Search

Introduction: We investigated the sex-specific risk of maternal smoking during pregnancy on the birth weight and the proportion of small-for-gestational-age (SGA) newborns in 888,632 (49.9%) of 1,815,318 singleton births (ca. 80% of all singleton births in Germany from 1995 to 1997) in whom data on maternal cigarette consumption were available., Results and Discussion: Newborns below the 10th percentile for weight and duration of pregnancy were classified SGA. Maternal smoking during pregnancy lowers the mean birth weight and increases the risk of SGA newborns. The negative effect depends on the daily number of cigarettes consumed, and is greater in girls than in boys. In non-smokers, 9.8% of the newborns were SGA, with a sex-ratio of females:males=1, but this percentage increased with increasing number of cigarettes consumed (p<0.001), as did the sex-ratio, i.e. the negative effect of smoking on growth was greater in girls than in boys. In mild smokers (1-5 cigarettes/day), the risk of giving birth to an SGA girl was 1.7275-fold (95% CI: 1.7266-1.7284) above normal, but was 1.7143-fold (95% CI: 1.7137-1.7150) in boys. More than 21 cigarettes/day increased the risk of SGA 3.15-fold for a boy, but 3.51-fold for a girl (p<0.001)., Conclusion: In conclusion, particularly in heavy smokers, the negative effect of maternal smoking during pregnancy on the mean birth weight and risk of SGA is significantly greater in newborn girls than in newborn boys.

According to the concept of canalisation, infants and children stay within one or two growth channels, and therefore, any crossing of height centiles always warrants further evaluation. In view of evidence against this concept we re-investigated the variability of individual growth in the First Zürich Longitudinal Growth Study. The investigation is based on height measurements of 232 children (112 females, 120 males) measured at annual intervals during childhood and half-yearly during adolescence. Height data were transformed into height standard deviation scores (SDS) and canalisation defined by the width of an individual's growth channel, i.e., by the differences between maximum and minimum height SDS, in the individual series of measurements. Many subjects of the First Zürich Longitudinal Growth Study crossed numerous centiles with patterns that often seemed to show characteristic features. For approximately two thirds of the subjects, the SDS channel during the whole growth process covers more than one SDS. In childhood, between the age of two and age of minimal height velocity, only about one fourth of the subjects have an SDS channel below 0.5, indicating acceptable canalisation. During childhood, growth in boys appeared slightly more canalised than in girls (P = 0.02). Conclusion. The present investigation does not support the concept of strict canalisation of individual growth. We suggest to consider crossing of centiles a normal event in child development, though in a clinical setting crossing centiles should still be taken seriously, at least at first until a medical cause for this has been excluded.

The study of human growth is traditionally based on investigations of body height. Differences of height which significantly surpass the technical error of the measuring device then by definition represent growth. However, this definition proved to be unsatisfying if applied to changes of body stature within very short time intervals. We have measured 73 healthy children, aged between 2.9 and 15.9 years, for periods of 180 to 306 days once or twice weekly, and 23 healthy children of similar ages for periods of 3 months, 4 to 5 times per week. The individual series of lower leg length measurements (technical error 160 microns) were analyzed by a smoothing procedure yielding mean daily lower leg growth rates. The series of almost daily measurements were additionally analyzed in order to find periodic elements. In the case of weekly measurements, marked periodic changes of mean daily lower leg growth rates were found with sharp growth spurts once every 30 to 55 days. Additional investigations of the series of almost daily lower leg length measurements showed evidence that the above periodic changes of growth rate were caused by aliasing between shorter periods overlapping each other and the exact 7-day intervals of measurements. We found a number of dominant periods particularly at 7 to 9-day intervals.

We studied the differential inhibitory effects of conjugated oestrogens on lower leg length and standing height increments in 17 excessively tall girls compared to a control group of 17 tall healthy untreated girls. Standing height, lower leg length and body weight were recorded at weekly or monthly intervals. Standing height velocity dropped from 150 microns/day to 122 microns/day, whereas daily weight gain increased from 17 to 48 g/day during oestrogen treatment. The oestrogen induced decrease of standing height velocity could be explained by a marked inhibition of lower leg growth velocity from 42 microns/day to 30 microns/day (native data) or 35 microns/day to 8 microns/day (data corrected for weight gain) (P less than 0.001), whereas no differences of trunk growth velocity could be detected. Thus, the findings strongly suggest that pharmacological doses of oestrogens only affect epiphyseal growth.

Recently a novel and non-invasive technique of lower leg length measurement (knemometry) was introduced. The method estimates the distance between heel and knee in the sitting child with an accuracy of 0.09 mm(SD). Two female patients with anorexia nervosa, aged 14:4 and 13:7 years, weighing minus 27 and minus 38% of normal weight for age, were measured repeatedly with this method within periods of 72 and 129 days during hospitalization und up to 133 days thereafter. During the first 40 days of hospitalization, patient 1 was measured 30 times and showed significant shrinkage of the lower leg length of -0.040 mm/day (P less than 0.001). Over the remainder of her hospital stay her mean lower leg length increment still was much less (+0.036 mm/day) than that expected just by increase of soft tissue due to rapid weight gain (+0.126 kg/day). The second patient also showed significant shrinkage of lower leg length during a 4 month period after discharge from the hospital (-0.009 mm/day, P less than 0.01). This is the first demonstration of long term lower leg shrinkage in children. Its origin remains unclear, but this shrinkage is clearly distinct from either arbitrary changes of lower leg length due to errors of measurement or changes of body diameters due to temporary alterations of soft tissue (i.e. during periods of weight loss). We speculate that progressive atrophic changes of the epiphyseal plates still open in both patients may account for the observed long term shrinkage of lower leg length.

Cross-sectional and longitudinal studies of human growth have revealed almost every detail of the typical human growth pattern. Yet, the description of this pattern is still limited to the traditional vocabulary of "growth rates", i.e. height or length differences divided by certain time intervals such as months or years. Almost no information is yet available on finer details of this pattern. This review concerns the existing experimental and clinical data collected by a novel and non-invasive technique of accurate lower leg length measurement named "knemometry" that has been used for the study of short-term growth. This technique estimates the distance between heel and knee of the sitting child with an accuracy (technical error) of 0.09-0.16 mm. Several authors have presented evidence that lower leg growth is non-linear. There is not only a marked day-to-day variation of the lower leg length which far exceeds the error of the measurement itself, but there is also a characteristic up-and-down pattern of lower leg growth consisting of sharp growth spurts ("mini-growth-spurts") alternating with periods of decreased growth velocity every 30-55 days in 45 out of 73 healthy children. This pattern can be visualized by the calculation of "mean daily lower leg growth velocities", an approach that gives information on the kinetic properties of the growth process. In spite of much initial criticism, knemometry has opened a fascinating new dimension of the physiology of human growth and provided finer details of growth than hitherto obtainable by conventional techniques of growth measurement.