Pre-gestational diabetes: Maternal body mass index and gestational weight gain are associated with augmented umbilical venous flow, fetal liver perfusion, and thus birthweight.

OBJECTIVES: To assess how maternal body mass index and gestational weight gain are related to on fetal venous liver flow and birthweight in pregnancies with pre-gestational diabetes mellitus. METHODS: In a longitudinal observational study, 49 women with pre-gestational diabetes mellitus were included for monthly assessments (gestational weeks 24-36). According to the Institute Of Medicine criteria, body mass index was categorized to underweight, normal, overweight, and obese, while gestational weight gain was classified as insufficient, appropriate or excessive. Fetal size, portal flow, umbilical venous flow and distribution to the fetal liver or ductus venosus were determined using ultrasound techniques. The impact of fetal venous liver perfusion on birthweight and how body mass index and gestational weight gain modified this effect, was compared with a reference population (n = 160). RESULTS: The positive association between umbilical flow to liver and birthweight was more pronounced in pregnancies with pre-gestational diabetes mellitus than in the reference population. Overweight and excessive gestational weight gain were associated with higher birthweights in women with pre-gestational diabetes mellitus, but not in the reference population. Fetuses of overweight women with pre-gestational diabetes mellitus had higher umbilical (p = 0.02) and total venous liver flows (p = 0.02), and a lower portal flow fraction (p = 0.04) than in the reference population. In pre-gestational diabetes mellitus pregnancies with excessive gestational weight gain, the umbilical flow to liver was higher than in those with appropriate weight gain (p = 0.02). CONCLUSIONS: The results support the hypothesis that umbilical flow to the fetal liver is a key determinant for fetal growth and birthweight modifiable by maternal factors. Maternal pre-gestational diabetes mellitus seems to augment this influence as shown with body mass index and gestational weight gain.

The added value of umbilical vein flow in predicting fetal macrosomia at 36 weeks of gestation: A prospective cohort study.

INTRODUCTION: Current models based on fetal biometry and maternal characteristics have a poor performance in predicting macrosomia. The primary aim of this study was to elucidate the diagnostic performance of fetal venous and arterial Dopplers in predicting macrosomia in the third trimester of pregnancy; the secondary aim was to build a multiparametric prediction model including pregnancy, ultrasound and Doppler characteristics able to predict macrosomia accurately. MATERIAL AND METHODS: Prospective cohort study including 2156 singleton pregnancies scheduled for routine ultrasound assessment at 36 weeks of gestation. Fetal biometry, estimated fetal weight (EFW), pulsatility index of the uterine, umbilical, and middle cerebral arteries, cerebroplacental ratio and umbilical vein blood flow (UVBF) normalized for fetal abdominal circumference (UVBF/AC) were recorded. Primary outcome was the prediction of fetal macrosomia, defined as a birthweight >90th percentile; secondary outcome was the prediction of newborns >4000 g. Logistic regression and area under the curve (AUC) analyses were used to analyze the data. RESULTS: Fetal macrosomia complicated 9.8% of pregnancies, and 7.7% of newborns had a birthweight >4000 g. At multivariate logistic regression analysis, maternal body mass index (adjusted odds ratio [aOR] 1.23), pregestational diabetes (aOR 1.83), a prior newborn with a birthweight >95th centile (aOR 1.49), EFW (aOR 2.23) and UVBF (aOR1.84) were independently associated with macrosomia, whereas gestational diabetes mellitus (P = .07) or any of the other Doppler parameters were not. EFW had an AUC of 0.750 and of 0.801 alone and in association with maternal characteristics for the prediction of macrosomia, respectively. The addition of UVBF to this model significantly improved the prediction of fetal macrosomia provided by maternal and ultrasound parameters with an AUC of 0.892 (De Long P = .044 and P = .0078, respectively). The predictive performance for birthweight >4000 g was similar and significantly improved when UVBF was included in the diagnostic algorithm. CONCLUSIONS: Umbilical vein blood flow evaluation in the third trimester improves the diagnosis of fetal macrosomia. The optimal diagnostic performance for macrosomia is achieved by a multiparametric model including umbilical vein flow, maternal characteristics and EFW.

The impact of umbilical vein blood flow and glucose concentration on blood flow distribution to the fetal liver and systemic organs in healthy pregnancies.

