Circulating biomarkers associated with placental dysfunction and their utility for predicting fetal growth restriction

Investigating the IGF axis as a pathway for intergenerational effects

Early nutritional and growth experiences can impact development, metabolic function, and reproductive outcomes in adulthood, influencing health trajectories in the next generation. The insulin-like growth factor (IGF) axis regulates growth, metabolism, and energetic investment, but whether it plays a role in the pathway linking maternal experience with offspring prenatal development is unclear. To test this, we investigated patterns of maternal developmental weight gain (a proxy of early nutrition), young adult energy stores, age, and parity as predictors of biomarkers of the pregnancy IGF axis (n = 36) using data from the Cebu Longitudinal Health and Nutrition Survey in Metro Cebu, Philippines. We analyzed maternal conditional weight measures at 2, 8, and 22 years of age and leptin at age 22 (a marker of body fat/energy stores) in relation to free IGF-1 and IGFBP-3 in mid/late pregnancy (mean age = 27). Maternal IGF axis measures were also assessed as predictors of offspring fetal growth. Maternal age, parity, and age 22 leptin were associated with pregnancy free IGF-1, offspring birth weight, and offspring skinfold thickness. We find that free IGF-1 levels in pregnancy are more closely related to nutritional status in early adulthood than to preadult developmental nutrition and demonstrate significant effects of young adult leptin on offspring fetal fat mass deposition. We suggest that the previously documented finding that maternal developmental nutrition predicts offspring birth size likely operates through pathways other than the maternal IGF axis, which reflects more recent energy status.

The Relationship between Placental Shear Wave Elastography and Fetal Weight-A Prospective Study

Background/Objectives: The utility of shear wave elastography (SWE) as an adjunct to ultrasound biometry and Doppler velocimetry for the examination of placental dysfunction and suboptimal fetal growth is unclear. To date, limited data exist correlating the mechanical properties of placentae with fetal growth. This study aimed to investigate the relationship between placental shear wave velocity (SWV) and ultrasound estimated fetal weight (EFW), and to ascertain if placental SWV is a suitable proxy measure of placental function in the surveillance of small-for-gestational-age (SGA) pregnancies. Methods: This prospective, observational cohort study compared the difference in placental SWV between SGA and appropriate-for-gestational-age (AGA) pregnancies. There were 221 women with singleton pregnancies in the study cohort-136 (61.5%) AGA and 85 (38.5%) SGA. Fetal biometry, Doppler velocimetry, the deepest vertical pocket of amniotic fluid, and mean SWV were measured at 2-4-weekly intervals from recruitment to birth. Results: There was no difference in mean placental SWV in SGA pregnancies compared to AGA pregnancies, nor was there any relationship to EFW. Conclusions: Although other studies have shown some correlation between increased placental stiffness and SGA pregnancies, our investigation did not support this. The mechanical properties of placental tissue in SGA pregnancies do not result in placental SWVs that are apparently different from those of AGA controls. As this study did not differentiate between constitutionally or pathologically small fetuses, further studies in growth-restricted cohorts would be of benefit.

Prediction of preterm birth in growth-restricted and appropriate-for-gestational-age infants using maternal PlGF and the sFlt-1/PlGF ratio-A prospective study

OBJECTIVE

To assess the utility of placental growth factor (PlGF) levels and the soluble fms-like tyrosine kinase-1/placental growth factor (sFlt-1/PlGF) ratio to predict preterm birth (PTB) for infants with fetal growth restriction (FGR) and those appropriate for gestational age (AGA).

DESIGN

Prospective, observational cohort study.

SETTING

Tertiary maternity hospital in Australia.

POPULATION

There were 320 singleton pregnancies: 141 (44.1%) AGA, 83 (25.9%) early FGR (<32+0 weeks) and 109 (30.0%) late FGR (≥32+0 weeks).

METHODS

Maternal serum PlGF and sFlt-1/PlGF ratio were measured at 4-weekly intervals from recruitment to delivery. Low maternal PlGF levels and elevated sFlt-1/PlGF ratio were defined as <100 ng/L and >5.78 if <28 weeks and >38 if ≥28 weeks respectively. Cox proportional hazards models were used. The analysis period was defined as the time from the first measurement of PlGF and sFlt-1/PlGF ratio to the time of birth or censoring.

