Repeat sudden unexpected and unexplained infant deaths: natural or unnatural?

BACKGROUND: There have been suggestions that when two or three unexpected unexplained infant deaths occur within a family they are more likely to be unnatural than natural. We aimed to estimate the probability that a second infant death is natural versus unnatural. METHODS: The Care of Next Infant programme (CONI) supports parents who have previously had an unexpected and apparently unexplained infant death and is currently available in over 90% of health districts in England, Wales, and Northern Ireland. We studied all deaths in 6373 infants who had completed the CONI programme by December, 1999. After a CONI death, we made detailed enquiries into the previous death and the CONI death, including a family interview, a review of autopsies, and case discussion. FINDINGS: 57 (8.9 per 1000) CONI infants died. Nine deaths were inevitable, and 48 were unexpected. 44 families lost one child, and two families lost two children. Of the 46 first CONI deaths, 40 were natural; the other six were probable homicides, five committed by one or both parents (two criminally convicted). The ratio of 40 natural to six unnatural deaths is 6.7 (95% CI 2.8-19.4). Enquiries identified 18 families with two SIDS(sudden infant death syndrome) deaths and two families with probable covert double homicides (ratio 9.0 [2.2 to 80.0]). There were no convictions in 13 incomplete cases. Families with three deaths are reported. INTERPRETATION: Repeat unexpected infant deaths are most probably natural.

Sudden unexplained infant death in 20 regions in Europe: case control study.

BACKGROUND: After striking changes in rates of sudden unexplained infant death (SIDS) around 1990, four large case-control studies were set up to re-examine the epidemiology of this syndrome. The European Concerted Action on SIDS (ECAS) investigation was planned to bring together data from these and new studies to give an overview of risk factors for the syndrome in Europe. METHODS: We undertook case-control studies in 20 regions. Data for more than 60 variables were extracted from anonymised records of 745 SIDS cases and 2411 live controls. Logistic regression was used to calculate odds ratios (ORs) for every factor in isolation, and to construct multivariate models. FINDINGS: Principal risk factors were largely independent. Multivariately significant ORs showed little evidence of intercentre heterogeneity apart from four outliers, which were eliminated. Highly significant risks were associated with prone sleeping (OR 13.1 [95% CI 8.51-20.2]) and with turning from the side to the prone position (45.4 [23.4-87.9]). About 48% of cases were attributable to sleeping in the side or prone position. If the mother smoked, significant risks were associated with bed-sharing, especially during the first weeks of life (at 2 weeks 27.0 [13.3-54.9]). This OR was partly attributable to mother's consumption of alcohol. Mother's alcohol consumption was significant only when baby bed-shared all night (OR increased by 1.66 [1.16-2.38] per drink). For mothers who did not smoke during pregnancy, OR for bed-sharing was very small (at 2 weeks 2.4 [1.2-4.6]) and only significant during the first 8 weeks of life. About 16% of cases were attributable to bed-sharing and roughly 36% to the baby sleeping in a separate room. INTERPRETATION: Avoidable risk factors such as those associated with inappropriate infants' sleeping position, type of bedding used, and sleeping arrangements strongly suggest a basis for further substantial reductions in SIDS incidence rates.

Is postnatal depression a risk factor for sudden infant death?

BACKGROUND: In New Zealand, an association has been shown between postnatal depression and sudden infant death syndrome (SIDS). AIM: To replicate the New Zealand study. DESIGN OF STUDY: Case-control study. SETTING: The city of Sheffield, UK. METHOD: The database of the Sheffield Child Development Study was used Demographic and obstetric data were collected and at one month postpartum the Edinburgh Postnatal Depression Scale (EPDS) was administered. Detailed information on the cause of all infant deaths was available. RESULTS: There were 32,984 live births during the study period (from the year 1988 to 1993) and 42 babies died with the cause registered as SIDS. Multivariate analysis showed that smoking was the most important risk factorfor SIDS (odds ratio [OR] = 7.24, 95% confidence interval [95% CI] = 2.76 to 19.01), followed by a high EPDS (OR = 3.20, 95% CI = 1.46 to 6.99) and residence in an area of poverty (OR = 2.33, 95% CI = 1.06 to 5.11). CONCLUSIONS: The Sheffield data confirm the New Zealand findings. A high EPDS score and, by implication, postnatal depression, may be risk factors for SIDS, however, there are many possible explanations for the association.

