Uterine artery blood flow volume in pregnant women with an abnormal pulsatility index of the uterine arteries delivering normal or intrauterine growth restricted newborns

Maternal tadalafil treatment does not increase uterine artery blood flow or oxygen delivery in the pregnant ewe

Increasing placental perfusion (PP) could improve outcomes of growth-restricted fetuses. One way of increasing PP may be by using phosphodiesterase (PDE)-5 inhibitors, which induce vasodilatation of vascular beds. We used a combination of clinically relevant magnetic resonance imaging (MRI) techniques to characterize the impact that tadalafil infusion has on maternal, placental and fetal circulations. At 116-117 days' gestational age (dGA; term, 150 days), pregnant ewes (n = 6) underwent fetal catheterization surgery. At 120-123 dGA ewes were anaesthetized and MRI scans were performed during three acquisition windows: a basal state and then ∼15-75 min (TAD 1) and ∼75-135 min (TAD 2) post maternal administration (24 mg; intravenous bolus) of tadalafil. Phase contrast MRI and T2 oximetry were used to measure blood flow and oxygen delivery. Placental diffusion and PP were assessed using the Diffusion-Relaxation Combined Imaging for Detailed Placental Evaluation-'DECIDE' technique. Uterine artery (UtA) blood flow when normalized to maternal left ventricular cardiac output (LVCO) was reduced in both TAD periods. DECIDE imaging found no impact of tadalafil on placental diffusivity or fetoplacental blood volume fraction. Maternal-placental blood volume fraction was increased in the TAD 2 period. FetalD O 2 ${D_{{{\mathrm{O}}_2}}}$ andV ̇ O 2 ${\dot V_{{{\mathrm{O}}_2}}}$ were not affected by maternal tadalafil administration. Maternal tadalafil administration did not increase UtA blood flow and thus may not be an effective vasodilator at the level of the UtAs. The increased maternal-placental blood volume fraction may indicate local vasodilatation of the maternal intervillous space, which may have compensated for the reduced proportion of UtAD O 2 ${D_{{{\mathrm{O}}_2}}}$ .

The association between fetal Doppler and uterine artery blood volume flow in term pregnancies: a pilot study

PURPOSE

To investigate the relationship between uterine artery blood volume flow and fetal Doppler indices in term pregnancies.

MATERIALS AND METHODS

A prospective observational study in a tertiary-care university hospital was performed between December 2021 and May 2022. We included only term pregnancies that received accurate ultrasound scans until a week before the birth. The uterine artery (UtA) diameter and UtA volume blood flow were estimated and recorded. The volume of each artery was summed to obtain the total uterine artery volume blood flow (QUtA). The following fetal Doppler indices were evaluated: Umbilical artery (UA), middle cerebral artery (MCA), ductus venosus (DV), and cerebroplacental ratio (CPR). Linear regression analysis was performed to investigate the relationship between the QUtA and the fetal Doppler indices.

RESULTS

49 pregnancies were included. The UA pulsatility index (PI) analysis showed a significant association with QUtA (r2=0.40, p=0.01), demonstrating a decrease of the UA PI when the QUtA increased. The same relationship was noted between the UtA mean PI and QUtA (r2=0.41, p=0.005). A weak correlation between the newborn weight and the QUtA was also noted (r2=0.31, p=0.048), with an elevated newborn weight when the QUtA was high.

CONCLUSION

This study showed that UA, UtA PI, and birth weight seem to be linked to QUtA. QUtA had an inverse correlation with UA and UtA PI. In addition, increasing the QUtA showed a linear increase in fetal birth weight. These findings could be helpful in high-risk pregnancy management, but additional research is needed to identify how QUtA in the third trimester impacts labor and fetal outcomes.

Pharmacological Interventions in Labor and Delivery

While there is not a wide range of pregnancy-specific drugs, there are some very specific high-risk areas of obstetric care for which unique pharmacological approaches have been established. In preterm birth, labor induction and augmentation, and the management of postpartum hemorrhage, these pharmacological approaches have become the bedrock in managing some of the most common and problematic areas of antenatal and intrapartum care. In this review, we summarize the existing established and emerging evidence that supports and broadens these pharmacological approaches to obstetric management and its impact on clinical practice. It is clear that existing therapeutics are limited. They have largely been developed from our knowledge of the physiology of the myometrium and act on hormonal receptors and their signaling pathways or on ion channels influencing excitability. Newer drugs in development are mostly refinements of these two approaches, but novel agents from plants and improved formulations are also discussed.

Hypertensive Disorders of Pregnancy and Fetal Growth Restriction: Clinical Characteristics and Placental Lesions and Possible Preventive Nutritional Targets

Background: The purpose of this study was to describe the placental lesions in pregnancies complicated by hypertensive disorders (HDP) and/or fetal growth restriction (FGR) and in uneventful control pregnancies. Methods: This is a case control study that included singleton pregnancies with HDP and normally grown fetus (HDP-AGA fetus), with HDP and FGR, early FGR, late FGR, and uneventful pregnancies. Feto-placental Doppler velocimetry and sFlt-1/PlGF ratio were performed. Placental histology was evaluated blinded according to the Amsterdam Consensus criteria. Results: Placental lesions with maternal vascular malperfusion (MVM) were significantly more frequent in HDP-FGR and early FGR (92% and 83%). MVM were significantly associated with abnormal feto-placental Doppler parameters, especially in early FGR. Delayed villous maturation (DVM) was associated with late FGR (83%). HDP-AGA fetus cases presented a heterogeneous pattern of placental lesions, including 60% of cases with MVM, but were not associated with abnormal Doppler feto-placental velocimetry. Conclusions: We found a prevalence of placental maternal vascular malperfusion in HDP-FGR and early FGR groups. These lesions were also associated with abnormal, anti-, and angiogenic markers. Conversely HDP-AGA fetus and late FGR presented more heterogeneous placental lesions not severe enough to cause feto-placental Doppler anomalies. These conditions are likely associated with different etiologies, such as maternal pre-pregnancy risk factors for metabolic syndrome. These findings suggest a possible preventive nutritional approach in addition to low-dose aspirin in pregnant women with predisposing factors for HDP-AGA fetuses and late FGR.

