Effect of parental smoking on cotinine levels in newborns.

BACKGROUND: Smoking is a major risk factor for cot death. Many infants smoke passively as a result of parental smoking. This paper reports on infants exposed to a smoking environment and how they accumulate metabolites of cigarette smoke, such as cotinine, which may be physiologically harmful. AIM: To assess cotinine levels in infants of smoking parents. METHOD: Cotinine excretion in urine was assessed in 104 infants, of whom 71 had smoking parents and 33 had non-smoking parents. All cotinine levels were measured at approximately 12 weeks of age. The subjects were selected from a database of infants in developmental physiological studies which assessed the impact of various factors on early postnatal development. RESULTS: On average babies with at least one parent who was a current cigarette smoker excreted 5.58 (95% CI 3.4 to 9.5) times as much cotinine in the urine as did the babies of non-smoking parents. Maternal smoking was the largest contributing factor. Co-sleeping (p = 0.037) and the minimum room temperature (p = 0.028) were significant contributory factors. CONCLUSION: Infants from smoking households accumulate cotinine, a metabolite of nicotine, which may have a detrimental effect on the cardiorespiratory system.

Participation of disadvantaged parents in child care research.

AIM: To assess the level to which parents from deprived and socially dysfunctional families collaborate in complex and time-consuming research. DESIGN: Home-based study, of early physiological development in infants from a severely deprived area. Overnight continuous recordings of deep-body temperature with twice daily urine collection, parental daily diary of life-events and completion of child care social and psychological assessment by interview questionnaire. Measurements taken between age 6-12 weeks, each lasted 8-12 h per night, averaging four nights per baby. Level of parental participation assessed in relation to ongoing lifestyle pressures. Setting Home based. Inner city deprived estate. PARTICIPANTS: Random sample of mothers with newborn healthy infants. MEASUREMENTS: A total of 87 overnight deep body temperature recordings were made on 22 infants each lasting 8-12 h; 174 urine samples were taken; and 22 sets of questionnaires were completed. RESULTS: Of 62 inner city deprived parents, 39 (62%) agreed to participate. 22 (35%) completed the study. Ongoing lifestyle pressures were high including incidents of burglary, fire and family violence. Family and partner pressures and life crises overwhelmed 10 non-participations. CONCLUSIONS: Research partnerships can be developed with underprivileged families facing severe life-events. Parents were highly motivated to complete what they perceived as important infant care research.

Early physiological development of infants with intrauterine growth retardation.

OBJECTIVES: To assess the patterns of early postnatal physiological adaptation and maturation in intrauterine growth retarded (IUGR) infants by measuring changes in sleeping deep body temperature, heart rate, and concentrations of urinary cortisol. SETTING: At home. PATIENTS: Sixty five IUGR babies and 127 controls matched for sex, social class, and levels of parental smoking. RESULTS: Night time sleeping deep body temperature, heart rate, and cortisol excretion fell with age, eventually establishing an adult type diurnal rhythm of physiological function. Minimum overnight temperature showed a linear decline with age (p < 0.001), but the IUGR infants and the controls had significant differences in intercept (p = 0.007) and slope (p = 0.02). The estimated rate of decline per week was 0.020 degrees C for IUGR infants and 0.031 degrees C for controls. Maximum temperature did not show similar changes. IUGR infants had a mean (SE) age adjusted minimum overnight heart rate that was 4.2 (1.5) beats/min (p = 0.005) higher than controls. Overnight cortisol/creatinine ratios declined with age at a rate of 4.1% per week (log ratio -0.421 (0.0165), p = 0.01), but the ratio for IUGR infants was on average 42% higher (log ratio 0.35 (0.11), p = 0.002) than for controls of the same age. Morning cortisol concentrations did not show a similar pattern. CONCLUSIONS: Postnatal physiological adaptation and maturation of IUGR infants is slower than normal and therefore they remain in a physiologically immature state for longer. The higher heart rates and greater cortisol excretion in such infants may be precursors to hypertension and cardiovascular disease seen in adults.

Overnight deep body temperature and urinary cortisol excretion in infants from economically deprived areas.

