Cooking with liquefied petroleum gas or biomass and fetal growth outcomes: a multi-country randomised controlled trial.

BACKGROUND: Household air pollution might lead to fetal growth restriction during pregnancy. We aimed to investigate whether a liquefied petroleum gas (LPG) intervention to reduce personal exposures to household air pollution during pregnancy would alter fetal growth. METHODS: The Household Air Pollution Intervention Network (HAPIN) trial was an open-label randomised controlled trial conducted in ten resource-limited settings across Guatemala, India, Peru, and Rwanda. Pregnant women aged 18-34 years (9-19 weeks of gestation) were randomly assigned in a 1:1 ratio to receive an LPG stove, continuous fuel delivery, and behavioural messaging or to continue usual cooking with biomass for 18 months. We conducted ultrasound assessments at baseline, 24-28 weeks of gestation (the first pregnancy visit), and 32-36 weeks of gestation (the second pregnancy visit), to measure fetal size; we monitored 24 h personal exposures to household air pollutants during these visits; and we weighed children at birth. We conducted intention-to-treat analyses to estimate differences in fetal size between the intervention and control group, and exposure-response analyses to identify associations between household air pollutants and fetal size. This trial is registered with ClinicalTrials.gov (NCT02944682). FINDINGS: Between May 7, 2018, and Feb 29, 2020, we randomly assigned 3200 pregnant women (1593 to the intervention group and 1607 to the control group). The mean gestational age was 14·5 (SD 3·0) weeks and mean maternal age was 25·6 (4·5) years. We obtained ultrasound assessments in 3147 (98·3%) women at baseline, 3052 (95·4%) women at the first pregnancy visit, and 2962 (92·6%) at the second pregnancy visit, through to Aug 25, 2020. Intervention adherence was high (the median proportion of days with biomass stove use was 0·0%, IQR 0·0-1·6) and pregnant women in the intervention group had lower mean exposures to particulate matter with a diameter less than 2·5 µm (PM2·5; 35·0 [SD 37·2] µg/m3vs 103·3 [97·9] µg/m3) than did women in the control group. We did not find differences in averaged post-randomisation Z scores for head circumference (0·30 vs 0·39; p=0·04), abdominal circumference (0·38 vs 0·39; p=0·99), femur length (0·44 vs 0·45; p=0·73), and estimated fetal weight or birthweight (-0·13 vs -0·12; p=0·70) between the intervention and control groups. Personal exposures to household air pollutants were not associated with fetal size. INTERPRETATION: Although an LPG cooking intervention successfully reduced personal exposure to air pollution during pregnancy, it did not affect fetal size. Our findings do not support the use of unvented liquefied petroleum gas stoves as a strategy to increase fetal growth in settings were biomass fuels are used predominantly for cooking. FUNDING: US National Institutes of Health and Bill & Melinda Gates Foundation. TRANSLATIONS: For the Kinyarwanda, Spanish and Tamil translations of the abstract see Supplementary Materials section.

Accuracy of prenatal and postnatal biomarkers for estimating gestational age: a systematic review and meta-analysis.