MAIN OUTCOME MEASURES

The primary study outcome was overall PTB. The relative risks (RR) of birth within 1, 2 and 3 weeks and for medically indicated and spontaneous PTB were also ascertained.

RESULTS

The early FGR cohort had lower median PlGF levels (54 versus 229 ng/L, p < 0.001) and higher median sFlt-1 levels (2774 ng/L versus 2096 ng/L, p < 0.001) and sFlt-1/PlGF ratio higher (35 versus 10, p < 0.001). Both PlGF <100 ng/L and elevated sFlt-1/PlGF ratio were strongly predictive for PTB as well as PTB within 1, 2 and 3 weeks of diagnosis. For both FGR and AGA groups, PlGF <100 ng/L or raised sFlt-1/PlGF ratio were strongly associated with increased risk for medically indicated PTB. The highest RR was seen in the FGR cohort when PlGF was <100 ng/L (RR 35.20, 95% CI 11.48-175.46).

CONCLUSIONS

Low maternal PlGF levels and elevated sFlt-1/PlGF ratio are potentially useful to predict PTB in both FGR and AGA pregnancies.

Prediction of preterm birth in women with fetal growth restriction - Is the weekly change in sFlt-1/PlGF ratio or PlGF levels useful?

INTRODUCTION

To assess the rate of change in soluble fms-like tyrosine kinase-1/placental growth factor (sFlt-1/PlGF) ratio and PlGF levels per week compared to a single sFlt-1/PlGF ratio or PlGF level to predict preterm birth for pregnancies complicated by fetal growth restriction.

MATERIAL AND METHODS

A prospective cohort study of pregnancies complicated by isolated fetal growth restriction. Maternal serum PlGF levels and the sFlt-1/PlGF ratio were measured at 4-weekly intervals from recruitment to delivery. We investigated the utility of PlGF levels, sFlt-1/PlGF ratio, change in PlGF levels per week or sFlt-1/PlGF ratio per week. Cox-proportional hazard models and Harrell's C concordance statistic were used to evaluate the effect of biomarkers on time to preterm birth.

RESULTS

The total study cohort was 158 pregnancies comprising 91 (57.6%) with fetal growth restriction and 67 (42.4%) with appropriate for gestational age controls. In the fetal growth restriction cohort, sFlt-1/PlGF ratio and PlGF levels significantly affected time to preterm birth (Harrell's C: 0.85-0.76). The rate of increase per week of the sFlt-1/PlGF ratio (hazard ratio [HR] 3.91, 95% confidence interval [CI]: 1.39-10.99, p = 0.01, Harrell's C: 0.74) was positively associated with preterm birth but change in PlGF levels per week was not (HR 0.65, 95% CI: 0.25-1.67, p = 0.37, Harrell's C: 0.68).

CONCLUSIONS

Both a high sFlt-1/PlGF ratio and low PlGF levels are predictive of preterm birth in women with fetal growth restriction. Although the rate of increase of the sFlt-1/PlGF ratio predicts preterm birth, it is not superior to either a single elevated sFlt-1/PlGF ratio or low PlGF level.

Placental growth factor and fetoplacental Doppler indices in combination predict preterm birth reliably in pregnancies complicated by fetal growth restriction

OBJECTIVE

To assess the association between placental biomarkers (placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFlt-1)/PlGF ratio) and fetoplacental Doppler indices (umbilical artery (UA) pulsatility index (PI) and uterine artery (UtA) PI) in various combinations for predicting preterm birth (PTB) in pregnancies complicated by fetal growth restriction (FGR).