OBJECTIVES: To assess the pattern of postnatal physiological maturation in economically deprived infants by measuring the age-related changes in deep body temperature during night-time sleep. SETTING: Inner city Leicester, UK. PARTICIPANTS: Forty-eight infants aged 6-21 weeks from economically deprived areas and 87 control infants from more affluent areas. OUTCOME MEASURES: Average deep body temperature between 2 and 4 h after bedtime, overnight and early morning urinary cortisol excretion. RESULTS: Both groups showed a decline in overnight deep body temperature with age that averaged 0.030 degrees C per week (SE = 0.003). Over the age range studied, the average age-adjusted overnight temperature in the infants from deprived homes was 0.090 degrees C (SE = 0.028) higher than that for the affluent group (P = 0.001). Deprived infants had on average 51% higher overnight urinary cortisol and 80% higher morning cortisol. The differences remained when the effects of room temperature, clothing, smoking, birthweight and gestational age were taken into account. CONCLUSION: These indicators of postnatal physiological maturation suggest that infants from economically deprived homes mature less quickly. This might increase their vulnerability to illness.

Prolonged hypothermia following respiratory syncytial viral infection in infancy.

Following proven respiratory syncytial viral infection, a previously healthy 2 year old boy displayed notable persistent hypothermia-the lowest temperature being 34.2 degrees C. No obvious ill effects were observed.

Child care decisions: parental choice or chance?

AIM: A study of the context of child care decision making by inner city and suburban mothers, using parents to help develop and administer a semi-structured questionnaire. METHODS: A total of 131 mothers were interviewed (73 inner city and 58 suburban) at home. RESULTS: Inner city mothers were more likely to bottle feed, smoke and adopt risky infant sleeping positions, for example the settee. Virtually all babies (98%) were fully vaccinated and placed prone (95%) to sleep at night. Inner city mothers smoked (71%) despite the known health risks and continued postnatally (55%), mainly as a means of relieving stress. In total, 30% of inner city mothers wanted to breast feed; 19% had succeeded to 6-8 weeks postnatally. Bottle feeding helped both mother and baby to have uninterrupted nights of sleep. Suburban mothers (59%) succeeded in breast feeding, with others choosing bottle feeding mostly because of returning to work. The average weekly alcohol consumption, 32 units inner city and 15 units suburban, was taken in weekend binges by inner city parents, but in daily small amounts by suburban mothers. CONCLUSIONS: The well-being of the baby was the prime concern of all mothers, irrespective of social background. However, inner city mothers made rational decisions to smoke and bottle feed to reduce the impact of stress and allow the mother much needed respite for the good of the entire family.

Sleeping O2 saturation levels in infants.

Longitudinal recording of O2 saturation during night-time sleep of 82 infants show significantly more falls below 93% in females and infants of mothers who smoke. Implications are discussed.

Deep body temperature changes in twins.

Twins show differences in physiological maturity within and between twin sets; where one infant is 5-weeks later than its sibling; while one pair may both be slow but develop together. Zygosity, birth weight and sex may be contributory but not causative factors. How vulnerability to illness may be affected, is discussed.

Changes in body temperature and urinary cortisol after routine immunization in babies with intrauterine growth retardation.

AIM: To investigate whether infants with intrauterine growth retardation (IUGR) experience different changes in temperature and cortisol excretion after routine immunization compared with normal healthy infants. METHODS: Overnight deep body temperature and urinary cortisol to creatinine ratios were measured on the night after immunization and a control night in normal and IUGR infants. RESULTS: In 60 normal infants, first vaccination at about 10 wk of age led to a significant increase in minumum overnight temperature compared to the control night, mean rise 0.25 degrees C (95% CI, 0.12 to 0.38). In 35 IUGR infants the mean rise in temperature between immunization night and control night was 0.35 degrees C (95% CI, 0.15 to 0.55). The increases in minimum temperature did not differ significantly between the normal and IUGR infants (p = 0.11). Cortisol to creatinine ratios measured from overnight urine samples showed that 23 IUGR infants had consistently higher levels than 39 normal infants: control night medians 34 and 15 (p=0.01) and immunization night medians 56 and 26 (p = 0.02), respectively. However, the percentage increase did not differ significantly between the IUGR infants and the normal infants. A smaller number of second immunizations were studied, but no significant differences were found. CONCLUSION: These results suggest that although the impact of immunization is the same for IUGR and normal infants, because IUGR infants are less mature and at greater stress before immunization, the absolute levels that they experience after immunization are higher than those for normal infants.