Background: Knowledge of gestational age (GA) is key in clinical management of individual obstetric patients, and critical to be able to calculate rates of preterm birth and small for GA at a population level. Currently, the gold standard for pregnancy dating is measurement of the fetal crown rump length at 11-14 weeks of gestation. However, this is not possible for women first presenting in later pregnancy, or in settings where routine ultrasound is not available. A reliable, cheap and easy to measure GA-dependent biomarker would provide an important breakthrough in estimating the age of pregnancy. Therefore, the aim of this study was to determine the accuracy of prenatal and postnatal biomarkers for estimating gestational age (GA). Methods: Systematic review prospectively registered with PROSPERO (CRD42020167727) and reported in accordance with the PRISMA-DTA. Medline, Embase, CINAHL, LILACS, and other databases were searched from inception until September 2023 for cohort or cross-sectional studies that reported on the accuracy of prenatal and postnatal biomarkers for estimating GA. In addition, we searched Google Scholar and screened proceedings of relevant conferences and reference lists of identified studies and relevant reviews. There were no language or date restrictions. Pooled coefficients of correlation and root mean square error (RMSE, average deviation in weeks between the GA estimated by the biomarker and that estimated by the gold standard method) were calculated. The risk of bias in each included study was also assessed. Findings: Thirty-nine studies fulfilled the inclusion criteria: 20 studies (2,050 women) assessed prenatal biomarkers (placental hormones, metabolomic profiles, proteomics, cell-free RNA transcripts, and exon-level gene expression), and 19 (1,738,652 newborns) assessed postnatal biomarkers (metabolomic profiles, DNA methylation profiles, and fetal haematological components). Among the prenatal biomarkers assessed, human chorionic gonadotrophin measured in maternal serum between 4 and 9 weeks of gestation showed the highest correlation with the reference standard GA, with a pooled coefficient of correlation of 0.88. Among the postnatal biomarkers assessed, metabolomic profiling from newborn blood spots provided the most accurate estimate of GA, with a pooled RMSE of 1.03 weeks across all GAs. It performed best for term infants with a slightly reduced accuracy for preterm or small for GA infants. The pooled RMSEs for metabolomic profiling and DNA methylation profile from cord blood samples were 1.57 and 1.60 weeks, respectively. Interpretation: We identified no antenatal biomarkers that accurately predict GA over a wide window of pregnancy. Postnatally, metabolomic profiling from newborn blood spot provides an accurate estimate of GA, however, as this is known only after birth it is not useful to guide antenatal care. Further prenatal studies are needed to identify biomarkers that can be used in isolation, as part of a biomarker panel, or in combination with other clinical methods to narrow prediction intervals of GA estimation. Funding: The research was funded by the Bill and Melinda Gates Foundation (INV-000368). ATP is supported by the Oxford Partnership Comprehensive Biomedical Research Centre with funding from the NIHR Biomedical Research Centre funding scheme. The views expressed are those of the authors and not necessarily those of the UK National Health Service, the NIHR, the Department of Health, or the Department of Biotechnology. The funders of this study had no role in study design, data collection, analysis or interpretation of the data, in writing the paper or the decision to submit for publication.

Automating the Human Action of First-Trimester Biometry Measurement from Real-World Freehand Ultrasound.

OBJECTIVE: Automated medical image analysis solutions should closely mimic complete human actions to be useful in clinical practice. However, more often an automated image analysis solution represents only part of a human task, which restricts its practical utility. In the case of ultrasound-based fetal biometry, an automated solution should ideally recognize key fetal structures in freehand video guidance, select a standard plane from a video stream and perform biometry. A complete automated solution should automate all three subactions. METHODS: In this article, we consider how to automate the complete human action of first-trimester biometry measurement from real-world freehand ultrasound. In the proposed hybrid convolutional neural network (CNN) architecture design, a classification regression-based guidance model detects and tracks fetal anatomical structures (using visual cues) in the ultrasound video. Several high-quality standard planes that contain the mid-sagittal view of the fetus are sampled at multiple time stamps (using a custom-designed confident-frame detector) based on the estimated probability values associated with predicted anatomical structures that define the biometry plane. Automated semantic segmentation is performed on the selected frames to extract fetal anatomical landmarks. A crown-rump length (CRL) estimate is calculated as the mean CRL from these multiple frames. RESULTS: Our fully automated method has a high correlation with clinical expert CRL measurement (Pearson's p = 0.92, R-squared [R2] = 0.84) and a low mean absolute error of 0.834 (weeks) for fetal age estimation on a test data set of 42 videos. CONCLUSION: A novel algorithm for standard plane detection employs a quality detection mechanism defined by clinical standards, ensuring precise biometric measurements.

Effects of a liquefied petroleum gas stove intervention on stillbirth, congenital anomalies and neonatal mortality: A multi-country household air pollution intervention network trial.