Glucose is a major energy substrate for the fetus, including liver, heart, and brain metabolism. The umbilical vein (UV) blood flow supplies the fetal liver directly from the placenta, whereas a fraction is shunted via ductus venosus (DV) to the fetal systemic circulation bypassing the fetal liver. We hypothesized UV glucose concentration to be a major regulator of the distribution of glucose supply between the fetal liver and DV, and explored the influence of maternal metabolic status on this distribution. We included 124 healthy women with normal singleton pregnancies, scheduled for elective cesarean section. UV and DV blood flow measurements were performed by Doppler ultrasound immediately before, and blood samples were obtained during surgery. UV blood flow was significantly correlated with DV blood flow, liver blood flow, and the DV shunting fraction, while UV glucose concentration was not. For normal-weight mothers, the maternal-fetal glucose gradient was positively correlated with DV shunting fraction, and negatively with liver blood flow. For the fetuses of the overweight mothers no such correlation was found. This indicates that within the normal physiological range the human fetus makes adaptations of blood flow to ensure individual needs related to the offered maternal energy supply.

A computational fluid dynamics modelling of maternal-fetal heat exchange and blood flow in the umbilical cord.

Human fetal thermoregulation, maternal-fetal heat exchange, and the role of the umbilical cord in these processes are not well understood. Ethical and technical limitations have restricted current knowledge to animal studies, that do not reflect human morphology. Here, we present the first 3-dimensional computational model of the human umbilical cord with finite element analysis, aiming to compute the maternal-fetal heat exchange. By modelling both the umbilical vein and the two umbilical arteries, we found that the coiled geometry of the umbilical artery, in comparison with the primarily straight umbilical vein, affects blood flow parameters such as velocity, pressure, temperature, shear strain rate and static entropy. Specifically, by enhancing the heat transfer coefficient, we have shown that the helical structure of the umbilical arteries plays a vital role in the temperature drop of the blood, along the arterial length from the fetal end to the placental end. This suggests the importance of the umbilical cord structure in maternal-fetal heat exchange and fetal heat loss, opening the way for future research with modified models and scenarios, as the basis for early detection of potential heat-transfer related complications, and/or assurance of fetal wellbeing.

Normal variants of ductus venosus spectral Doppler flow patterns in normal pregnancies.

Objectives: Ductus venosus (DV) Doppler examinations in pregnancy have a widespread use for several important indications and play a crucial role in order to determine the fetal well-being. DV is usually visualized by the color Doppler mapping. We observed the instantaneous spectral flow type changes in pulsed Doppler examinations in spite of performing with the correct technique published by several authors. The variability of the pattern makes the sonographer/physician to be unsure for the correct placements of the sample gate despite fulfilling the all the criteria required for the vessel sampling. It is aimed in the study to define variations of the normal DV spectral flow types in the duration of the pulsed Doppler examinations instead of in a single cardiac cycle in normal pregnancies.Methods: This prospective study was conducted between January 2016 and February 2017. Wide-band Doppler technique was used for color mapping of the DV. Normal spectral Doppler waveforms in pregnancies are classified as types. When DV spectral flow pattern was not in the standard type, the spectral flow patterns were obtained from not only the umbilical artery and/or middle cerebral artery. Maximum and minimum blood flow velocities in the umbilical vein are measured. All Doppler examinations are performed by a single experienced specialist (CG), who had been certificated for DV flow and Doppler examinations by the Fetal Medicine Foundation.Results: A total of seven types of flow patterns were recorded during the study period and DV flow patterns were divided into two main categories as classic flow pattern and the other patterns. The classic pattern was observed in 160 (99.4%) cases in the first trimester, 495 (94.1%) cases in the second trimester and 206 (60.8%) cases in the third trimester.Conclusions: We think that the fetal circulation is complicated more than estimated. There might be some endocrine agents released in the instantaneous physiologic reactions and changing the venous return abruptly or due to decreasing of the cardiac output directed to the placenta after 34 weeks influence the volume of the circulating blood in the fetus and so thereby the flow velocities instantaneously. The spectral waveform recognition approach is not reliable to identify if the DV spectral Doppler pattern is not the classic (standard) type and the DV should be visualized by wide-band color Doppler techniques particularly in the third trimester for the pulsed Doppler examinations. Studies are needed to evaluate the normal spectral variants of the flows correlated with the physiological compensatory mechanisms.

Is umbilical vein varix associated with changes in cerebroplacental ratio?