METHODS

This was a prospective observational cohort study, performed at Mater Mother's Hospital in Brisbane, Queensland, Australia, from May 2022 to June 2023, of pregnancies complicated by FGR and appropriate-for-gestational-age (AGA) pregnancies. Maternal serum PlGF levels, sFlt-1/PlGF ratio, UA-PI and UtA-PI were measured at 2-4-weekly intervals from recruitment until delivery. Harrell's concordance statistic (Harrell's C) was used to evaluate multivariable Cox proportional hazards regression models featuring various combinations of placental biomarkers and fetoplacental Doppler indices to ascertain the best combination to predict PTB (< 37 weeks). Multivariable Cox regression models were used with biomarkers as time-varying covariates.

RESULTS

The study cohort included 320 singleton pregnancies, comprising 179 (55.9%) affected by FGR, defined according to a Delphi consensus, and 141 (44.1%) with an AGA fetus. In the FGR cohort, both low PlGF levels and elevated sFlt-1/PlGF ratio were associated with significantly shorter time to PTB. Low PlGF was a better predictor of PTB than was either sFlt-1/PlGF ratio or a combination of PlGF and sFlt-1/PlGF ratio (Harrell's C, 0.81, 0.78 and 0.79, respectively). Although both Doppler indices were significantly associated with time to PTB, in combination they were better predictors of PTB than was either UA-PI > 95th centile or UtA-PI > 95th centile alone (Harrell's C, 0.82, 0.75 and 0.76, respectively). Predictive utility for PTB was best when PlGF < 100 ng/L, UA-PI > 95th centile and UtA-PI > 95th centile were combined (Harrell's C, 0.88) (hazard ratio, 32.99; 95% CI, 10.74-101.32).

CONCLUSIONS

Low maternal serum PlGF level (< 100 ng/L) and abnormal fetoplacental Doppler indices (UA-PI > 95th centile and UtA-PI > 95th centile) in combination have the greatest predictive utility for PTB in pregnancies complicated by FGR. Their assessment may help guide clinical management of these complex pregnancies. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

The influence of birthweight on mortality and severe neonatal morbidity in late preterm and term infants: an Australian cohort study

Background

The aim of this study was to detail incidence rates and relative risks for severe adverse perinatal outcomes by birthweight centile categories in a large Australian cohort of late preterm and term infants.

Methods

This was a retrospective cohort study of singleton infants (≥34+0 weeks gestation) between 2000 and 2018 in Queensland, Australia. Study outcomes were perinatal mortality, severe neurological morbidity, and other severe morbidity. Categorical outcomes were compared using Chi-squared tests. Continuous outcomes were compared using t-tests. Multinomial logistic regression investigated the effect of birthweight centile on study outcomes.

Findings

The final cohort comprised 991,042 infants. Perinatal mortality occurred in 1944 infants (0.19%). The incidence and risk of perinatal mortality increased as birthweight decreased, peaking for infants <1st centile (perinatal mortality rate 13.2/1000 births, adjusted Relative Risk Ratio (aRRR) of 12.96 (95% CI 10.14, 16.57) for stillbirth and aRRR 7.55 (95% CI 3.78, 15.08) for neonatal death). Severe neurological morbidity occurred in 7311 infants (0.74%), with the highest rate (19.6/1000 live births) in <1st centile cohort. There were 75,243 cases of severe morbidity (7.59% livebirths), with the peak incidence occurring in the <1st centile category (12.3% livebirths). The majority of adverse outcomes occurred in infants with birthweights between 10 and 90th centile. Almost 2 in 3 stillbirths, and approximately 3 in 4 cases of neonatal death, severe neurological morbidity or other severe morbidity occurred within this birthweight range.

Interpretation

Although the incidence and risk of perinatal mortality, severe neurological morbidity and severe morbidity increased at the extremes of birthweight centiles, the majority of these outcomes occurred in infants that were apparently "appropriately grown" (i.e., birthweight 10th-90th centile).

Funding

National Health and Medical Research Council, Mater Foundation, Royal Australian College of Obstetricians and Gynaecologists Women's Health Foundation - Norman Beischer Clinical Research Scholarship, Cerebral Palsy Alliance, University of Queensland Research Scholarship.

Mediation analysis quantifying the magnitude of stillbirth risk attributable to small for gestational age infants

BACKGROUND

Many risk factors for stillbirth are linked to placental dysfunction, which leads to suboptimal intrauterine growth and small for gestational age infants. Such infants also have an increased risk for stillbirth.