Time of delivery among low-risk women at 37-42 weeks of gestation and risks of stillbirth and infant mortality, and long-term neurological morbidity

BACKGROUND

The most important knowledge gap in connection with obstetric management for time of delivery in term low-risk pregnancies relates to the absence of information on long-term neurodevelopmental outcomes.

OBJECTIVES

We examined risks of stillbirth, infant mortality, cerebral palsy (CP) and epilepsy among low-risk pregnancies.

METHODS

In this population-based Swedish study, we identified, from 1998 to 2019, 1,773,269 singleton infants born between 37 and 42 completed weeks in women with low-risk pregnancies. Poisson log-linear regression models were used to examine the association between gestational age at delivery and stillbirth, infant mortality, CP and epilepsy. Adjusted rate ratios (RR) and 95% confidence intervals expressing the effect of birth at a particular gestational week compared with birth at a later gestational week were estimated.

RESULTS

Compared with those born at a later gestation, RRs for stillbirth and infant mortality were higher among births at 37 weeks' and 38 weeks' gestation. The RRs for infant mortality were approximately 20% and 25% lower among births at 40 or 41 weeks compared with those born at later gestation, respectively. Infants born at 37 and 38 weeks also had higher RRs for CP (vs infants born at ≥38 and ≥39 weeks, respectively), while those born at 39 gestation had similar RRs (vs infants born at ≥40 weeks); infants born at 40 and 41 weeks had lower RRs of CP (vs those born at ≥41 and 42 weeks, respectively). The RRs for epilepsy were higher in those born at 37 and 38 weeks compared with those born at later gestation.

CONCLUSIONS

Among low-risk pregnancies, birth at 37 or 38 completed weeks' gestation is associated with increased risks of stillbirth, infant mortality and neurological morbidity, while birth at 39-40 completed weeks is associated with reduced risks compared with births at later gestation.

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

OBJECTIVES

To investigate the umbilical vein and uterine arteries blood flow volume (UV-Q, UtA-Q) in late-term pregnancies.

STUDY DESIGN

This was a prospective observational cohort study of singleton pregnancies ≥40 + 0 weeks in which UV-Q and UtA-Q, both absolute and normalized for estimated fetal weight (EFW) values, were evaluated in relation to AC drop of ≥20 percentiles from 20 weeks to term, Doppler signs of fetal cerebral blood flow redistribution and composite adverse perinatal outcome. The presence of neonatal hypoglycaemia and the need of formula milk supplementation were also examined.

RESULTS

The study population comprised 200 women. Fetuses with AC drop (n = 34) had a significantly lower UV-Q and UV-Q/EFW than fetuses without AC drop (n = 166): median UV-Q 184 ml/min (IQR 143-225) vs 233 ml/min (IQR 181-277), p = 0.0006; median UV-Q/EFW 55 ml/min/kg (IQR 42-66) vs 63 ml/min/kg (IQR 48-74), p = 0.03. Fetuses with cerebral blood flow redistribution (n = 48) had a significantly lower UV-Q and UV-Q/EFW than those without (n = 134): median UV-Q 210 ml/min (IQR 155-263) vs 236 ml/min (IQR 184-278), p = 0.04; median UV-Q/EFV 58 ml/min/kg (IQR 45-70) vs 65 ml/min/kg (IQR 50-76), p = 0.04. There was a significant moderate correlation between middle cerebral artery pulsatility index (MCA-PI) and UV-Q and UV-Q/EFW (Spearman Rho -0.20 and -0.20; p = 0.008 and p = 0.006).

CONCLUSIONS

The umbilical vein blood flow volume might have a potential role to identify fetuses with stunted growth in late-term pregnancies.

Cross-modality and in-vivo validation of 4D flow MRI evaluation of uterine artery blood flow in human pregnancy

OBJECTIVES

Clinical assessment of uterine artery (UtA) hemodynamics is currently limited to Doppler ultrasound (US) velocimetry. We have demonstrated previously the feasibility of applying four-dimensional (4D) flow magnetic resonance imaging (MRI) to evaluate UtA hemodynamics during pregnancy, allowing flow quantification of the entire course of the vessel. In this study, we sought to further validate the physiological relevance of 4D flow MRI measurement of UtA blood flow by exploring its association with pregnancy outcome relative to US-based metrics.

METHODS

Recruited into this prospective, cross-sectional study were 87 women with a singleton pregnancy who underwent 4D flow MRI between May 2016 and April 2019 to measure the UtA pulsatility index (MRI-PI) and blood flow rate (MRI-flow, in mL/min). UtA-PI was also measured using US (US-PI). The primary outcome was a composite (COMP) of pre-eclampsia (PE) and/or small-for-gestational-age (SGA) neonate, and secondary outcomes were PE and SGA neonate individually. We assessed the ability of MRI-flow, MRI-PI and US-PI to distinguish between outcomes, and evaluated whether MRI-flow changed as gestation progressed.