Objective: We aimed to review a single-center experience in follow-up and management of fetuses with umbilical vein varix (UVV) and to assess the effect of UVV on fetal Doppler parameters.Methods: We reviewed retrospectively maternal antenatal records, delivery records, and newborn records to identify cases of UVV. Further, we retrospectively compared 25 fetuses with isolated UVV and available cerebroplacental ratio (CPR) analysis with 75 matched controls.Results: We identified 67 cases of UVV. The median gestational age (GA) at diagnosis was 34 weeks (range: 26-41 weeks). The average diameter of UVV at diagnosis was 10.1 mm (range: 9-14 mm). The median GA at delivery was 36 + 6 (range: 33-41 weeks), with an average birth weight of 2918 g (range: 1278-4140 g). There was a single case of intrauterine death at 35 weeks. CPR was 2.13 ± 0.62 in isolated UVV group compared with 1.84 ± 0.61 in the control group (p < .05). Other Doppler parameters did not differ between fetuses with UVV compared with controls.Conclusions: CPR was significantly increased in the UVV group compared with control fetuses. This finding suggests that UVV is not associated with chronic fetal oxygen deprivation; it, therefore, may contribute to our understanding of the pathophysiology explaining abnormal pregnancy outcome in cases with UVV.

Large fetal intra-abdominal umbilical vein varix: Antenatal sonographic diagnosis and follow-up.

Fetal intra-abdominal umbilical vein varix is an uncommon antenatal finding defined as focal dilatation of umbilical vein >9 mm or more than two standard deviations above the mean for the gestational age. We report the case of a 28-year-old gravida 2 diabetic lady, who presented at 35 weeks of gestation, whose antenatal ultrasonography showed a cystic lesion of size 4 × 3.8 cm showing turbulent venous flow in the fetal abdomen in continuity with the umbilical vein, diagnosed as umbilical vein varix without any other anomaly. Postnatal ultrasonography showed size reduction and thrombosis of varix. Isolated umbilical vein varix has a favorable outcome, whereas those associated with other structural anomalies have a variable prognosis. This case was reported because of the unusually large size of varix with a good outcome and also to stress the importance of detailed sonography and close fetal monitoring in the presence of umbilical vein varix.

Fetal Intra-abdominal Umbilical Vein Aneurysm.

IMPORTANCE: Fetal umbilical vein aneurysm is an uncommon anomaly that accounts for approximately 4% of umbilical cord abnormalities. The rate of intrauterine fetal death is reported to be approximately 4% to 5%, higher than the background rate of 0.7% that is generally reported during pregnancy. OBJECTIVE: The aim of this study was to review the pathophysiology, diagnosis, and clinical management of fetal umbilical vein aneurysm. EVIDENCE ACQUISITION: Advances in high-resolution ultrasound combined with color Doppler and 3-dimensional rendering have contributed to an increased understanding of the fetal venous circulation in recent years. RESULTS: When the diagnosis of umbilical vein aneurysm is made, the patient should undergo a detailed ultrasound evaluation of the fetal anatomy, including fetal echocardiography, to exclude associated anomalies. Amniocentesis should be offered when other anomalies are found. Patients should be informed about the potential for an unfavorable outcome of pregnancy and should undergo close ultrasound surveillance to assess the size of the aneurysm, as well as any evidence of thrombosis or signs of hydrops. CONCLUSIONS: The main prognostic feature associated with a poor outcome of umbilical vein aneurysm seems to be the presence of other anomalies. Early diagnosis is associated with a somewhat worse prognosis, and most fetal deaths have been observed between 27 and 30 weeks of gestation. In the third trimester, it is reasonable to perform serial ultrasound examinations to assess fetal growth, the size of the aneurysm, and the blood flow pattern within the aneurysm.

The 4-vessel Sampling Approach to Integrative Studies of Human Placental Physiology In Vivo.

The human placenta is highly inaccessible for research while still in utero. The current understanding of human placental physiology in vivo is therefore largely based on animal studies, despite the high diversity among species in placental anatomy, hemodynamics and duration of the pregnancy. The vast majority of human placenta studies are ex vivo perfusion studies or in vitro trophoblast studies. Although in vitro studies and animal models are essential, extrapolation of the results from such studies to the human placenta in vivo is uncertain. We aimed to study human placenta physiology in vivo at term, and present a detailed protocol of the method. Exploiting the intraabdominal access to the uterine vein just before the uterine incision during planned cesarean section, we collect blood samples from the incoming and outgoing vessels on the maternal and fetal sides of the placenta. When combining concentration measurements from blood samples with volume blood flow measurements, we are able to quantify placental and fetal uptake and release of any compound. Furthermore, placental tissue samples from the same mother-fetus pairs can provide measurements of transporter density and activity and other aspects of placental functions in vivo. Through this integrative use of the 4-vessel sampling method we are able to test some of the current concepts of placental nutrient transfer and metabolism in vivo, both in normal and pathological pregnancies. Furthermore, this method enables the identification of substances secreted by the placenta to the maternal circulation, which could be an important contribution to the search for biomarkers of placenta dysfunction.

