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The purpose of our study was to establish the guidelines for interpreting neonatal flash visual-evoked potentials (FVEPs) by examining the correlation between maturation of the waveforms and conceptual age (CA). We retrospectively analyzed 220 consecutive neonatal FVEPs performed on premature and full-term infants. The CA of the participants ranged from 28 to 52 weeks. The FVEPs were categorized into 6 groups according to CA: 28 to 31+ weeks, 32 to 35+ weeks, 36 to 39+ weeks, 40 to 43+ weeks, 44 to 47+weeks, and 48 to 52 weeks. The data were analyzed in each group and compared among these 6 groups. The waveforms changed from 28 weeks to 52 weeks of CA. In the CA age range 28 to 31+ weeks N3 was well visualized, followed by P3. The morphology of P2 including both latency and amplitude became prominent starting from CA age range 32 to 35+ weeks. The triphasic waveform with clear negative-positive-negative components (N2-P2-N3) presented after 32 weeks. Mean P2 latencies decreased steadily with increasing age. Mean amplitudes of all waveforms (P2-N3 and N3-P3) varied except that of N2-P2 which increased steadily with CA. We conclude that FVEPs can be useful in the evaluation of maturation and function of the visual pathway in neonates. The FVEP is abnormal when the waveforms N3 and P3 are nondetectable in neonates at 28 weeks of CA or older; and when the waveform P2 is non-detectable, or has low amplitude or prolonged latency, in neonates at 36 weeks of CA or older.

The relative composition of skin, muscle, and bone and their distribution patterns throughout the body are given for a series of Macaca mulatta from 171 days conceptual age through adulthood. In terms of percent of total body weight, the musculature of these animals doubles during the firs postnatal year whereas bone and skin decrease. Regionally, the muscles of the thighs, back extensors, truncal-forelimb and upper arms increase most markedly. The thighs double and the upper arms increase whereas the trunk, hands, feet, and tail decrease. The biomechanical implications of these changes for motor development are discussed.

The accuracy and precision of gestational dating, based on single measurements of the fetal biparietal diameter (BPD), was estimated in a consecutive series of 970 apparently normal, singleton pregnancies. The BPD sizes used varied between 11 and 60 mm, corresponding to 9-22 postconceptional weeks. The 'conceptual ages', used for reference, were estimated by means of ultrasonic measurements of the fetal crown--rump lengths (CRL). The association between the estimated conceptual age (dependent variable) and BPD size (independent variable) was found to be well represented (R2 = 0.972) by a second order polynomial: conceptual age = 44.7 + 1.069 X BPD + 0.01382 X BPD X BPD. To check the validity of the proposed equation, we used 23 fetuses conceived by artificial insemination with donor semen as controls. There was good agreement between the virtual conceptual ages of the control cases and their corresponding BPD-estimated conceptual ages (0.5 days mean difference, 3.6 days SD) when the suggested regression equation was used. The estimated precision of BPD-dating was minumum +/- 4.4 days (= +/- 2SD) at 9-10 completed postconceptional weeks. At 14 completed weeks the corresponding precision was found to be +/- 11 days (+/- 2SD). At the end of the studied BPD size interval, i.e. 56-60 mm BPD corresponding to 22 conceptual weeks, the precision was +/- 15 days. From an obstetrical point of view it seems obvious that the imprecision of gestational dating associated with BPD measurements greater than 35 mm should call for ultrasonic dating procedures to be performed earlier in pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Summary. The association between fetal anthropometric measurements and conceptual age was determined for the femur length and the mean of two abdominal diameters for conceptual ages between 10 and 20 completed weeks. The conceptual age used for reference was determined by the fetal crown-rump length measured at an earlier examination. Two equations are presented for the calculation of conceptual age from isolated estimations of the femur length or the mean of two abdominal diameters. Mean abdominal diameter and femur length measurement values were found to have similar precisions of dating.

In a study of individual differences in neonates, frequencies and durations of spontaneous visual alertness were recorded and visual pursuit was measured in 32 2- to 3-day-old healthy neonates. Rank correlations of .60, .65, and .74 between the three visual measures suggested that infants who alerted frequently tended also to be the infants who alerted longest and who were most capable of visual pursuit. The results showed not only this intra-individual stability in the visual behaviors but also high variance between infants in their capacity for visual alertness. The infants' sex, parity, birthweight, estimated conceptual age, and postnatal age were not significantly related to the capacity for visual alertness, nor were the moderate levels of obstetric sedation used in this sample. The three visual measures, while tapping a shared capacity, had different correlates. Frequencies and durations of visual alertness were significantly related to a number of variables which had in common, moderate degrees of underlying activation and arousal. These factors did not contribute to visual pursuit. Sensitivity to auditory stimuli was significantly correlated with the capacity for visual pursuit but was unrelated to other visual measures.

The mean concentration of citric acid in male and non-pregnant female adult guinea pig plasma was 0.308 ± 0.042 mM. Pregnant females with fetuses of 49–69 days gestational age had mean maternal and fetal plasma concentrations of 0.440 ± 0.011 and 0.217 ± 0.053 mM, respectively. Maternal and fetal values were not correlated. Neonates up to 96 h old had plasma citrate values similar to those in the fetus. The citrate concentration of the amniotic fluid was lower than that in fetal plasma and showed a negative correlation with conceptual age (p < 0.01).

Plasma from six chronically catheterised sheep fetuses of 113–126 days conceptual age showed high levels of corticotrophin at all ages with somewhat higher values towards term. Plasma cortisol was not clearly related to corticotrophin in individual samples but was highly correlated in the pooled data. Short bouts of hypoxia (5–10 min 10% O2 in N2 to the mother) produced no significant change in either corticotrophin or cortisol although small transient changes in PO2 and lactate occurred. The high levels of corticotrophin suggest that the possibility of stress in the chronically catheterised preparation must be considered.

The effect on plasma insulin of elevating plasma glucose levels was studied in exteriorized sheep fetuses of 68 to 142 days conceptual age and in 2 lambs, 1 and 7 days old. Fetuses of less than 110 days showed, at most, only a very small and delayed rise in plasma insulin following an injection of glucose (1.67–3.45 g/kg body weight) into the umbilical vein. In 5 out of 6 fetuses of 110 days and older intravenous glucose (0.54–1.38 g/kg) was followed by a marked but delayed rise in plasma insulin reaching a peak 25–100 min after glucose administration. In the lambs intravenous glucose (1 g/kg) gave an immediate response in plasma insulin. Intraduodenal glucose was also seen to give a marked rise in plasma insulin in a 123 day fetus and 2 lambs. Intravenous fructose (0.65 and 0.55 g/kg) to two older fetuses caused no rise in plasma insulin although glucose given subsequently evoked a marked response. The onset of appearance of a marked response to glucose in the fetus was preceded by a proliferation of secondary islets in the pancreas. The changes in plasma insulin in the exteriorized fetuses and in 2 isolated fetuses suggest that the placenta must be relatively impermeable to insulin, fetal insulin must largely be derived from the fetal pancreas and fetal tissues must take up insulin.