Non-fatal work related injuries in a cohort of Brazilian steelworkers.

OBJECTIVES: Workers in the steel industry are exposed to various severe hazards. This study investigated risk factors for non-fatal injury occurring in the workplace and during travel to and from work in steelworkers in Brazil. METHODS: Non-fatal work related injuries during employment from January 1977 to September 1992 were analysed in a cohort of 21 732 male workers in the steel plant of USIMINAS, Brazil. RESULTS: There were 14 972 non-fatal injuries during follow up, with 10 891 injuries in the workplace and 4081 during travel to and from work (travel to work injury). The rate of injury in the workplace was 5.6/100 person-years and that of travel to work injury was 2.1/100 person-years. The most common injuries were to hands, arms, and eyes, with 90% of the eye injuries caused by a foreign body. Both rates of workplace and travel to work injury increased significantly with the number of injuries previously experienced, and decreased with number of years in employment and calendar period. The rates of travel to work injury also seemed to decrease with age, but age was not an independent predictor of workplace injury when we controlled for duration of employment. The rate of workplace injury was increased eightfold for workers who had experienced more than six previous injuries compared with those with no previous workplace injuries after adjusting for duration of employment and calendar period. Labourers were most at risk of workplace injury, with about eight injuries per 100 person-years. Travel to work injury was most common among support workers, with nearly half of the travel to work injuries affecting the eyes. CONCLUSION: The rate of injury was high in these steelworks, both for workplace and travel to work injuries. Characteristics of the work areas and the employees can identify high risk groups; protective measures, safety, health training, and injury programmes should concentrate particularly on these groups. Prevention of eye injury needs special attention in steelworks.

Body mass index reference curves for Iran.

Body Mass Index (BMI) charts for boys and girls aged 2-18 years in Iran are presented. The charts are based on a random cluster sample survey of 1702 boys and 1599 girls living in urban Tehran, whose height and weights were measured in the 1990-1992 National Health Survey of the whole country. Charts were constructed using Healy's method as modified by Pan, Goldstein and Yang (1990), and for boys at one point were smoothed manually. The resulting charts are shown to fit the data well and adequately describe raw BMI centiles of urban and rural children elsewhere in Iran. Comparison of these BMI charts with corresponding UK charts showed substantial differences at every age and emphasizes the necessity for the use of locally based BMI norms for assessing body mass of Iranian children.

Weight-for-height of children in Iran.

Weight and height data were obtained from the 1990-1992 National Health Survey, a random cluster sample survey of 1 in 1000 families in Iran. Weight-for-height centiles of children and adolescents aged 2 to 18 in Tehran have been computed from relationships between weight for age and height for age Z-scores. The resulting centiles are compared to weight-for-height centiles based on BMI (weight/height2) charts. Investigation of the data points age by age revealed that there are very few observations between the two sets of 3rd and 97th centiles, so that the normal range of BMI for age is effectively equivalent to the normal range of weight-for-height by age. Further analysis shows that BMI charts based on the subset of children living in urban Tehran may be reliably used for all children in Iran to determine the normal range of weight-for-height except for short children aged 2 to 5 for whom a table of the upper centiles is given.

Standardized percentile curves of body mass index of Iranian children compared to the US population reference.

OBJECTIVE: To present standardized percentile curves of body mass index (BMI) for Iranian children, and compare these to the US population reference. SUBJECTS: 1599 boys and 1702 girls aged 2-18 y living in urban Tehran as a part of a random cluster sample survey of 1 in 1000 families throughout Iran. MEASUREMENTS: Heights (cm) and weights (kg) were collected by trained health staff. RESULTS: Standardized BMI reference curves for Iranian boys and girls were constructed. The curves are shown to fit the data well. The development pattern of BMI for boys and girls are compared. CONCLUSIONS: The major differences observed between Iranian and the US BMI charts underline the need for population-specific reference data. For children over six years the 5th and 95th percentiles of our data may be used provisionally as cut-off points for defining thinness and obesity for Iranian children and adolescents.

Doppler fetal circulation in pregnancies complicated by pre-eclampsia or delivery of a small for gestational age baby: 2. Longitudinal analysis.

