儿RDS患儿以产程未发动的剖宫产为主.开始应用呼吸机时间较晚,氧合情况较差,表面活性物质应用效果较差,易发生气胸和PPHN.     

Fetal and neonatal mortality of small-for-gestational age infants

Fetal and neonatal mortality of small-for-gestational age (SGA) infants in 1968–1982 were studied in the region of the University Central Hospital of Turku, Finland. During the study period, there were 254 fetal and 127 neonatal deaths in SGA infants. The fetal mortality rate of SGA infants declined from 49.9/1000 to 14.0/1000. The neonatal mortality rate of SGA infants declined from 23.8/1000 to 8.3/1000. The severely SGA infants with a birth weight below the 2.5th percentile had three times higher neonatal mortality rates than SGA infants with a birth weight between the 2.5th and the 10th percentiles. The main causes of fetal deaths were maternal diseases, placental and cord complications and fetal malnutrition, even though there was a decline in all these groups. Malformations remained the main cause of neonatal death during the study period, while there was a decline in deaths due to asphyxia and respiratory distress syndrome (RDS). The high mortality rates of SGA infants emphasize the need for early diagnosis and special attention during pregnancy, delivery and the neonatal period.Abbreviations SGA small-for-gestational age - AGA appropriate-for-gestational age - UCHT University Central Hospital of Turku - RDS respiratory distress syndrome     

Neonatal polycythemia: I. Early diagnosis and incidence relating to time of sampling

The dynamic changes occurring in hematocrit and blood viscosity within the first 18 hours of life were studied in 50 full-term infants who were vaginally delivered and had weight appropriate for gestational age. In all cases, the cord was clamped within 30 seconds and cord blood was collected from the vein and artery. Subsequently, samples were taken from a peripheral vein at ages 15 minutes, and 2, 4, 6, and between 12 to 18 hours. Both the Hct and blood viscosity reach their peak at age 2 hours. The incidence of neonatal polycythemia varied greatly with age. Thus at the age of 2 hours, ten infants (20%) were polycythemic, whereas by age 6 hours only six (12%) of these infants were still polycythemic and by age 12 to 18 hours only one infant (2%) was polycythemic. A linear correlation was found between cord Hct levels and peripheral venous Hct levels by age 2 hours. None of the infants with cord blood Hct levels less than or equal to 56% had developed polycythemia, whereas ten of the 12 infants with cord Hct levels greater than 56% developed polycythemia. In this particular group of infants, cord blood Hct levels may be used for the screening of neonatal polycythemia.     

Neonatal red cell superoxide dismutase enzyme levels: possible role as a cellular defense mechanism against pulmonary oxygen toxicity

Red cell superoxide dismutase (SOD) enzyme activity was determined in 58 cord blood specimens obtained from infants over a range of gestational ages. An inverse relationship between red cell SOD activity and gestational age was demonstrated. Red cell SOD activity showed a progressive fall from 263.1 +/- 30.5 units/mg non-hemoglobin protein (NHP) in infants of less than 29 weeks of gestation to 168.9 +/- 21.3 units/mg NHP in infants of more than 36 weeks of gestation (P less than 0.05). Infants treated for RDS showed an increase in red cell SOD activity which reached significance at 72 hr when compared to cord blood levels from the same population (P less than 0.05). No similar significant difference could be demonstrated in gestational age-matched control subjects over the same time period. However, initial cord blood SOD enzyme levels were lower in premature infants with RDS (229.5 +/- 30.6 units/mg NHP) than in premature infants without RDS (264.0 +/- 38.0 units/mg NHP). When infants with RDS were examined for oxygen toxicity and survival, red cell SOD levels were noted to decrease over 24 hr in four of five infants who died, three of whom developed bronchopulmonary dysplasia. In the surviving infants, red cell SOD levels showed a significant increase by 48 hr (P less than 0.05). None developed bronchopulmonary dyplasia and all survived.     

Ureaplasma urealyticum in a neonatal intensive care population

The incidence of Ureaplasma colonization at birth and its effect on the development of chronic lung disease (CLD) and on mortality was studied in a neonatal intensive care population. Ureaplasma colonization was associated with a birthweight < 1000 g (odds ratio [OR] 3.45 confidence intervals [CI] 2.13-5.60) and a gestational age < 30 weeks (OR 2.54 CI 1.71–3.79). In a case-controlled study of 112 infants, significant associations with Ureaplasma colonization were maternal pyrexia in labour ( n = 38 vs 21; P = 0.015), the requirement for antibiotics in labour ( n = 39 vs 16; P = 0.0005) and vaginal delivery ( n = 78 vs 58; P = 0.009). Risk factors associated with the development of CLD were birthweight < 1000 g (OR 3.77 CI 2.53–5.62) and delivery by Caesarean section (OR 1.65 CI 1.11–2.43). Within the group delivered by Caesarean section. Ureaplasma colonization was also associated with an increased risk of CLD (OR 1.97 CI 1.08–3.62). Ureaplasma colonization of infants at birth is associated with factors suggestive of maternal chorioamnionitis as well as preterm birth and low birthweight. In infants delivered by Caesarean section, Ureaplasma colonization is associated with an increased risk of chronic lung disease.     