RESULTS

Following 4D flow postprocessing and exclusions from the analysis, 74 women had 4D flow MRI data analyzed for both UtAs. Of these, 18 developed a COMP outcome: three developed PE only, 11 had a SGA neonate only and four had both. A comparison of the COMP group vs the no-COMP group found no differences in maternal age, body mass index, nulliparity, gravidity or race. For 66 of the 74 subjects, US data were also available. In these subjects, both median MRI-PI (0.95 vs 0.70; P < 0.01) and median US-PI (0.95 vs 0.73; P < 0.01) were significantly increased in subjects in the COMP group compared with those in the no-COMP group. The UtA blood-flow rate, as measured by MRI, did not increase significantly from the second to the third trimester (median flow (interquartile range (IQR)), 543 (419-698) vs 575 (440-746) mL/min; P = 0.77), but it was significantly lower overall in the COMP compared with the no-COMP group (median flow (IQR), 486 (366-598) vs 624 (457-749) mL/min; P = 0.04). The areas under the receiver-operating-characteristics curves for MRI-flow, MRI-PI and US-PI in predicting COMP were not significantly different (0.694, 0.737 and 0.731, respectively; P = 0.87).

CONCLUSIONS

4D flow MRI can yield physiological measures of UtA blood-flow rate and PI that are associated with adverse pregnancy outcome. This may open up new avenues in the future to expand the potential of this technique as a robust tool with which to evaluate UtA hemodynamics in pregnancy. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Is there a relationship between high birth weight and umbilical vein diameter?

OBJECTIVE

The aim of the study was to evaluate the associations between sonographical measurements of the umbilical cord and birth weight in 20-24 weeks of gestations.

METHODS

This cross-sectional study was conducted with the participation of 220 low-risk pregnant women between 20-24 gestational weeks. Biparietal diameter, head and abdominal circumference, and femur length were measured for anthropometric calculations. Umbilical cord including umbilical vein diameters, placental thickness, umbilical artery. Doppler measurements (RI, PI) were recorded.

RESULTS

In accordance with the results of statistical computations, an inverse relationship was found between umbilical vein diameter and birth weight of a large gestational age (LGA) newborn in 20-24 gestational weeks (p < .05). There was no significant relationship between other parameters and birth weight of LGA newborns.

CONCLUSION

There is an inverse relationship between birth weights of newborns with LGA and umbilical vein diamater at 20-24 weeks of pregnancy. The umbilical vein diameter in the second trimester may be a promising measurement on predicting LGA fetus. The researches have not confirmed the physiopathology of this finding yet, but it is paving the path for future studies.

Uterine artery Doppler in singleton pregnancies conceived after in-vitro fertilization or intracytoplasmic sperm injection with fresh vs frozen blastocyst transfer: longitudinal cohort study

OBJECTIVE

Pregnancies conceived by frozen blastocyst transfer (FBT) have higher gestational age and weight at birth as compared to those derived by fresh blastocyst transfer. The aim of this study was to evaluate uterine artery pulsatility index (UtA-PI) in pregnancies conceived by in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) techniques using fresh vs cryopreserved blastocysts.

METHODS

This was a prospective longitudinal study of viable singleton IVF/ICSI pregnancies conceived after FBT or fresh blastocyst transfer, that underwent serial ultrasound assessment at San Raffaele Hospital, Milan, Italy at 7-37 gestational weeks. We excluded pregnancies conceived using other assisted reproductive techniques such as egg donation, twin gestation, pregnancy with abnormality and those resulting in miscarriage. Pregnant women underwent ultrasound assessment at 7-10, 11-14, 18-25 and 26-37 weeks' gestation. Mean UtA-PI was measured using Doppler ultrasound according to The Fetal Medicine Foundation criteria. Pregnancy outcomes were recorded. The primary outcome was mean UtA-PI measurement and secondary outcomes were gestational age at birth, birth weight and fetal and maternal complications, including small-for-gestational age (SGA), pre-eclampsia and large-for-gestational age. UtA-PI values were made Gaussian after log₁₀ transformation. Analysis of repeated measures using a multilevel linear mixed model (fixed effects and random effects) was performed. The possible effect of other covariates on UtA-PI Doppler values, including body mass index, SGA and pre-eclampsia, was also evaluated.

RESULTS

A total of 367 IVF/ICSI cycles, comprising 164 with fresh blastocyst transfer and 203 with FBT, were included and a total of 625 observations (median, 2.5 (range, 1-4)) were collected and analyzed. The FBT group had on average 14% lower UtA-PI compared with the fresh-blastocyst-transfer group. In pregnancies with SGA fetuses, UtA-PI was 18% higher compared to pregnancies without, irrespective of the study group. Pregnancies that underwent fresh blastocyst transfer had significantly lower birth-weight centile (43.4 ± 23.3 vs 50.0 ± 23.1; P = 0.007) and a higher rate of SGA (7.9% vs 2.0%; P = 0.008) compared to those that underwent FBT. No significant differences were found between the two groups with respect to gestational age at birth and rates of preterm birth, pre-eclampsia, gestational diabetes mellitus and large-for-gestational age.

