Fetal growth retardation in sudden infant death syndrome (SIDS) babies and their siblings

Evaluation of the Nutritional Status in Institutionalized Children and its Relationship to the Development of Epilepsy

Malnutrition as defined by the World Health Organization (WHO) in 1973 is an association of pathologic conditions caused by a lack of calories or protein intake in variable proportions. It is still one of the leading causes of infant mortality in developing countries. Risk factors for early malnutrition are absence of perinatal care and low birth weight. Epilepsy is also a very prevalent condition in childhood. A relationship between malnutrition and epilepsy has been suggested in many basic studies but it has never been proven in humans. In order to verify if malnutrition can lead to epilepsy, we reviewed anthropometric and medical files from infants in a governmental institution and tried to relate to an outcome of epilepsy. We defined malnutrition as height/weight below two pattern deviations from the NCHS tables. Two hundred and forty three children were included, 101 with malnutrition and 133 nourished. Our results indicate a predominance of malnutrition in girls (49%) and a comorbidity of malnutrition and neurological disorders. Although there were more cases of epilepsy in the malnourished group, the difference was not significant, and we could not assume that malnutrition was the cause of epilepsy in these cases because of the association of many other diseases that could also damage the central nervous system.

Small for gestational age: short stature and beyond

Depending on the definitions used, up to 10% of all live-born neonates are small for gestational age (SGA). Although the vast majority of these children show catch-up growth by 2 yr of age, one in 10 does not. It is increasingly recognized that those who are born SGA are at risk of developing metabolic disease later in life. Reduced fetal growth has been shown to be associated with an increased risk of insulin resistance, obesity, cardiovascular disease, and type 2 diabetes mellitus. The majority of pathology is seen in adults who show spontaneous catch-up growth as children. There is evidence to suggest that some of the metabolic consequences of intrauterine growth retardation in children born SGA can be mitigated by ensuring early appropriate catch-up growth, while avoiding excessive weight gain. Implicitly, this argument questions current infant formula feeding practices. The risk is less clear for individuals who do not show catch-up growth and who are treated with GH for short stature. Recent data, however, suggest that long-term treatment with GH does not increase the risk of type 2 diabetes mellitus and the metabolic syndrome in young adults born SGA.

Sudden infant death syndrome and complications in other pregnancies

BACKGROUND

The likelihood of recurrence of sudden infant death syndrome (SIDS) is an issue of biological, clinical, and legal interest. Obstetric complications are associated with an increased risk of SIDS and are likely to recur in subsequent pregnancies. We postulated that women whose infants died from SIDS would be more likely to have had obstetric complications in their other pregnancies.

METHODS

We linked national UK databases of maternity-hospital discharges, perinatal deaths, and death certifications. We studied 258 096 women who had consecutive births in Scotland between 1985 and 2001.

FINDINGS

Women who had an infant who died from SIDS were at increased risk in their next pregnancy of delivering an infant small for gestational age (odds ratio 2.27, 95% CI 1.54-3.34, p<0.0001) and of preterm birth (2.53, 1.82-3.53, p<0.0001). The risk of SIDS was higher for the children of women whose previous infant had been small for gestational age (1.87, 1.19-2.94, p=0.007) or preterm (1.93, 1.24-3.00, p=0.004). Multivariate analysis showed that all associations were explained by common maternal risk factors for SIDS and obstetric complications and by the likelihood of recurrence of fetal growth restriction and preterm birth.

INTERPRETATION

Women whose infants die from SIDS are more likely to have complications in their other pregnancies. Recurrence of pregnancy complications predisposing to SIDS could partly explain why some women have recurrent SIDS.

Identification of novel polymorphisms in the glucokinase and glucose-6-phosphatase genes in infants who died suddenly and unexpectedly

