The risk of unexplained antepartum stillbirth in second pregnancies following caesarean section in the first pregnancy

OBJECTIVE

To determine if a previous caesarean section increases the risk of unexplained antepartum stillbirth in second pregnancies.

STUDY DESIGN

Retrospective cohort study.

SETTING

Large Canadian perinatal database.

POPULATION

158 502 second births.

METHODS

Data were obtained from a large perinatal database, which supplied data on demographics, pregnancy complications, maternal medical conditions, previous caesarean section and pregnancy outcomes.

MAIN OUTCOME MEASURES

Total and unexplained stillbirth.

RESULTS

The antepartum stillbirth rate was 3.0/1000 in the previous caesarean section group compared with 2.7/1000 in the previous vaginal delivery group (P= 0.46). Multivariate logistic regression modelling, including terms for maternal age (polynomial), weight >91 kg, smoking during pregnancy, pre-pregnancy hypertension and diabetes, did not document an association between previous caesarean section and unexplained antepartum stillbirth (OR 1.27, 95% CI 0.92-1.77).

CONCLUSION

Caesarean section in the first birth does not increase the risk of unexplained antepartum stillbirth in second pregnancies.

ATP regulation of a large conductance voltage-gated cation channel in rough endoplasmic reticulum of rat hepatocytes

ATP-sensitive K+ channels play an important role in regulating membrane potential during metabolic stress. In this work we report the effect of ATP and ADP-Mg on a K+ channel present in the membrane of rough endoplasmic reticulum (RER) from rat hepatocytes incorporated into lipid bilayers. Channel activity was found to decrease in presence of ATP 100 microM on the cytoplasmic side and was totally inhibited at ATP concentrations greater than 0.25mM. The effect appeared voltage dependent, suggesting that the ATP binding site was becoming available upon channel opening. Channel activity was suppressed by the nonhydrolyzable ATP analog (ATPgammaS), ruling out a phosphorylation-based mechanism. Notably addition of 2.5mM ADP-Mg to the cytosolic side increased the channel open probability at negative potentials. We conclude that the large conductance voltage-gated cation channel in RER of rat hepatocytes is an ATP and ADP sensitive channel likely to be involved in cellular processes such as Ca(2+) signaling or control of membrane potential across the endoplasmic reticulum membrane.

Maternal haemolysis, elevated liver enzymes and low platelets syndrome: perinatal and neurodevelopmental neonatal outcomes for infants weighing less than 1250 g

OBJECTIVES

To study mortality and short-term morbidity of infants born to women with HELLP (haemolysis, elevated liver enzymes, and low platelets) syndrome and to compare the long-term neurodevelopmental morbidity of a subgroup with birth weight (BWT) less than 1250 g (study group) with weight matched controls.

METHODS

Retrospective chart review and prospective neurodevelopmental follow-up through a Perinatal Follow-up clinic. Analysis of perinatal and neonatal data for women diagnosed with HELLP from 1993 to 1996. Neurodevelopmental outcome for the study group was compared to a group of weight matched controls.

RESULTS

A total of 109 infants (mean gestational age 32.6 weeks, mean BWT 1766 g) were born to 104 women with HELLP syndrome. There was a significant decrease in mortality (P = 0.002) and morbidity (P < 0.05) with increasing gestational age and birthweight. No significant differences in neonatal mortality and morbidity were present between the infants weighing less than 1250 g study and weight matched control group. However, at 3 years, the study group had fewer children with cerebral palsy (P = 0.024) and mental disability (P trend = 0.07). Mean cognitive index was 99 versus 91 in the controls (P = 0.101).

CONCLUSION

Improved health outcomes occur with increased gestational age. Infants with BWT less than 1250 g born to women with HELLP syndrome were not at risk of increased neurodevelopmental disability compared to controls.

The risk of stillbirth in pregnancies before and after the onset of diabetes

AIMS

There is significant controversy as to whether or not stillbirth is increased in pregnancies prior to the onset of diabetes. An observed increase may be indicative of risks associated with untreated gestational diabetes. It is generally accepted that the risk of stillbirth in pregnancies that occur after the onset of diabetes has been diminished by modern obstetric care. However, the degree of residual risk is not well quantified. This study sought to examine the rates of stillbirth before and after the onset of diabetes compared with the general population.

METHODS

Retrospective cohort and nested case-control study. The study population was drawn from the UK-based General Practice Research Database, comprising some 300 practices, with data collection from the late 1980s until September 1999. From the base population, 913 diabetic women who had had a pregnancy were identified and 10,000 subjects without diabetes were randomly chosen as controls. Stillbirth was defined as death in utero after 20 weeks or with birth weight >500 g.