CONCLUSION

UtA-PI and the proportion of SGA are lower in IVF/ICSI pregnancies conceived after FBT as compared to fresh blastocyst transfer. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Towards a unified perinatal theory: Reconciling the births-based and fetus-at-risk models of perinatal mortality

BACKGROUND

There is a need to reconcile the opposing perspectives of the births-based and fetuses-at-risk models of perinatal mortality and to formulate a coherent and unified perinatal theory.

METHODS

Information on births in the United States from 2004 to 2015 was used to calculate gestational age-specific perinatal death rates for low- and high-risk cohorts. Cubic splines were fitted to the fetuses-at-risk birth and perinatal death rates, and first and second derivatives were estimated. Births-based perinatal death rates, and fetuses-at-risk birth and perinatal death rates and their derivatives, were examined to identify potential inter-relationships.

RESULTS

The rate of change in the birth rate dictated the pattern of births-based perinatal death rates in a triphasic manner: increases in the first derivative of the birth rate at early gestation corresponded with exponential declines in perinatal death rates, the peak in the first derivative presaged the nadir in perinatal death rates, and late gestation declines in the first derivative coincided with an upturn in perinatal death rates. Late gestation increases in the first derivative of the fetuses-at-risk perinatal death rate matched the upturn in births-based perinatal death rates. Differences in birth rate acceleration/deceleration among low- and high-risk cohorts resulted in intersecting perinatal mortality curves.

CONCLUSION

The first derivative of the birth rate links a cohort's fetuses-at-risk perinatal death rate to its births-based perinatal death rate, and cohort-specific differences in birth rate acceleration/deceleration are responsible for the intersecting perinatal mortality curves paradox. This mechanistic explanation unifies extant models of perinatal mortality and provides diverse insights.

A data-driven model to study utero-ovarian blood flow physiology during pregnancy

In this paper, we describe a mathematical model of the cardiovascular system in human pregnancy. An automated, closed-loop 1D-0D modelling framework was developed, and we demonstrate its efficacy in (1) reproducing measured multi-variate cardiovascular variables (pulse pressure, total peripheral resistance and cardiac output) and (2) providing automated estimates of variables that have not been measured (uterine arterial and venous blood flow, pulse wave velocity, pulsatility index). This is the first model capable of estimating volumetric blood flow to the uterus via the utero-ovarian communicating arteries. It is also the first model capable of capturing wave propagation phenomena in the utero-ovarian circulation, which are important for the accurate estimation of arterial stiffness in contemporary obstetric practice. The model will provide a basis for future studies aiming to elucidate the physiological mechanisms underlying the dynamic properties (changing shapes) of vascular flow waveforms that are observed with advancing gestation. This in turn will facilitate the development of methods for the earlier detection of pathologies that have an influence on vascular structure and behaviour.

Correlation Between Fetal Weight Gain and Birth Weight with Blood Flow in the Uterine Arteries Calculated with the PixelFlux Technique

Introduction

The aim was to investigate correlations between fetal weight gain/day and birthweight with blood flow estimates in the uterine arteries calculated with the PixelFlux technique and with measurements from TAmax. We also aimed to examine the agreement between estimates using the two methods.

Material and methods

We conducted a prospective observational pilot study in pregnancy week 24-25 in women with risk pregnancies referred to the fetal medical centre at St. Olavs Hospital, Trondheim, Norway from March 2016 to June 2016. Blood flow in the uterine arteries was calculated using time-averaged peak velocity (TAmax) and the PixelFlux technique. PixelFlux is a method based on pixelwise calculation of spatially angle-corrected velocities and areas of all pixels inside a vessel during a heart cycle.

Results

The mean flow calculated from PixelFlux and TAmax was 811 ml/minute and 787 ml/minute, respectively. The intra-class correlation coefficient was 0.83 (95% CI 0.72-0.90) and limits of agreement were -441 ml/minute (95% CI -558 to -324 ml/minute) to 489 ml/minute (95% CI 372 to 606 ml/minute). We observed a significant correlation between mean flow calculated from PixelFlux and birthweight (r=0.41; p<0.01) and between flow calculated from PixelFlux and weight gain/day (r=0.33; p=0.02). Calculation based on TAmax was significant correlated to birthweight (r=0.34; p=0.02), but not to weight-gain/day. Pulsatile index was not correlated to flow, birthweight or fetal weight-gain/day.

Conclusions

We found significant correlations between estimated blood flow in the uterine arteries using the PixelFlux technique with fetal weight-gain/day and with birthweight. Estimates from two methods showed good agreement.

THERMAL IMAGING AS AN ADJUNCT TOOL FOR IDENTIFYING FETAL GROWTH – A PILOT STUDY

Monitoring the fetal growth and diagnosing any possible abnormality plays a vital role in ensuring the healthy growth of a fetus. Certain health issues like Hyperthermia, Premature Rupture of Membranes (PROM) and Intrauterine Growth Restriction (IUGR) has to be diagnosed early. A pilot study comprising of 27 pregnant and 2 non-pregnant subjects was conducted to check the effectiveness of Thermal imaging in predicting the fetal growth. The heat dissipated by the fetus to the maternal abdominal wall is acquired as a surface thermal distribution. These images were processed qualitatively and quantitatively for better understanding. There was a consistent higher thermal pattern for pregnant women. A more pronounced temperature pattern is notable in the umbilical region that correlates with gestation age. However, as thermal pattern varies with age, gestation period and BMI, it is advisable to track the same person and compare the images for better assessment. This pilot study justifies the need for more elaborate study in building a database for classification and interpretation of thermogram to detect fetal abnormality with reduced human interpretation.

