Evaluation of serum cortisol levels in a relatively large and mature group of ventilated and nonventilated preterm infants with respiratory distress syndrome

Severity of respiratory distress syndrome (RDS) and mechanical ventilation may affect the endogenous cortisol secretion in preterm infants. The aim of this study was to compare the serum cortisol concentrations of a relatively large and mature group of preterm infants with RDS who are ventilated or nonventilated and control preterm infants without RDS. Infants (group I) of comparable gestational ages without RDS served as controls. Infants with RDS who did not need ventilator support and surfactant therapy were considered to have mild RDS (group II). Those requiring mechanical ventilation and surfactant therapy were considered to have severe RDS (group III). Serum cortisol levels were determined after birth and on day 3 of life. The study groups consisted of 79 preterm infants with gestational ages ranging from 31 to 36 weeks, and birthweights ranging from 1086 to 1685 g. All preterm infants showed high cortisol levels after delivery regardless of respiratory distress (group I, n = 25, 34.1 +/- 10.7 microg/dL; group II, n = 23, 33.6 +/- 12.0 microg/dL; and group III, n = 31, 36.4 +/- 12.3 microg/dL). In group III, the cortisol levels (50.8 +/- 16.8 microg/dL) were higher than in group II (40.4 +/- 10.5 microg/dL) and in controls (22.0 +/- 7.2 microg/dL), and the cortisol levels of controls were lower than in group II on day 3 of life. Although the cortisol levels in severe and mild RDS infants increased significantly from their corresponding levels on day 1, they decreased in controls. The cortisol levels on day 3 of life were not significantly different in infants with poor outcome compared with infants with better outcome. Severity of RDS and mechanical ventilation were related to serum cortisol levels of preterm infants. Our study suggests that large and mature preterm infants who are ventilated and/or more severely ill release more cortisol than those less severely ill.     

Fetal catecholamines and the Apgar score

The association between Apgar score, pH and catecholamine levels was investigated in 181 newborn infants with a gestational age between 29 and 43 completed weeks. Umbilical arterial blood was obtained before the first breath with the double clamp technique and pH was measured. Plasma adrenaline and noradrenaline were analyzed by high performance liquid chromatography. The Apgar score at 1 minute was above or equal to seven in 167 infants. Forty-four per cent of these infants had pH below 7.25. A negative correlation between log noradrenaline and pH (r = 0.52, p less than 0.001) and between log adrenaline and pH (r = 0.40, p less than 0.001) was found. In 14 infants the Apgar score was below seven. The median pH was 7.21 (range 7.02-7.32). Also in this group a negative correlation between log noradrenaline and pH (r = 0.60, p less than 0.05) and between log adrenaline and pH (r = 0.77, p less than 0.01) was noted. We concluded that the Apgar score is an insufficient measure of fetal asphyxia defined as fetal acidosis but rather reflects the vitality of the newborn.     

Maternal plasma corticotrophin-releasing hormone--elevated in preterm labour but unaffected by indomethacin or nylidrin

The role of corticotrophin-releasing hormone (CRH) in preterm labour was studied in 23 women in preterm labour at between 26 and 33 weeks gestation who were randomly allocated to receive treatment with indomethacin (n = 11) or with nylidrin a beta-sympathomimetic agent (n = 12). Maternal plasma CRH in the preterm group (median 70, range 9-597 pmol/l) before therapy was higher (P less than 0.05) than that in 23 control pregnancies, without uterine contractions, matched for gestational age (median 51, range 4-127 pmol/l). CHR levels determined after 3 and 24 h of treatment showed a 10% decrease in the indomethacin group and 10-20% decrease in the nylidrin group, but these changes were not statistically significant. After cessation of uterine contractions during tocolysis, 12 women proceeded to give birth preterm (less than 37 weeks) and their pretreatment CRH levels (median 195, range 9-597 pmol/l) were higher (P less than 0.05) than those in women whose pregnancy proceeded to term (median 52, range 16-207 pmol/l). In another group of women, full-term labour was not accompanied by any changes in maternal CRH levels. Umbilical plasma CRH levels were 1.1-9.8% of the paired maternal levels and did not rise with advancing gestational age. Nor had the type of delivery (elective caesarean section before labour, or preterm or term vaginal delivery) any effect on fetal CRH levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cesarean section, gestational age, and transient tachypnea of the newborn: timing is the key