Parity Conditions the Risk for Low Birth Weight after Maternal Exposure to Air Pollution.

Multiparous mothers have greater umbilical blood flow and thus more efficient transport of pollutants than primiparous mothers. We tested a hypothesis that multiparous mothers are more prone to have an infant with low birth weight (LBW) after prenatal exposure to air pollution. A study was conducted on a representative group of more than 74,000 singleton, live, full-term infants. Birth data were obtained from the birth registry, while pollution data were from an environmental monitoring system (Poland). Multiple comparisons were controlled by the false discovery rate procedure (FDR). After standardization, the harmful effect of carbon monoxide (CO) on the odds ratio (OR) for LBW was seen among the multiparous mothers (OR = 1.28; 95% CI 1.06-1.54), while in primiparous mothers it was nonsignificant. The effect of CO on the OR for LBW differed according to parity, which was confirmed by the test for interaction (FDR-adjusted p = 0.03). The interaction between parity and sulfur dioxide (SO2) was statistically nonsignificant (FDR-adjusted p = 0.08). Multiparous mothers may be more vulnerable to CO than primiparous mothers. Parity may be the modifier of the association between pollutants and the risk of LBW.

[Ectopic varices in the terminal ileum causing gastrointestinal bleeding]. / Ektopiske varicer i den distale ileum som årsag til gastrointestinal blødning.

Varices of the terminal ileum are not a common complication to portal hypertension but we describe a case where a 60-year-old male patient had massive, recurrent intestinal bleeding due to collateral blood supply from umbilical veins to varicose veins of the terminal ileum.

Fetal liver blood flow distribution: role in human developmental strategy to prioritize fat deposition versus brain development.

Among primates, human neonates have the largest brains but also the highest proportion of body fat. If placental nutrient supply is limited, the fetus faces a dilemma: should resources be allocated to brain growth, or to fat deposition for use as a potential postnatal energy reserve? We hypothesised that resolving this dilemma operates at the level of umbilical blood distribution entering the fetal liver. In 381 uncomplicated pregnancies in third trimester, we measured blood flow perfusing the fetal liver, or bypassing it via the ductus venosus to supply the brain and heart using ultrasound techniques. Across the range of fetal growth and independent of the mother's adiposity and parity, greater liver blood flow was associated with greater offspring fat mass measured by dual-energy X-ray absorptiometry, both in the infant at birth (r = 0.43, P<0.001) and at age 4 years (r = 0.16, P = 0.02). In contrast, smaller placentas less able to meet fetal demand for essential nutrients were associated with a brain-sparing flow pattern (r = 0.17, p = 0.02). This flow pattern was also associated with a higher degree of shunting through ductus venosus (P = 0.04). We propose that humans evolved a developmental strategy to prioritize nutrient allocation for prenatal fat deposition when the supply of conditionally essential nutrients requiring hepatic inter-conversion is limited, switching resource allocation to favour the brain if the supply of essential nutrients is limited. Facilitated placental transfer mechanisms for glucose and other nutrients evolved in environments less affluent than those now prevalent in developed populations, and we propose that in circumstances of maternal adiposity and nutrient excess these mechanisms now also lead to prenatal fat deposition. Prenatal developmental influences play important roles in the human propensity to deposit fat.

The relationships of umbilical venous volume flow, birthweight and placental share in monochorionic twin pregnancies with and without selective intrauterine growth restriction.