Relations between the development of patterns of sleeping heart rate and body temperature in infants.

Overnight patterns of rectal temperature and heart rate were recorded from 119 normal infants at weekly intervals from 7 to about 16 weeks of age. All data were collected in the infants' own homes. As previously reported, different infants developed an adult-like night time rectal temperature pattern abruptly at different ages. When heart rate data were collated by age, there was an apparently gradual fall in sleeping heart rate from 7 to about 14 weeks of age. This was, however, an artefact of data collation. Individual infants showed abrupt falls in heart rate at the time that the adult-like body temperature pattern appeared, but this occurred at different ages in different babies, so when data were collated cross sectionally, an apparently gradual fall resulted. The relation between the developmental changes in sleeping heart rate and rectal temperature was different in boys and girls, with girls showing a more abrupt and greater change in heart rate at the time of development of the adult-like body temperature pattern. Infants whose parents smoked had significantly lower heart rates once the adult-like body temperature pattern had appeared.

Higher rectal temperatures in co-sleeping infants.

The effect on deep body temperature of infants co-sleeping (with either or both parents) is investigated in this case control study. Overnight continuous recordings of rectal temperature were made from 34 babies co-sleeping with one or both parents throughout the night and 34 infants matched for age, feeding regimen, parental smoking, thermal environment, sleeping position, and sex who slept alone. The co-sleeping infants had significantly higher rectal temperatures from two hours after bedtime, when the initial fall in sleeping body temperature was complete. The mean rectal temperature of co-sleeping infants between two and eight hours was 0.1 degree C higher than that of infants sleeping alone (p < 0.04). Given the very small variance in rectal temperature this probably reflects a considerable physiological difference between the two groups.

Factors affecting rectal temperature in infancy.

The recordings of 1197 overnight rectal temperatures from infants of up to 24 weeks of age have been analysed with respect to 12 variables, including a number of risk factors for sudden infant death syndrome. Multivariable regression was used to identify if parental smoking, bottle feeding, sleeping position, and birth weight affect the overnight rectal temperature of infants. The rectal temperature, averaged over the period from three to five hours after the infants were put to bed, correlated well (R = 0.36) with the collected variables. An increase in the infant's age, birth weight, and the supine sleeping position all decreased the night time rectal temperatures. However, an increase in the night time room temperature, weight, and the combination of bottle feeding and parental smoking produced an increase in rectal temperature. The individual effects of bottle feeding and parental smoking were not significant. The results show that some of the major risk factors have the effect of raising the rectal temperature of sleeping infants.

Prone sleeping infants have a reduced ability to lose heat.

The heat loss coefficients of a group of infants have been calculated and compared to see if there is a difference in the ability to lose heat between prone and non-prone sleeping infants. For a group of 43 infants aged 4-29 weeks, a simple mathematical model of exponential cooling in a body has been fitted to the fall in rectal temperature which occurs in infants at bedtime. One of the parameters yielded by the fitting process is the coefficient of thermal heat loss. After validation against the estimated heat loss from supine sleeping infants, the heat loss coefficient was compared at different sleep positions and gender. The mean heat loss coefficient, measured from the non-prone sleeping infants (0.269 W/degrees C, S.D. 0.197) agreed well with the value calculated for supine sleepers with the same tog levels (0.4 W/degrees C). Prone sleeping infants were found to have a considerably smaller heat loss coefficient which was approximately 60% of the value for non-prone sleeping infants (P = 0.000097). Female infants were found to have a heat loss coefficient that was approximately 70% of that of male infants but this gender difference was only significant (P = 0.025) for non-prone sleeping infants. These results suggest that infants sleeping in the prone position may be unable to lose heat as rapidly as those infants sleeping non-prone.