The purpose of this study was to identify risk factors and to characterize infants with transient tachypnea of the newborn (TTN). A total of 67 newborns with TTN, born at gestational age (GA)>or=35 weeks, were studied. Newborns delivered before and after each study case served as controls. Mean GA was lower and cesarean section (CS) rate was higher in the TTN group (38.2+/-2.3 versus 39.5+/-1.4 weeks, p<0.001; 50.7% versus 22.4%, p<0.001). GA<38 weeks was found to be associated with increased risk for TTN in infants delivered by elective CS. TTN was associated with significant morbidities and longer hospital stay (7.2+/-5.6 versus 2.9+/-1.4 days; p<0.001). Delivery by CS and younger GA are risk factors for TTN. Although TTN is a self-limited disease, it is associated with significant morbidities. Scheduling elective CS at GA of not less than 38 weeks may decrease the frequency of TTN.     

Relationship between thyroid hormone levels and transient tachypnea of the newborn in late-preterm,early-term,and term infants

Purpose: We aimed to investigate the association between thyroid hormone levels and transient tachypnea of the newborn (TTN) among late-preterm, early-term, and term infants admitted to neonatal intensive care unit (NICU).

Materials and method: In the current retrospective study, neonates admitted to the NICU due to TTN were assigned to the TTN group (n?=?404). Healthy neonates who were followed up in the well-baby nursery comprised the control group (n?=?7335). Infants were grouped by gestational age into late-preterm (34–36⁶ weeks), early-term (37–38⁶ weeks), and term subgroups (39–41⁶ weeks). Serum levels of thyroid-stimulating hormone (TSH) and thyroxin (T₄) were determined from venipuncture samples taken at least 48?hours after birth. The relationship between thyroid hormone levels and the need for NICU admission for TTN was compared between groups.

Results: Compared to control infants, term neonates with TTN had significantly higher TSH levels, whereas late-preterm and early-term neonates with TTN had significantly lower T₄ levels. Birth weight and mode of delivery had no effect on NICU admission for TTN.

Conclusions: Infants admitted to NICU due to TTN had significantly different thyroid hormone levels with differences depending on gestational age.     

A program of uterine activity monitoring and its effect on neonatal morbidity

In a recent study 34 patients at high risk for preterm delivery who received uterine activity monitoring were compared with 33 similar patients who attempted to detect contractions by palpation. The incidence of preterm delivery was significantly reduced among those using the uterine activity detection device, although all patients in both groups had the same prenatal care and educational intervention. When short-term neonatal morbidity associated with preterm delivery was compared between the two groups, adverse effects decreased significantly among those in the monitored group (p = 0.001). The majority of short-term morbidity in both groups was noted in those delivering preterm and thus was gestational age related. No significant difference was found in neonatal morbidity between the groups when the infants were delivered at less than 37 weeks' gestation. Uterine activity monitoring, which is effective in preventing preterm birth, is also efficacious in decreasing short-term neonatal morbidity.     

The effect of integrating substance abuse treatment with prenatal care on birth outcome.

OBJECTIVE: To determine whether engaging pregnant substance abusers in an integrated program of prenatal care and substance abuse treatment would improve neonatal outcomes. STUDY DESIGN: The subjects were women who voluntarily enrolled in Project Link, an intensive outpatient substance abuse treatment program at Women and Infants Hospital, Providence, RI. A total of 87 women received substance abuse treatment in conjunction with their prenatal care; the comparison group of 87 women received equivalent prenatal care but did not enroll in the substance abuse treatment program until after they delivered. The two groups of women were similar demographically and socioeconomically and had similar substance abuse histories. Univariate and multivariate analyses were performed. The key outcomes were gestational age at delivery, birth weight, preterm delivery, Apgar scores, and neonatal intensive care admission rate. Factors controlled in the multivariate models included demographics, socioeconomic status, parity, and prenatal care. RESULTS: Infants born to women who enrolled prenatally were 400 gm heavier (p < 0.001), and their gestational age was 2 weeks longer (p < 0.001) than infants of mothers enrolled postpartum. In addition, they were approximately one-third as likely to be born with a low birth weight (p < 0.01) and approximately one-half as likely to be admitted to the neonatal intensive care unit (p < 0.05). CONCLUSION: Neonatal outcome is significantly improved for infants born to substance abusers who receive substance abuse treatment concurrent with prenatal care compared with infants born to substance abusers who enter treatment postpartum.     