Dynamic modeling of uteroplacental blood flow in IUGR indicates vortices and elevated pressure in the intervillous space - a pilot study

Ischemic placental disease is a concept that links intrauterine growth retardation (IUGR) and preeclampsia (PE) back to insufficient remodeling of uterine spiral arteries. The rheological consequences of insufficient remodeling of uterine spiral arteries were hypothesized to mediate the considerably later manifestation of obstetric disease. However, the micro-rheology in the intervillous space (IVS) cannot be examined clinically and rheological animal models of the human IVS do not exist. Thus, an in silico approach was implemented to provide in vivo inaccessible data. The morphology of a spiral artery and the inflow region of the IVS were three-dimensionally reconstructed to provide a morphological stage for the simulations. Advanced high-end supercomputing resources were used to provide blood flow simulations at high spatial resolution. Our simulations revealed turbulent blood flow (high-velocity jets and vortices) combined with elevated blood pressure in the IVS and increased wall shear stress at the villous surface in conjunction with insufficient spiral artery remodeling only. Post-hoc histological analysis of uterine veins showed evidence of increased trophoblast shedding in an IUGR placenta. Our data support that rheological alteration in the IVS is a relevant mechanism linking ischemic placental disease to altered structural integrity and function of the placenta.

Total uterine artery blood volume flow rate in nulliparous women is associated with birth weight and gestational age at delivery

OBJECTIVES

To investigate the relationship between total uterine artery blood volume flow rate (TVFR) and birth weight and gestational age at delivery, and to establish normal ranges of TVFR throughout pregnancy.

METHODS

This was a prospective cohort study of 334 nulliparous women booking antenatal care at University College London Hospital between August 2008 and September 2009. Women underwent a transabdominal ultrasound examination of uterine arteries for measurement of TVFR at 12, 20 and 24 weeks' gestation. Pregnancy outcomes were recorded and linear regression was used to study the relationship between TVFR and gestational age at delivery and birth weight.

RESULTS

A total of 551 ultrasound scans were performed. There was a significant, positive correlation between TVFR at 11-13 weeks (TVFR1) and at 22-26 weeks (TVFR3) and birth weight. For every 100-mL/min increase in TVFR1 and TVFR3, there was an increase in birth weight of 45 g and 27 g, respectively. There was also a positive association between TVFR1 and gestational age at delivery, with a 1.4-day increase in gestational age for every 100-mL/min increase of TVFR1.

CONCLUSION

Ultrasound measurement of TVFR in the first trimester is significantly associated with both birth weight and gestational age at delivery. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Heterogeneity of respiratory distress syndrome: risk factors and morbidity associated with early and late gestation disease

BACKGROUND

Although respiratory distress syndrome (RDS) is considered a disease of prematurity, there is evidence to suggest heterogeneity between early and late gestation RDS. We examined the epidemiologic features of RDS occurring at early and late gestation.

METHODS

We conducted a retrospective cohort study including live births in the United States in 2005-06, with information obtained from the National Center for Health Statistics. Early (<32 weeks) and late gestation RDS (≥39 weeks) were contrasted in terms of risk factors and associations with pregnancy complications, obstetric intervention and co-morbidity. Logistic regression was used to quantify the effects of risk factors, while other associations were quantified descriptively.

RESULTS

There were 27,971 RDS cases, yielding an incidence of 6.4 per 1000 live births. Early and late gestation RDS differed in terms of risk factors, with factors such as multi-fetal gestation more strongly associated with early (adjusted odds ratio [aOR] 11.6, 95 % confidence interval 11.0-12.2) compared with late gestation RDS (aOR 3.66, 95 % confidence interval 2.68-4.98). The morbidity correlates of early and late gestation RDS also differed substantially; neonatal seizures were less strongly associated with early (OR 5.90, 95 % confidence interval 3.67-9.47) compared with late gestation RDS (OR 33.1, 95 % confidence interval 27.2-40.2), while meconium aspiration syndrome was not significantly associated with early gestation RDS (OR 1.87, 95 % confidence interval 0.94-3.72) and very strongly associated with late gestation RDS (OR 39.8, 95 % confidence interval 34.7-45.6).

CONCLUSIONS

Differences in risk factors and morbidity correlates of early and late gestation RDS suggest that these entities represent two distinct diseases.

Bedside diagnosis of two major clinical phenotypes of hypertensive disorders of pregnancy

OBJECTIVE

To investigate the hypothesis that fetal abdominal circumference (AC) and uterine artery (UtA) Doppler pulsatility index (PI) could be used to select two homogeneous subgroups of women affected by hypertensive disorders of pregnancy (HDP), characterized by the coexistence of maternal hypertension with and without intrauterine growth restriction (IUGR).

METHODS

This was a multicenter retrospective study of cases affected by HDP in whom fetal AC and UtA-PI had been measured at admission to fetomaternal medicine units. Maternal characteristics, pregnancy complications and outcome were recorded. These data allowed us to model the characteristics of fetal growth in cases affected by HDP, and to design composite indicators of risk factors for maternal metabolic syndrome and of severity for maternal functional organ damage.

