A. Scott

Quantitative structural studies on human placentas associated with pre‐eclampsia, essential hypertension and intrauterine growth retardation

Summary. Placentas from pregnancies complicated by pre‐eclampsia, essential hypertension, hypertension complicated by pre‐eclampsia and from normotensive pregnancies resulting in the birth of a singleton small‐for‐dates (SFD) infant have been studied by quantitative mor‐phometry. The findings have been compared with those from placentas of uncomplicated pregnancies. The placentas from pregnancies compli‐cated by pre‐eclampsia and those resulting in a SFD baby had a signifi‐cantly lower total volume, volume of parenchyma and villous surface area when compared with normal pregnancies of comparable gestation. They also had an increase in areas of multiple infarction and in the volume proportions occupied by fetal capillaries. The placentas from women with essential hypertension uncomplicated by pre‐eclampsia were as large as those from normal pregnancies and the villous surface areas were as high. Villous surface arca measurements in the different groups were related to gestation and to fetal weight.

Risk factors associated with small‐for‐dates and large‐for‐dates infants

Summary. Relative risks were calculated to assess the potency of different factors associated with the two extremes of the birthweight distribution. Maternal height affected the chances of having a small‐for‐dates (SED) or large‐for‐dates (LFD) baby to an equal and opposite extent; but the risks associated with maternal weight were greater for LFD than SFD infants. Smoking increased the SFD risk by 3.5 times, whereas the LFD risk was only reduced by a half. Pre‐eclampsia was associated with a very high SFD risk (14·6); in the LFD group it was insignificantly raised. The LFD relative risk steadily rose with increasing parity, but in the SFD group it fluctuated around unity. Among multiparae the risks of an SFD or LFD infant when previous siblings had been of relatively low or high birthweight for gestational age, respectively, were much increased. Estimates of attributable risk showed that if pathological factors such as smoking, hypertensive disorders and congenital abnormalities could be completely eliminated the number of SFD babies in this population would be reduced by about 60%; conversely the number of LFD babies would be increased by about 30%.

Children of deviant birthweight at the age of seven years: health, handicap, size and developmental status

138 small-for-dates (SFD), 138 average-for-dates (AFD) and 136 large-for-dates (LFD) children who had been followed up from birth were examined at the age of 7 years. Nine children had major congenital abnormalities (SFD 5, AFD 2, LFD 2). In addition gross and/or fine motor incoordination was noted in 25 children (SFD 9, AFD 10, LFD 6). There were no differences between the groups in the incidence of chronic or specific ill-health, hearing, sight and speech defects. Highly significant differences were found between the groups for weight, height, head circumference and triceps skinfold thickness; and significant differences were also found between the total developmental scores in the three groups. In every case SFD children had the lowest and LFD children the highest mean values. Within each group analyses were made of 22 parental, pregnancy, perinatal and postnatal factors which might affect growth or development. The net effects of those factors for which significant differences had been found were then assessed, adjustment being made for confounding between variables. In all three groups the childrens genetic potential for size was strongly evident by this age, and boys had larger heads than girls. All three groups showed the powerful influence of social class on intellectual ability; and sex on gross and fine-motor function. The other main contributor to developmental differences in the AFD group was gestational age. In the SFD group maternal hypertension was associated with slightly decreased intellectual ability, and in all areas first-born SFD children performed better than subsequent born. Among LFD children instrumental delivery had an adverse effect on all areas of ability, and first-born children had higher intellectual scores. When all the children were considered together and birthweight included as an additional variable the differences in developmental scores between the groups were much reduced. In the SFD and LFD groups some significant correlations were found between size and developmental scores; but none were found among AFD children.

Growth in the first four years: II. Diversity within groups of small-for-dates and large-for-dates babies

238 small-for-dates (SFD), 246 average-for-dates (AFD) and 241 large-for-dates (LFD) infants were personally examined at birth, and measured thereafter in their own homes at the ages of 2, 6, 12 and 18 months, 2, 3 and 4 years. At each age weight, length or height, and head circumference measures in the SFD and LFD groups were distributed around the appropriate sex AFD mean values. In both extreme groups major shifts towards the mean occurred in the first six months for all three measures. From one year onwards only small within group fluctuations were seen. Correlations between one and four year values for weight, height and head circumference were high. At four years about 50% SFD children were within 1 S.D. of the mean, and 10% were still very small. Slightly more LFD children (55-60%) were near to the mean at this age, particularly for their head circumference values (70%), and only about 8% LFD children had very large heads. Trajectories of individual SFD and LFD children illustrate the great diversity of growth patterns within and between groups.

Quantitative structural studies on placentas from pregnancies complicated by diabetes mellitus.

Summary. Fourteen placentas from pregnancies complicated by insulin‐dependent diabetes mellitus have been examined by quantitative morphometry. The results have been compared with those from 22 placentas of comparable gestation from uncomplicated pregnancies. The volume of parenchymatous tissue in the placentas from diabetic mothers was significantly increased while the volume of non‐parenchyma was decreased. The villous surface area was increased in placentas from the diabetic group, the mean value being 17·3 m2 compared with the 11·4 m2of the normal group. This increase was larger than would be expected when the increase in fetal weight of some babies born to diabetic mothers is taken into account.

