Per Holmgren

Survival and 2-year outcome with expectant management of second-trimester rupture of membranes.

Objective To evaluate the perinatal and 2-year outcomes in pregnancies complicated by preterm premature rupture of membranes (PROM) during the second trimester. Methods Fifty-three consecutive singleton pregnancies with PROM at 14 to 28 weeks of gestation were studied retrospectively. Management goals were to prolong the pregnancies to 32 weeks through expectant management and to avoid fetal compromise through closer monitoring and active intervention, when necessary, after 23 weeks. Outcome of the surviving infants was based on neurologic, audiometric, and ophthalmologic examinations at 2 years of corrected age. Results Rupture of membranes occurred at 14–19 weeks (mean 17.4 weeks) in 10 women, at 20–25 weeks (mean 24.0 weeks) in 24, and at 26–28 weeks (mean 27.6 weeks) in 19. The median latency periods to delivery were 72 days, 12 days, and 10 days when rupture of membranes occurred at 14–19 weeks, 20–25 weeks, and 26–28 weeks, respectively. The overall incidence of chorioamnionitis was 28%. There were no fetal deaths and nine neonatal deaths. When rupture of membranes occurred at 14–19 weeks, 20–25 weeks, and 26–28 weeks, the perinatal survival rates were 40%, 92%, and, 100%, respectively. Pulmonary hypoplasia accounted for seven deaths. Of the live-born infants, 81% were alive at 2 years of corrected age. Survival without major impairment was observed in 75%, 80%, and 100% of the survivors when rupture of membranes occurred at 14–19 weeks, 20–25 weeks, and 26–28 weeks, respectively. Conclusion Expectant management of second-trimester PROM offers better perinatal and long-term survival than previously thought.

Short-term outcome after active perinatal management at 23—25 weeks of gestation. A study from two Swedish tertiary care centres. Part 2: infant survival

Aim: To determine neonatal survival rates based on both foetal (stillborn) and neonatal deaths among infants delivered at 23–25 wk, and to identify maternal and neonatal factors associated with survival. Methods: The medical records of 224 infants who were delivered in two tertiary care centres in 1992–1998 were reviewed retrospectively. At these centres, policies of active perinatal and neonatal management were universally applied. Data were analysed by gestational age groups and considered in three time periods. Logistic regression models were used to identify factors associated with survival. Results: The rate of foetal death was 5%. Of infants born alive, 63% survived to discharge. Survival rates including foetal deaths in the denominator at 23, 24 and 25 wk were 37%, 61% and 74%, respectively, and survival rates excluding foetal deaths were 43%, 63% and 77%, respectively. Of infants born with 1‐min Apgar scores of 0–1, 43% survived. In the total cohort, survival rates including foetal deaths in the denominator increased from 52% in time period 1 to 61% in time period 2 and 74% in time period 3 (p > 0.02). On multivariate logistic regression analysis, higher birthweight (OR: 1.91 per 100 g increment; 95% CI: 1.45–2.52), female gender (OR: 3.33; 95% CI: 1.65–6.75), administration of antenatal steroids (OR: 2.95; 95% CI: 1.46–5.98) and intrauterine referral from a peripheral hospital (OR: 2.35; 95% CI: 1.18–4.68) were associated with survival. Apgar score ± 3 at 1 min (OR: 0.46; 95% CI: 0.22–0.95) was associated with decreased survival. The use of antenatal steroids was protective at 23–24 wk (OR: 5.2; 95% CI: 2.0–13.7), but not at 25 wk.

Infant mortality of very preterm infants by mode of delivery, institutional policies and maternal diagnosis

Objective. The aim of this study was to analyse infant mortality among infants born extremely preterm in relation to mode of delivery, maternal diagnosis, and different institutional policies. Methods. We conducted a national tertiary health care center study using Swedish Medical Birth Register (MBR) data from 1990 to 2002, to examine the 2,094 live births of infants at 23+0 to 27+6 weeks gestation. We assessed the association between mode of delivery, gestational age (GA), calendar year, maternal condition, and institutional policies on infant mortality outcome. Results. At 23–25 weeks, 38% of infants (range: 34–69%) were delivered by cesarean section (CS), while at 26–27 weeks, 66% (59–80%) were delivered by CS. The CS rate for fetal or maternal indications was 98% in cases of pre‐eclampsia/eclampsia, 42% for premature rupture of membranes (PROM), 68% for hemorrhage, 76% for PROM+hemorrhage, 56% for breech presentation, and 30% for preterm vertex with no other complications. After cases of pre‐eclampsia/eclampsia were excluded, vaginal delivery was associated with a small increase of risk for infant death. Vaginal delivery was associated with a significantly increased risk for infant death in breech presentations and multiple births, while vaginal delivery posed a non‐significant risk increase for PROM and hemorrhage. For preterm vertex without any other complications, 4 out of 5 infants were delivered vaginally without any risk increase. Conclusion. This study reports high CS rates for very preterm births at Swedish hospitals. In performing CS for very preterm infants, this study suggests a survival advantage for certain maternal conditions, but not for preterm labor with a vertex presentation without other obstetrical complications.

Short-term outcome after active perinatal management at 23-25 weeks of gestation. A study from two Swedish perinatal centres. Part 3: neonatal morbidity.