Sudden and unexpected infant deaths can be unexplained [sudden infant death syndrome (SIDS)] or explained (non-SIDS) but risk factors including lower birthweight are similar in both groups. Mutations in the glucokinase (GK) gene result in Maturity Onset Diabetes of the Young type 2 (MODY 2) and are associated with lower birthweight. Low hepatic glucose-6-phosphatase (G6PC1) expression occurs in both low birthweight and SIDS infants. We investigated whether polymorphisms are prevalent in the GK and G6PC1 genes in infants who died suddenly and unexpectedly. Mutation analysis was performed by polymerase chain reaction (PCR) and denaturing high-performance liquid chromatography (DHPLC) in samples from 126 infants who died suddenly and unexpectedly (78 SIDS, 48 non-SIDS) and from 70 healthy, living infants. G6PC1 promoter polymorphism significance was investigated by transfection of reporter gene constructs into a H4IIE cell line. Heterozygous GK polymorphisms were identified in 17.9% of SIDS and 20.8% of non-SIDS infants: two rare silent polymorphisms, Y215Y and S263S, in the coding region; a third rare polymorphism, -45G>A, in the hepatic promoter and the most prevalent polymorphism, c.484-29G>C, in a non-coding region upstream from the intron 4-exon 5 junction. A novel heterozygous polymorphism -77G>A in the G6PC1 promoter in 6.3% of non-SIDS and 2.9% of control infants decreased basal G6PC1 promoter activity (p<0.001). We describe three novel polymorphisms in the GK gene, S263S, -45G>A, and a common (14.3%) intronic substitution, c.484-29G>C, in infants who died suddenly and unexpectedly. We identified the first G6PC1 promoter polymorphism, which lowers expression, potentially increasing risk of hypoglycaemia and hence risk of sudden and unexpected death.

Sudden infant death syndrome among twin births: United States, 1995-1998

OBJECTIVES

To compare the incidence and risk factors for sudden infant death syndrome (SIDS) in twin and singleton births and to estimate the concordance of SIDS in twins.

STUDY DESIGN

A cohort analysis using the National Center for Health Statistics Linked Birth and Infant Death files (1995-1998).

RESULTS

Twins had higher SIDS rate (1.3/1000 live births) compared to singletons (0.7/1000 live births), relative risk: 1.9, 95% confidence interval: 1.68, 2.01. Male and small- for-gestational age infants as well as infants of black, unmarried, and smoking mothers were at increased risk for SIDS in both twins and singletons. Placental abnormalities also were associated with SIDS in singletons and twins, although this association failed to achieve statistical significance in twins. There is a higher rate of SIDS in the second twin after a first twin SIDS.

CONCLUSIONS

Twins are at higher risk of SIDS than are singletons. Overall, the epidemiology of SIDS in twins is quite similar to that seen in singletons.

Risk factors for unexplained antepartum fetal death in Norway 1967-1998

OBJECTIVE

To relate unexplained antepartum fetal death with maternal and fetal characteristics in order to identify risk factors.

DESIGN

Population-based study based on records of 1,676,160 singleton births with gestational age > or =28 weeks. Unexplained antepartum fetal death was defined as fetal death before labour without known fetal, placental, or maternal pathology.

RESULTS

Although unexplained fetal mortality in general declined from 2.4 per 1000 births in 1967-1976 to 1.6 in 1977-1998, the proportion among all fetal deaths increased from 30% to 43% during the same period of observation. Unexplained fetal death occurred later in gestation than explained. From 39 weeks of gestation, the risk increased progressively to 50/10,000 in women aged > or =35 years and <10/10,000 in women <25 years. In birth order > or =5, the risk was particularly high after 39 weeks of gestation. For birth weight percentile 2.5-9.9 and > or =97.5, unexplained fetal death was four and three times more likely to occur, respectively. We found an additive effect of maternal age and birth weight percentile 2.5-9.9. Women with less than 10 years education had higher risk than women with 13 years or more (OR=1.6). Weaker associations were observed with female gender, unmarried mothers, and winter season.

CONCLUSIONS

Unexplained antepartum fetal death occurred later in gestation than explained and was associated with high maternal age, multiparity, low education, and moderately low and high birth weight percentile. The increased risk in post-term pregnancies and the additive effect of maternal age and birth weight percentile 2.5-9.9 suggests that older women would benefit from monitoring of fetal growth.

Quantitative neuropathological analysis of sudden infant death syndrome

Detailed stereological analyses of specific regions of brains of children who had died from Sudden Infant Death Syndrome (SIDS) was undertaken to determine whether global evidence of an underlying pathology exists, contributing to an increased susceptibility to SIDS. A significant reduction in the total number of neocortical neurones and neurone volume was observed in SIDS normal birth weight (NBW) infants in comparison to controls. A significant reduction in both volume and total neurone number were also noted in the dorsal motor nucleus of the vagus in SIDS NBW group when compared with controls. Anomalies in regions of the brain involved with cardiorespiratory control (brainstem) and arousal (brainstem and neocortex) may play a crucial role in the chain of events resulting in a SIDS event.