A hypothetical model suggesting suboptimal intrauterine growth in infants delivered preterm

Infants delivered preterm often reflect accelerated maturation. The present study examines the occurrence of suboptimal intrauterine growth in infants delivered preterm by comparing their birth weights to the weights sonographically predicted for in utero fetuses at similar gestational ages but who ultimately deliver at term. Two weight-predicting formulas based on different sonographic parameters were used. In the fifth, tenth, and 50th percentiles of birth weight, the predicted weights were persistently and significantly greater than the actual birth weights between 24 and 31 weeks' gestation. The results of this model support the concept that the growth of infants delivered prematurely has been suboptimal. The authors hypothesize that preterm delivery may be in some instances another manifestation of the same underlying stress that hastens pulmonary and neurologic maturity.     

Neonatal outcome in growth-restricted versus appropriately grown preterm infants

The objective of this paper is to examine whether growth-restricted preterm infants have a different neonatal outcome than appropriately grown preterm infants. All consecutive, singleton preterm deliveries between 27-35 weeks' gestation were included over a 4-year period. Infants with congenital anomalies and infants of diabetic mothers were excluded. Infants were categorized as small-for-gestational-age (SGA) when birth weight was at or below the 10th percentile, and appropriate-for-gestational-age (AGA) when between the 11th and 90th percentiles. Outcome variables included: neonatal death, respiratory distress syndrome (RDS), sepsis, intraventricular hemorrhage (IVH), and necrotizing enterocolitis (NEC). Neonatal morbidity and mortality were examined by univariate and stepwise multivariate logistic regression analyses. Factors controlled for during the analysis included: maternal age; gestational age; mode of delivery; presence of preeclampsia, HELLP syndrome, prolonged premature rupture of membranes (PROM), placental abruption, placenta previa, prenatal steroid exposure, infant gender, and low Apgar score. Seventy-six infants were included in the SGA group and 209 in the AGA group. SGA infants had a higher mortality rate (p = 0.003). They also had more culture-proven sepsis episodes (p = 0.001). No differences were found with respect to the other outcomes. The results were similar when analyzed separately for the group of infants born at or below 32 weeks' gestation. Growth-restricted preterm infants were found to have both higher mortality and infection rates compared with AGA preterm infants. Growth restriction in the preterm neonate was not found to protect against other neonatal outcomes associated with prematurity. When considering elective preterm delivery for this high-risk group of pregnancies, the increased risks in the neonatal period should be taken into account.     

Implication of cord blood myeloperoxidase but not of soluble p-selectin levels in preterm deliveries

Although maternal amniotic and vaginocervical cytokines are known to play a role in triggering preterm delivery, the effects of activating fetal phagocytes and platelets are not clear. In an attempt to clarify this issue, we measured levels of myeloperoxidase (MPO), a phagocyte activation marker, and soluble p-selectin (sCD62p), a platelet activation marker, in umbilical cord blood samples from 2200 consecutive cord blood collections, 106 of which were from preterm infants. MPO and sCD62p levels were correlated to gestational age and preterm delivery. It was found that MPO levels were significantly higher in preterm infants and were not significantly correlated to gestational age. In contrast, sCD62p levels were lower in preterm infants and were negatively correlated to gestational age. In summary, we showed that fetal phagocyte activation as demonstrated by higher cord blood MPO levels is associated with preterm delivery, but platelet activation as shown by lower sCD62p levels is not. This suggests that fetal phagocyte activation may be implicated in preterm delivery, and subsequently in prematurity-related inflammatory insults.     

Antioxidant levels in the cord blood of term fetus.

The aim of this study was to compare the differences in the total antioxidant levels in the cord blood after a normal vaginal delivery and after an elective caesarean section. This was a prospective study approved by the Wirral Hospital ethical research committee. The study was carried out in a district general hospital. We investigated 96 healthy pregnant women who had normal antenatal period with singleton pregnancies between 37 and 42 completed weeks of gestation. Sixty-five women had a spontaneous normal vaginal delivery and 31 underwent elective caesarean section. Umbilical cord blood was obtained immediately after delivery. Antioxidants such as glutathione peroxidase (GPX) and superoxide dismutase (SOD) were measured and compared between the normal vaginal delivery and elective ceasarean sections. The mean values for GPx in umbilical cord arterial blood (95; 86-103, n=74) was found to be significantly higher (P=0.0133) than that found in umbilical cord venous blood (84; 80-88, n=95). The arterial SOD values were found to be significantly higher (P=0.0337) in infants who had been delivered by caesarean section (1188; 1065-1311, n=22) than by vaginal delivery (1021;958-1083, n=39). The differences in the levels of GPX between the arterial and venous systems is not well documented but may be due to differences in the level of selenium, hydroperoxides or glutathione. In addition, why infants delivered by ceasarian section have a higher level of arterial SOD than those delivered by vaginal delivery remains unclear, but it may be a reflection of a relatively low level in infants subjected to the stress of labour.     