Household air pollution (HAP) from cooking with solid fuels used during pregnancy has been associated with adverse pregnancy outcomes. The Household Air Pollution Intervention Network (HAPIN) trial was a randomized controlled trial that assessed the impact of a liquefied petroleum gas (LPG) stove and fuel intervention on health in Guatemala, India, Peru, and Rwanda. Here we investigated the effects of the LPG stove and fuel intervention on stillbirth, congenital anomalies and neonatal mortality and characterized exposure-response relationships between personal exposures to fine particulate matter (PM2.5), black carbon (BC) and carbon monoxide (CO) and these outcomes. Pregnant women (18 to <35 years of age; gestation confirmed by ultrasound at 9 to <20 weeks) were randomly assigned to intervention or control arms. We monitored these fetal and neonatal outcomes and personal exposure to PM2.5, BC and CO three times during pregnancy, we conducted intention-to-treat (ITT) and exposure-response (E-R) analyses to determine if the HAPIN intervention and corresponding HAP exposure was associated with the risk of fetal/neonatal outcomes. A total of 3200 women (mean age 25.4 ± 4.4 years, mean gestational age at randomization 15.4 ± 3.1 weeks) were included in this analysis. Relative risks for stillbirth, congenital anomaly and neonatal mortality were 0.99 (0.60, 1.66), 0.92 (95 % CI 0.52, 1.61), and 0.99 (0.54, 1.85), respectively, among women in the intervention arm compared to controls in an ITT analysis. Higher mean personal exposures to PM2.5, CO and BC during pregnancy were associated with a higher, but statistically non-significant, incidence of adverse outcomes. The LPG stove and fuel intervention did not reduce the risk of these outcomes nor did we find evidence supporting an association between personal exposures to HAP and stillbirth, congenital anomalies and neonatal mortality.

Liquefied Petroleum Gas or Biomass Cooking and Severe Infant Pneumonia.

BACKGROUND: Exposure to household air pollution is a risk factor for severe pneumonia. The effect of replacing biomass cookstoves with liquefied petroleum gas (LPG) cookstoves on the incidence of severe infant pneumonia is uncertain. METHODS: We conducted a randomized, controlled trial involving pregnant women 18 to 34 years of age and between 9 to less than 20 weeks' gestation in India, Guatemala, Peru, and Rwanda from May 2018 through September 2021. The women were assigned to cook with unvented LPG stoves and fuel (intervention group) or to continue cooking with biomass fuel (control group). In each trial group, we monitored adherence to the use of the assigned cookstove and measured 24-hour personal exposure to fine particulate matter (particles with an aerodynamic diameter of ≤2.5 µm [PM2.5]) in the women and their offspring. The trial had four primary outcomes; the primary outcome for which data are presented in the current report was severe pneumonia in the first year of life, as identified through facility surveillance or on verbal autopsy. RESULTS: Among 3200 pregnant women who had undergone randomization, 3195 remained eligible and gave birth to 3061 infants (1536 in the intervention group and 1525 in the control group). High uptake of the intervention led to a reduction in personal exposure to PM2.5 among the children, with a median exposure of 24.2 µg per cubic meter (interquartile range, 17.8 to 36.4) in the intervention group and 66.0 µg per cubic meter (interquartile range, 35.2 to 132.0) in the control group. A total of 175 episodes of severe pneumonia were identified during the first year of life, with an incidence of 5.67 cases per 100 child-years (95% confidence interval [CI], 4.55 to 7.07) in the intervention group and 6.06 cases per 100 child-years (95% CI, 4.81 to 7.62) in the control group (incidence rate ratio, 0.96; 98.75% CI, 0.64 to 1.44; P = 0.81). No severe adverse events were reported to be associated with the intervention, as determined by the trial investigators. CONCLUSIONS: The incidence of severe pneumonia among infants did not differ significantly between those whose mothers were assigned to cook with LPG stoves and fuel and those whose mothers were assigned to continue cooking with biomass stoves. (Funded by the National Institutes of Health and the Bill and Melinda Gates Foundation; HAPIN ClinicalTrials.gov number, NCT02944682.).

Effects of Cooking with Liquefied Petroleum Gas or Biomass on Stunting in Infants.