OBJECTIVE: To observe the longitudinal changes in growth, and associated Doppler measurements, of the fetal circulation in pregnancies with a normal outcome and those complicated by pre-eclampsia, birth of a small for gestational age baby, or a combination of these complications. METHODS: Two hundred and ninety-two women had serial ultrasound scans performed from the 24th week of pregnancy. Measurements obtained included: the abdominal circumference, umbilical artery pulsatility index, the middle cerebral artery pulsatility index and time-averaged velocity, and the thoracic aorta pulsatility index and time-averaged velocity. Outcome measures included the birth of a small for gestational age infant, pre-eclampsia or a combination of these complications. RESULTS: One hundred and sixty-seven pregnancies ended in the normal birth of an appropriately grown infant at term, while 105 had a complicated outcome. They were divided into three categories: preeclampsia only (i.e. with the birth of an appropriately grown fetus, n = 13); small for gestational age only with no evidence of pre-eclampsia, n = 55; and pre-eclampsia complicated by the birth of a small for gestational age infant, n = 37. The group with pre-eclampsia complicated by small for gestational age was closest in characteristics to true clinical intrauterine growth restriction. A reduction in the abdominal circumference mirrored a rise in the umbilical artery pulsatility index and preceded changes in the middle cerebral artery and thoracic aorta. The greatest degree of change in the fetal circulation was observed during the three weeks preceding delivery. Ratios of the values obtained from the fetal and umbilical circulation demonstrated the greatest deviation from normal. CONCLUSIONS: A reduction in fetal growth velocity preceded changes observed in the fetal circulation. Ratios of the fetal Doppler parameters provided the clearest evidence of deterioration in the fetal condition. The information provided may be of use in the diagnosis and management of the growth-restricted fetus.

Obstetric outcome in women who present with a reduction in fetal movements in the third trimester of pregnancy.

A complaint of decreased fetal movements is a common indication for the assessment of fetal well being. The aim of this study was to review the outcome of a group of women whose primary indication for referral was decreased fetal movements. Over a 20 month period, 435 patients were seen in the fetal assessment unit of an inner London teaching hospital, following a primary complaint of reduced fetal movements. Investigations included: the fetal abdominal circumference (AC), amniotic fluid volume (AFV), the umbilical artery pulsatility index (UAPI) derived from Doppler ultrasound waveforms and a computerised analysis of fetal heart rate (FHR) recordings or cardiotocograph (CTG). Outcome measures were: gestational age at delivery, Apgar score < 7 at 5 minutes, admission to the Special Care Baby Unit (SCBU), the need for delivery by an emergency cesarean section for fetal compromise (CSFC), and any perinatal deaths. A comparison of actual versus expected outcome for women with decreased fetal movement revealed the following relative risks, with the 95% confidence intervals (CI) in brackets; low 5 minute Apgar score 0.03 vs. 0.05 expected (CI = 0.01, 0.05), SCBU admission, 0.06 vs. 0.07 (0.04, 0.08), and preterm delivery, 0.08 vs. 0.11 (0.05, 0.10). Cesarean sections for fetal compromise, 0.07 vs. 0.053 (0.050-0.096). The addition of FHR monitoring to standard ultrasound assessment of well being did not appear to confer any added benefit. There were no fetal deaths. The outcome for pregnancies where the mother presents with decreased fetal movements in the third trimester is comparable with the outcome for the general population.

Growth charts for Iran.

Growth charts for children aged 2-18 years old in Iran are presented. The charts are based on a random cluster sample survey of 3301 children living in urban Tehran, whose heights and weights were measured during the 1990-1992 National Health Survey of Iran. Because of differences between the data from the different provinces, these data were used as a representative subset of the total data. Charts were constructed using Healy's method, as modified by Pan, Goldstein and Yang, and are shown to fit the data well. Simulations show that the structure of the data does not affect the centile estimates. These charts may be used for all urban children in Iran and modifications are suggested to enable them to be used for rural children, who are generally smaller than urban children.

Growth of children in Iran.