Perinatal factors associated with the respiratory distress syndrome

Perinatal factors related to the incidence of respiratory distress syndrome were analyzed by the multiple logistic regression statistical method in 263 mothers and their 298 offspring delivered between 24 and 35 weeks' gestation in a 1-year period in a regional referral perinatal center. The risk of respiratory distress syndrome in white infants rose with decreasing gestational age (p less than 0.0001) while prolonged rupture of membranes of greater than 24 hours in the absence of maternal infection (28% of cases) was highly protective (p less than 0.0001). Compared with vaginal delivery, cesarean delivery without labor increased the risk of respiratory distress syndrome (p = 0.03). The administration of tocolytic drugs was unrelated to the incidence of respiratory distress syndrome, but corticosteroid therapy given at least 72 hours before delivery was protective (p = 0.03). Male and female infants were equally at risk for respiratory distress syndrome as were black and white infants, but other races had a lower incidence (p = 0.004). Infants with respiratory distress syndrome were on mechanical ventilators longer than those with other respiratory illnesses.     

Neonatal Outcome after Trial of Labor Compared with Elective Repeat Cesarean Section

ABSTRACT: Background: Trial of labor after cesarean section has been an important strategy for lowering the rate of cesarean delivery in the United States, but concerns regarding its safety remain. The purpose of this study was to evaluate the outcome of newborns delivered by elective repeat cesarean section compared to delivery following a trial of labor after cesarean. Methods: All low‐risk mothers with 1 or 2 previous cesareans and no prior vaginal deliveries, who delivered at our institution from December 1994 through July 1995, were identified. Neonatal outcomes were compared between 136 women who delivered by elective repeat cesarean section and 313 women who delivered after a trial of labor. To investigate reasons for differences in outcome between these groups, neonatal outcomes within the trial of labor group were then compared between those mothers who had received epidural analgesia (n = 230) and those who did not (n = 83). Results: Infants delivered after a trial of labor had increased rates of sepsis evaluation (23.3% vs 12.5%, p = 0.008); antibiotic treatment (11.5% vs 4.4%, p = 0.02); intubation to evaluate for the presence of meconium below the cords (11.5% vs 1.5%, p < 0.001); and mild bruising (8.0% vs 1.5%, p = 0.008). Within the trial of labor group, infants of mothers who received epidural analgesia were more likely to have received diagnostic tests and therapeutic interventions including sepsis evaluation (29.6% vs 6.0%, p = 0.001) and antibiotic treatment (13.9% vs 4.8%, p = 0.03) than within the no‐epidural analgesia group. Conclusions: Infants born to mothers after a trial of labor are twice as likely to undergo diagnostic tests and therapeutic interventions than infants born after an elective repeat cesarean section, but the increase occurred only in the subgroup of infants whose mothers received epidural analgesia for pain relief during labor. The higher rate of intervention could relate to the well‐documented increase in intrapartum fever that occurs with epidural use. (BIRTH 30:2 June 2003)     

The effect of cesarean section on intraventricular hemorrhage in the preterm infant.

