Late-term fetuses with reduced umbilical vein blood flow volume: An under-recognized population at increased risk of growth restriction

Effect of abnormal placental cord insertion on hemodynamic change of umbilical cord in a tertiary center: a prospective cohort study

BACKGROUND

Our study aims to evaluate the umbilical vein (UV) hemodynamic change in the prenatal cohort of pregnancies diagnosed with abnormal placental cord insertion (aPCI).

METHODS

From January 2022 to December 2022, the fetal umbilical cord insertion site was sonographically examined in singleton fetuses, and umbilical cord blood flow was calculated. The umbilical artery and UV Doppler flow indexes were assessed in cases of normal and abnormal cord insertion.

RESULTS

Among 570 singleton fetuses between 18 + 0 and 40 + 6 weeks of gestation in the final study, the umbilical vein blood flow (UVBF) in the 3 groups of normal umbilical cord insertions, marginal umbilical cord insertions, and velamentous umbilical cord insertions was 145.39 ml/min, 146.18 ml/min, and 93.96 ml/min, respectively. UVBF was significantly lower in the velamentous cord insertion (VCI) group than in the other groups (P < 0.05). Compared with the normal cord insertions group, lower birth weight (2820 ± 527 g vs. 3144 ± 577 g, P < 0.05), delivery at an earlier gestational age (38.0 ± 1.55 weeks vs. 38.8 ± 2.34 weeks, P < 0.05), higher bicarbonate (25.08 ± 1.72 mmol/L vs. 22.66 ± 4.05 mmol/L, P < 0.05), and higher standard base excess (-1.14 ± 1.50 mmol/L vs. -3.30 ± 3.22 mmol/L, P < 0.05) were found in the VCI group.

CONCLUSIONS

We observed lower UVBF volume with aPCI. Hence, we propose UVBF analysis to evaluate fetal aPCI according to UV hemodynamics as an advisory in prenatal care. This would be useful and improve obstetricians' clinical explanation about the potential prenatal consequences so that parents can opt for future prenatal care during pregnancy.

The role of umbilical vein blood flow assessment in the prediction of fetal growth velocity and adverse outcome: a prospective observational cohort study

BACKGROUND

Identifying fetal growth restriction and distinguishing it from a constitutionally small fetus can be challenging. The umbilical vein blood flow is a surrogate parameter of the amount of oxygen and nutrients delivered to the fetus, providing valuable insights about the function of the placenta. Nevertheless, currently, this parameter is not used in the diagnosis and management of fetal growth restriction.

OBJECTIVE

To evaluate the umbilical vein blood flow and fetal growth velocity in small for gestational age fetuses and in fetal growth restriction, and to evaluate their capacity to predict adverse perinatal outcome and iatrogenic preterm birth. Secondly, to assess the correlation between umbilical vein blood flow and fetal growth velocity.

STUDY DESIGN

This was a prospective multicentric observational cohort study of women with a diagnosis of small for gestational age or fetal growth restriction in which fetal biometry and Doppler assessment, including umbilical vein blood flow measurement, were performed. The fetal growth velocity was derived from the difference between the estimated fetal weight calculated in 2 consecutive sonographic evaluations. The pregnancies were followed until delivery. Between-group differences were evaluated, and Pearson or Spearman correlation coefficients were reported to assess the relationship between variables of interest. Optimal cutoffs on the resulting receiver operating characteristic curve were determined and used to predict the outcomes of interest. Simple and multiple logistic regression models were estimated using umbilical vein blood flow and fetal growth velocity to predict adverse perinatal outcomes and iatrogenic preterm birth.