Small-for-dates babies at the age of four years: health, handicap and developmental status

221 small-for-dates (SFD) and 244 average-for-dates (AFD) children were personally examined at birth, and seen thereafter at regular intervals up to 4 years, when a thorough assessment was made. There was an excess of SFD children with major congenital abnormalities; but no difference between the groups in the number of children who were handicapped without congenital abnormality. Their general health was good, and the prevalence of specific disease or major ill-health did not differ. SFD girls seemed to have less acute hearing than AFD girls; but there was not difference for boys. The prevalence of squint, impaired vision, speech defects, and abnormalities of gross and fine motor movements were equally low in both groups. At 4 years the mean scores for five sectors of development were significantly lower in the SFD than the AFD group. Within group analyses of 16 variables and their effects on developmental scores showed no associations in either group according to maternal height and weight, birthweights of previous siblings, the presence or not of hypertension and pre-eclampsia, bleeding during pregnancy, asphyxia and injury at birth, or birth order. Within each group the net effect of the remaining eight factors was assessed; adjustment being made for the other seven variables. In the SFD group social class and method of delivery made a significant contribution to total scores. In the AFD group significant differences were found according to social class, sex, gestational age at birth and smoking. Method of infant feeding just failed to achieve significance. When all the children were considered together, and birthweight group included as an additional variable, no significant differences remained between the SFD and AFD groups for any sector of development.

Neurological development of small-for-gestational age babies during the first year of life

137 small-for-gestational age (SGA) infants were examined in the neonatal period and at 2, 6 and 12 months. At each age a structured assessment was used for which a score denoting neurological maturation could be given. The SGA infants were significantly retarded compared with average-for-gestational age (AGA) infants from 2 months onwards. Within the SGA group the mean scores for boys, those who were first-born, breast-fed and/or born to mothers who smoked during pregnancy were in each case significantly higher than the rest at 6 and 12 months. Maternal smoking influenced all aspects of development at 12 months; whereas sex and method of infant feeding mainly affected the motor items, and birth order only those that were socially oriented. Positive associations were found between changes in somatic measures and changes in neurological scores from birth through to 6 months. Infants who grew faster also matured faster during this period of time, and vice versa. Positive correlations were found between size and scores at 2 and 6 months, but not at 12 months.

Growth in the first four years: I. The relative effects of gender and weight for gestational age at birth

The growth of 238 small-for-dates (SFD), 246 average-for-dates (AFD) and 241 large-for-dates (LFD) babies was assessed at regular intervals from birth to four years. At all ages, and for both sexes, the mean weight, length or height, and head circumference values for the two extreme groups differed significantly from the AFD group (P less than 0.001). During the first six months actual and relative growth was highest in the SFD group and lowest in the LFD group. With the exception of length in the LFD group it was higher for boys than for girls. Thereafter differences in actual values were slight, while the proportional increases for the three groups were almost identical. Differences from the AFD mixed-sex mean value were plotted for each group and sex combination. Stabilization of the mean trajectories in the two extreme groups occurred at six months for weight and head circumference, but not until 12 months for length. For each child a straight line was fitted on a log scale to these differences from six months (12 months for length) to four years, and analyses of variance of the slopes and intercepts obtained. The sex difference for weight and height gradually decreased, but for head circumference held constant. Estimates of the difference in intercepts of the birthweight groups and sexes showed that within the LFD group the difference in height between boys and girls was much less than in the other two groups. The sex difference for head circumference was slightly larger than the difference between SFD and AFD groups, and twice the difference between the LFD and AFD groups. At the age of four years the mean value for AFD boys was higher than LFD girls (P less than 0.01), and those for SFD boys and AFD girls were almost identical.

Factors Affecting Development: Similarities and Differences among Children Who Were Small, Average, and Large for Gestational Age at Birth

ABSTRACT. The development of 118 small‐for‐gestational age (SGA), 137 average‐for‐gestational age (AGA), and 118 large‐for‐gestational age (LGA) children was assessed at 7 years. The contributions of different factors to the variance in developmental scores were investigated by multiple regression analyses. All three groups showed the powerful influence of social class on intellectual ability at this age; and in the SGA and AGA groups the gross and fine‐motor skills of girls were superior to boys. Smoking had a small effect in the AGA group, and in the two extreme groups first‐born children did slightly better than later‐born. Hypertension was associated with reduced scores in the SGA group, and LGA children who had spontaneous vaginal deliveries had higher scores than those delivered instrumentally or by caesarean section. There was a significant positive correlation between gestational age and developmental scores in the AGA group; but in the SGA group the relationship was in the reverse direction. Social class and sex affect the development of most children aged 7 years. Other factors seem to manifest an effect only under specified conditions.

Social class and birthweight: A new look

The effects of social class on birthweight, and its interactions with other maternal factors, were examined in groups of women bearing small-for-dates (SFD), average-for-dates (AFD) and large-for-dates (LFD) babies. The relative risk of a lower social class woman having an SFD baby steadily decreased from 1.75 to 1.20 as adjustment was cumulatively made for smoking, hypertension, maternal age and height. The subsequent addition of weight and weight-for-height made little change. The unadjusted risk of a lower social class woman having a LFD baby was very close to unity (0.99). Adjustment for other maternal factors, in the same order as at the other extreme, showed a steady rise to a significant level (1.45) when height was included; but there was a sharp reversal to a non-significant risk of 1.12 when weight was added. The large contribution of obesity in the lower classes seems to counterbalance those for height, age and smoking in the upper classes in the LFD group. The interactional effects of other maternal factors and social class are not operating to an equal and opposite degree at the two extremes of the birthweight range.