BACKGROUND: Household air pollution is associated with stunted growth in infants. Whether the replacement of biomass fuel (e.g., wood, dung, or agricultural crop waste) with liquefied petroleum gas (LPG) for cooking can reduce the risk of stunting is unknown. METHODS: We conducted a randomized trial involving 3200 pregnant women 18 to 34 years of age in four low- and middle-income countries. Women at 9 to less than 20 weeks' gestation were randomly assigned to use a free LPG cookstove with continuous free fuel delivery for 18 months (intervention group) or to continue using a biomass cookstove (control group). The length of each infant was measured at 12 months of age, and personal exposures to fine particulate matter (particles with an aerodynamic diameter of ≤2.5 µm) were monitored starting at pregnancy and continuing until the infants were 1 year of age. The primary outcome for which data are presented in the current report - stunting (defined as a length-for-age z score that was more than two standard deviations below the median of a growth standard) at 12 months of age - was one of four primary outcomes of the trial. Intention-to-treat analyses were performed to estimate the relative risk of stunting. RESULTS: Adherence to the intervention was high, and the intervention resulted in lower prenatal and postnatal 24-hour personal exposures to fine particulate matter than the control (mean prenatal exposure, 35.0 µg per cubic meter vs. 103.3 µg per cubic meter; mean postnatal exposure, 37.9 µg per cubic meter vs. 109.2 µg per cubic meter). Among 3061 live births, 1171 (76.2%) of the 1536 infants born to women in the intervention group and 1186 (77.8%) of the 1525 infants born to women in the control group had a valid length measurement at 12 months of age. Stunting occurred in 321 of the 1171 infants included in the analysis (27.4%) of the infants born to women in the intervention group and in 299 of the 1186 infants included in the analysis (25.2%) of those born to women in the control group (relative risk, 1.10; 98.75% confidence interval, 0.94 to 1.29; P = 0.12). CONCLUSIONS: An intervention strategy starting in pregnancy and aimed at mitigating household air pollution by replacing biomass fuel with LPG for cooking did not reduce the risk of stunting in infants. (Funded by the National Institutes of Health and the Bill and Melinda Gates Foundation; HAPIN ClinicalTrials.gov number, NCT02944682.).

The COVID-19 International Drug Pregnancy Registry (COVID-PR): Protocol Considerations.

BACKGROUND AND OBJECTIVE: Over the past 2 years, several drugs have been approved for coronavirus disease 2019 (COVID-19) treatment, but their safety during pregnancy remains poorly understood. This study aims to assess the relative risk of obstetric, neonatal, and infant outcomes associated with the use of drugs specifically indicated for the treatment of COVID-19 compared with other drug treatment strategies. The purpose of this article is to present elements of the study protocol. METHODS: The COVID-19 International Drug Pregnancy Registry (COVID-PR) is a noninterventional, postmarketing cohort study. Pregnant women receiving treatment with monoclonal antibodies (mAbs) or antiviral drugs for mild, moderate, or severe COVID-19 are matched 1:1 with pregnant women not receiving these study-specific drugs, based on calendar time, country, gestational age at enrollment, and COVID-19 severity. Participants complete online questionnaires at enrollment, during pregnancy, and for 12 months after delivery of liveborn infants. The study began enrolling participants on 1 December 2021 and is set to span 5 years for each drug of interest. DISCUSSION: The COVID-PR is designed to evaluate the safety profile of each studied drug. Additionally, it may allow for an analysis of the effects of COVID-19 drug exposure during relevant gestational periods on specific neonatal outcomes. Although the sample size will be too small to detect associations with rare outcomes, the study has the potential to generate hypotheses for future research. Ultimately, these data can provide valuable insights for evidence-based decisions about COVID-19 treatment during pregnancy. TRIAL REGISTRATION: ClinicalTrials.gov: NCT05013632. EU PAS EUPAS42517.

Risk factors associated with stillbirth and adverse perinatal outcomes in dichorionic twin pregnancies complicated by selective fetal growth restriction: a cohort study.