OBJECTIVE: The null hypothesis is that active labor is a more important factor with regard to both timing and progression of periventricular-intraventricular hemorrhage than is route of delivery. Infants delivered by cesarean section after entering the active phase of labor will behave in a manner similar to that of previously studied infants delivered vaginally as to when periventricular-intraventricular hemorrhage occurs and frequency of progression. STUDY DESIGN: The 106 infants of 85 women delivered by cesarean section were the subjects of this study. Forty-six infants were in the no-labor group, 33 in the latent-phase labor group, and 27 in the active-phase labor group. Head ultrasonographic examinations were performed at delivery, at 1, 6, 12, and 24 hours, and then daily for the first 7 days of life. Continuous variables were compared by one-way analysis of variance among those infants with no hemorrhage or with periventricular-intraventricular hemorrhage. Categoric variables were compared by chi 2 analysis and Fisher's exact test when appropriate. A p value of less than 0.05 was considered significant. RESULTS: There was no difference in the frequency of early hemorrhage (less than or equal to 1 hour of age), late hemorrhage (greater than 1 hour of age), or overall periventricular-intraventricular hemorrhage in the infants not in labor, in latent-phase labor, or in active-phase labor at the time of cesarean section. However, the frequency of grade 3 or 4 hemorrhage and the progression of hemorrhage were significantly higher in the infants whose mothers had an active phase of labor compared with infants whose mothers had no labor or did not progress beyond the latent phase. Infants who had early periventricular-intraventricular hemorrhage (less than or equal to 1 hour of age) also had a higher frequency of progression of hemorrhage. CONCLUSIONS: Cesarean section before the active phase of labor does not change the overall frequency of hemorrhage but results in a lower frequency of progression to grade 3 or 4 hemorrhage. We do not feel that these data support performing more cesarean sections for preterm delivery as a method of preventing progression of periventricular-intraventricular hemorrhage in the preterm infant.     

Perinatal substance abuse intervention in obstetric clinics decreases adverse neonatal outcomes.

OBJECTIVE: To evaluate the effect of Early Start, a managed care organization's obstetric clinic-based perinatal substance abuse treatment program, on neonatal outcomes. STUDY DESIGN: Study subjects were 6774 female Kaiser Permanente members who delivered babies between July 1, 1995 and June 30, 1998 and were screened by completing prenatal substance abuse screening questionnaires and urine toxicology screening tests. Four groups were compared: substance abusers screened, assessed, and treated by Early Start ("SAT," n=782); substance abusers screened and assessed by Early Start who had no follow-up treatment ("SA," n=348); substance abusers who were only screened ("S," n=262); and controls who screened negative ("C," n=5382). RESULTS: Infants of SAT women had assisted ventilation rates (1.5%) similar to control infants (1.4%), but lower than the SA (4.0%, p=0.01) and S groups (3.1%, p=0.12). Similar patterns were found for low birth weight and preterm delivery. CONCLUSION: Improved neonatal outcomes were found among babies whose mothers received substance abuse treatment integrated with prenatal care. The babies of SAT women did as well as control infants on rates of assisted ventilation, low birth weight, and preterm delivery. They had lower rates of these three neonatal outcomes than infants of either SA or S women.     

Neonatal respiratory morbidity following elective caesarean section in term infants. A 5-year retrospective study and a review of the literature

Respiratory morbidity is an important complication of elective caesarean section. The presence of labour preceding caesarean section reduces the risk of neonatal respiratory morbidity. Recently, it has been shown that the incidence of respiratory morbidity is lower in infants with a gestational age of at least 39(+0) weeks at elective caesarean section compared to infants with a gestational age less than 39(+0) weeks.This article describes the results of a 5-year retrospective study on the incidence of respiratory distress in term neonates delivered by elective caesarean section in relation to gestational age and provides a literature review on neonatal respiratory morbidity following elective caesarean section.     

Triplet and quadruplet pregnancies--a forthcoming challenge also for the 'general' obstetrician

Data from 14 triplet and 2 quadruplet pregnancies (50 infants) during the period 1974-1988 were analysed. The perinatal mortality rate was only 6%, despite a preterm delivery rate of 88%. Preterm delivery was more common in young (less than or equal to 29 years) multiparous women. Perinatal complications were, as expected, strongly associated with immaturity. Respiratory problems of the infants occurred significantly more often among women delivered by elective Cesarean section than among those planned for vaginal delivery, but the mean gestational duration was 1 week longer in the latter group. Few problems arise in infants weighing 2000 g or more, or at delivery at 34 weeks or later, and under optimal conditions it would therefore seem safe to allow these women to give birth vaginally. Nor did birth order affect the outcome for infants born vaginally. It is recommended that quadruplets be delivered by Cesarean section because of the difficulty of ensuring satisfactory fetal surveillance in labor.     