Families with a perinatal death: is there an association between the loss and the birthweight of surviving siblings?

Our objective was to study birthweight among surviving siblings in families with and without a perinatal loss, and to evaluate whether different causes of death were associated with the results. Data were for 1967-98 from the Norwegian Medical Birth Registry. Births were organised with the mother as the observation unit through the personal identification number, providing sibship files. We analysed 550 930 sibships with at least two singletons, 208 586 sibships with at least three singletons and 45 675 sibships with at least four singleton births. We compared mean birthweight and gestational age between infants in sibships with and without a perinatal loss, total losses and the different causes of death. Surviving siblings in families with a perinatal loss had significantly lower mean birthweights than their counterparts in unaffected families, after adjusting for gestational age, interpregnancy interval, time period and marital status. An exception was found when cause of death was a birth defect, when growth retardation among surviving siblings was not found on average. We conclude that families who have lost an infant because of a birth defect do not appear to have an increased risk of adverse birth outcome associated with growth restriction.

Developmental changes in cardio-respiratory responses to hypoxia and hypercapnia in anesthetized low-birth-weight rats

The present study compared the developmental changes in the cardio-respiratory responses to hypoxia and hypercapnia between full-term low-birth-weight (LBW) and control rats during the postnatal period. The heart rate (HR), respiratory frequency (fR) and amplitude (aR) were measured during hypoxia (10% O(2) for 10 min) and hypercapnia (5% CO(2) for 10 min) in rats aged 7, 14 and 21 days, anesthetized with urethane. During hypoxia, HR was not significantly modified in the younger rats of both groups. In the older rats, aged 14 and 21 days, HR was markedly diminished, with a more pronounced decrease in LBW rats. The HR recovery was never observed in the older LBW rats. The fR and aR showed an age-related increase in both groups: a biphasic fR pattern observed on day 7 was replaced by a sustained increase on days 14 and 21. In contrast to controls, LBW rats never displayed a fR recovery during reoxygenation. In controls, aR shifted from a biphasic pattern in the younger rats to a sustained increase in the older ones. The LBW rats only displayed a decrease of aR in the younger, while in the older ones, a transient and slight increase preceded this decrease. During hypercapnia, the only significant difference detected between these two groups was that aR increased in LBW rats to a greater extent than in controls on days 14 and 21. Altogether, our results revealed a markedly attenuated cardio-respiratory response to hypoxia in LBW rats, but no such effect in response to hypercapnia.

International variations in intrauterine growth

International variations in intrauterine growth have consistently been judged in terms of average birthweight, low birthweight or birthweight-for-gestational age criteria. Neither of these provide an appropriate assessment of fetal growth. Notwithstanding these limitations the available evidence indicates that variations in growth, both within and among populations, relate predominantly to differences in the prevalence of factors that restrain growth rather than to inherent differences in growth potential. The evidence also indicates that differences in the frequency of low weight-for-gestation among populations do not only reflect factors that restrict fetal growth. They are also intimately linked to variations in gestational age and to frequencies of preterm birth in particular. Hence, if weight-for-gestational standards are to become more informative and more universally applied than they have been so far, it may be useful to acknowledge their limitations more explicitly and simplify their implementation in a wider range of communities.

The influence of race and gestational age on the age of maximum risk of SIDS in infancy

Risk of sudden infant death syndrome (SIDS) reaches a maximum in the third month. Thereafter, it decreases by half every 40 days or so. It is proposed that the relative sparing of the very young infant is a consequence of an innate (but temporary) characteristic possessed by the newborn infant. Interpretation of available data suggests that this innate characteristic is negatively associated with the infant's level of maturity. This is the basis for the hypothesis that the age at which the risk of SIDS begins to decline at a uniform rate decreases as the infant's gestational age increases. Because of a greater level of maturity at birth, the age at which this occurs in the black infant should be earlier than average. An analysis of data on 32 573 instances of SIDS within the United States between 1985 and 1991 provides support for the hypothesis.