RESULTS

The stillbirth rates were higher in prediabetic pregnancies (19.7/1000), and in those occurring after the diagnosis of diabetes (33.7/1000), compared with the non-diabetic population (5.5/1000). Stillbirths were matched to four live births by maternal age and year of birth. Prediabetic pregnancy and pregnancy after the onset of diabetes were strongly associated with stillbirth: odds ratio (OR)=4.68 (1.67, 13.08) and OR=4.39 (2.22, 8.64), respectively.

CONCLUSIONS

The risk of stillbirth was increased in both prediabetic and post-diabetic pregnancy.

Beyond biology: the social context of prenatal behaviour and birth outcomes

OBJECTIVES

In this study we examine the factors that are associated with adverse birth outcomes using a representative national sample. In our analysis we take into account factors which are related to the mother's behaviour during pregnancy and also consider the socio-economic circumstances of the family.

METHODS

A series of logistic regression models are used to determine the increased risks of low birth weight, preterm, and small for gestational age births associated with maternal smoking, alcohol consumption and high blood pressure in relation to socio-economic factors, such as family dysfunction, social support, income adequacy, age, and education.

RESULTS

All socio-economic factors showed gradients of maternal smoking during pregnancy while only mother's education and socio-economic status demonstrated gradients of alcohol use and high blood pressure. Maternal smoking, high blood pressure, higher levels of family dysfunction, and lower levels of mother's education were found to significantly increase the risk of an adverse birth outcome.

CONCLUSIONS

Interventions designed to mitigate the hazards of adverse birth outcomes should be designed to reflect the gradients of risky prenatal maternal behaviours associated with age, education, income, and family dysfunction.

Secular trends in congenital anomaly-related fetal and infant mortality in Canada, 1985-1996

Prenatal diagnosis of major congenital anomalies and subsequent termination of affected pregnancies has been widely available as part of routine obstetric care in recent years. In this study, vital statistical data on stillbirths, live births, and infant deaths were used to examine secular trends in gestational age-specific and category-specific fetal and infant mortality due to congenital anomalies in Canada (excluding Ontario and Newfoundland) from 1985-1996. Comparisons of the rates between 1985-1987 and 1994-1996 were made using relative risks and 95% confidence intervals (CI). The overall fetal mortality rate due to congenital anomalies increased significantly, from 68.0 per 100,000 total births in 1985-1987 to 78.6 per 100,000 total births in 1994-1996, while the overall infant mortality rate due to congenital anomalies decreased significantly over the same period, from 2.47 to 1.79 per 1,000 live births. The fetal death rate due to congenital anomalies at 20-21 weeks of gestation increased approximately five-fold (relative risk [RR] = 4.83, 95% CI = 3.28-7.11) from 4.5 to 21.5 per 100,000 fetuses at risk, while the rate at 37-41 weeks decreased by 30% (RR = 0.70, 95% CI = 0.50-0.97). Fetal death rates among pregnancies at 20-25 weeks of gestation increased in all categories of congenital anomaly except anencephaly and respiratory system anomalies. Congenital anomaly-related fetal and infant deaths have increased at early gestation but declined at later gestation in Canada. These changes suggest an increase in prenatal diagnosis and selective termination of pregnancies with congenital anomalies in recent years.

Prediabetes and perinatal mortality

OBJECTIVE

The association between gestational diabetes mellitus (GDM) and perinatal outcome is largely based on case series and retrospective studies that found an increased risk of perinatal mortality and stillbirth as the onset of diabetes approached. Our objective was to assess the relationship between latency to diabetes and perinatal outcome of prediabetic pregnancies in a contemporary population of women with adult-onset diabetes.

RESEARCH DESIGN AND METHODS

A population of 403 diabetic women from two recruitment sites completed a pretested questionnaire.

RESULTS

Details of 1,181 pregnancy outcomes were obtained. This comprised 1,024 live births, 22 stillbirths, and 8 early neonatal deaths. Crude analysis suggested a relationship between time to diabetes (latency) < or =20 years and both perinatal death and stillbirth: odds ratio (95% CI), 2.41 (1.17-4.95) and 2.15 (0.93-4.98). Generalized additive modeling revealed a nonlinear relationship between the variables time to diabetes, and maternal age and perinatal outcome. Final logistic regression analysis was then performed for the outcomes perinatal death and stillbirth, with maternal age as a second-degree polynomial, year of birth as a continuous variable, and time to diabetes dichotomized < or =20 years to diagnosis and >20 years. This final analysis documented a significant association between time to diabetes < or =20 years and both perinatal death (4.06 [1.79-9.36]) and stillbirth (3.35 [1.25-9.05]).

