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Biomedical subjects

Torvid Kiserud

Publications and source records attributed to Torvid Kiserud.

16 recordsLinked to original sources
PubMed2006

Foetal size and body proportion at 17-19 weeks of gestation and neonatal size, proportion, and outcome.

OBJECTIVE: To determine whether proportionate or disproportionate foetal smallness at 17 to 19 weeks of gestation in low-risk pregnancies was associated with size, body constitution, and adverse outcome at birth. METHODS: We included ultrasound measurements at 17-19 weeks of gestation in 7285 uncomplicated pregnancies with reliable information on last menstrual period. We considered a foetus with both mean abdominal diameter (MAD) and biparietal diameter (BPD) below the 10th percentile for gestational age, gender, and parity as symmetrically small. Those who had MAD below the 10th percentile and BPD at or above the 10th percentile were asymmetrically small (thin and small). RESULTS: The occurrence of small for gestational age (SGA) (birth weight below the 10th percentile) decreased with increasing second trimester MAD percentile (P<0.0001). The risk in foetuses which were both thin and extremely small (MAD below the 2.5th percentile) of having weight, ponderal index, crown-heel length, or head circumference below the 10th percentile at birth was 19-28%. The risk of perinatal composite outcome (prenatal death, Apgar score after 5 min < or =7, birth weight below the 10th percentile, or <1500 g, or preterm birth) was 37%. Apgar score of < or =7 at 5 min and explained foetal death both occurred in 7%, which was significantly higher than those with larger MAD. CONCLUSION: Asymmetric as well as symmetric foetal smallness may start early in pregnancy. Symmetric and particularly asymmetric small foetuses at 17-19 weeks of gestation were generally lighter, shorter, and thinner at birth and had more often adverse perinatal outcome.

Abdomen↗
PubMed2006

Longitudinal reference ranges for estimated fetal weight.

OBJECTIVE: The aims of the present study were to establish reference ranges for the growth of estimated fetal weight (EFW) between gestational weeks 20 and 42 and to determine the effect of fetal and maternal factors. METHODS: This prospective longitudinal study was based on 634 low-risk pregnancies and a total of 1799 examinations. Gestational age was computed from last menstrual period. Head circumference, abdominal circumference, and femur length were measured using ultrasound, and EFW was calculated using the formula of Combs et al. The statistical analysis was based on regression analysis and multilevel modeling. RESULTS: Intrauterine growth expressed by EFW showed a continuous pattern until term. Males were calculated to be 5% heavier than female fetuses at 20 gestational weeks and 3% at 40 weeks. Otherwise, the fetal and maternal effects on intrauterine growth correspond to a weight shift of 1.3% for breech/nonbreech, 2.5% for each increase in maternal height tertile, and -4% for smoking/nonsmoking. Maternal age higher than 34 years had a significant increased EFW of 4.5% compared with maternal age less than 24 years. Cephalic index in the third tertile had a 1.1% lower EFW compared with the first tertile. Maternal weight, body mass index, and parity did not influence the EFW. Terms for customization to individualize the growth patterns are presented. CONCLUSIONS: The present growth chart is recommended as robust reference ranges for assessing EFW and growth. Fetal and maternal variables can be added into the models to individualize the prediction of EFW.

Adult↗
PubMed2006

Accuracy of second trimester fetal head circumference and biparietal diameter for predicting the time of spontaneous birth.

