Available standard intrauterine growth curves based on birthweights underestimate foetal growth in preterm period. New growth curves are presented based on data from four Scandinavian centres for 759 ultrasonically estimated foetal weights in 86 uncomplicated pregnancies. Mean weight of boys exceeded that of girls by 2-3%. A uniform SD value of 12% of the mean weight was adopted for the standard curves as the true SD varied non-systematically between 9.1 and 12.4%. Applied to an unselected population of 8663 singleton births, before 210 days of gestation, 32% of birthweights were classified as small-for-gestational age (SGA; i.e. below mean - 2 SD); the corresponding figures were 11.1% for gestational ages between 210 and 258 days, and 2.6% for ages of 259 days or longer. The new growth curves reveal better the true distribution of SGA foetuses and neonates, and are suggested for use in perinatological practice.

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The reliability of ultrasound fetometry for estimating gestational age (GA) in the second trimester was evaluated, using the fetal variables: biparietal diameter (BPD), occipitofrontal diameter (OFD), mean abdominal diameter (AD), and femur length (FL), each value being taken as the mean of five measurements. Of the individual variables, BPD gave the best precision, with a standard deviation (SD) from true GA of 3.2 days. Using a combination of all four variables, GA could be estimated with a SD of 2.2 days, which was not significantly better than the formula, GA = BPD X 1.2 + FL X 1.0 + 49, which gave results with a SD of 2.4 days. Equations obtained from regression analysis of the variables against true GA were tested in 44 cases where the precise date of conception was known, GA being estimated by BPD with a SD of 3.2 days, and by the combination of BPD and FL with a SD of 2.7 days; the maximum difference between GA estimated by BPD and by FL was 7 days. Using a combination of BPD and FL to estimate GA in the total population, the number of post-term deliveries was only marginally less than when using BPD alone.

Using multiple regression analysis, a formula was evolved for estimating fetal weight in utero, based on fetal biparietal diameter (BPD), abdominal diameter (AD) (mean of two orthogonal readings), and femur length (FL), measured by ultrasound within 48 hours before delivery or legal abortion in a stratified sample of 89 pregnancies, approx. 10 in each 500-g weight class up to 5 000 g. Tested on 135 neonates of varying birth weights, the formula evolved, wt = BPD0.972 X AD1.743 X FL0.367 X 10(-2.647), neither under- nor over-estimated weight in any weight class, the error in estimates having a standard deviation of 7.1%, and maximum error being 18% of true weight. To establish an intrauterine growth curve, the formula was applied to 177 longitudinal measurements in 19 normal pregnancies; the estimated weight against gestational age (GA) curve so obtained best fitted a third-degree equation, wt = 1443.4 - 32.32 X GA + 0.203 X GA2 - 0.000215 X GA3 (r2 = 0.978), tallying closely with the birth weight curve obtained in the same population from 4743 pregnancies where gestational age had been assessed by ultrasound in early pregnancy. The present two growth curves, based on fetometry and on birth weight, differ from previous curves used almost universally by pediatricians.

Normal range curves for the growth of fetal biparietal diameter (BPD), occipitofrontal diameter (OFD), mean abdominal diameter (AD), and femur length (FL) were obtained in a longitudinal series of ultrasound measurements in 19 normal pregnancies. Regression analysis was used to fit the data to equations. The best equations for BPD and AD on gestational are close to similar longitudinally obtained regression curves from other Scandinavian countries.

A prospective study was made to evaluate whether bedrest in hospital is beneficial in pregnancies where intra-uterine growth retardation (IUGR) was suspected. Diagnosis was based on routine fetometry at 32 weeks of gestation, in conjunction with general ultrasound screening. 107 patients with suspected IUGR-pregnancies were divided into two groups, 49 in a hospital bedrest group and 58 in an 'out-patient' group. Fifteen women in the bedrest group refused hospitalization, and 8 women in the out-patient group had to be hospitalized for medical reasons other than suspected growth retardation, leaving 79% of the women in their allocated group. The women in the bedrest group were hospitalized for a mean duration of 29.2 days (range 5-54). The results suggest that bedrest in hospital is not beneficial, either to fetal growth or to pregnancy outcome.

Abstract. The present study describes the evolution over a 5‐year period of an ultrasonic routine screening programme of a pregnant population with participation of approximately 90 % of the pregnant women. One obvious result obtained in the screening programme is the pronounced improvement of early detection of twins, the incidence now approaching 95 % with the mean gestational age for the detection being 20 (median 19) weeks. Early detection in combination with clinical measures was associated with a decrease in the incidence of twins born preterm (before week 37) from 33 % to 10 %. The perinatal mortality rate of twins fell from 6 to 0.6 % after the introduction of this programme. The power of an early measurement of the fetal biparietal diameter (BPD) to predict the date of confinement was high. Of 848 pregnant women with an early BPD measurement (96.5 % were measured before the 21st gestational week), 95 % were delivered spontaneously within 12 days according to the estimates from the BPD, only 1.5 % being delivered later than the 42nd gestational week. The corresponding figures estimated from the last menstrual period was 79.3 % and 11.6 %. The experience gained from the programme recognized BPD for estimate of actual gestational age and the 17th gestational week was for practical reasons chosen for the first ultrasonic examination. As dating of the gestation is an important prerequisite in a screening programme for neural tube defect, the estimate of serum alphafetoprotein (AFP) was conveniently added to the ultrasonic screening programme. When ultrasound is used for exclusion of twins, dead fetuses, and erroneous dates, the percentage of amniocentesis occasioned by raised serum AFP value has hitherto been low (1.3 %). The introduction of ultrasound at our department has enabled us to reduce by 50 % the number of X‐ray examinations of pregnant women. The calculated cost for each examination made by midwives in our programme is Skr. 50:‐ (US $ 11).

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