CONCLUSIONS

There appeared to be an increased risk of perinatal death and stillbirth in pregnancies occurring in the last 20 years before the diagnosis of diabetes.

Two-year survey of Alberta laboratories processing of antenatal group B streptococcal (GBS) screening specimens: implications for GBS screening programs

We evaluated specimen types received and methods used by laboratories to process screening GBS specimens from pregnant women. Surveys during 1995 and 1997 of all laboratories in the province of Alberta, Canada that culture GBS from screening genital specimens were completed. Between surveys, there was dissemination of information about appropriate culture techniques. Survey completion rates were 100% in both years (38/38 in 1995 and 20/20 in 1997). During 1995 as compared to 1997, laboratories were less likely to a) have a specific written protocol for identification of genital GBS screening specimens (1995: 78.2% versus 1997: 100%, p = 0.08) b) be receiving combined vaginal-anorectal swabs (1995: 18% of all swabs received versus 1997: 60.4%, p < 0.001), and c) be using selective GBS culture media (1995: 45.5% versus 1997: 86.7%, p = 0.01). Regions using screening based approaches for GBS prevention need to ensure that their laboratories are using adequate techniques for GBS detection.

Outcome at 1-year adjusted age of 957 infants weighing more than 1250 grams with respiratory distress syndrome randomized to receive synthetic surfactant or air placebo. American and Canadian Exosurf Neonatal Study Groups

This study determined outcomes at 12-months adjusted age of 957 infants weighing more than 1250 gm at birth who were subjects in a randomized, double-blind, controlled trial of synthetic surfactant or air placebo administered in a rescue trial at 23 hospitals in the United States and 13 hospitals in Canada. Follow-up results were available for 475 of 563 surviving infants who received air placebo (84%) and 482 of 571 infants who received synthetic surfactant (84%). Developmental outcome was equivalent in the two groups. Morbidity was less in the synthetic surfactant group as assessed by the need for medication for chronic lung disease (52 of 475 (11%) for the air placebo group vs 32 of 482 (7%) for the synthetic surfactant group) or respiratory support (10 of 475 (2%) for the air placebo group vs 1 of 482 (< 1%) for the synthetic surfactant group) at 1-year adjusted age. Bayley Scales of Infant Development (mental development Index: 102 for both the air placebo and synthetic surfactant groups; psychomotor development index: 95 for the air placebo group vs 94 for the synthetic surfactant group) and impairment rates (94 of 475 (20%) for the air placebo group vs 86 of 482 (18%) for the synthetic surfactant group) were similar in the two groups. Infants weighing more than 1250 gm who have respiratory distress syndrome have previously been shown to have improved survival rates and lower neonatal morbidity after treatment with synthetic surfactant. These follow-up data confirm that developmental outcome as determined at 12-months adjusted age is at least as good in those receiving synthetic surfactant.

Double-blind 1-year follow-up of 1540 infants with respiratory distress syndrome randomized to rescue treatment with two doses of synthetic surfactant or air in four clinical trials. American and Canadian Exosurf Neonatal Study Groups

Synthetic surfactant has been shown to reduce neonatal and 1-year mortality and neonatal morbidity in infants with respiratory distress syndrome. However, less is known about the effects of synthetic surfactant on developmental outcome and long-term morbidity. Four multicenter, randomized, placebo-controlled trials of synthetic surfactant administered as rescue therapy were conducted in the United States and Canada, with a total enrollment of 2224 patients. Double-blind developmental evaluations of survivors were conducted at 1 year of age (adjusted for prematurity) in all four trials. Of the 1802 patients enrolled in the placebo-controlled rescue trials who survived to 1 year, 1540 (85%) completed the 1-year follow-up evaluation. Height, weight, and head circumference measurements were not different in the treatment and control groups. Mean and median Bayley Scores of Infant Development for both the Mental Development Index and the Psychomotor Development Index were also equivalent. The incidence of impairments was not different in the two groups (mild to moderate impairment, 12% (92 of 745) for the air placebo group vs 11% (86 of 771) for the synthetic surfactant group; severe impairment, 15% (114 of 745) for the air placebo group vs 13% (102 of 771) for the synthetic surfactant group). No differences in rates of retinopathy of prematurity or hearing impairment were found in the treatment groups. The need for surgery after day 28 of life (relative risk, 0.779; 95% confidence interval, 0.665, 0.927) and the need for respiratory support at 1 year (relative risk, 0.525; 95% confidence intervals, 0.303, 0.911) were both reduced in the synthetic surfactant group. These results indicate that developmental outcome at 1 year of age is at least as good among infants with respiratory distress syndrome who received rescue therapy with synthetic surfactant as it is in infants who received air placebo; the results also indicate that the incidence of long-term morbidity is reduced.