OBJECTIVE: The main aim of this study was to investigate the perinatal outcomes of dichorionic twin pregnancies complicated by selective fetal growth restriction (sFGR). DESIGN: Retrospective cohort study. SETTING: Tertiary reference centre. POPULATION: Dichorionic twin pregnancies complicated by sFGR between 2000 and 2019 in St George's University Hospital. METHODS: Regression analyses were performed using generalised linear models and mixed-effects generalised linear models where appropriate to account for pregnancy level dependency in variables. Time to event analyses were performed with mixed-effects Cox regression models. MAIN OUTCOME MEASURES: Stillbirth, neonatal death or neonatal unit admission with morbidity in one or both twins. RESULTS: A total of 102 (of 2431 dichorionic twin pregnancies) pregnancies complicated by sFGR were included in the study. The Cochrane-Armitage test revealed a significant trend for increased adverse perinatal outcome rates with more severe forms of umbilical artery flow impedance, i.e. reversed, absent, positive with resistant flow and positive flow without resistance. A multivariable model including maternal and conception characteristics had poor predictive accuracy for stillbirth (area under the curve: 0.68, 95% confidence interval [CI] 0.55-0.81) and composite adverse perinatal outcomes (area under the curve: 0.58, 95% CI 0.47-0.70). When umbilical artery Doppler parameters were added to the models, the area under the curve values improved to 0.95 (95% CI 0.89-0.99) and 0.83 (95% CI 0.73-0.92) for stillbirth and composite adverse perinatal outcomes, respectively. CONCLUSION: In dichorionic twin pregnancies complicated by sFGR, the umbilical artery Z-scores were associated with both intrauterine death and adverse perinatal outcomes.

Vaginal micronised progesterone for the prevention of hypertensive disorders of pregnancy: A systematic review and meta-analysis.

BACKGROUND: Treatment with vaginal progesterone reduces the risk of miscarriage and preterm birth in selected high-risk women. The hypothesis that vaginal progesterone can reduce the risk of hypertensive disorders of pregnancy (HDP) is unexplored. OBJECTIVES: To summarise the evidence on the effectiveness of vaginal progesterone to reduce the risk of HDP. SEARCH STRATEGY: We searched Embase (OVID), MEDLINE (OVID), PubMed, CENTRAL and clinicaltrials.gov from inception until 20 June 2023. SELECTION CRITERIA: We included placebo-controlled randomised trials (RCTs) of vaginal progesterone for the prevention or treatment of any pregnancy complications. DATA COLLECTION AND ANALYSIS: We extracted absolute event numbers for HDP and pre-eclampsia in women receiving vaginal progesterone or placebo, and meta-analysed the data with a random effects model. We appraised the certainty of the evidence using GRADE methodology. MAIN RESULTS: The quantitative synthesis included 11 RCTs, of which three initiated vaginal progesterone in the first trimester, and eight in the second or third trimesters. Vaginal progesterone started in the first trimester of pregnancy lowered the risk of any HDP (risk ratio [RR] 0.71, 95% confidence interval [CI] 0.53-0.93, 2 RCTs, n = 4431 women, I2 = 0%; moderate-certainty evidence) and pre-eclampsia (RR 0.61, 95% CI 0.41-0.92, 3 RCTs, n = 5267 women, I2 = 0%; moderate-certainty evidence) when compared with placebo. Vaginal progesterone started in the second or third trimesters was not associated with a reduction in HDP (RR 1.19, 95% CI 0.67-2.12, 3 RCTs, n = 1602 women, I2 = 9%; low-certainty evidence) or pre-eclampsia (RR 0.97, 95% CI 0.71-1.31, 5 RCTs, n = 4274 women, I2 = 0%; low-certainty evidence). CONCLUSIONS: Our systematic review found first-trimester initiated vaginal micronised progesterone may reduce the risk of HDP and pre-eclampsia.

Normative spatiotemporal fetal brain maturation with satisfactory development at 2 years.