Weights and Heights of 22,349 children and adolescents aged 2 to 18 in Iran are reported. Data are from the 1990-1992 National Health Survey, a random cluster sample survey of 1 in 1000 families in all provinces of Iran. Multilevel models (Goldstein 1995) which take account of the survey design, reveal significant differences between provinces and between urban and rural children. Differences between urban and rural children, like differences between girls and boys, persist across all provinces and are certainly real. Differences between provinces may be partly due to differences in calibration. Charts based on the homogeneous subset of children living in urban Tehran may be used for all urban children, and in modified form, for all rural children. All the centiles of these charts are substantially below those of the NCHS charts, but the spread is similar so that there is no suggestion that the difference is due to the prevalence of gross malnutrition. The difference shows that the use of locally based growth charts are essential for assessing the growth of children in Iran.

PIP: This study explored the growth of Iranian children 2-18 years old by using weight and height measurements. Data were obtained from a National Health Survey of families in 1990-92, which covered all provinces of Iran. After excluding discordant measurements, the data set included measurement on 22,349 individuals; 11,159 (49.9%) boys and 11,190 (50.1%) girls. Weights were recorded to the nearest kilogram, and heights to the nearest centimeter. Multilevel models were constructed to investigate regional variations in growth patterns. In the results, the interaction terms of sex with age show that the girls were putting on weight significantly faster than the boys and also growing slightly faster on average. The differences between provinces may be partly due to differences in calibration. Charts based on the homogenous subset of children living in urban Tehran may be used for all urban children and, in modified form, for all rural children. All the centiles of these charts were substantially below those of the National Center for Health Statistics charts, but the spread was similar so that there was no suggestion that the difference was due to the prevalence of gross malnutrition. The difference showed that the use of locally based growth charts was essential for assessing the growth of children in Iran.

Transvaginal Doppler ultrasound of the uteroplacental circulation in the early prediction of pre-eclampsia and intrauterine growth retardation.

OBJECTIVE: To evaluate the predictive value of transvaginal Doppler ultrasound studies of the uterine and umbilical arteries in early pregnancy, in identifying pregnant women at risk of subsequently developing pre-eclampsia, or the delivery of a small for gestational age infant. DESIGN: A multivariate logistic regression of Z scores of Doppler indices obtained from the uterine and umbilical arteries of 652 women with singleton pregnancies at 12 to 16 weeks of gestation. Measurements included the presence or absence of a notch, bilateral (right and left waveform) notching, vessel diameter, the resistance index, the pulsatility index, time averaged mean velocity (cm/s), maximum systolic velocity (cm/s), and volume flow (mL/min). Stepwise logistic regression and multivariate analysis of all the parameters measured was used to construct several scoring systems. MAIN OUTCOME MEASURES: Pre-eclampsia, birthweight, preterm delivery. RESULTS: In women that developed complications, there was a trend towards increased resistance and reduced velocity and volume flow. If bilateral notches were present there was an increased risk of pre-eclampsia (odds ratio [OR] 21.99, 95% CI 6.55-73.79), premature delivery (OR 2.38, 95% CI 1.19-4.75), and the delivery of a small for gestational age baby (OR 8.63, 95% CI 3.95-18.84). Using multivariate analysis, a seven parameter model was selected (after removal of vessel diameter, uterine and umbilical resistance index). This model produces a scoring system with a sensitivity of 92.9% and a specificity of 85.1% for the prediction of pre-eclampsia. A three parameter model (bilateral notches, uterine resistance index, umbilical pulsatility index) provides similar sensitivities, but lower specificities, when compared with the seven parameter model. CONCLUSION: These data indicate that there are differences in uterine and umbilical artery Doppler blood flow indices at 12 to 16 weeks, in pregnancies with a normal or complicated outcome. Scoring systems derived from multivariate analysis of Doppler indices demonstrate the potential of being able to identify, in early pregnancy, a group of women at increased risk of the subsequent development of pre-eclampsia, premature delivery, or the birth of a small for gestational age baby.

Transvaginal uterine and umbilical artery Doppler examination of 12-16 weeks and the subsequent development of pre-eclampsia and intrauterine growth retardation.