The relationship between intrauterine growth restriction and preterm delivery: an empirical approach using data from a European case-control study

Objective To test whether being small for gestational age, defined as having a birthweight less than the 10th centile of intrauterine growth references, is a risk factor for preterm delivery for singleton live births.
Design A case-control study.
Setting Maternity hospitals in 16 European countries.
Sample Four thousand and seven hundred preterm infants between 22 and 36 completed weeks of gestation and 6460 control infants between 37 and 40 weeks of gestation.
Methods Newborn babies are identified as being small for gestational age using customised reference standards derived from models of fetal growth. The impact of being small for gestational age on preterm delivery is estimated using logistic regression.
Main outcome measure Spontaneous or induced preterm delivery.
Results Being small for gestational age is significantly associated with preterm birth, although the magnitude of this association differs greatly by type of delivery and gestational age. Over 40% of induced preterm births for reasons other than the premature rupture of membranes are small for gestational age compared with 10.7% of control infants (OR 6.41). For spontaneous or premature rupture of membranes related preterm births, the association is also significant, but weaker (OR 1.51). The relationship between growth restriction and preterm delivery is strongest for preterm births before 34 weeks of gestation.
Conclusions These findings highlight the phenomenon of abnormal fetal growth in all premature infants and, in particular, infants delivered by medical decision for reasons other than premature rupture of membranes. The observed association between being small for gestational age and preterm delivery among spontaneous preterm births merits further attention because the causal mechanisms are not well understood.     

Delivery of breech presentation infants at term. An analysis of 304 breech-deliveries

304 breech presentation infants greater than or equal to 2.500 g were delivered at the University Women's Clinic, Kiel, between 1984 and 1987. Only 2 of the vaginally delivered infants died; both had severe malformations sonographically diagnosed prior to delivery. The umbilical cord arterial PH was found to be significantly (p less than 0.001) higher in infants delivered per Caesarean Section as compared to those vaginally delivered. The same ratio was found in a control group of vaginally delivered infants compared to sectioned infants in the vertex presentation. In 13.3% of cases post primary section and in 14.4% of cases post vaginal delivery from breech presentation we found an apgar of less than or equal to 7 one minute post-partum. The transfer rate to a paediatric unit of vaginally delivered infants (7.2%) appeared to be double that of the infants delivered per Caesarean Section (3.6%). However, the indication for transferral is principally independent of the mode of delivery. Taking the 3-12fold increased maternal mortality rate post section as compared to vaginal delivery into consideration, a vaginal delivery of a breech presentation infant at term appears to be justifiable under certain presuppositions: exclusion of cranio-pelvic disproportion, and normal progression of labour. The indication for secondary Caesarean Section should be generously applied in cases of a suspicious C.T.G. and a slow progression of labour.     

Randomised trial of patient triggered ventilation versus high frequency positive pressure ventilation in acute respiratory distress.

Synchronous respiration during mechanical ventilation of preterm neonates with acute respiratory distress is extremely beneficial as it improves oxygenation and is associated with a very low incidence of pneumothorax. We have assessed which form of ventilation: patient triggered ventilation (PTV) or high frequency positive pressure ventilation (HFPPV) is most successful in provoking this beneficial respiratory interaction, synchrony. Preterm infants of less than 4 hours of age and gestational age greater than or equal to 27 weeks were entered into a randomised controlled trial. Thirteen patients received PTV, median gestational age 30 weeks (range 27-36) and 36 HFPPV, median gestational age, 29 weeks (range 27-40). HFPPV was delivered by Sechrist ventilators at rates between 61 and 120 breaths/minute. Patient triggered ventilation was delivered by an SLE ventilator and an airway pressure trigger was used. Inflation times during PTV were between 0.2 and 0.45 seconds. HFPPV provoked synchrony which persisted until extubation in 25 patients, but PTV provoked persistent synchrony only in four patients (p less than 0.05). No infant developed a pneumothorax. Eleven of 36 patients became asynchronous on HFPPV and 5 of 13 on PTV. In addition, four patients on PTV developed recurrent apnoea with deteriorating blood gases. Thus, 11 of 36 patients on HFPPV and 9 of 13 on PTV required transfer to conventional ventilation (p less than 0.05). Transfer occurred at a median of 30 hours (range 6-84) on HFPPV and 1 hour (range 1-25) on PTV, p less than 0.01. Infants who required transfer from the randomised mode of ventilation required a longer period of intubation (median 174 hours, range 30-2928) compared to 38 hours (range 1.5-456) for successful cases, regardless of randomisation (p less than 0.01). This study demonstrates PTV is significantly less successful in promoting synchrony than HFPPV. We therefore conclude HFPPV is a more useful form of respiratory support than PTV for preterm infants with acute respiratory distress.