First-Trimester Placental Growth Factor for the Prediction of Preeclampsia in Nulliparous Women: The Great Obstetrical Syndromes Cohort Study

First-Trimester PlGF and PAPP-A and the Risk of Placenta-Mediated Complications: PREDICTION Prospective Study

OBJECTIVES

This study aimed to estimate the association between low first-trimester maternal serum PlGF (placental growth factor) and PAPP-A (pregnancy-associated plasma protein A) and the risk of placenta-mediated complications.

METHODS

We performed a secondary analysis of the PREDICTION study, including nulliparous participants recruited at 11 to 14 weeks of pregnancy. First-trimester PlGF and PAPP-A levels were reported in multiples of the median (MoM) adjusted for maternal characteristics and gestational age. Participants were stratified into 4 groups based on absence/presence of low (<0.4 MoM) PlGF and PAPP-A values. A composite of adverse pregnancy outcomes (including preeclampsia, fetal growth restriction, fetal death, and placental abruption) was calculated for deliveries occurring before 34 weeks, before 37 weeks, and at or after 37 weeks.

RESULTS

Out of the 7262 participants, 86 (1.2%) experienced the composite outcome before 37 weeks of gestation, including 35 (0.4%) before 34 weeks. The combination of low PAPP-A and low PlGF levels was associated with the greatest risk of adverse outcomes before 37 weeks (21%) and before 34 weeks (12%) compared with low PlGF alone (7% and 3%), low PAPP-A alone (2% and 1%), or neither marker (1% and 0.4%, respectively; P < 0.001). For preterm preeclampsia specifically, the combination of low PAPP-A and low PlGF was also associated with a greater risk (12%) compared with low PlGF alone (6%), low PAPP-A alone (0.5%), or neither marker (0.7%; P < 0.001).

CONCLUSIONS

The combination of low PAPP-A and low PlGF levels is associated with a very high risk for adverse outcomes before 34 and 37 weeks. An isolated low PAPP-A should not be considered a risk factor for adverse pregnancy outcomes.

Machine Learning Algorithms Versus Classical Regression Models in Pre-Eclampsia Prediction: A Systematic Review

PURPOSE OF REVIEW

Machine learning (ML) approaches are an emerging alternative for healthcare risk prediction. We aimed to synthesise the literature on ML and classical regression studies exploring potential prognostic factors and to compare prediction performance for pre-eclampsia.

RECENT FINDINGS

From 9382 studies retrieved, 82 were included. Sixty-six publications exclusively reported eighty-four classical regression models to predict variable timing of onset of pre-eclampsia. Another six publications reported purely ML algorithms, whilst another 10 publications reported ML algorithms and classical regression models in the same sample with 8 of 10 findings that ML algorithms outperformed classical regression models. The most frequent prognostic factors were age, pre-pregnancy body mass index, chronic medical conditions, parity, prior history of pre-eclampsia, mean arterial pressure, uterine artery pulsatility index, placental growth factor, and pregnancy-associated plasma protein A. Top performing ML algorithms were random forest (area under the curve (AUC) = 0.94, 95% confidence interval (CI) 0.91-0.96) and extreme gradient boosting (AUC = 0.92, 95% CI 0.90-0.94). The competing risk model had similar performance (AUC = 0.92, 95% CI 0.91-0.92) compared with a neural network. Calibration performance was not reported in the majority of publications. ML algorithms had better performance compared to classical regression models in pre-eclampsia prediction. Random forest and boosting-type algorithms had the best prediction performance. Further research should focus on comparing ML algorithms to classical regression models using the same samples and evaluation metrics to gain insight into their performance. External validation of ML algorithms is warranted to gain insights into their generalisability.

First-trimester biomarkers and ultrasound biometries in relation to growth discordance in monochorionic diamniotic twins