AIMS: Previous studies suggested that head circumference (HC) predicts the date of confinement better than the biparietal diameter (BPD). The present study aimed to prospectively test this assumption. METHODS: A prospective study including 4179 consecutive women attending the second trimester routine ultrasound examination at 17-20 weeks of gestation. Outer-outer BPD and HC were determined as the average of three repeated measurements. Twins were excluded. Time of delivery was noted, the differences between this and the predicted date of delivery calculated with HC and BPD (based on a pregnancy duration of 282 days), and the two methods were compared using Wilcoxon signed rank test. RESULTS: For the entire group, the median differences between actual and predicted delivery with HC and BPD were 0.9 and 1.2 days, respectively. For deliveries with a spontaneous onset of labor (n=3336) the corresponding differences were 0.9 and 1.4 days. The difference between the HC and BPD methods was significant (P<0.0001). In the group of spontaneous onset of labor, there were 05.6% post-term pregnancies (>or=296 days) according to HC and 5.7% according to BPD. CONCLUSION: Provided that the expected pregnancy duration was 282 days, both HC and BPD predicted spontaneous birth with a mean accuracy of one day, HC being significantly better than BPD.

Anthropometry↗
PubMed2005

Longitudinal reference charts for growth of the fetal head, abdomen and femur.

OBJECTIVES: The aims of the present study were to establish improved reference charts for growth of the fetal head, abdomen and femur, and to determine the effect of fetal and maternal factors. STUDY DESIGN: This prospective longitudinal study included 650 low-risk pregnancies. Outer-outer biparietal diameter (BPD), head circumference (HC), mean abdominal diameter (MAD), abdominal circumference (AC) and femur length (FL) were measured by ultrasound, and the statistical analysis was based on regression analysis and multilevel modeling. RESULTS: Reference percentiles for the growth of MAD, AC and FL showed continuous growth in gestational week 10-40, while BPD and HC showed a slightly blunted growth toward the end of pregnancy. FL was the only variable that was not influenced by gender. There was a significant negative association between breech presentation and all five biometrical variables, while maternal weight was positively associated with all five variables. Cephalic index significantly influenced BPD and HC. Maternal height had a positive effect on BPD, HC, AC and FL, and parity had a positive effect on MAD and AC, while smoking influenced negatively HC, MAD, and FL. Terms for calculating conditional reference values and customisation for individualised growth assessment are presented. CONCLUSIONS: New reference charts for the growth of fetal head, abdomen and femur are suggested for assessing fetal size and growth, and can be adjusted for maternal and fetal factors to suite individual pregnancies.

Abdomen↗
PubMed2005

Physiology of the fetal circulation.

Our understanding of fetal circulatory physiology is based on experimental animal data, and this continues to be an important source of new insight into developmental mechanisms. A growing number of human studies have investigated the human physiology, with results that are similar but not identical to those from animal studies. It is time to appreciate these differences and base more of our clinical approach on human physiology. Accordingly, the present review focuses on distributional patterns and adaptational mechanisms that were mainly discovered by human studies. These include cardiac output, pulmonary and placental circulation, fetal brain and liver, venous return to the heart, and the fetal shunts (ductus venosus, foramen ovale and ductus arteriosus). Placental compromise induces a set of adaptational and compensational mechanisms reflecting the plasticity of the developing circulation, with both short- and long-term implications. Some of these aspects have become part of the clinical physiology of today with consequences for surveillance and treatment.

Blood Circulation↗
PubMed2005

Reference ranges for umbilical vein blood flow in the second half of pregnancy based on longitudinal data.

OBJECTIVES: To construct new reference ranges for serial measurements of umbilical vein (UV) blood flow. METHODS: Prospective longitudinal study of blood flow velocities and diameter of the UV measured at four-weekly intervals during 19 to 42 weeks' gestation in 130 low-risk singleton pregnancies. Regression models and multilevel modeling were used to construct the reference ranges. RESULTS: On the basis of 511 sets of longitudinal observations, we established new reference percentiles of UV diameter, blood flow velocities, volume flow, and blood flow normalized for fetal weight and abdominal circumference. They reflected some of the developmental patterns of previous cross-sectional studies, but with important differences, particularly near term. The UV blood flow showed a continuous increase until term, whereas the flow normalized per unit fetal weight, a corresponding reduction. Calculating the blood flow on the basis of intensity-weighted mean velocity or 0.5 of the maximum velocity gave almost interchangeable results for most fetuses. CONCLUSION: New reference ranges for UV blood flow based on longitudinal observations appear slightly different from cross-sectional studies, and should be more appropriate for serial evaluation of fetal circulation.

