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Objective It has been suggested that constriction of the umbilical vein (UV) at the umbilical ring has hemodynamic effects. We aimed to determine the occurrence and extent of such constriction in serial observations. Methods This was a prospective longitudinal study of UV velocities at the umbilicus measured at approximately 4-week intervals between 19 and 42 weeks' gestation in 129 low-risk singleton pregnancies. Each participant was examined three to five times. Multilevel modeling was used to construct the reference ranges and to test associations between variables. Results Gestational age-specific reference percentiles of UV velocities at the umbilicus were established based on 469 observations. Fetuses were able to alter the UV velocities considerably during the second half of pregnancy, signifying a varying degree of UV constriction. Of a total of 129 fetuses, 56 (43.4%) never had high UV blood velocity (i.e. > 46 cm/s, the highest quartile), 42 (32.6%) fetuses had high UV blood velocity on one occasion and 31 (24.0%) fetuses on two or more occasions. In 36 (27.9%) fetuses the UV velocity at the umbilical ring was > 300% of the mean gestational age-specific reference value at the intra-abdominal section on at least one occasion. Constriction of the UV at the umbilical ring did not affect the pulsatility of the umbilical artery, and was not associated with adverse perinatal outcome in this study. Conclusions Low-risk fetuses may well constrict the UV at the abdominal wall with velocities extending over wide ranges on one or more occasions during the second half of pregnancy. Rather than being a risk for complications, the constriction seems to be part of physiological development and possibly a regulatory mechanism. [ABSTRACT FROM AUTHOR]

Objective To construct reference ranges for serial measurements of umbilical artery (UA) blood flow velocity and pulsatility index (PI) at standardized insonation sites during the second half of pregnancy. Methods This was a prospective longitudinal study of the umbilical circulation. UA blood flow velocities were measured at the intra-abdomninal portion, fetal end and placental end at 4-weekly intervals at 19–42 weeks of gestation in 130 low-risk singleton pregnancies. A total of 513 observations were used to construct the reference ranges using regression statistics and multilevel modeling. Results UA blood velocities and PI were higher at the intra-abdominal portion and fetal end than at the placental end. The gestational age-related increase of end-diastolic velocity was greater than the corresponding increase of the peak systolic velocity at all locations. The mean differences (delta values) of UA blood velocities between the fetal and placental ends increased and that of PI decreased with advancing gestational age. Conclusion UA Doppler parameters vary significantly at different locations. We have established new reference ranges for the UA velocities and PI at standardized locations based on longitudinal observations, which should be useful for the surveillance of fetuses with repeated observations. [ABSTRACT FROM AUTHOR]

Objectives: To construct reference ranges for serial measurements of the umbilical artery (UA) absolute blood flow velocities in the second half of pregnancy and to test the hypothesis that significant associations exist between UA velocities and placental volume blood flow assessed from umbilical vein blood flow velocities and diameter. Methods: This was a prospective longitudinal study of the umbilical circulation. UA absolute velocities and umbilical vein blood flow were measured at 4-weekly intervals between 19 and 42 weeks' gestation in 130 low-risk singleton pregnancies. A total of 511 observations were used to construct the reference ranges and assess the association between UA absolute velocities and placental volume flow using multilevel modeling. Results: Both UA absolute velocities and placental volume blood flow showed a steady increase throughout the second half of pregnancy. However, the gestational age-related increase in the UA end-diastolic velocity (EDV) was greater than the corresponding increase in the peak systolic velocity (PSV). The time-averaged intensity-weighted mean velocity (TAWMV)/time-averaged maximum velocity (TAMXV) was 0.6 indicating probably not a completely parabolic velocity profile. There was a significant positive association (P < 0.00001) between UA absolute velocities and placental volume blood flow, but this association was modified by the gestational age. The intraobserver coefficients of variation for the UA PSV, EDV, TAMXV and TAWMV and placental volume blood flow were 10.17%, 16.29%, 11.46%, 18.18% and 8.61%, respectively. Conclusion: We have established new reference ranges for the UA absolute velocities based on longitudinal data. They show a significant association with fetoplacental volume blood flow and may have a clinical value in the assessment of the umbilical circulation. [ABSTRACT FROM AUTHOR]

. In a material of 144 samples of amniotic fluid from the last trimester, creatinine concentration, lecithin/sphingomyelin (L/S) ratio and their correlation, have been examined. Amniotic fluid creatinine concentration (a.f.c.) increased gradually through the last trimester up to 39 weeks (273-279 days p.m.) with median values of 2 mg/100 ml at 37 weeks and 2.5 mg/100 ml at 39 weeks gestation. The great range makes a.f.c. of doubtful value in assessment of gestional age in individual samples. The correlation between a.f.c. and L/S ratio was highly significant (Kendall's T=0.56). Even so lung maturity cannot be predicted from a.f.c. A low L/S ratio with a.f.c. ≥2 mg/100 ml was found in 8-9%, while a.f.c. 1.1-1.9 mg/100 ml was combined with L/S ratios ≥2 in a great number of cases. A.f.c. <1.1 mg/100 ml was invariably correlated with low L/S ratios. [ABSTRACT FROM AUTHOR]

The frequency and severity of retinal hemorrhages were studied in 200 newborns within the first 72 hours of life. One hundred of the neonates were delivered instrumentally by either forceps (49 cases) or vacuum extraction (51 cases). Another hundred neonates were delivered spontaneously and served as controls. Both the highest and the lowest frequency of retinal hemorrhages were found among the babies delivered by instrumentation. The actual values were 50 per cent in the vacuum group and only 16 per cent in the forceps group (p<0.01). The spontaneously delivered babies, who served as controls, showed retinal hemorrhages in 41 per cent of the cases. The frequency of severe retinal hemorrhages was five times higher in the vacuum group compared to both the forceps group and the control group (p<0.01, p<0.001). [ABSTRACT FROM AUTHOR]