Spinal cord injury at birth: diagnostic and prognostic data in twenty-two patients

OBJECTIVES

To establish criteria, evident soon after birth, that predict long-term outcome of neonates with spinal cord injury (SCI) at birth.

DESIGN

Retrospective case-series.

SETTING

Five Canadian regional neonatal tertiary care centers.

PATIENTS

Consecutive samples of patients referred to five centers for a total of 22 subjects, in whom SCI was diagnosed during life. Sites of lesions were above the fourth cervical vertebrae (n = 14), at the fourth cervical to the fourth thoracic vertebrae (n = 6), and at the thoracolumbar region (n = 2).

MEASUREMENTS AND MAIN RESULTS

All 14 patients with upper cervical SCI had cephalic presentations, whereas all 6 patients with cervicothoracic SCI had breech presentations (p < 0.0001). The site and extent of lesion were best diagnosed by clinico-imaging correlations. Ultrasonography appeared to be the most useful imaging study. In patients with upper cervical SCI who had no coexistent central nervous system abnormality associated with early death, long-term outcome in survivors (dependency on mechanical ventilation and on aids for upper limb activity and for ambulation) was best predicted by age when breathing was first observed and by rate of recovery of limb motor function in the first 3 months. The presence of breathing movements on day 1 (n = 2) was associated with mild disability. The absence of breathing movements on day 1 and little or no recovery of motor function in the first 3 months was associated with permanent total dependency on mechanical ventilation and severe quadriplegia (n = 5). Apnea on day 1 and intermediate recovery rates in the first 3 months was associated with variable long-term prognoses (n = 3).

A randomized controlled trial of early amniotomy

OBJECTIVE-To determine if a policy of early amniotomy resulted in a reduction in mean labour duration when compared to a policy of conservation of the membranes. DESIGN-A single-centre randomized controlled trial. SETTING-A tertiary care teaching hospital in Alberta, Canada. SUBJECTS-Ninety-seven term nulliparae in spontaneous labour, baby in cephalic presentation. INTERVENTION-Early amniotomy versus intent to keep membranes intact. MAIN OUTCOME MEASURES-Interval from randomization to delivery, rate of abnormalities of fetal heart rate tracings, cord artery blood pH, Apgar scores. RESULTS-The mean interval from randomization to delivery was 390.9 (SE 29.1) min in the amniotomy group and 442.9 (SE 34.1) min in the control group (P = 0.251). There were no differences between groups in the occurrence of fetal heart rate tracing abnormalities, nor was there a difference in the proportion of babies with abnormal Apgar scores, or abnormal cord pH (less than 7.20). CONCLUSION-The results of the study fail to support the long held belief that early amniotomy is an effective method for reducing labour duration.

External ATP triggers a biphasic activation process of a calcium-dependent K+ channel in cultured bovine aortic endothelial cells

We have used the patch-clamp method in order to investigate the single-channel events underlying the effect of external ATP on the potassium permeability of bovine aortic endothelial cells (BAE). The results obtained from cell-attached and inside-out experiments led first to conclude that BAE cells possess an inward rectifying potassium channel activated by internal calcium at micromolar concentrations. The channel conductance for inward currents was estimated at 40 pS in symmetrical 200 mM KCl and the open-channel probability was found to be voltage insensitive within the membrane voltage range -50 to -100 mV. Based on results obtained in the cell-attached configuration, it could next be established that external ATP and ADP at micromolar concentrations could trigger, via the stimulation of P2 purinergic receptors, a time variable activation process of the observed calcium-dependent potassium channel. This activation process was found to occur in a biphasic manner with an initial phase independent of the presence of calcium in the cell bathing medium. The second phase which could be blocked by calcium channel blockers such as Co2+ or La3+ required, however, the presence of external calcium and could be abolished by depolarizing the cells using high K+ external solutions. Another important aspect related to this phenomenon was the observation that removing ATP from the external medium during the second phase led to a complete abolition of the associated calcium-dependent potassium channel activation process. It is suggested from these results that the action of ATP on the potassium permeability of BAE cells is related to a second messenger mediated release of calcium from internal calcium stores coupled to an ATP-dependent calcium influx abolished at depolarizing voltages.

Pulmonary hypoplasia testing in clinical obstetrics

An ultrasound-based diagnostic test for predicting pulmonary hypoplasia antenatally by measurements of fetal chest circumference was applied prospectively to 45 patients at risk for developing this disorder. The outcome for the newborn infant and the autopsy findings were correlated with the antenatal prediction. The results of this test demonstrated a sensitivity and a specificity of 88% and 96%, respectively. The application of this test to clinical practice is recommended.