Adolescent↗
PubMed2005

Reference ranges for serial measurements of umbilical artery Doppler indices in the second half of pregnancy.

OBJECTIVE: The purpose of this study was to construct new reference ranges for serial measurements of commonly used umbilical artery Doppler indices (pulsatility index, resistance index, and systolic:diastolic ratio). STUDY DESIGN: This was a prospective longitudinal study of the umbilical artery Doppler indices that were obtained serially at the free-loop of umbilical cord at 4-week intervals at 19 to 42 weeks of gestation in 130 low-risk singleton pregnancies. A total of 513 observations were used to construct the reference ranges with the use of multilevel modeling. RESULTS: Longitudinally established percentiles of Doppler indices from the present study show a continuous reduction throughout the second half of pregnancy without any plateau or increase near term, as reported previously. There was a significant negative association between Doppler indices and placental weight and neonatal birth weight, but not with gender. The intraobserver coefficients of variation for the umbilical artery pulsatility index, resistance index, and systolic:diastolic ratio were 10.5%, 6.8 %, and 13.0 %, respectively. CONCLUSION: New reference ranges for umbilical artery Doppler indices that are based on longitudinal observations appear to be slightly different from cross-sectional studies and are more appropriate for serial evaluation of fetal hemodynamics.

Adolescent↗
PubMed2005

Fetal age assessment based on femur length at 10-25 weeks of gestation, and reference ranges for femur length to head circumference ratios.

BACKGROUND: The aim of the present study is to establish new reference charts for gestational age assessment based on fetal femur length (FL), and new reference ranges for FL to head ratios at gestational weeks 10-25, and to determine the effect of maternal and fetal factors on these charts. METHODS: Six hundred fifty low-risk women with regular menstrual periods and singleton pregnancies were recruited to a prospective cross-sectional study after obtaining written consent. FL, outer-outer biparietal diameter (BPD), and head circumference (HC) were measured at 10-25 weeks of gestation. We used regression analysis in order to construct mean curves and to assess the effect of maternal and fetal factors on age assessment. RESULTS: The new chart for age assessment by means of FL was based on 636 measurements. The 95% CI of the mean corresponded to <1 day. The variation between the mean and the 90th percentile was 5, 6, and 7 days at 13, 18, and 23 weeks, respectively, similar to the results when using BPD or HC. Maternal age modestly influenced gestational age assessment (1.3 days/10 years, P = 0.005), whereas smoking, height, body mass index, multiparity, fetal sex, cephalic index, and breech presentation had no impact. Reference charts for FL to head ratios have been presented. Maternal age, fetal sex, and cephalic index influenced the FL/BPD ratio, whereas only fetal sex influenced FL/HC. CONCLUSIONS: Fetal age assessment based on FL is an equally robust method as using HC. FL/HC is a more robust ratio to characterize fetal proportions than is FL/BPD.

Adolescent↗
PubMed2004

The fetal circulation.

Accumulating data on the human fetal circulation shows the similarity to the experimental animal physiology, but with important differences. The human fetus seems to circulate less blood through the placenta, shunt less through the ductus venosus and foramen ovale, but direct more blood through the lungs than the fetal sheep. However, there are substantial individual variations and the pattern changes with gestational age. The normalised umbilical blood flow decreases with gestational age, and, at 28 to 32 weeks, a new level of development seems to be reached. At this stage, the shunting through the ductus venosus and the foramen ovale reaches a minimum, and the flow through the lungs a maximum. The ductus venosus and foramen ovale are functionally closely related and represent an important distributional unit for the venous return. The left portal branch represents a venous watershed, and, similarly, the isthmus aorta an arterial watershed. Thus, the fetal central circulation is a very flexible and adaptive circulatory system. The responses to increased afterload, hypoxaemia and acidaemia in the human fetus are equivalent to those found in animal studies: increased ductus venosus and foramen ovale shunting, increased impedance in the lungs, reduced impedance in the brain, increasingly reversed flow in the aortic isthmus and a more prominent coronary blood flow.