The influence of the mode of delivery on the umbilical cord serum aldosterone levels in preterm newborn infants

The influence of the mode of delivery on the umbilical cord serum aldosterone levels in preterm newborn infants was studied. Sixty-four newborn infants gestational age less than 37 weeks were sequentially included in the study. Umbilical cord blood was collected just after birth and the aldosterone level was measured by radioimmunoassay. The median aldosterone level of the whole studied sample was 74.5 ng/dl (range: 22.00-280.00 ng/dl). The aldosterone level of the 31 newborn infants delivered vaginally was similar of the 33 newborn infants delivered by cesarean-section. When the cesarean group was subdivided in presence or not of labor prior to delivery, the aldosterone levels of those delivered after labor was significantly higher than those without labor. It is suggested that some event associated to the mode of delivery or the presence of labor prior to delivery may influence aldosterone levels in preterm newborn infants.     

HYPERTENSIVE PEAKS IN THE PATHOGENESIS OF INTRAVENTRICULAR HEMORRHAGE IN THE NEWBORN. ABOLITION BY PHENOBARBITONE SEDATION

ABSTRACT. Mean arterial blood pressure (MABP) was measured continuously for 3 to 5 days after birth in 27 premature infants with a birth weight under 1500 g, and who required umbilical artery catheterisation. All had respiratory distress syndrome (RDS). Intraventricular hemorrhage (IVH) occurred in 9 infants (33%), diagnosed by computered tomography (CT). IVH was more common in infants of lower gestational age, in infants delivered vaginally and in infants with perinatal asphyxia. Variable increases in MABP over the resting value occurred in all infants associated with increases in both active and passive motor activity. In 6 infant pairs matched for birth weight, gestational age, mode of delivery and severity of perinatal asphyxia, the infants who developed IVH had higher peak MABP valued compared to matched controls. Resting and minimum MABP values were not different in the two groups. We conclude that the large increases in arterial blood pressure which occur with both spontaneous motor activity and in association with nursing procedures, are an important cause of development of IVH in very low birth weight infants. An example is given to show that pressure peaks can be abolished by phenobarbitone sedation.     

Method of birth alters interferon-gamma and interleukin-12 production by cord blood mononuclear cells

Many uncertainties exist regarding the capability of cord blood mononuclear cells (CBMC) to produce cytokines. A number of conflicting reports led us to examine the effects of method of birth on CBMC production of interferon-gamma (IFN-γ), interleukin-4 (IL-4) and interleukin-12 (IL-12). While constitutive production of IL-4 was found in both vaginally and cesarean-delivered infants, constitutive IFN-γ or IL-12 production was found in neither. CBMC from vaginally delivered infants responded to stimulation with concanavalin A/phorbol 12-myristate 13-acetate (Con A/PMA), phytohemagglutinin (PHA), and lipopolysaccharide (LPS) with significantly higher levels of IFN-γ than CBMC from unlabored cesarean section (CS) infants. Production of IL-12 was increased in the vaginally delivered group in response to LPS and PHA but not to ConA/PMA. In contrast, mode of delivery was not associated with differences in IL-4 production. These results indicate that mode of delivery significantly alters the capability of CBMC to produce some cytokines and therefore should be taken into account in interpreting fetal/neonatal mononuclear cell function studies.     

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目的 探讨早期、晚期早产儿与足月儿呼吸窘迫综合征(RDS)的发病趋势和临床特征的差异,为临床合理诊治提供依据。方法 2006年1月至2010年12月在郑州大学第三附属医院住院的963例RDS患儿根据胎龄不同分为早期早产儿组(<34周)679例,晚期早产儿组(34～<37周)204例,足月儿组(≥37周)80例,分别对各组患儿的发病率、入院情况、高危因素、临床诊治、预后及并发症进行比较。结果 RDS的发病率逐年增加,均以早期早产儿占多数,晚期早产儿和足月儿RDS比例有增多趋势;RDS患儿男婴超过女婴(P<0.05),且胎龄和体重越大,男婴比例越高;足月儿RDS组产前糖皮质激素使用率明显低于早产儿组;早产儿发生RDS的高危因素主要有胎膜早破、胎盘异常、母亲妊娠高血压疾病,足月儿发生RDS的高危因素主要是择期剖宫产与感染;晚期早产儿与足月儿RDS的临床诊断和应用肺泡表面活性物质(PS)时间均晚于早期早产儿;足月儿RDS应用机械通气比例明显高于早产儿,其临床治愈率高(P<0.05),在死亡率方面与早产儿组无差别;但并发气胸的比例高于早产儿组(P<0.05)。结论 新生儿呼吸窘迫综合征(NRDS)发病率逐年增高,晚期早产儿和足月儿RDS比例有增多趋势;早期、晚期早产儿与足月儿RDS在性别比例、高危因素、起病特点、治疗反应与并发症方面均存在差异,RDS的诊治需要考虑胎龄因素。足月儿RDS多与择期剖宫产、感染有关,发病相对较晚,容易合并气胸,应引起足够重视。     