RESULTS

Measurements of fetal AC and UtA-PI allowed us to define a group of HDP cases with appropriate-for-gestational-age (AGA) fetuses (HDP-AGA), diagnosed by normal fetal AC and UtA-PI (n = 205), and a group of HDP cases with IUGR fetuses (HDP-IUGR), diagnosed by fetal AC < 5(th) centile and UtA-PI > 95(th) centile (n = 124). Curves fitted to the birth weights of these two groups were significantly different, but gestational age at admission for HDP (< 34 or ≥ 34 weeks) did not show an independent association with birth weight. When birth weight was expressed as a Z-score with respect to local reference charts, the average corresponded to the 6(th) and 48(th) centiles, respectively. The occurrence of HDP-AGA (as compared with HDP-IUGR) was significantly associated with risk factors for maternal metabolic syndrome (odds ratio, 2.79 (95% CI, 1.57-4.97)), independent of gestational age. The same risk factors yielded non-significant odds ratios for the development of late-onset (vs early-onset) HDP. Women with HDP-IUGR had worse clinical outcomes.

CONCLUSIONS

This study provides new information based on simple prenatal bedside examinations that might help to differentiate HDP-IUGR from HDP-AGA fetuses. These groups are associated with different fetal growth patterns and risk factors, independent of gestational age at onset of the disease. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

The association between temporal changes in the use of obstetrical intervention and small-for-gestational age live births

BACKGROUND

The literature attributes secular declines in small-for-gestational age (SGA) live births to changes in maternal smoking and other maternal characteristics. However, there are reasons to believe that the observed reductions in SGA may be a consequence of early delivery following obstetric intervention.

METHODS

We examined temporal trends in obstetrical intervention and SGA among singleton live births in the United States from 1990 to 2010. The modified Kitagawa decomposition, based on the fetuses-at-risk approach, was used to assess the relative contribution of changes in the gestational age distribution and gestational age-specific SGA to overall changes in SGA. Reductions in SGA rates due to a left shift in the gestational age distribution were assumed to primarily reflect increased obstetrical intervention, whereas decreases in overall SGA due to decreases in gestational-age-specific SGA rates were assumed to reflect declines in risk factors.

RESULTS

Temporal trends in SGA followed a non-linear pattern, with substantial declines from 10.1% in 1990-92 to 8.9% in 2002-04, followed by a small increase to 9.1% in 2008-10. Rates of maternal smoking steadily decreased throughout the same time period and changes in SGA rates were more consistent with changes in the gestational age distribution. The modified Kitagawa decomposition analysis also attributed the initial decline in SGA rates to changes in the gestational age distribution.

CONCLUSIONS

Complex temporal pattern in SGA rates cannot be explained by the linear pattern of changes in factors like maternal smoking. Changes in the gestational age distribution are more consistent with the observed secular trends in SGA rates.

Doppler Assessment of Uterine Blood Flow in Pre-eclampsia: A Review

Doppler ultrasonography plays an ever-increasing role in obstetric imaging. Although commonly purported to assess blood flow, most studies in this area report purely on velocimetric parameters, rather than true volumetric flow. This review article highlights the physiological importance of this distinction, and reports on a literature review of uterine artery Doppler interrogation in the context of pre-eclampsia, which identified only four original research papers that attempted to assess blood flow. Attention is needed for true volumetric flow assessment in pre-eclampsia research, which may permit a more complete conceptualisation of the pathogenesis and haemodynamic consequences of this condition.

[Pathophysiological changes of umbilical vessels in intrauterine growth restriction]

INTRODUCTION

The prevalence of intrauterine growth restriction is 4-5000/100,000 births, and they give the majority of perinatal morbidity.

AIM

The aim of the authors was to compare the pathomorphologic data and vasoreactivity of umbilical vessels and placenta of small for date newborns to that of the normal pregnancies.

METHOD

Samples of the umbilical cord and placenta were divided into case and control groups. Two 10 cm long segments were cut of the umbilical cord at placental insertion. Tissue bath experiment was performed on umbilical vessels and pathomorphologic data were collected according to the Royal College of Pathologists' protocol.

RESULTS

After the development of basal tone, oxytocin and desmopressin did not enhance the vascular contraction, but the pathomorphological and ultrasonographic data were significantly different in the two groups.

CONCLUSIONS

The results indicate that umbilical vessels might not have oxytocin or vasopressin receptors. The pathomorphologic and flowmetric differences could be the causes of small birth weight.

A triple risk model for unexplained late stillbirth

BACKGROUND

The triple risk model for sudden infant death syndrome (SIDS) has been useful in understanding its pathogenesis. Risk factors for late stillbirth are well established, especially relating to maternal and fetal wellbeing.

DISCUSSION

We propose a similar triple risk model for unexplained late stillbirth. The model proposed by us results from the interplay of three groups of factors: (1) maternal factors (such as maternal age, obesity, smoking), (2) fetal and placental factors (such as intrauterine growth retardation, placental insufficiency), and (3) a stressor (such as venocaval compression from maternal supine sleep position, sleep disordered breathing). We argue that the risk factors within each group in themselves may be insufficient to cause the death, but when they interrelate may produce a lethal combination.

SUMMARY

Unexplained late stillbirth occurs when a fetus who is somehow vulnerable dies as a result of encountering a stressor and/or maternal condition in a combination which is lethal for them.

Third-trimester abnormal uterine artery Doppler findings are associated with adverse pregnancy outcomes

OBJECTIVES

To evaluate the association between third-trimester abnormal uterine artery Doppler findings and pregnancy outcomes.