Objective: The aim of this study was to investigate the association and predictive value between intertwin discordance in first trimester biometries crown-rump length (CRL) and nuchal translucency (NT), and the first trimester biochemical markers PAPP-A and free β-hCG in relation to birth weight discordance (BWD) ≥25% in monochorionic diamniotic (MCDA) twin pregnancies.Methods: First trimester screening information and pregnancy outcome data on MCDA twin pregnancies with delivery from July 2008 to July 2017 were retrieved from the Danish Fetal Medicine Database. CRL discordance was divided into: <10% (reference group) and ≥10%. NT discordance was divided into: <20% (reference group) and ≥20%. The twin pregnancies were classified according to BWD into the following groups: <10% (reference group), 10-24.9%, and ≥25% including cases undergoing umbilical cord occlusion due to selective fetal growth restriction (sFGR). The twin pregnancies with the most severe BWD (BWD ≥25%) were subdivided into three groups including cases with only one growth-restricted (<10th centile) infant defined as sFGR, and cases where both twins were <10th centile. Median multiples of the median (MoM) values of PAPP-A and free ß-hCG were compared with the group with BWD <10% using the Wilcoxon two-sample test. The ability of CRL discordance and NT discordance to predict BWD ≥25% was examined by the area under the receiver operator characteristic (ROC) curve.Results: A total of 762 MCDA pregnancies were included. The proportion of pregnancies with CRL discordance ≥10% and NT discordance ≥20% was significantly higher in the group with severe BWD discordance (27.0% vs. 4.7% (p < 0.001) and 40.9% vs. 23.9% (p = 0.001), respectively). When examining the three subgroups of severe BWD, we found a significantly higher percentage of pregnancies with CRL discordance ≥10% in the group where umbilical cord occlusion was performed (52.6% vs. 4.7% in the group with BWD <10% (p < 0.001)) and in the group of BWD ≥25% with sFGR (21.7% vs. 4.7% (p < 0.001)). Additionally, a significantly higher percentage of pregnancies with NT discordance ≥20% was found in the group where umbilical cord occlusion was performed (52.6% vs. 23.9% (p = 0.005)) and in the group with both twins <10th centile (66.7% vs. 23.9% (p = 0.003)). No statistically significant differences were found when comparing levels of PAPP-A and free β-hCG MoMs with the group with BWD <10%. In ROC curves, CRL discordance yielded an AUC for prediction of BWD ≥25% of 0.70 (95% CI 0.63-0.76), and for NT discordance AUC was 0.59 (95% CI 0.52-0.66)). OR for any BWD ≥ 25% was 6.7 (95% CI 3.8-12.0) for pregnancies with a CRL discordance ≥10% compared to pregnancies with a CRL discordance <10%.Conclusions: This study shows that a discordance in CRL and NT in MCDA twins are both significantly associated with development of BWD. The most important predictor remains CRL discordance ≥10%, thereby suggesting the unequal growth pattern in many cases with BWD is evident already in the first trimester of the pregnancy. No association was found between first trimester biochemical markers and severe BWD.

Maternal First-Trimester Alpha-Fetoprotein and Placenta-Mediated Pregnancy Complications

BACKGROUND

Maternal serum markers used for trisomy 21 screening are associated with placenta-mediated complications. Recently, there has been a transition from the traditional first-trimester screening (FTS) that included PAPP-A (pregnancy-associated plasma protein-A) and beta-hCG (human chorionic gonadotropin), to the enhanced FTS test, which added first-trimester AFP (alpha-fetoprotein) and PlGF (placental growth factor). However, whether elevated first-trimester AFP has a similar association with placenta-mediated complications to that observed for elevated second-trimester AFP remains unclear. Our objective was to estimate the association of first-trimester AFP with placenta-mediated complications and compare it with the corresponding associations of second-trimester AFP and other first-trimester serum markers.

METHODS

Retrospective population-based cohort study of women who underwent trisomy 21 screening in Ontario, Canada (2013-2019). The association of first-trimester AFP with placenta-mediated complications was estimated and compared with that of the traditional serum markers. The primary outcome was a composite of stillbirth or preterm placental complications (preeclampsia, birthweight less than third centile, or placental abruption).

RESULTS

A total of 244 990 and 96 167 women underwent FTS and enhanced FTS test screening, respectively. All markers were associated with the primary outcome, but the association for elevated first-trimester AFP (adjusted relative risk [aRR], 1.57 [95% CI, 1.37-1.81]) was weaker than that observed for low PAPP-A (aRR, 2.48 [95% CI, 2.2-2.8]), low PlGF (aRR, 2.28 [95% CI, 1.97-2.64]), and elevated second-trimester AFP (aRR, 1.97 [95% CI, 1.81-2.15]). When the models were adjusted for all 4 enhanced FTS test markers, elevated first-trimester AFP was no longer associated with the primary outcome (aRR, 0.77 [95% CI, 0.58-1.02]).

CONCLUSIONS

Unlike second-trimester AFP, elevated first-trimester AFP is not an independent risk factor for placenta-mediated complications.

First-trimester screening for Down syndrome using quadruple maternal biochemical markers

OBJECTIVES

Placental growth factor (PlGF) is used for first-trimester preeclampsia screening and could be combined with other biochemical markers for Down syndrome screening. We aim to estimate the predictive value of the combination of pregnancy-associated plasma protein (PAPP-A), free β-human chorionic gonadotropin (free β-hCG), placental growth factor (PlGF) and α-fetoprotein (AFP) with and without nuchal translucency.