Lack of correlation between NADPH-oxidase priming and elevated alkaline phosphatase activity in cord blood neutrophils

Human neutrophils were isolated from cord blood drawn after Caesarean section deliveries without labour and from peripheral blood from healthy adults. The alkaline phosphatase (ALP) activity in the cell populations was compared with the release of respiratory burst products after activation with the chemoattractant n-formyl-methionyl-leucyl-phenylalanine (fMLP). In contrast to cord blood neutrophils obtained from babies after normal vaginal deliveries, the Caesarean section neutrophils were not metabolically primed. However, like the neutrophils from vaginally delivered babies, the Caesarean section neutrophils showed an increased ALP activity compared to adult control neutrophils. These findings indicate that priming of cord blood neutrophils appears to be induced by labour and can be dissociated from increased ALP activity.     

Neonatal respiratory morbidity risk and mode of delivery at term: influence of timing of elective caesarean delivery

AIM: To establish whether the timing of delivery between 37 + 0 and 41 + 6 wk gestation influences neonatal respiratory outcome in elective caesarean delivery, following uncomplicated pregnancy, thus providing information that can be used to aid planning of elective delivery at term. METHODS: All pregnant women who were delivered by elective caesarean delivery at term during a 3-y period were identified from a perinatal database and compared retrospectively with pregnant women matched for week of gestation, who were vaginally delivered. Maternal characteristics, neonatal outcome, incidence of respiratory distress syndrome (RDS) and transient tachypnea of the newborn (TTN) were analysed. During this time, 1284 elective caesarean section deliveries occurred at or after 37 + 0 wk of gestation. RESULTS: Neonatal respiratory morbidity risk (odds ratio, OR), including RDS and TTN, was significantly higher in the infant group delivered by elective caesarean delivery compared with vaginal delivery (OR 2.6; 95% CI: 1.35-5.9; p < 0.01). While TTN risk in caesarean delivery was not increased (OR 1.19; 95% CI: 0.58-2.4; p > 0.05), the RDS risk was significantly increased (OR 5.85; 95% CI: 2.27-32.4; p < 0.01). This RDS risk is greatly increased in weeks 37 + 0 to 38 + 6 (OR 12.9; 95% CI: 3.57-35.53; p < 0.01). After 39 + 0 wk, there was no significant difference in RDS risk. CONCLUSIONS: Infants born by elective caesarean delivery at term are at increased risk for developing respiratory disorders compared with those born by vaginal delivery. A significant reduction in neonatal RDS would be obtained if elective caesarean delivery were performed after 39 + 0 gestational weeks of pregnancy.     

Plasma methionine enkephalin levels in the human newborn at birth

Plasma met-enkephalin immunoreactivity (MET-ENKi) and catecholamine levels were measured in umbilibal cord blood from 46 healthy newborn infants. Clinical data including Apgar scores, birth weight, gestational age, route of delivery, fetal heart tracings and arterial blood gas values were also obtained. Thirty-nine infants were delivered by the vaginal route. All but 1 infant delivered by cesarian section had undergone a trial of labor. Plasma MET-ENKi in the newborn infants was markedly greater than levels found in healthy adult volunteers: 360 +/- 25 versus 25 +/- 2 pg/ml, respectively. MET-ENKi levels were similar in umbilical arterial and umbilical venous blood, and in infants delivered vaginally or by cesarian section.     