Aim: To determine major neonatal morbidity in surviving infants born at 23–25 weeks, and to identify maternal and infant factors associated with major morbidity. Methods: The medical records of 224 infants who were delivered at two tertiary care centres in 1992–1998 were reviewed retrospectively. At these centres, policies of active perinatal and neonatal management were universally applied. Of the 213 liveborn infants, 140 (66%) survived to discharge. Data were analysed by gestational age and considered in three time periods. Logistic regression models were used to identify factors associated with morbidity. Results: Of the survivors, 6% had intraventricular haemorrhage grade ± 3 (severe IVH) or periventricular leukomalacia (PVL), 15% retinopathy of prematurity ± stage 3 (severe ROP) and 36% bronchopulmonary dysplasia (BPD). On logistic regression analysis, severe IVH or PVL was associated with duration of mechanical ventilation (odds ratio, OR: 1.53 per 1‐wk increment in duration; 95% confidence interval, CI: 1.01–2.33). Severe ROP was associated with the presence of a patent ductus arteriosus (PDA) (OR: 3.31; 95% CI: 1.11–9.90) and birth in time period 3 versus time periods 1 and 2 combined (OR: 6.28; 95% CI: 2.10–18.74). BPD was associated with duration of mechanical ventilation (OR: 2.71 per 1‐wk increment in duration; 95% CI: 1.76–4.18) and with the presence of any obstetric complication (OR: 2.67; 95% CI: 1.07–6.65). Gestational age and birthweight were not associated with major morbidity. Of all survivors, 81% were discharged home without severe IVH, PVL or severe ROP.

Short-term outcome after active perinatal management at 23-25 weeks of gestation. A study from two Swedish tertiary care centres. Part 1 : maternal and obstetric factors.

Aims: To provide descriptive data on women who delivered at 23–25 wk of gestation, and to relate foetal and neonatal outcomes to maternal factors, obstetric management and the principal reasons for preterm birth. Methods: Medical records of all women who had delivered in two tertiary care centres in 1992–1998 were reviewed. At the two centres, policies of active perinatal and neonatal management were universally applied. Logistic regression models were used to identify prenatal factors associated with survival. Results: Of 197 women who delivered at 23–25 wk, 65% had experienced a previous miscarriage, 15% a previous stillbirth and 12% a neonatal death. The current pregnancy was the result of artificial reproduction in 13% of the women. In 71%, the pregnancy was complicated either by preeclampsia, chorioamnionitis, placental abruption or premature rupture of membranes. Antenatal steroids were given in 63%. Delivery was by caesarean section in 47%. The reasons for preterm birth were idiopathic preterm labour in 36%, premature rupture of membranes in 41% and physician‐indicated deliveries in 23% of the mothers. Demographic details, use of antenatal steroids, caesarean section delivery and birthweight differed between mothers depending on the reason for preterm delivery. Of 224 infants, 5% were stillbirths and 63% survived to discharge. On multivariate logistic regression analysis comprising prenatally known variables, reasons for preterm birth were not associated with survival. Advanced gestational duration (OR: 2.43 per wk; 95% CI: 1.59–3.74), administration of any antenatal steroids (OR: 2.21; 95% CI: 1.14–4.28) and intrauterine referral from a peripheral hospital (OR: 2.93; 95% CI: 1.5–5.73) were associated with survival.

Extremely preterm cesarean delivery: a clinical study

Objectives. To describe indications for cesarean section for extremely preterm delivery, peri‐ and postoperative complications and perinatal outcome. Design. A case‐referent study with clinical follow‐up. Setting. A tertiary perinatal center. Population. All deliveries at gestational age <28 weeks at Umeå University Hospital in 1997–2003. For preterm cesarean section referents were women with elective first‐time term cesarean section. Methods. Indications for cesarean section delivery were assessed. Peri‐ and postoperative complications, asphyxia, and infant survival at discharge were described. Results. The cesarean section rate was 75%, in one third the operation was considered as difficult. Indications for extremely preterm abdominal delivery were severe disease during pregnancy and delivery complications. Six out of ten cesarean sections were performed on fetal indication. Nonisthmic incision was performed in 20% of cases. No major postoperative complications and few minor postoperative complications were noted. Irrespective of mode of delivery, few of the infants had severe asphyxia. Conclusion. In balancing the risks of complications related to the surgical procedure against the purported benefits of the infant, this study adds support to the argument to deliver even extremely preterm infants by cesarean section.

Design and validation of an advanced entrained flow reactor system for studies of rapid solid biomass fuel particle conversion and ash formation reactions

The design and validation of a newly commissioned entrained flow reactor is described in the present paper. The reactor was designed for advanced studies of fuel conversion and ash formation in powder flames, and the capabilities of the reactor were experimentally validated using two different solid biomass fuels. The drop tube geometry was equipped with a flat flame burner to heat and support the powder flame, optical access ports, a particle image velocimetry (PIV) system for in situ conversion monitoring, and probes for extraction of gases and particulate matter. A detailed description of the system is provided based on simulations and measurements, establishing the detailed temperature distribution and gas flow profiles. Mass balance closures of approximately 98% were achieved by combining gas analysis and particle extraction. Biomass fuel particles were successfully tracked using shadow imaging PIV, and the resulting data were used to determine the size, shape, velocity, and residence time of converting particles. Successful extractive sampling of coarse and fine particles during combustion while retaining their morphology was demonstrated, and it opens up for detailed time resolved studies of rapid ash transformation reactions; in the validation experiments, clear and systematic fractionation trends for K, Cl, S, and Si were observed for the two fuels tested. The combination of in situ access, accurate residence time estimations, and precise particle sampling for subsequent chemical analysis allows for a wide range of future studies, with implications and possibilities discussed in the paper.