Effects of intra-uterine growth restriction on the control of breathing and lung development after birth

1. Low birthweight is now recognized as an important risk factor for early postnatal respiratory illness and it is becoming evident that low birthweight can increase the risk for airway dysfunction in children and adults. Our studies have been aimed at determining how low birthweight, resulting from intra-uterine growth restriction (IUGR), affects the control of breathing and the structural and functional development of the lung. 2. We have measured ventilatory responsiveness to progressive hypoxia and progressive hypercapnia during the first weeks after birth in postnatal lambs in which IUGR was induced by chronic placental insufficiency. It was found that the postnatal increase in ventilatory sensitivity to hypoxia observed in control lambs was diminished in low birthweight lambs; in contrast, the sensitivity to hypercapnia was not affected. In other studies, we found that IUGR caused by maternal anaemia led to elevated CO2 levels during sleep and wakefulness. 3. Our findings suggest that the prenatal development of the brain-stem or respiratory chemoreceptors may be affected by intra-uterine factors associated with IUGR, such as foetal hypoxaemia or hypoglycaemia. It is also possible that the structure of respiratory muscles and, hence, their ability to maintain a high level of ventilation may be affected by IUGR. 4. Recently, we studied the influence of IUGR on foetal lung development, in particular its effects on foetal lung liquid, a major determinant of lung growth, as well as alveolar structure and pulmonary surfactant. Lung liquid secretion and volume, in relation to bodyweight, were unaffected; however, there was evidence of structural and functional immaturity in the lungs. In foetuses exposed to IUGR, the air-blood barrier was thicker and, after birth, the diffusing capacity of the lungs for carbon monoxide was lower. In contrast, surfactant protein gene expression was enhanced, particularly in foetuses with high levels of circulating cortisol. 5. Further studies are needed to characterize the effects of specific types of prenatal compromise on postnatal control of ventilation and lung function, to determine mechanisms underlying these effects and to determine the capacity for postnatal recovery.

Foetal nutrition, foetal growth restriction and health later in life

Retarded intrauterine growth has been linked to increased risk of perinatal mortality and morbidity, sudden infant death and poorer health later in life. The independent variables used in these studies are mainly neonatal size parameters, such as weight, ponderal index and ratios of head and abdominal measures. These are, in terms of foetal development and growth, crude parameters. This paper discusses the concepts of growth retardation used in most clinical and epidemiological studies. It is again emphasized that small for gestational age (SGA) and intrauterine growth retardation (IUGR) are different concepts. SGA is a size parameter that may or may not reflect restricted foetal growth and is therefore of limited value. Even IUGR, defined as retarded foetal growth rate, may be a too crude a criterion to select foetuses with short- and long-term health risks. Other biophysical measurements, such as foetal blood flow patterns and biochemical parameters, may be helpful in a better selection of these foetuses and infants. Furthermore, different causes of IUGR, e.g. poor maternal nutrition versus insufficient placental function, may not have the same effects on the foetus. The discrepancies in the results of studies on the relationship between IUGR or foetal malnutrition and short- and long-term health risks may be explained by the crudeness of the independent variables used. In the future, research on the biology of the developing human foetus should be more focused in the studies of the relationship between the intrauterine environment and nutrition and risk of poor health later in life.

Optimality of the birth population reduces learning and behaviour disorders and sudden infant death after the first month