METHODS

Singleton pregnancies recruited at 11-14 weeks and followed until delivery. The four maternal markers were measured using Kryptor (ThermoFisher-BRAHMS) and adjusted for gestational age and maternal characteristics. The risk of Down syndrome was calculated using the Fetal Medicine Foundation algorithm and multivariate linear regression analyses in all cases and in 2,200 controls. Receiver-operator characteristic (ROC) curves were used to calculate the detection and false-positive rates.

RESULTS

Twenty-six (0.2%) cases of Down syndrome were diagnosed among 13,386 participants. The combination of the four biomarkers could have detected 88% (95% CI: 72-97%) of the cases at a false-positive rate of 13% (95% CI: 12-15%). The addition of nuchal translucency would have increased the detection rate to 96% (95% CI: 82-99%) at a false-positive rate of 4% (95% CI: 4-5%) using a 1:300 cut-off and to 100% (95% CI: 89-100%) at a false-positive rate of 6% (95% CI: 5-8%) using a 1:500 cut-off.

CONCLUSIONS

First-trimester screening using biochemical markers allows the identification of approximately 88% of Down syndrome cases for a false-positive rate of 13%. The addition of nuchal translucency raises the detection rate above 95% with a false-positive rate below 5%.

Blood biomarkers to predict the onset of pre-eclampsia: A systematic review and meta-analysis

Pre-eclampsia is one of the most common pregnancy complications, and a major cause of fetal and maternal morbidity and mortality globally. Diagnosis currently takes place in the third trimester based on clinical symptoms. This systematic review and meta-analysis sought to determine the blood biomarkers that are associated with pre-eclampsia, and in particular, the biomarkers that could predict pre-eclampsia in early pregnancy. We searched the electronic databases (Medline, Embase, Cochrane Library) from inception up to March 2022. Prospective studies with 1000 or more participants that measured blood biomarkers to predict or diagnose pre-eclampsia have been included in this systematic review. Biomarkers' measurements were considered from the first up to the third trimester, but not during labor. Data concerning pre-eclampsia, biomarker measurements and study characteristics were extracted. Meta-analysis was performed when possible. We found a total of 43 studies (assessing 62 different biomarkers in 18,170 pregnancies, have been included in this systematic review, and a total of 6 studies (assessing 2 biomarkers have been included in the meta-analysis). Statistical analysis was performed for PlGF and sFlt-1. Mean difference in PlGF levels between pre-eclampsia and healthy pregnancies, appear to increase as the pregnancy progresses. Results of sFlt-1 meta-analysis were inconclusive. No significant publication bias was identified. This is the most comprehensive and up to date systematic review and meta-analysis on this important topic on blood biomarkers for the early prediction of pre-eclampsia. Further This research highlights the urgent needed for further discovery research to identify blood biomarkers that could predict the development of pre-eclampsia.

Clinical Application of Multi-Index Combined Risk Assessment in Early Pregnancy for Screening of Preeclampsia

Objective

To explore the predictive value of single-index screening or multi-index combined screening for preeclampsia.

Methods

From January 1, 2019, to December 31, 2021, pregnant women with a singleton pregnancy who had been regularly checked in each center since the first trimester (between 11 and 14 weeks of gestation) were retrieved from multiple participating centers. The risk calculation software LifeCycle 7.0 was used to calculate the risk values before 32 weeks, 34 weeks, and 37 weeks of gestation, and through a receiver operating characteristic (ROC) curve analysis, the predictive values of pregnancy-associated protein A (PAPP-A), the placental growth factor (PLGF), the mean arterial pressure (MAP), the uterine artery pulsatility index (UTPI), or a combined multi-index were calculated for preeclampsia.

Results

Finally, 22 pregnant women developed preeclampsia, and the area under the ROC curve of the PAPP-A + PLGF + MAP + UTPI combined screening program was greater than that of other screening programs before 37 weeks of gestation (AUC = 0.975, 0.946, or 0.840 for <32 weeks, <34 weeks, or <37 weeks, respectively). At 32 weeks, the Youden index was at its maximum.

Conclusion

PAPP-A + PLGF + MAP + UTPI combined screening is the optimal screening mode for preeclampsia screening before 37 weeks of gestation, and the combined prediction using multiple indicators in early pregnancy is more suitable for predicting the risk of early-onset preeclampsia.