OBJECTIVE

This study aimed to investigate the effect of known causal risk factors for stillbirth, and to identify those that have a large proportion of their risk mediated through small for gestational age birth.

STUDY DESIGN

This retrospective cohort study used data from all births in the state of Queensland, Australia between 2000 and 2018. The total effects of exposures on the odds of stillbirth were determined using multivariable, clustered logistic regression models. Mediation analysis was performed using a counterfactual approach to determine the indirect effect and percentage of effect mediated through small for gestational age. For risk factors significantly mediated through small for gestational age, the relative risks of stillbirth were compared between small for gestational age and appropriate for gestational age infants. We also investigated the proportion of risk mediated via small for gestational age for late stillbirths (≥28 weeks).

RESULTS

The initial data set consisted of 1,105,612 births. After exclusions, the final study cohort constituted 925,053 births. Small for gestational age births occurred in 9.9% (91,859/925,053) of the study cohort. Stillbirths occurred in 0.5% of all births (4234/925,053) and 1.5% of small for gestational age births (1414/91,859). Births at ≥28 weeks occurred in 99.4% (919,650/925,053) of the study cohort and in 98.9% (90,804/91,859) of all small for gestational age births. Of the ≥28-week births, stillbirths occurred in 0.2% (2156/919,650) of all births and 0.8% (677/90,804) of the small for gestational age births. Overall, increased odds of stillbirth were significantly mediated through small for gestational age for age <20 years, low socioeconomic status, Indigenous ethnicity, birth in sub-Saharan and North Africa or the Middle East, smoking, nulliparity, multiple pregnancy, assisted conception, previous stillbirth, preeclampsia, and renal disease. Preeclampsia had the largest proportion mediated through small for gestational age (66.7%), followed by nulliparity (61.6%), smoking (29.4%), North-African or Middle Eastern ethnicity (27.6%), multiple pregnancy (26.3%), low socioeconomic status (25.8%), and Indigenous status (18.7%). Sensitivity analysis showed that for late stillbirths, the portions mediated through small for gestational age remained very similar for many of the risk factors.

CONCLUSION

Although small for gestational age is an important mediator between many pregnancy risk factors and stillbirth, mitigating the risk of small for gestational age is likely to be of value only when it is a major contributor in the pathway to fetal demise.

Quantitative Proteomics of Maternal Blood Plasma in Isolated Intrauterine Growth Restriction

Intrauterine growth restriction (IUGR) remains a significant concern in modern obstetrics, linked to high neonatal health problems and even death, as well as childhood disability, affecting adult quality of life. The role of maternal and fetus adaptation during adverse pregnancy is still not completely understood. This study aimed to investigate the disturbance in biological processes associated with isolated IUGR via blood plasma proteomics. The levels of 125 maternal plasma proteins were quantified by liquid chromatography-multiple reaction monitoring mass spectrometry (LC-MRM MS) with corresponding stable isotope-labeled peptide standards (SIS). Thirteen potential markers of IUGR (Gelsolin, Alpha-2-macroglobulin, Apolipoprotein A-IV, Apolipoprotein B-100, Apolipoprotein(a), Adiponectin, Complement C5, Apolipoprotein D, Alpha-1B-glycoprotein, Serum albumin, Fibronectin, Glutathione peroxidase 3, Lipopolysaccharide-binding protein) were found to be inter-connected in a protein-protein network. These proteins are involved in plasma lipoprotein assembly, remodeling, and clearance; lipid metabolism, especially cholesterol and phospholipids; hemostasis, including platelet degranulation; and immune system regulation. Additionally, 18 proteins were specific to a particular type of IUGR (early or late). Distinct patterns in the coagulation and fibrinolysis systems were observed between isolated early- and late-onset IUGR. Our findings highlight the complex interplay of immune and coagulation factors in IUGR and the differences between early- and late-onset IUGR and other placenta-related conditions like PE. Understanding these mechanisms is crucial for developing targeted interventions and improving outcomes for pregnancies affected by IUGR.