The weight distribution pattern of all births can be divided into a "skewing to the left" to lower weights and high neonatal mortality, a "skewing to the right" to higher weights (>3500g) and minimum neonatal and postneonatal mortality, and a "symmetrical distribution" with mortality in between. This study was initiated with the hypothesis that a deficit in newborns of more than 3500 g would adversely affect postneonatal death. Higher and rising postneonatal mortality solely attributable to sudden infant death of unknown cause (sudden infant death syndrome; SIDS) was observed in the Nordic countries with a lower proportion of heavy newborns. Minor environmental intervention almost eliminated excess mortality from this cause, supporting raised susceptibility with a depressed birthweight in postneonatal SIDS. This contrasts with classical neonatal low birthweight SIDS, which is stable despite numerous attempts at reduction, supporting a multi-factorial aetiology: low maternal age, low education, low socioeconomic status, maternal smoking, infection, etc. The postneonatal SIDS epidemic associated with a deficit in heavy newborns is thought to be a result of changing behaviour in pregnancy: moderate iatrogenic dietary restriction and young women favouring a low-calorie, low-fat diet, especially in the third trimester when the foetus is most vulnerable, which delays myelination and somatic growth and renders the infant susceptible to minor morbidity and irregularity. The timing of death and neuropathological findings suggestive of repeated hypoxic episodes in more than 80% of cases of SIDS prior to death support this theory. The similar weight distribution patterns in SIDS and all births in Denmark, the UK and the USA suggest a substantial proportion of the neonates in these countries could be growth-retarded and at risk of hypoxic episodes in infancy. A few cases, particularly males (sex-ratio = 1.7), suffer SIDS, the majority survive. Many, mostly males, present minor CNS signs and learning and behaviour problems. The male predominance accords with males more than 500 g higher optimal birthweight than females and susceptibility to a depressed weight at birth. In order to prevent postneonatal dying, SIDS and reduce learning/behaviour disorders it is necessary to raise the proportion of heavy newborns by promoting foetal growth rate equal to the maternal intrinsic rate by eating to one's appetite a balanced diet, favouring a diet high in marine fat, especially in third trimester, in order to ensure maturation of the CNS and prolong gestation, thereby increasing birthweight. Although the increased survival of some very low birthweight neonates confounds the issue, a division between SIDS in neonatal and postneonatal death is recommended in order to assess the proportion of "avoidable infant death" as opposed to persistent classical neonatal SIDS.

Case-control study of current validity of previously described risk factors for SIDS in The Netherlands

This study aimed to assess whether previously established risk factors for sudden infant death syndrome (SIDS) are still valid now that the incidence in the Netherlands has dropped to 0.26 per 1000 liveborn infants. A distinction was made between immutable and mutable risk factors. This case-control study (part of the European Concerted Action on SIDS) comprised 73 SIDS cases and 146 controls and lasted from March 1995 to September 1996. Adjustments were made for sleeping position and bedding factors by treating them as covariables. Apart from these factors, well known risk factors that remain of importance in the Netherlands are: male sex, young maternal age, twins, and low socioeconomic status. These factors are largely immutable. Other well known risk factors which might reflect attitudes to child care and could possibly be mutable are: smoking, alcohol consumption by the mother, bottle feeding, and change of babycare routine. Intervention strategies should focus on early signalling, thereby assisting parents in changing these unfavourable parenting attitudes. Information on optimal child care and extra support by public health nurses specifically aimed at families at risk could help to decrease further the incidence of SIDS in the Netherlands.

Paternal age affects fertility and progeny outcome in the Brown Norway rat

OBJECTIVE

To investigate the effects of paternal age on fertility and progeny outcome using the Brown Norway rat model.

DESIGN

Controlled prospective study.

SETTING

McIntyre Animal Centre, McGill University, Montreal, Quebec, Canada.

INTERVENTION(S)

Brown Norway male rats of increasing age were mated to young Sprague-Dawley females.

MAIN OUTCOME MEASURE(S)

Pregnancy outcome was assessed by counting the numbers of corpora lutea, resorptions, and live fetuses on day 20 of gestation. To evaluate progeny outcome, pups were examined for external malformations and weighed daily for 2 months.

RESULT(S)

There were no significant changes in the numbers of resorptions, offspring, or in the incidence of external malformations. However, there was an increase in preimplantation loss (corpora lutea minus implantation sites) in litters fathered by older males. Furthermore, a significant decrease in the average fetal weight was found with increasing paternal age. A significant increase in neonatal deaths for progeny fathered by older males also was found.

CONCLUSION(S)

These results indicate that the quality of spermatozoa decreases as males age.

Combined effects of sleeping position and prenatal risk factors in sudden infant death syndrome: the Nordic Epidemiological SIDS Study

OBJECTIVE

Prone sleeping is a strong risk factor for sudden infant death syndrome (SIDS). We investigated whether the combined effect of prone sleeping position and prenatal risk factors further increased the SIDS risk.

METHODS

In the Nordic Epidemiological SIDS Study, parents of SIDS victims in Denmark, Norway, and Sweden completed a questionnaire on potential risk factors for SIDS. Forensic pathologists verified the SIDS diagnosis. Four controls of the same gender, age, and place of birth were selected. This matched case-control study, which included 244 SIDS cases and 869 controls from 1992 to 1995, was analyzed by conditional logistic regression.