Animals↗
PubMed2004

Fetal liver-sparing cardiovascular adaptations linked to mother's slimness and diet.

Fetal adaptations to impaired maternoplacental nutrient supply include altered regional blood flow. Whether such responses operate within the normal range of maternal body composition or diet is unknown, but any change in fetal liver perfusion could alter hepatic development, with long-term consequences for the risk of cardiovascular and metabolic disease. In 381 low-risk pregnancies, we found that the fetuses of slimmer mothers with lower body fat stores and those eating an unbalanced diet had greater liver blood flow and shunted less blood away from the liver through the ductus venosus at 36 weeks gestation. Consequences of such "liver-sparing" may underlie the increased cardiovascular risk of people whose mothers were slimmer and had lower body fat stores in pregnancy.

Adaptation, Physiological↗
PubMed2004

The effect of umbilical venous constriction on placental development, cord length and perinatal outcome.

BACKGROUND: Umbilical vein constriction at the fetal abdominal inlet is a common finding after week 13, when the period of umbilical herniation is brought to an end. AIMS: To test the hypothesis that a constricting umbilical ring within physiological ranges affects fetal hemodynamics by either pooling blood in the placenta or restricting nutrient transfer to the fetus and thus shift the birthweight/placental weight (BW/PW) ratio. A constriction could also cause pressure changes and elongation of the cord and possibly be a disadvantage during labour. STUDY DESIGN: Cross-sectional. SUBJECTS: 359 Low-risk singleton pregnancies at 13-40 weeks of gestation. OUTCOME MEASURES: Standard deviation score (z-score) and regression analysis were used to determine the effect of umbilical vein constriction (expressed by increased blood velocity) on birthweight/placental weight ratio (BW/PW), cord length, Apgar score and emergency delivery due to fetal distress. RESULTS: Umbilical venous constriction had a mild but significant effect on BW/PW in male (p=0.018) but not in female fetuses. Increased constriction was also associated with increased length of the cord but only in female fetuses (p=0.019). Cord length was positively related to birthweight and placental weight, but an increased length of the cord was also associated with decreasing BW/PW ratio for the male fetuses only (p=0.044). Increasing degree of venous constriction was associated with Apgar score < or =7 at 1 (p=0.009) but not at 5 min after birth and was not associated with emergency delivery. CONCLUSION: Physiological umbilical venous constriction exerts a mild but significant gender-specific hemodynamic impact on intrauterine development.

Adolescent↗
PubMed2004

[Parvovirus B19 infection--dangerous for the fetus].

BACKGROUND: Human parvovirus B19 infection is a common and usually benign disease in children, but may cause severe complications in pregnancy. We determined the proportion of the pregnant population at risk of infection and present a recent cluster of cases with fetal complications, hoping to raise the general awareness. MATERIAL AND METHODS: Five cases of fetal parvovirus B19 infection during 2001--2 illustrate the delay in diagnosis, treatment and outcome. During the same period, the number of positive and negative serological tests was noted for the catchment area and the entire country. Additionally, 206 consecutive pregnant women were tested to determine susceptibility. RESULTS: Out of the five cases of fetal complications, all had cardiac involvement, three had anaemia, and two fetuses died. Lag-time to fetal diagnosis was six, eight, and 13 weeks for those with known maternal disease. In Norway, seroconversion is similar to that found in other Nordic countries; 36 % (74/206) of the pregnant population is seronegative. In Norway, parvovirus B19 infection is more frequently reported in the January-June period. A third of the pregnant population is susceptible to infection. Early testing in cases of exposure or suspected infection in pregnancy is recommended in order to ensure appropriate follow-up and treatment.