RESULTS

The study population included 64 small for gestational age and 58 growth restricted fetuses. When compared to reference ranges, small for gestational age fetuses had significantly lower fetal growth velocity and umbilical vein blood flow (P<.001). When compared to small for gestational age, fetuses with growth restriction had lower umbilical vein blood flow (P<.001), umbilical vein blood flow corrected for estimated fetal weight and abdominal circumference (P<.01 and P<.001), and fetal growth velocity (P<.001). Fetal growth velocity was positively correlated with umbilical vein blood flow (r=0.46, P<.001). The multivariable logistic regression analyses showed that, after adjusting for diagnosis of fetal growth restriction, umbilical vein blood flow ≤0.65 multiple of the median (adjusted odds ratio [aOR] 3.5; 95% confidence interval [CI] 1.0-11.8) and fetal growth velocity ≤0.63 multiple of the median (adjusted odds ratio 3.0, 95% CI 1.2-7.9) were associated with adverse perinatal outcome. Furthermore, when accounting for fetal growth restriction diagnosis, umbilical vein blood flow ≤0.60 multiple of the median (adjusted odds ratio 5.2, 95% CI 1.7-15.9), and fetal growth velocity ≤0.63 multiple of the median (adjusted odds ratio 3.6, 95% CI 1.1-12.6) were significant predictors of iatrogenic preterm birth.

CONCLUSION

Umbilical vein blood flow could play a role to identify fetuses with fetal growth restriction and to predict fetal growth at the subsequent biometric evaluation. We found a significant correlation between umbilical vein blood flow and fetal growth. Umbilical vein blood flow and fetal growth velocity are independent predictors of iatrogenic preterm birth and adverse perinatal outcome in a population of small fetuses, regardless of the Delphi consensus criteria. These results support future study on the predictive value of this parameter in fetuses with a suspected fetal growth restriction.

Association of umbilical vein flow with abnormal fetal growth and adverse perinatal outcome in low-risk population: multicenter prospective study

OBJECTIVE

To investigate the relationship of umbilical vein flow (UVF) measured close to term with abnormal fetal growth and adverse perinatal outcome in a cohort of pregnancies at low risk of placental insufficiency.

METHODS

This was a prospective multicenter observational study conducted across two tertiary maternity units. Patients with a singleton appropriate-for-gestational-age fetus between 35 and 38 weeks' gestation were included. Pregnancies at higher risk of placental insufficiency or with fetal anomalies were excluded. At ultrasound examination, the abdominal circumference (AC), umbilical vein diameter and peak velocity of the umbilical vein were measured, and, using these variables, a new variable, UVF/AC, was calculated. The primary outcome was the occurrence of severely stunted fetal growth, defined as a greater than 40-percentile drop between estimated fetal weight at the third-trimester ultrasound and birth weight. The occurrence of adverse perinatal outcome (defined as one of the following: neonatal acidosis (umbilical artery pH < 7.15 and/or base excess > 12 mmol/L) at birth, 5-min Apgar score < 7, neonatal resuscitation or neonatal intensive care unit admission) was analyzed as a secondary outcome.

RESULTS

Between April 2021 and March 2023, 365 women were included in the study. The mean UVF/AC at enrolment was 6.4 ± 2.6 mL/min/cm, and 35 (9.6%) cases were affected by severely stunted fetal growth. Severely stunted fetal growth was associated with a lower mean UVF/AC (5.4 ± 2.6 vs 6.5 ± 2.6 mL/min/cm; P = 0.02) and a higher frequency of UVF/AC < 10th percentile (8/35 (22.9%) vs 28/330 (8.5%); P = 0.01). Moreover, UVF/AC showed an area under the receiver-operating-characteristics curve (AUC) of 0.65 (95% CI, 0.55-0.75; P = 0.004) in predicting the occurrence of severely stunted fetal growth, and the optimal cut-off value of UVF/AC for discriminating between normal and severely stunted fetal growth was 7.2 mL/min/cm. This value was associated with a sensitivity and specificity of 0.77 (95% CI, 0.60-0.90) and 0.33 (95% CI, 0.28-0.39), and positive and negative predictive values of 0.11 (95% CI, 0.07-0.15) and 0.93 (95% CI, 0.87-0.97), respectively. Regarding the occurrence of adverse perinatal outcome, this was associated independently with maternal age (adjusted odds ratio (aOR), 0.93 (95% CI, 0.87-0.99); P = 0.04), UVF/AC Z-score (aOR, 0.53 (95% CI, 0.30-0.87); P = 0.01) and augmentation of labor (aOR, 2.69 (95% CI, 1.28-5.69); P = 0.009). UVF/AC showed an AUC of 0.65 (95% CI, 0.56-0.73; P = 0.005) in predicting the occurrence of adverse perinatal outcome, and the optimal cut-off value of UVF/AC for discriminating between normal and adverse perinatal outcome was 6.7 mL/min/cm. This value was associated with a sensitivity and specificity of 0.70 (95% CI, 0.54-0.83) and 0.40 (95% CI, 0.34-0.45), and positive and negative predictive values of 0.14 (95% CI, 0.09-0.19) and 0.91 (95% CI, 0.85-0.95), respectively.