RESULTS

Odds ratios (ORs) for prone and side sleeping compared with supine sleeping for the last sleep were 13.9 (95% confidence interval 8.2-24) and 3.5 (2.1-5.7). Infants 13 to 24 weeks old had particularly high risk in prone and side sleeping, at 28.5 (7.9-107) and 5.9 (1.6-22). OR for prone sleeping was higher in girls, at 30.4 (11-88), than in boys, 10.3 (5.5-19). We found strong combined effects of sleeping position and prenatal risk factors (more than multiplicative). The OR for prone and side sleeping was increased for infants with birth weight <2500 g, at 83 (25-276) and 36.6 (13-107); for preterm infants, at 48.8 (19-128) and 40.5 (14-115); and for intrauterine growth retarded, at 38.8 (14-108) and 9.6 (4.3-22), compared with supine position in infants without these prenatal factors. The combined effect of nonsupine positions and intrauterine growth retarded was highest among 13- to 24-week-old infants. Effects of combined presence of nonsupine sleeping positions and each of the factors of smoking in pregnancy, young maternal age, higher parity, low level of maternal education, and single motherhood were more than additive. Attributable fractions in the population for prone and side sleeping were 18.5% and 26.0%.

CONCLUSIONS

Both prone and side sleeping increased the risk of SIDS. The risk was increased further in low birth weight infants, preterm infants, and infants at the age of 13 to 24 weeks, suggesting that SIDS may be triggered by nonsupine sleeping in infants with prenatal risk factors during a vulnerable period of postnatal development.

Interactions between maternal smoking and other prenatal risk factors for sudden infant death syndrome (SIDS)

In numerous investigations, maternal smoking increases the risk of sudden infant death syndrome (SIDS). In the present study we investigated whether prenatal risk factors for SIDS modify the effect of maternal smoking on SIDS mortality. We analysed data from a population-based cohort study (222 cases, 260,604 infants at risk) within the Westphalian Perinatal Inquiry in Germany between 1990 and 1994. In the stratified analysis, smoking was classified into non-smoking, moderate (1-10 cigarettes/d) and heavy smoking (> 10 cigarettes/d). Multiplicative interactions between smoking and other prenatal risk factors were assessed in a logistic regression model. The relative risk (RR) for maternal smoking was 2.4 (95% confidence interval 1.7-5.4) for moderate and 7.2 (5.3, 9.7) for heavy smokers. Previous established risk factors for SIDS, such as preterm birth, low birthweight, and number of prenatal visits did not increase the risk of SIDS among non-smokers, but became important risk factors among smokers. In preterm infants (< 37 weeks) of heavy smokers, the RR was 19.6 (10.4, 36.8) compared to term infants of non-smokers. Low birthweight infants (< 2500 g) of heavy smokers had a RR of 16.3 (8.4, 31.2) compared to normal weighted infants of non-smokers. Adjustment for occupational status did not change the crude estimates. The RR of < 6 prenatal visits in the heavy smoking subgroup was 14.8 (7.2, 29.6) compared to > 9 prenatal visits in the non-smoking strata. Heavy smoking potentiates other prenatal risk factors for SIDS suggesting an increased susceptibility towards the adverse effects of tobacco smoke in utero. In infants born to non-smoking mothers, prenatal risk factors are absent and postnatal factors may be of major importance.

Chronic placental insufficiency in the fetal guinea pig affects neurochemical and neuroglial development but not neuronal numbers in the brainstem: a new method for combined stereology and immunohistochemistry