Disease Susceptibility↗
PubMed2004

Fetal age assessment based on ultrasound head biometry and the effect of maternal and fetal factors.

BACKGROUND: Maternal height and weight have increased during the past 20 years, as has birthweight. The aim of the present study was to establish new reference charts for gestational age (GA) assessment using fetal biparietal diameter (BPD) and head circumference (HC), and to determine the effect of maternal and fetal factors on age assessment. METHODS: This was a prospective, cross-sectional study of 650 healthy women with regular menstrual periods and singleton uncomplicated pregnancies, recruited after written consent. BPD (outer-outer) and HC were measured at 10-24 weeks of gestation. We used regression analysis to construct mean curves and assess the effect of maternal and fetal factors on age assessment. RESULTS: BPD and HC were successfully measured in 642 participants. Using BPD and HC before 20 weeks, the new charts gave 3-8 days higher GA assessment than the charts presently in use, and <1 day difference compared to other recently established charts. Maternal age, multiparity, fetal gender, breech position and shape of fetal head affect GA estimation by 1-2 days when using BPD (p = 0.0001-0.02). Only maternal age and fetal gender affected GA estimation when using HC (</= 1 day, p = 0.001). CONCLUSIONS: Our new charts for assessing gestational age based on fetal head biometry are notably different from charts presently in use. Maternal and especially fetal factors affect gestational age assessment when using BPD, but less so for the HC method, which is suggested as the more robust method.

Adolescent↗
PubMed2003

The left portal vein is the watershed of the fetal venous system.

Critical fetal organs are preferentially supplied with oxygenated blood from the umbilical vein (UV) by way of the ductus venosus (DV). Under normal conditions a significant part of UV-blood flows steadily forward through the left portal vein (LPV). Blood flow through the LPV could reverse, however, in cases of absent or reversed endodiastolic flow in the umbilical arteries. We tested when fetal blood flow reversal occurs by studying 28 cases with pathological flow in the umbilical artery. In the LPV we observed normal nonpulsatile forward flow in 9 cases, pulsatile forward flow in 10 cases, and reversed flow in 9 cases. Reverse flow in the LPV correlated significantly with an elevated resistance index of the umbilical arteries. This reversal could have major physiological implications: Deoxygenated blood may be added via the LPV to the blood shifted through the DV and ultimately reach critical fetal organs. In extremis there could be a waterhose effect, whereby more blood flows through the DV than the UV that supplies it. The LPV is thus the watershed of the venous circulation of the fetus.

Female↗
PubMed2002

Degree of fetal umbilical venous constriction at the abdominal wall in a low-risk population at 20-40 weeks of gestation.

OBJECTIVES: To determine the degree of constriction of the umbilical vein at the abdominal wall in the second half of pregnancy. METHODS: A total of 283 low-risk singleton pregnancies were recruited for a cross-sectional study, and examined once at 20-40 weeks of gestation. Two sets of ultrasound measurements of the umbilical vein were taken: one at the fetal end of the umbilical cord and another at the inlet through the abdominal wall, the umbilical ring. The diameter was determined as an average of >or=5 repeat measurements. The blood velocity was recorded at the same site. RESULTS: The time-averaged maximum venous blood velocity in the cord was low (mean 13-19 cm/s during 20-40 weeks of gestation), and the corresponding mean diameter 3.6-8.2 mm. In contrast, the mean of the venous blood velocity at the umbilical ring was 34-41 cm/s and the diameter was 2.8-5.9 mm during the same period. Of 191 pairs of observations, 41 (21%) had a velocity increment of >or=300 %, which corresponds to a diameter reduction to half or more at the umbilical ring. CONCLUSION: Constriction of the umbilical ring is a common phenomenon in the second half of pregnancy.

Adult↗