Maturation of the human fetal brain should follow precisely scheduled structural growth and folding of the cerebral cortex for optimal postnatal function1. We present a normative digital atlas of fetal brain maturation based on a prospective international cohort of healthy pregnant women2, selected using World Health Organization recommendations for growth standards3. Their fetuses were accurately dated in the first trimester, with satisfactory growth and neurodevelopment from early pregnancy to 2 years of age4,5. The atlas was produced using 1,059 optimal quality, three-dimensional ultrasound brain volumes from 899 of the fetuses and an automated analysis pipeline6-8. The atlas corresponds structurally to published magnetic resonance images9, but with finer anatomical details in deep grey matter. The between-study site variability represented less than 8.0% of the total variance of all brain measures, supporting pooling data from the eight study sites to produce patterns of normative maturation. We have thereby generated an average representation of each cerebral hemisphere between 14 and 31 weeks' gestation with quantification of intracranial volume variability and growth patterns. Emergent asymmetries were detectable from as early as 14 weeks, with peak asymmetries in regions associated with language development and functional lateralization between 20 and 26 weeks' gestation. These patterns were validated in 1,487 three-dimensional brain volumes from 1,295 different fetuses in the same cohort. We provide a unique spatiotemporal benchmark of fetal brain maturation from a large cohort with normative postnatal growth and neurodevelopment.

Gaze-probe joint guidance with multi-task learning in obstetric ultrasound scanning.

In this work, we exploit multi-task learning to jointly predict the two decision-making processes of gaze movement and probe manipulation that an experienced sonographer would perform in routine obstetric scanning. A multimodal guidance framework, Multimodal-GuideNet, is proposed to detect the causal relationship between a real-world ultrasound video signal, synchronized gaze, and probe motion. The association between the multi-modality inputs is learned and shared through a modality-aware spatial graph that leverages useful cross-modal dependencies. By estimating the probability distribution of probe and gaze movements in real scans, the predicted guidance signals also allow inter- and intra-sonographer variations and avoid a fixed scanning path. We validate the new multi-modality approach on three types of obstetric scanning examinations, and the result consistently outperforms single-task learning under various guidance policies. To simulate sonographer's attention on multi-structure images, we also explore multi-step estimation in gaze guidance, and its visual results show that the prediction allows multiple gaze centers that are substantially aligned with underlying anatomical structures.

Memory-based unsupervised video clinical quality assessment with multi-modality data in fetal ultrasound.

In obstetric sonography, the quality of acquisition of ultrasound scan video is crucial for accurate (manual or automated) biometric measurement and fetal health assessment. However, the nature of fetal ultrasound involves free-hand probe manipulation and this can make it challenging to capture high-quality videos for fetal biometry, especially for the less-experienced sonographer. Manually checking the quality of acquired videos would be time-consuming, subjective and requires a comprehensive understanding of fetal anatomy. Thus, it would be advantageous to develop an automatic quality assessment method to support video standardization and improve diagnostic accuracy of video-based analysis. In this paper, we propose a general and purely data-driven video-based quality assessment framework which directly learns a distinguishable feature representation from high-quality ultrasound videos alone, without anatomical annotations. Our solution effectively utilizes both spatial and temporal information of ultrasound videos. The spatio-temporal representation is learned by a bi-directional reconstruction between the video space and the feature space, enhanced by a key-query memory module proposed in the feature space. To further improve performance, two additional modalities are introduced in training which are the sonographer gaze and optical flow derived from the video. Two different clinical quality assessment tasks in fetal ultrasound are considered in our experiments, i.e., measurement of the fetal head circumference and cerebellar diameter; in both of these, low-quality videos are detected by the large reconstruction error in the feature space. Extensive experimental evaluation demonstrates the merits of our approach.

COMFormer: Classification of Maternal-Fetal and Brain Anatomy Using a Residual Cross-Covariance Attention Guided Transformer in Ultrasound.

Monitoring the healthy development of a fetus requires accurate and timely identification of different maternal-fetal structures as they grow. To facilitate this objective in an automated fashion, we propose a deep-learning-based image classification architecture called the COMFormer to classify maternal-fetal and brain anatomical structures present in 2-D fetal ultrasound (US) images. The proposed architecture classifies the two subcategories separately: maternal-fetal (abdomen, brain, femur, thorax, mother's cervix (MC), and others) and brain anatomical structures [trans-thalamic (TT), trans-cerebellum (TC), trans-ventricular (TV), and non-brain (NB)]. Our proposed architecture relies on a transformer-based approach that leverages spatial and global features using a newly designed residual cross-variance attention block. This block introduces an advanced cross-covariance attention (XCA) mechanism to capture a long-range representation from the input using spatial (e.g., shape, texture, intensity) and global features. To build COMFormer, we used a large publicly available dataset (BCNatal) consisting of 12 400 images from 1792 subjects. Experimental results prove that COMFormer outperforms the recent CNN and transformer-based models by achieving 95.64% and 96.33% classification accuracy on maternal-fetal and brain anatomy, respectively.