We aimed to determine whether Doppler measurements obtained from the uterine and umbilical arteries in early pregnancy correlate with the subsequent development of pre-eclampsia, or the delivery of a small-for-gestational-age (SGA) baby. A follow-up study was carried out in 652 women with singleton pregnancies who had transvaginal uterine and umbilical artery Doppler examinations performed at 12-16 weeks' gestation. Measurements included: the presence or absence of an early diastolic notch, vessel diameter, resistance index (RI), pulsatility index (PI), time-averaged mean velocity (TAV), maximum systolic velocity and volume flow in the right and left uterine arteries and RI and PI in the umbilical arteries. The main outcome measures were: intrauterine death, birth weight, pre-eclampsia (proteinuric pregnancy-induced hypertension, PPIH) and antepartum hemorrhage. Twelve pregnancies terminated in the second trimester, and in 14 the outcome is unknown. In the remaining 626 women, 44 (7.0%) pregnancies ended in a premature delivery, 30 (4.7%) women developed PPIH, 60 (9.6%) infants were SGA (< 10th centile), of which 19 were < 5th centile and five were < 3rd centile, and 23 (3.7%) women suffered an antepartum hemorrhage. At 12-16 weeks, 205 (32.7%) women had bilateral (right and left) notching of the uterine artery waveforms. When compared to values from women with a normal pregnancy outcome, women who subsequently developed PPIH demonstrated a significant difference in mean uterine artery TAV (24.6 cm/s for PPIH vs. 33.25 cm/s for normal outcome, p < 0.003), volume flow (120.5 ml/min vs. 184.5 ml/min, p < 0.001) and elevated resistance (mean RI = 0.80 vs. 0.695, p < 0.001). In women with bilateral notching, there were significant differences between values for pregnancies with PPIH (odds ratio (OR) 42.02, 95% confidence interval (CI) 5.66, 311.99), being SGA at birth (OR 8.61, 95% CI 4.0, 20.0) or delivering prematurely (OR 2.38, 95% CI 1.19, 4.75), compared with pregnancies with a normal outcome. We conclude that abnormal Doppler values, indicative of a failure to modify the uterine circulation in early pregnancy, are associated with premature delivery, the development of PPIH and the delivery of an SGA baby. This information may be of value in increasing our understanding of the pathophysiological events that lead to the subsequent development of uteroplacental complications such as pre-eclampsia.

Family structure, neonatal infection, and hay fever in adolescence.

OBJECTIVE: To determine whether increased numbers of siblings and infection in early life protect against allergic sensitisation. DESIGN: Historical cohort study. SETTING: Sheffield, UK. SUBJECTS: 11,765 children aged 11-16 years for whom a history of neonatal infectious illness had been recorded systematically at 1 month of age. METHODS: A history of hay fever and family structure was obtained by postal questionnaire; neonatal illness history was ascertained from health visitor records; 723 children underwent skin prick testing with mixed grass pollen extract. RESULTS: The prevalence of hay fever was reduced (p < 0.0001) among children of younger mothers, and those from larger families. The number of older siblings exerted a stronger independent effect than the number of younger siblings (p < 0.001). Infants breast fed exclusively during the first month were at higher risk (p < 0.05) of subsequent hay fever, independent of demographic factors. Adolescents at high risk of hay fever by virtue of their family structure were more likely to be sensitised to grass pollen (p < 0.002). No significant relations emerged between hay fever and infection in the first month of life, even among children born in June. CONCLUSIONS: The association of hay fever with family structure is not due to reporting bias and reflects an environmental influence on allergic sensitisation. The effects of sibship size, birth order, and infant feeding are consistent with a protective influence of postnatal infection. The first month of life and the first postnatal exposure to allergen are not the critical periods during which this protective effect is determined.

Changes observed in Doppler studies of the fetal circulation in pregnancies complicated by pre-eclampsia or the delivery of a small-for-gestational-age baby. I. Cross-sectional analysis.