早产儿出生时25羟基维生素D水平与呼吸窘迫综合征关系分析

目的研究早产儿出生时血清25羟基维生素D[25(OH)D]水平与呼吸窘迫综合征(RDS)的关系。方法将2014年1月至2016年12月于新生儿病房住院的符合入组标准和排除标准的早产儿112例分为RDS组(n=72)和对照组(n=40)。收集两组患儿的一般临床资料,包括胎龄、出生体重、性别、分娩方式、1 min及5 min Apgar评分,以及母妊娠期糖尿病和产前激素使用情况。采集患儿的外周静脉血,分离血清,采用化学发光免疫分析法检测血清25(OH)D水平;采用二元logistic回归模型分析25(OH)D水平与RDS发生的关系。结果 RDS组1 min及5 min Apgar评分、血清25(OH)D水平显著低于对照组(P0.05),新生儿窒息及维生素D缺乏发生率显著高于对照组(P0.05)。经二元logistic回归分析结果显示,新生儿窒息(OR=2.633,95%CI:1.139~6.085)、维生素D缺乏(OR=4.064,95%CI:1.625~10.165)是导致早产儿RDS发生的危险因素(P0.05)。结论早产儿出生时维生素D缺乏可能与RDS发病风险增加有关,母孕期合理补充维生素D可能降低早产儿RDS发病率。     

The effects of acute and chronic perinatal stress on plasma vasopressin concentration and renin activity at birth

The effects of acute and chronic intrauterine stress on plasma vasopressin (AVP) concentration and renin activity (PRA) in the cord blood of 36 newborn infants were studied. AVP concentrations in the umbilical artery were significantly higher than those in the umbilical vein in all infants, except in those delivered by elective cesarean section after normal pregnancy. AVP concentrations in the umbilical arterial blood after normal term pregnancy and vaginal delivery (779 pg/ml, log mean) were higher than those in the cord blood of infants delivered vaginally after maternal hypertensive disease (198 pg/ml). Compared to the values of the latter group, the AVP values were significantly lower (39 pg/ml) in infants delivered by cesarean section without labor because of severe growth retardation and decreased heart rate variability. The group of normal term infants delivered by elective cesarean section after normal pregnancy had the lowest AVP concentrations (13 pg/ml). PRA in the umbilical arterial blood was not different from that in the umbilical venous blood. The highest mean level of PRA (14.5 ng/ml/h) was observed in premature infants delivered by cesarean section because of fetal growth retardation and pathological heart rate variability, and the lowest mean level in term infants delivered by elective cesarean section (3.4 ng/ml/h). PRA was significantly increased in term infants delivered vaginally after normal pregnancy (7.8 ng/ml/h) or after hypertensive pregnancy (11.7 ng/ml/h) in comparison to that of term infants delivered by elective cesarean section.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neonatal blood glucose concentrations in caesarean and vaginally delivered term infants

Background: Little is known about the glucose concentrations at and after birth of infants delivered by caesarean section (CS), when compared with infants born vaginally (VD). Aim: To compare venous cord blood glucose concentrations of term infants born after elective CS to infants born by VD. We studied the null hypothesis that mode of delivery does not affect neonatal blood glucose values. Methods: We compared cord blood glucose concentrations in healthy term infants born after VD (n = 16) or by elective CS (n = 21). Glucose concentrations were obtained immediately at birth from the umbilical cord. Kruskal–Wallis was used to compare glucose concentrations and demographic variables between the groups. Results: Gestational age was 39.6 ± 0.8 weeks in VD group vs. 38.7 ± 0.9 weeks in CS group, and birthweight was 3359 ± 494 vs. 3500 ± 528 g. Cord blood glucose concentration was higher in VD (81.3 ± 16.9 mg/dL) than CS infants (70.3 ± 9.7 mg/dL, p = 0.039). The change in blood glucose concentration over the first 2‐h of life differed significantly between the two groups, being an increase in CS versus a decrease in VD infants (?3.5 ± 15.2 vs. ?15.4 ± 24.6 mg/dL, p = 0.013). Conclusions: Glucose concentrations in VD infants are higher than in infants born by elective CS without labour.     

Catecholamine surge and lung function after delivery.

Lung function was measured at 30 minutes and again at 2 hours after birth in 12 infants delivered vaginally, in 15 infants delivered by elective caesarean section under general anaesthesia (GA), and in 15 delivered under epidural anesthesia (EDA). Umbilical arterial blood was analysed for pH and for concentrations of catecholamines and cortisol. No important differences in gestational age, birthweight, Apgar scores, or haematocrit were found among the three groups. Tidal volume and minute ventilation measured 30 minutes after birth were lower in infants delivered by caesarean section than in those delivered vaginally and at 2 hours the tidal volume was still lower in the babies delivered by caesarean section than in those delivered vaginally. Dynamic compliance was lower at 30 minutes in the group that had a caesarean section than in the vaginal group, and this difference was significant at two hours. Tidal volume, minute ventilation, and dynamic compliance in the GA and EDA groups did not differ. The catecholamine and cortisol concentrations at birth were higher in the vaginal group than in the group delivered by caesarean section. Two hours after birth there was a significant correlation (r = 0.84) between the catecholamine concentrations of the infants born vaginally and lung compliance. The lower dynamic lung compliance in infants delivered by elective caesarean section might be explained by delayed absorption of liquid in the lung due to lack of catecholamine surge.