A risk model that combines MAP, PlGF, and PAPP-A in the first trimester of pregnancy to predict hypertensive disorders of pregnancy

Whether the first trimester maternal mean arterial pressure (MAP), placental growth factor (PlGF), and pregnancy-associated plasma protein A (PAPP-A) can predict hypertensive disorders of pregnancy (HDP) is unclear. We conducted a retrospective case-control study with the total population of 539 gravidas, of these 447 had normal pregnancy, 27 had gestational hypertension (GH), 36 had preeclampsia (PE), and 29 had preeclampsia with severe features (SPE). Prediction for HDP was determined by the area under curve (AUC). Compared to the healthy group, the multiple of the median (MoM) for MAP was increased in the study groups, while PlGF and PAPP-A were decreased. When the cutoff values for MAP, PlGF, and PAPP-A were 1.069, 0.769, and 0.673 MoM, respectively, the sensitivities for predicting HDP were 0.517, 0.446, and 0.500 and the specificities were 0.744, 0.826, and 0.769, respectively. To predict GH, the highest AUC was 0.755 (95% CI: 0.655-0.856, p < 0.001) based on MAP, PlGF, and PAPP-A. The combined PlGF and PAPP-A had the highest AUC (0.683 [95% CI: 0.584-0.782, p < 0.001] and 0.755 [95% CI: 0.682-0.829, p < 0.001]) for prediction of PE and SPE. We found that MAP, serum levels of PlGF, and PAPP-A in the first trimester pregnancy are markers that predict HDP in the third trimester. The combination of markers is far superior to single markers alone. To improve the diagnostic value, specific cutoff values should be applied to GH, PE, SPE in each condition.

Pregnancy outcomes in nulliparous women with positive first-trimester preterm preeclampsia screening test: the Great Obstetrical Syndromes cohort study

BACKGROUND

The Fetal Medicine Foundation proposed a competing risks model for early identification of women at a high risk of preterm preeclampsia, typically associated with deep placentation disorders. The Great Obstetrical Syndromes include a spectrum of pregnancy complications (preeclampsia, intrauterine growth restriction, preterm birth, late spontaneous abortion, and abruptio placentae) that are also associated with deep placentation disorders.

OBJECTIVE

This study aimed to estimate the rate of placenta-mediated pregnancy complications in nulliparous women with a positive first-trimester Fetal Medicine Foundation preterm preeclampsia screening test.

STUDY DESIGN

We conducted a prospective cohort study of nulliparous women recruited at 11 to 14 weeks of gestation. Maternal characteristics, mean arterial blood pressure, levels of maternal serum biomarkers (pregnancy-associated plasma protein-A, placental growth factor, and soluble fms-like tyrosine kinase-1), and mean uterine artery pulsatility index were obtained to calculate the risk of preterm preeclampsia according to the Fetal Medicine Foundation algorithm. The predicted risks were dichotomized as a positive or negative test according to 2 risk cutoffs (1 in 70 and 1 in 100). The detection rate, false-positive rate, and positive and negative predictive values were calculated for placenta-mediated complications, including preeclampsia, small for gestational age (birthweight <10th percentile), fetal death, preterm birth, and a composite outcome, including any of the foregoing. The same analyses were computed for a composite of severe outcomes, including preterm preeclampsia, severe small for gestational age (less than third percentile), and fetal death.

RESULTS

We included 4575 participants with complete observations, of whom 494 (10.8%) had an estimated risk of preterm preeclampsia of ≥1 in 70 and 728 (15.9%) had a risk of ≥1 in 100. The test based on a risk cutoff of 1 in 70 could have correctly predicted up to 27% of preeclampsia, 55% of preterm preeclampsia, 18% of small for gestational age, 24% of severe small for gestational age, and 37% of fetal deaths at a 10% false-positive rate. The test based on a cutoff of 1 in 100 could have predicted correctly up to 35% of preeclampsia, 69% of preterm preeclampsia, 25% of small for gestational age, 30% of severe small for gestational age, and 53% of fetal deaths at a 15% false-positive rate. The positive predictive value of a screening test for preterm preeclampsia of ≥1 in 70 was 3% for preterm preeclampsia, 32% for the composite outcome, and 9% for the severe composite outcome.

CONCLUSION

Nulliparous women with a first-trimester positive preterm preeclampsia Fetal Medicine Foundation screening test are at a higher risk of both preterm preeclampsia and other severe placenta-mediated pregnancy complications. Approximately 1 woman of 10 identified as high risk by the Fetal Medicine Foundation algorithm developed at least 1 severe placenta-mediated pregnancy complication.

First-Trimester Preterm Preeclampsia Screening in Nulliparous Women: The Great Obstetrical Syndrome (GOS) Study

OBJECTIVES

To estimate the ability of a combination of first-trimester markers to predict preterm preeclampsia in nulliparous women.