The aim of this study was to compare changes in Doppler ultrasound studies of the fetal circulation in normal pregnancies with a group of pregnancies complicated by proteinuric pregnancy-induced hypertension (PPIH), delivery of a small-for-gestational-age (SGA) baby, or both. A total of 167 uncomplicated pregnancies with a term delivery of an appropriately grown baby (AGA) were used to define the normal range. Altogether, 123 high-risk pregnancies with a known outcome constituted the study group. A color duplex ultrasound machine was used to perform biometry and fetal Doppler studies. Measurements obtained from the fetal circulation included the umbilical artery (UA) pulsatility index (PI), the middle cerebral artery (MCA) PI and time-averaged velocity (TAV), the thoracic aorta (AO) PI and TAV. In addition, the ratio between the MCA PI and UA PI, the MCA PI and the AO PI, and the product of the MCA PI and AO TAV were used in the analysis. A total of 105 pregnancies had a complicated outcome. They were divided into three categories: PPIH only (pregnancies complicated by PPIH with the delivery of an AGA fetus, n = 17), SGA only (delivery of an SGA baby, with no evidence of PPIH, n = 55), and PPIH + SGA (pregnancies complicated by pre-eclampsia and delivery of an SGA baby, n = 37). The PPIH + SGA group represented true clinical intrauterine growth retardation. Cross-sectional reference ranges were created using the observations from the normal group. z-scores (standard deviation from the mean of the normal range) of the last observations made before delivery were calculated for each of the vessel velocimetry measurements and ratios. The statistical significance of z-score values was calculated using analysis of variance. The MCA and UA PI values showed the greatest deviation for any single-vessel parameter. The ratios of fetal Doppler indices (MCA/UA PI ratio, MCA/AO PI ratio and the MCA PI/AO TAV index) demonstrated greater deviation from normal than any individual vessel. The UA PI z-score for PPIH+SGA delivering < 34 weeks gestation (2.92) was significantly greater than the z-score for PPIH+SGA delivering > or = 34 weeks (1.20, p < 0.05). Fetal Doppler indices, in particular ratios that include measurements obtained from the cerebral circulation, help in the recognition of the small fetus that is growth-retarded. At term, evidence of fetal hemodynamic redistribution may exist in the presence of a normal umbilical artery PI. Fetal Doppler indices provide information that is not readily obtained from more conventional tests of fetal well-being.(ABSTRACT TRUNCATED AT 400 WORDS)

Reducing postneonatal mortality in West Virginia: a statewide intervention program targeting risk identified at and after birth.

OBJECTIVES: Excessive postneonatal mortality in West Virginia has been associated with inadequate health care. This paper describes two interventions aimed at those infants at greatest risk of dying. METHODS: Two systems of risk-related intervention were simultaneously introduced and funded statewide from 1985 through 1987. Risk status was determined by a multifactorial score at birth or clinical risk factors later. At-risk infants were linked with physicians who provided specified care plans. All infants were followed for 1 year for mortality. RESULTS: Of 4570 infants with a high Sheffield Birth Score, 45%, together with 1003 infants with clinical risk factors, received specified care plans. High-risk infants constituted 7.6% of total resident births. Odds ratios for overall postneonatal mortality and sudden infant death syndrome in high-birth-score infants compared with low-birth-score infants were 6.2 (95% confidence interval [CI] = 4.2, 9.3) and 11.2 (95% CI = 5.4, 23.2), respectively. The relative risks of postneonatal mortality were similarly significant for infants with most clinical risk factors. During the program there was a 21.4% reduction in the trend of yearly standardized mortality ratios, which differed markedly from the trend in surrounding states. The data suggest that 33 lives were saved at a cost of $36,363 per infant. CONCLUSION: Ensuring affordable, available, accessible, and acceptable care for a small group of at-risk infants was associated with a dramatic drop in overall postneonatal mortality in West Virginia.

Evaluation of attempted prevention of unexpected infant death in very high-risk infants by planned health care.

Three hundred and ninety-six babies born in Sheffield between 1982 and 1990 identified as being at "very high risk" of unexpected infant death by means of a scoring system, received an intensive programme of health care including a case discussion between a paediatrician, the GP and the health visitor held in the family doctor's surgery, weekly visits from the health visitor and informal hospital admission. Significantly fewer sudden unexpected infant deaths occurred in this group than were expected by logistic regression analysis or occurred in the best available control group with comparable scores (p = 0.024). Problems in evaluation include identification of an adequate control population, ethical difficulties in introducing a controlled study when the programme is already perceived as effective, and the calculation of "expected death rates". The results of this study indicate that very energetic programmes of intervention may prevent some deaths in vulnerable infants.

Height, weight, BMI and weight-for-height of adults in southern Iran: how should obesity be defined?

Height, weight, body mass index (BMI) and weight for height are reported for 2210 parents of a random sample of school children in Shiraz, Iran. Weight for age and weight for height centiles have been computed by the Healy, Rasbash and Yang's nonparametric method and are presented graphically. The Iranian adults are taller and heavier than previously reported for people in the region but are smaller than European and US white adults. The distribution of BMI is broadly similar to that reported for UK adults but curves corresponding to BMI-constant, i.e. weight proportional to height, cut across the centiles of weight for height.