METHODS

A prospective study was designed, including 198 consecutive singleton pregnancies between 27 and 41 weeks' gestation. In the study population, 144 had normal uterine artery Doppler waveforms, 37 had unilateral pathologic waveforms, and 17 had bilateral pathologic waveforms. Eighty patients had intrauterine growth restriction (IUGR), preeclampsia toxemia, or both, and 118 had no complications and served as a control group. The uterine artery Doppler waveform was considered abnormal when a notch or pulsatility index above the 90th percentile was noted.

RESULTS

In patients with bilateral pathologic uterine artery Doppler waveforms, the rates of cesarean delivery, small-for-gestational-age (SGA) neonates, preterm delivery, and low Apgar scores were increased compared to patients with normal or pathologic unilateral waveforms (P = .009; P > .001; P = .007; P > .001, respectively). The incidence rates for SGA neonates, cesarean delivery, and preterm delivery were significantly higher among patients without IUGR or preeclampsia toxemia when associated with pathologic bilateral waveforms in comparison to normal waveforms (P = .01 for all). A bilateral pathologic waveform was found to be an independent risk factor for cesarean delivery and SGA neonates. The incidence rates for SGA neonates and preterm delivery were significantly higher among patients with IUGR and/or preeclampsia toxemia when associated with bilateral abnormalities in comparison to normal waveforms (P = .01 for both).

CONCLUSIONS

Third-trimester abnormal uterine artery Doppler findings are associated with worse perinatal outcomes among patients both with and without pregnancy complications.

The relationship of a family history for hypertension, myocardial infarction, or stroke with cardiovascular physiology in young women

Cardiovascular disease (CVD) and preeclampsia share several pathophysiologic risk factors. We examined family history (FH) and physiologic status in 60 healthy, nulliparous women to determine the relationship between FH and known risk factors for CVD. Data are presented as mean ± standard error (SE). Decreased uterine blood flow was observed in women with FH of hypertension (+FH: 21.5 ± 1.7, no FH: 33.3 ± 9.0 mL/min; P = .04). Women reporting an FH of stroke showed increased alpha- and beta-adrenergic response, as measured by Valsalva maneuver (α: FH: 24.7 ± 1.9, -FH: 18.9 ± 1.1 mm Hg, P = .02; β: FH: 22.0 ± 2.1, -FH: 16.9 ± 1.4 mm Hg; P = .04), and increased cardiac output (4.83 ± 0.22 vs 4.31 ± 0.12 L/min; P = .01). We identified no significant physiologic associations linked to an FH of myocardial infarction. Our observations show significant differences in physiologic characteristics in women with specific CVD family histories. These data, coupled with known heritable contributions to CVD and preeclampsia, suggest a distinct physiologic phenotype that may link preeclampsia risk with FH of CVD, independent of pregnancy.

THE EVIDENCE FOR LATE-ONSET PRE-ECLAMPSIA AS A MATERNOGENIC DISEASE OF PREGNANCY

It is our opinion that the evidence from epidemiological observations, clinical trials and biological studies is strong enough to support the view of different origin and phenotypes of pre-eclampsia: placental, which usually occurs (but not exclusively) early in pregnancy and is associated with poor early placentation of different severity with subsequent restriction of foetal growth, at different stages of gestation; and maternogenic, which generally occurs late in pregnancy and it is not related to placental insufficiency and foetal growth restriction.

Fetal growth: a review of terms, concepts and issues relevant to obstetrics

The perinatal literature includes several potentially confusing and controversial terms and concepts related to fetal size and growth. This article discusses fetal growth from an obstetric perspective and addresses various issues including the physiologic mechanisms that determine fetal growth trajectories, known risk factors for abnormal fetal growth, diagnostic and prognostic issues related to restricted and excessive growth and temporal trends in fetal growth. Also addressed are distinctions between fetal growth 'standards' and fetal growth 'references', and between fetal growth charts based on estimated fetal weight vs those based on birth weight. Other concepts discussed include the incidence of fetal growth restriction in pregnancy (does the frequency of fetal growth restriction increase or decrease with increasing gestation?), the obstetric implications of studies showing associations between fetal growth and adult chronic illnesses (such as coronary heart disease) and the need for customizing fetal growth standards.

Significance of uteroplacental Doppler at midtrimester in patients with favourable obstetric history

OBJECTIVE

To reassess the usefulness of midtrimester uterine Doppler in low-risk multiparous women.

METHODS

We prospectively recruited low-risk pregnant women at 20-22 weeks attending our clinic. Among those, women with a favourable obstetric history (group A) were distinguished from nulliparous (group B) and of each group we measured uterine artery Doppler (pulsatility index (PI)). We evaluated the accuracy of uterine artery Doppler in the prediction of preeclampsia and small for gestational age (SGA) neonates.

RESULTS

Between January 2009 and October 2010, 382 women were included in the study of which 147 in group A and 235 in group B. Overall, 26/382 (6.8%) women presented preeclampsia and SGA occurred in 59/382 (15.4%) cases. In our population, at a 10% false positive rate (FPR) uterine artery Doppler showed a detection rate (DR) of 19.2% for preeclampsia and of 37.3% for SGA, with a higher sensitivity for SGA neonates delivered ≤ vs. >34 weeks (87% vs. 29.4%). The univariable receiver operating characteristics (ROC) curve by uterine artery PI yielded a significant prediction only for SGA in nulliparous women (areas under the curve (AUC) of 0.70; 95% CI 0.60-0.79).