This study has examined the development of the brainstem in a suboptimal intrauterine environment induced via chronic placental insufficiency in the fetal guinea pig. Placental insufficiency was produced by unilateral ligation of the maternal uterine artery at mid-gestation (term = 66-68 days) resulting in the production of growth-retarded fetuses that are chronically hypoxic and malnourished. The structural and neurochemical development of brainstem nuclei either directly or indirectly related to cardiorespiratory control were analysed by using new stereological methods and immunohistochemistry. A technique was devised to enable the procedures to be performed on alternate frozen sections. There were no significant differences between control and growth-retarded fetuses in the total number of neurons, area of neuronal somata or volume of the hypoglossal nucleus. Quantitative densitometry was used to measure immunohistochemical staining in the brainstem of growth-retarded fetuses compared to controls and revealed a significant (P < 0.02) decrease in substance P(SP)-immunoreactivity in the spinal trigeminal nucleus and a significant (P < 0.05) increase in met-enkephalin-immunoreactivity in the hypoglossal nucleus. Counts of stained neurons demonstrated a significant increase in the density of SP-positive neurons in the nucleus tractus solitarius (P < 0.05) and of met-enkephalin-positive neurons in the ventral medullary reticular formation (P < 0.05). There was also a proliferation of astrocytes, as determined by immunoreactivity to glial fibrillary acidic protein in the dorsal motor nucleus of the vagus, nucleus tractus solitarius and more generally around blood vessels throughout the brainstem. Thus, these results have been shown that although chronic intrauterine deprivation does not alter neuronal numbers, at least in the hypoglossal nucleus, there is a proliferation of astrocytes, and the expression of neurotransmitters/neuromodulators is markedly effected in some of the nuclei involved with cardiorespiratory control.

Effectiveness of interventions to prevent or treat impaired fetal growth

This is an overview of 126 randomized controlled trials (RCTs) evaluating 36 prenatal interventions to prevent or treat impaired fetal growth (IFG). Results are based on systematic reviews including the meta-analyses of these RCTs. Most of the prenatal interventions do not show any significant effects on short-term perinatal outcomes. There are, however, a few interventions likely to be beneficial: smoking cessation, antimalarial chemoprophylaxis in primigravidae, and balanced protein/energy supplementation. Others merit further research: zinc, folate, and magnesium supplementation during gestation. Appropriate combinations of interventions should be a priority for evaluation because it is unlikely that a single intervention will reduce a multicausal outcome like IFG that is so dependent on socioeconomic disparities. Of concern is the discrepancy between the importance given in the epidemiological and clinical literature to the problem of IFG and the methodological quality and sample size of the RCTs conducted for the evaluation of preventive or treatment modalities.

Maternal smoking and feto-infant mortality: biological pathways and public health significance

Smoking during pregnancy has in many countries replaced poverty as the most important preventable risk factor for an unsuccessful pregnancy outcome. Maternal smoking induces fetal hypoxia and morphological changes in the placenta, which increase the risks of intrauterine growth retardation and placental abruption, which may cause late fetal death and possibly also neonatal mortality. Smoking influences post-neonatal mortality through increased risk of sudden infant death syndrome (SIDS), but why maternal smoking increases the risk of SIDS is essentially unknown. In reducing the overall smoking prevalence in society, general preventive measures have been successful. Such measures, which aim at preventing young girls from starting to smoke are in the long run the most effective way to reduce smoking during pregnancy.

Development of ventilatory responsiveness to progressive hypoxia and hypercapnia in low-birth-weight lambs

Our aim was to determine the effects of low birth weight on ventilatory responses to progressive hypoxia and hypercapnia during early postnatal life. Seven low-birth-weight (2.7 +/- 0.3 kg) and five normal-birth-weight (4.8 +/- 0.2 kg) lambs, all born at term, underwent weekly rebreathing tests during wakefulness while arterial PO2, PCO2, and pH were measured. Hypoxic ventilatory responsiveness (HOVR; percent increase in ventilation when arterial PO2 fell to 605 of resting values) increased in normal lambs from 86.6 +/- 7.1% at week 1 to 227.4 +/- 24.9% at week 6. In low-birth-weight lambs, HOVR was not significantly different at week 1 (60.1 +/- 18.7%) from that of normal lambs but did not increase with postnatal age (56.6 +/- 19.3% at week 6). HOVR of all lambs at 6 wk was significantly correlated with birth weight (r2 = 0.8). Hypercapnic ventilatory responsiveness (gradient of ventilation vs. arterial PCO2) did not change with age and was not significantly different between groups [84.7 +/- 7.5 (low-birth-weight lambs) vs. 89.4 +/- 6.6 ml.min-1.kg-1.mmHg-1 (normal lambs)]. We conclude that intrauterine conditions that impair fetal growth lead to the failure of HOVR to increase with age.