This study was conducted to investigate the relationship among umbilical venous volume flow, birthweight and placental share in monochorionic twins with or without selective growth restriction. Having excluded cases complicated with twin-to-twin transfusion syndrome and one co-twin suffering intrauterine fetal death, a total of 51 monochorionic twin pregnancies were divided into two groups as with (group 1) and without (group 2) selective intrauterine growth restriction. Umbilical venous volume flow was calculated by multiplying the umbilical vein cross-sectional area by half of the maximal velocity around mid-trimester. The placentas were cut along the vascular equator into two individual placental masses. The discordance of birthweight was calculated as [(birthweight of larger twin-birthweight of smaller twin)/birthweight of larger twin 100%]. The discordances of umbilical venous volume flow and placental share were calculated in a similar fashion. The median umbilical venous volume flow discordances (68.4% and 15.3% in groups 1 and 2 monochorionic twins, respectively) were similar and correlated well with the placental share discordances (66.6% and 18.5% in groups 1 and 2 monochorionic twins, respectively) but not with the birthweight discordance (28.6% and 6.4% in groups 1 and 2 monochorionic twins, respectively) in both groups. We concluded that the umbilical venous volume flow discordance reflects the placental share discordance rather than the birthweight discordance in monochorionic twin pregnancies.

Caput medusae in alcoholic liver disease.

Caput medusae and palmar erythema are cardinal signs in cirrhosis of liver with portal hypertension. Palmar erythema is described more often as a marker for alcoholic etiology of chronic liver disease. The peripheral stigmata of chronic liver disease are not routinely seen now a days due to early diagnosis and better therapy. We recently encountered an interesting patient of alcoholic liver disease with two classical signs of the disease and report the same for this unusual presentation.

First-trimester measurement of the ductus venosus pulsatility index and the prediction of congenital heart defects.

OBJECTIVE: This study was carried out to evaluate the additional predictive value of ductus venosus pulsatility index for veins (DV-PIV) in the identification of congenital heart defects (CHDs) in fetuses with an enlarged nuchal translucency (NT) and a normal karyotype. METHODS: All chromosomally normal fetuses referred to our Fetal Medicine Unit between September 1996 and December 2008 with known NT, DV-PIV and ductus venosus (DV) a-wave measurements were included. Intrafetus variation in DV-PIV was overcome by averaging three recordings. Follow-up included special focus on CHD. The odds of CHD at any NT and DV-PIV value were evaluated using logistic regression analysis. RESULTS: Of 792 fetuses included, the NT was enlarged (equal to or above the 95(th) percentile (P95)) in 318 (40.2%). The DV-PIV was abnormal (≥ P95) in 41.8% of the fetuses with an enlarged NT and the a-wave was abnormal (negative or reversed) in 29.9%. CHD was diagnosed in 35 fetuses, 33 of which had an enlarged NT. Amongst the fetuses with an enlarged NT, the sensitivities for CHD of abnormal DV-PIV and DV a-wave were 73% and 55%, with specificities of 62% and 73%, respectively. Logistic regression analysis showed that in this risk group the DV-PIV multiple of the median (MoM) (as a continuous variable) was significantly associated with the risk of CHD (odds ratio = 2.4), independent of the degree of NT enlargement, whereas the DV a-wave did not significantly add to the prediction of CHD. CONCLUSION: Two-thirds of fetuses with an enlarged NT, a normal karyotype and CHD have an increased DV-PIV. DV-PIV can be used as continuous variable in combination with NT to increase specificity in the identification of CHD and to refine the individual risk assessment.

Ductus venosus pulsatility index measurement reduces the false-positive rate in first-trimester screening.

OBJECTIVE: To investigate if ductus venosus (DV) pulsatility index for veins (PIV) and a-wave measurements can increase the accuracy of first-trimester Down syndrome screening in a high-risk population. METHODS: The database of our fetal medicine unit was searched for all cases at increased first-trimester Down syndrome risk. Multivariable logistic regression was used to construct a prediction rule for chromosomal anomalies at any given maternal age, nuchal translucency multiples of the median (NT-MoM) and DV-PIV MoM. The discriminative ability of the model was assessed by using receiver-operating characteristics (ROC) analysis. RESULTS: The study population included 445 fetuses. DV-PIV was increased (≥ 95(th) percentile) in 239 (54%) and DV a-wave was abnormal in 187 fetuses (42%). In this cohort, 80% of all chromosomal anomalies were identified by an increased DV-PIV and 68% by an abnormal a-wave. The odds of chromosomal anomalies increased by a factor of 4.2 per MoM increase in DV-PIV, adjusted for NT and maternal age. The area under the ROC curve for the prediction of chromosomal anomalies was 0.79. After correction for DV-PIV, DV a-wave did not significantly add to the prediction of chromosomal anomalies. CONCLUSION: In a population of fetuses at increased first-trimester risk for Down syndrome, the combination in a logistic regression model of NT, DV-PIV and maternal age can improve the accuracy of screening for trisomy 21 and other chromosomal anomalies. This is the first study that models the additional value of DV-PIV as a continuous variable to NT measurement alone in a high-risk first-trimester population.