CONCLUSIONS

Our data demonstrate an association between reduced UVF close to term, severely stunted fetal growth and adverse perinatal outcome in a cohort of low-risk pregnant women, with a moderate ability to rule out and a poor ability to rule in either outcome. Further studies are needed to establish whether the assessment of UVF can improve the identification of fetuses at risk of subclinical placental insufficiency and adverse perinatal outcome. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

A longitudinal study on the effect of obesity upon circulating renin-angiotensin system in normal pregnancy

BACKGROUND AND AIMS

Obesity is the most common health issue in women of reproductive age, which profoundly affects maternal-fetal health. Despite progress in understanding key inflammatory and metabolic changes, the pathogenesis of the cardiovascular phenotype of obese pregnant women remains to be fully understood. This study aimed at: (i) evaluating the changes of the renin-angiotensin system (RAS) throughout pregnancy in obese vs normal weight (control) women, and (ii) evaluating the presence of any associations between maternal hemodynamic status and RAS changes.

METHODS AND RESULTS

Thirty-eight normal weight and nineteen obese pregnant women were included. Clinical assessment, blood samples and maternal hemodynamic evaluation were performed at 12, 20, 30, and 36 weeks, while ultrasound assessment was scheduled at 20, 30, and 36 weeks of gestation. Measurements of sFlt-1, PlGF, Angiotensinogen, Renin, AngII, Ang1-7, ACE and ACE2 were performed by ELISA. Our data show that normotensive obese women had lower placental blood supply, as assessed by UV-Q and UV-Q/EFW, as compared to controls, and significantly higher levels of AngII and AngII/Ang1-7 ratio, which were inversely related to placental blood supply.

CONCLUSIONS

Our study shows for the first time that normotensive obese women exhibited a significant progressive increase of AngII and AngII/Ang1-7 throughout pregnancy, which were inversely related to placental blood supply as assessed by UV-Q and UV-Q/EFW. Our data shed light on the early changes in pregnant obese women and suggest that RAS dysregulation is a prerequisite rather than a consequence of hypertensive disorders of pregnancy and other maternal neonatal complications.

Umbilical Vein Blood Flow in Uncomplicated Pregnancies: Systematic Review of Available Reference Charts and Comparison with a New Cohort

The objectives of the study were (1) to perform a systematic review of the available umbilical vein blood flow volume (UV-Q) reference ranges in uncomplicated pregnancies; and (2) to compare the findings of the systematic review with UV-Q values obtained from a local cohort. Available literature in the English language on this topic was identified following the PRISMA guidelines. Selected original articles were further grouped based on the UV sampling sites and the formulae used to compute UV-Q. The 50th percentiles, the means, or the best-fitting curves were derived from the formulae or the reported tables presented by authors. A prospective observational study of uncomplicated singleton pregnancies from 20⁺⁰ to 40⁺⁶ weeks of gestation was conducted to compare UV-Q with the results of this systematic review. Fifteen sets of data (fourteen sets belonging to manuscripts identified by the research strategy and one obtained from our cohort) were compared. Overall, there was a substantial heterogeneity among the reported UV-Q central values, although when using the same sampling methodology and formulae, the values overlap. Our data suggest that when adhering to the same methodology, the UV-Q assessment is accurate and reproducible, thus encouraging further investigation on the possible clinical applications of this measurement in clinical practice.

Umbilical vein blood flow: State-of-the-art

Placental blood supply to the fetus can be measured by evaluating the umbilical vein blood flow. Despite its potential application in healthcare, the umbilical vein blood flow volume is still used only in research setting. One of the reasons is a concern regarding its reproducibility, partly due to technology issues. Nowadays, technology improvements make this evaluation accurate and reproducible. The aim of this review is to refresh basic elements of the physiology of umbilical vein blood flow and its analysis. Its evaluation in normal and abnormal fetal growth is also discussed.