CONCLUSIONS

Our data confirmed that midtrimester uterine artery Doppler is not an efficient strategy in anticipating the risk of pregnancy complications among low-risk multiparous women.

Uterine artery Doppler velocimetry and obstetric outcomes in connective tissue diseases diagnosed during the first trimester of pregnancy

OBJECTIVE

To evaluate the effect of connective tissue disease (CTD) diagnosed during the first trimester on uterine arteries (UtA) Doppler velocities and on pregnancy outcomes.

METHOD

Pregnant women were screened for CTDs during the first trimester, using a questionnaire, testing for autoantibodies, rheumatologic examination and UtA Doppler evaluations.

RESULTS

Out of 3932 women screened, 491 (12.5%) were screened positive at the questionnaire; of them, 165(33.6%) tested positive for autoantibodies, including 66 eventually diagnosed with undifferentiated connective tissue disease (UCTD), 28 with a definite CTD and 71 with insufficient criteria for a diagnosis. Controls were 326 women screened negative for autoantibodies. In logistic analysis, women diagnosed with either UCTD (OR = 7.9, 95% CI = 2.3-27.3) or overt CTD (OR = 24.9, 95% CI = 6.7-92.4), had increased rates of first trimester bilateral UtA notches compared with controls. The rates of bilateral UtA notches persisting in the second (15/94 vs 0/326, p < 0.001) and third trimesters (7/94 vs 0/326, p < .001) were higher among women with CTDs than in controls. The risk of complications (preeclampsia, fetal growth restriction, prematurity, diabetes, fetal loss) was higher (OR = 7.8, 95% CI = 3.6-17.0) among women with CTDs than in controls.

CONCLUSION

Women with undiagnosed CTDs have higher rates of bilateral UtA Doppler notches throughout pregnancy and increased rates of adverse pregnancy outcomes than controls.

Melatonin supplementation alters uteroplacental hemodynamics and fetal development in an ovine model of intrauterine growth restriction

Using a mid- to late-gestation ovine model of intrauterine growth restriction (IUGR), we examined uteroplacental blood flow and fetal growth during melatonin supplementation as a 2 × 2 factorial design. At day 50 of gestation, 32 ewes were supplemented with 5 mg of melatonin (MEL) or no melatonin (CON) and were allocated to receive 100% [adequate; (ADQ)] or 60% [restricted (RES)] of nutrient requirements until day 130 of gestation. Umbilical artery blood flow was increased from day 60 to day 110 of gestation in MEL vs. CON dams, while umbilical artery blood flow was decreased from day 80 to day 110 of gestation in RES vs. ADQ dams. At day 130 of gestation, uteroplacental hemodynamics, measured under general anesthesia, and fetal growth were evaluated. Uterine artery blood flow was decreased in RES vs. ADQ dams, while melatonin supplementation did not affect uterine artery blood flow. Total placentome weight and placentome number were not different between treatment groups. Fetal weight was decreased by nutrient restriction. Abdominal girth and ponderal index were increased in fetuses from MEL-ADQ dams vs. all other groups. Fetal biparietal distance was decreased in CON-RES vs. CON-ADQ dams, while melatonin supplementation rescued fetal biparietal distance. Fetal kidney length and width were increased by maternal melatonin treatment. Fetal cardiomyocyte area was altered by both maternal melatonin treatment and nutritional plane. In summary, melatonin may negate the consequences of IUGR during specific abnormalities in umbilical blood flow as long as sufficient uterine blood perfusion is maintained during pregnancy.

The natural history of pregnancy: diseases of early and late gestation

OBJECTIVE

To identify the disease processes underlying the increasing rate of gestational age-specific perinatal mortality observed under the fetuses-at-risk model.

DESIGN

Retrospective cohort study.

SETTING

USA and Nova Scotia, Canada.

POPULATION

Births in the USA (1995 and 2005) and Nova Scotia, Canada (1988-2007).

METHODS

Incidence rates of perinatal death and serious neonatal morbidity were calculated using the fetuses-at-risk approach (e.g. cumulative incidence of stillbirth during any gestational week per 1000 fetuses at risk of stillbirth).

MAIN OUTCOME MEASURES

Perinatal mortality and serious neonatal morbidity.

RESULTS

Perinatal mortality rates increased with advancing gestation. Rates of bronchopulmonary dysplasia, intraventricular haemorrhage, periventricular leucomalacia and retinopathy of prematurity were highest in early gestation, whereas rates of meconium aspiration syndrome and aspiration pneumonitis were highest at late term and post-term gestation. Respiratory depression (i.e. delay in initiating and maintaining respiration after birth, low 5-minute Apgar score or seizures caused by neonatal encephalopathy) showed an increase from 34 weeks onwards. The increase in perinatal mortality rates at late gestation was congruent with increases in respiratory depression. Other findings included a high incidence of respiratory distress syndrome at late gestation, a nonspecific pattern in the gestational age-specific rates of necrotising enterocolitis and high rates of sudden infant death syndrome at late gestation.

CONCLUSIONS

The natural history of pregnancy is characterised by diseases of early and late gestation, with the latter largely determining patterns of gestational age-specific perinatal mortality. These findings have implications for obstetric theory and provide insight into various contemporary phenomena, including the rise in iatrogenic late preterm birth.