Urinary excretion of cortisol after immunisation.

Urinary cortisol excretion and rectal temperature were measured in 66 infants before and after immunisation against diphtheria, tetanus, pertussis, and Haemophilus influenzae type b. Immunisation produced a significant increase of rectal temperature the next night at all ages. Infants without an adult-like night time body temperature pattern had a significant increase in urinary cortisol excretion night and morning after immunisation. Once an adult-like night time body temperature pattern developed immunisation no longer significantly raised urinary cortisol output.

Lower body temperature in sleeping supine infants.

Night time rectal temperature recordings were made from 103 infants sleeping in their own home in different sleeping positions. In most cases sleeping position was verified by video monitoring throughout the night. In the period before an adult-like night time body temperature pattern appeared there was no significant effect of sleeping position upon night time body temperature, in line with previous reports. Once an adult-like night time temperature pattern appeared, infants sleeping supine reached significantly lower rectal temperatures than those sleeping prone or lateral. Babies sleeping supine moved significantly more during the night and were more likely to uncover their hands and arms. These findings suggest that supine sleepers are in a different physiological condition from those sleeping prone or lateral, which may be associated with their lower vulnerability to sudden unexpected infant death.

Interactions between infant care practices and physiological development in Asian infants.

Asian infants are less likely to suffer cot death despite apparently higher prevalence of some risk factors. This paper compares the development of night time body temperature patterns in a small sample of Asian babies with the pattern already established for white infants, where babies who develop an adult-like night time temperature pattern later than usual share characteristics with victims of SIDS. The Asian infants had similar body temperature patterns to whites, but tended to develop the adult-like pattern later, not earlier as might have been expected. More Asian infants than white in our sample slept in the parental bed, and, before the adult-like body temperature patterns appeared, co-sleeping infants had higher body temperatures than those in their own cots. Asian infants slept in significantly warmer rooms than whites, but under similar amounts of bedding. These studies do not therefore reveal any physiological difference between Asians and whites which might account for low vulnerability to cot death, indeed, if anything the reverse.

Body temperature changes before minor illness in infants.

This study aimed to examine the overnight temperature pattern of babies during the prodromal phase of minor illnesses. The overnight rectal temperature pattern of 123 babies was recorded weekly from about 6 to at least 16 weeks old, while parents maintained detailed records of signs of illness. By analysis of patterns of signs and visits to the general practitioner, 86 periods of minor illness were identified, mostly upper respiratory tract infections, though it was not usually possible to identify the infection by conventional virology. Data were analysed separately for babies who had developed an adult-like night time temperature pattern and those who had not. In both groups, obvious signs of illness were preceded by a disturbance of night time temperature pattern. Temperature was significantly raised over control weeks, though few babies were clinically febrile. The greatest temperature disturbances were seen in the three days before illness, though some disturbances were seen up to seven days before. A similar disturbance of temperature was seen the night after diphtheria, pertussis, and tetanus immunisation, and individual responses to natural infection and immunisation were well correlated, suggesting that the temperature change is more a function of the host response than the infecting agent.

Factors affecting the development of night time temperature rhythms.

The rectal temperature of 26 infants between 6 and 16 weeks old was monitored continuously for one night each week. Rectal temperature always decreased with sleep but the minimum temperature attained changed with age. Some time between 8 and 16 weeks old the minimum sleeping rectal temperature decreased abruptly from around 36.8 degrees C to around 36.4 degrees C. This change was complete within one week and did not normally revert unless the infant became ill. Some infants changed as early as 8 weeks old, others not until 16 weeks. Breast fed infants changed significantly earlier than bottle fed infants. Girls changed significantly earlier than boys. First born infants changed significantly earlier than second or subsequent infants. Early changes were significantly more likely to be sleeping lateral or supine, and to have older mothers. They tended to come from more affluent families. There was no association between the time of change and the thermal environment in which the infant slept or the number of episodes of minor illness in the early weeks of life.