METHODS

We conducted a prospective cohort study of nulliparous women with singleton gestations, recruited between 11⁰ and 13⁶ weeks gestation. Data on the following were collected: maternal age; ethnicity; chronic diseases; use of fertility treatment; body mass index; mean arterial blood pressure (MAP); serum levels of pregnancy-associated plasma protein A (PAPP-A), placental growth factor (PlGF), soluble fms-like tyrosine kinase-1 (sFlt-1), alpha fetoprotein (AFP), free beta human chorionic gonadotropin (ß-hCG); and mean uterine artery pulsatility index (UtA-PI). We constructed a proportional hazard model for the prediction of preterm preeclampsia selected based on the Akaike information criterion. A receiver operating characteristic curve was created with the predicted risk from the final model. Our primary outcome was preterm preeclampsia and our secondary outcome was a composite of preeclampsia, small for gestational age, intrauterine death, and preterm birth.

RESULTS

Among 4659 nulliparous women with singleton gestations, our final model included 4 variables: MAP MoM, log₁₀PlGF MoM, log₁₀AFP MoM and log₁₀UtA-PI MoM. We obtained an area under the curve of 0.84 (95% CI 0.75-0.93) with a detection rate of preterm preeclampsia of 55% (95% CI 37%-73%) and a false-positive rate of 10%. Using a risk cut-off with a false-positive rate of 10%, the positive predictive value for our composite outcome was 33% (95% CI 29%-37%).

CONCLUSIONS

The combination of MAP, maternal serum PlGF and AFP, and UtA-PI are useful to identify nulliparous women at high risk of preterm preeclampsia but also at high risk of other great obstetrical syndromes.

Incidence and risk factors for Preeclampsia in a cohort of healthy nulliparous pregnant women: a nested case-control study

The objective of this study is to determine the incidence, socio-demographic and clinical risk factors for preeclampsia and associated maternal and perinatal adverse outcomes. This is a nested case-control derived from the multicentre cohort study Preterm SAMBA, in five different centres in Brazil, with nulliparous healthy pregnant women. Clinical data were prospectively collected, and risk factors were assessed comparatively between PE cases and controls using risk ratio (RR) (95% CI) plus multivariate analysis. Complete data were available for 1,165 participants. The incidence of preeclampsia was 7.5%. Body mass index determined at the first medical visit and diastolic blood pressure over 75 mmHg at 20 weeks of gestation were independently associated with the occurrence of preeclampsia. Women with preeclampsia sustained a higher incidence of adverse maternal outcomes, including C-section (3.5 fold), preterm birth below 34 weeks of gestation (3.9 fold) and hospital stay longer than 5 days (5.8 fold) than controls. They also had worse perinatal outcomes, including lower birthweight (a mean 379 g lower), small for gestational age babies (RR 2.45 [1.52-3.95]), 5-minute Apgar score less than 7 (RR 2.11 [1.03-4.29]), NICU admission (RR 3.34 [1.61-6.9]) and Neonatal Near Miss (3.65 [1.78-7.49]). Weight gain rate per week, obesity and diastolic blood pressure equal to or higher than 75 mmHg at 20 weeks of gestation were shown to be associated with preeclampsia. Preeclampsia also led to a higher number of C-sections and prolonged hospital admission, in addition to worse neonatal outcomes.

Beneficial effects of nicotinamide on the mouse model of preeclampsia

Preeclampsia (PE) is a pregnancy related disorder that is characterized by hypertension and proteinuria in the mother. It is associated with impaired coagulation and liver function, and a variety of other detrimental effects. In severe cases without treatment, PE can progress to eclampsia and result in seizures, a life-threatening condition. Although the etiology of PE is largely unknown, sFlt-1 (soluble vascular endothelial growth factor receptor 1) released by the impaired placenta resulting from insufficient perfusion plays a critical role in PE, and phenotypes of PE can be induced by experimentally increasing sFlt-1. We and other investigators have proposed that endothelin-1 (ET-1) system is the mediator of the pathological effects of excess sFlt-1, and antagonists of ET-1 receptor block the effects of sFlt-1. Unfortunately, this class of drugs is teratogenic and unsuitable for treating pregnant women. Nicotinamide is a naturally occurring derivative of vitamin B3 in the body and inhibits ADP-ribosyl cyclase, which is activated by the ET-1 receptor. Therefore, if utilized, it would be expected to play a beneficial role in PE. In mouse models of PE, a high dose of nicotinamide shows great success in lowering blood pressure, correcting renal function and structure, prolonging pregnancy as well as increasing fetal weight/number. Nicotinamide, being generally regarded as safe, could be a promising substance to further investigate for use in clinical trials.