First-trimester umbilical vein blood flow in pregnancies with low serum pregnancy-associated plasma protein-A levels: an early predictor of fetal growth restriction.

OBJECTIVE: To investigate umbilical vein blood flow (UVBF) during the first trimester in pregnancies with low serum pregnancy-associated plasma protein-A (PAPP-A) levels and to relate umbilical vein (UV) diameter, time-averaged maximum velocity (TAMXV) and UVBF values to the subsequent development of fetal intrauterine growth restriction (IUGR). METHODS: UVBF assessment was performed at 11 + 0 to 13 + 6 weeks' gestation in 102 singleton pregnancies with PAPP-A concentrations of < 0.3 multiples of the median. UV diameter, UV-TAMXV and UVBF were calculated and analyzed in relation to pregnancy outcome. RESULTS: Pregnancy outcomes were: 51 pregnancies with birth weight ≥ 10(th) centile (Group A), 30 pregnancies with birth weight < 10(th) centile with normal Doppler in the umbilical artery throughout gestation (Group B) and 21 pregnancies with birth weight < 10(th) centile and abnormal umbilical artery Doppler later in gestation (Group C). No differences were found in PAPP-A levels between groups. Group C fetuses exhibited significantly lower values of UV-TAMXV (z-score - 1.99 SDs, t = 8.527, P ≤ 0.0001) and UVBF (z-score - 0.97 SDs, t = 7.420, P ≤ 0.0001) in comparison with normal reference ranges, while no differences were found in Groups A or B. CONCLUSIONS: Decreased UV-TAMXV and UVBF at 11 + 0 to 13 + 6 weeks' gestation identify fetuses at risk of developing IUGR among pregnancies with low levels of PAPP-A.

Longitudinal reference values for ductus venosus Doppler in low-risk pregnancies.

The aim of this study was to establish normal ranges of blood flow velocities and indices in the fetal ductus venosus (DV) during the second half of normal pregnancy. A Doppler study of 60 healthy pregnant women without fetal pathologies was performed during the second half of pregnancy. The peak systolic velocity (PSV), peak diastolic velocity (PDV), maximum velocity during atrial contraction (VAC), peak systolic velocity/maximum velocity during atrial contraction (S/A ratio), pulsatility index for the vein (PIV), preload index (PLI) and velocity index for the vein (VIV) were calculated from the DV at 4-week intervals. A significant increase in PSV, PDV and VAC was observed from the 20-23(6/7) to the 28-31(6/7) weeks, with stabilization of values until the end of the pregnancy. On the other hand, the study showed a significant decrease for the S/A ratio, PIV, PLI and VIV from the 20-23(6/7) to the 28-31(6/7) weeks and remaining stable from then until term.

Umbilical vein blood flow at 11 + 0 to 13 + 6 weeks of gestation.

OBJECTIVE: To establish reference intervals for fetal umbilical vein (UV) diameter, UV time averaged maximum velocity (TAMXV) and UV flow (UVBF) at 11 + 0 to 13 plus; 6 weeks of gestation and to determine the intraobserver reliability of these measurements. METHODS: We considered, in a cross-sectional study, 162 fetuses from uncomplicated singleton pregnancies at 11 + 0 to 13 + 6 weeks of gestation. UV diameter and TAMXV were measured in its intraabdominal portion by real-time and Doppler ultrasonography and UVBF calculated. Relationships between these parameters and fetal crown rump length were tested by regression analysis. In 25 cases UVBF was measured twice by the same investigator and the intraobserver agreement of these measurements was calculated. RESULTS: A significant increase was evidenced in the gestational age period considered in UV diameter (r = 0.729, p < 0.0001), TAMXV (r = 0.691, p < 0.0001) and UVBF (r = 0.777, p < 0.0001). UVBF increased from 2.26 ml/min at 11 weeks to 15.62 ml/min at 13 + 6 weeks of gestation. The intraobserver ICCs were 0.96, 0.92 and 0.88, respectively, for UV diameter, TAMXV and UVBF. CONCLUSIONS: In normal fetuses, UV diameter, TAMVX and flow increase between 11 + 0 and 13 + 6 weeks of gestation. In this gestational age interval, the calculation of UV blood flow and its components shows an intraobserver agreement reliable enough for clinical use.