Interventions affecting the nitric oxide pathway versus placebo or no therapy for fetal growth restriction in pregnancy.

BACKGROUND: Fetal growth restriction (FGR) is a condition of poor growth of the fetus in utero. One of the causes of FGR is placental insufficiency. Severe early-onset FGR at < 32 weeks of gestation occurs in an estimated 0.4% of pregnancies. This extreme phenotype is associated with a high risk of fetal death, neonatal mortality, and neonatal morbidity. Currently, there is no causal treatment, and management is focused on indicated preterm birth to prevent fetal death. Interest has risen in interventions that aim to improve placental function by administration of pharmacological agents affecting the nitric oxide pathway causing vasodilatation. OBJECTIVES: The objective of this systematic review and aggregate data meta-analysis is to assess the beneficial and harmful effects of interventions affecting the nitric oxide pathway compared with placebo, no therapy, or different drugs affecting this pathway against each other, in pregnant women with severe early-onset FGR. SEARCH METHODS: We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (16 July 2022), and reference lists of retrieved studies. SELECTION CRITERIA: We considered all randomised controlled comparisons of interventions affecting the nitric oxide pathway compared with placebo, no therapy, or another drug affecting this pathway in pregnant women with severe early-onset FGR of placental origin, for inclusion in this review. DATA COLLECTION AND ANALYSIS: We used standard Cochrane Pregnancy and Childbirth methods for data collection and analysis. MAIN RESULTS: We included a total of eight studies (679 women) in this review, all of which contributed to the data and analysis. The identified studies report on five different comparisons: sildenafil compared with placebo or no therapy, tadalafil compared with placebo or no therapy, L-arginine compared with placebo or no therapy, nitroglycerin compared with placebo or no therapy and sildenafil compared with nitroglycerin. The risk of bias of included studies was judged as low or unclear. In two studies the intervention was not blinded. The certainty of evidence for our primary outcomes was judged as moderate for the intervention sildenafil and low for tadalafil and nitroglycerine (due to low number of participants and low number of events). For the intervention L-arginine, our primary outcomes were not reported. Sildenafil citrate compared to placebo or no therapy (5 studies, 516 women) Five studies (Canada, Australia and New Zealand, the Netherlands, the UK and Brazil) involving 516 pregnant women with FGR were included. We assessed the certainty of the evidence as moderate. Compared with placebo or no therapy, sildenafil probably has little or no effect on all-cause mortality (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.80 to 1.27, 5 studies, 516 women); may reduce fetal mortality (RR 0.82, 95% CI 0.60 to 1.12, 5 studies, 516 women), and increase neonatal mortality (RR 1.45, 95% CI 0.90 to 2.33, 5 studies, 397 women), although the results are uncertain for fetal and neonatal mortality as 95% confidence intervals are wide crossing the line of no effect. Tadalafil compared with placebo or no therapy (1 study, 87 women) One study (Japan) involving 87 pregnant women with FGR was included. We assessed the certainty of the evidence as low. Compared with placebo or no therapy, tadalafil may have little or no effect on all-cause mortality (risk ratio 0.20, 95% CI 0.02 to 1.60, one study, 87 women); fetal mortality (RR 0.11, 95% CI 0.01 to 1.96, one study, 87 women); and neonatal mortality (RR 0.89, 95% CI 0.06 to 13.70, one study, 83 women). L-Arginine compared with placebo or no therapy (1 study, 43 women) One study (France) involving 43 pregnant women with FGR was included. This study did not assess our primary outcomes. Nitroglycerin compared to placebo or no therapy (1 studies, 23 women) One study (Brazil) involving 23 pregnant women with FGR was included. We assessed the certainty of the evidence as low. The effect on the primary outcomes is not estimable due to no events in women participating in both groups. Sildenafil citrate compared to nitroglycerin (1 study, 23 women) One study (Brazil) involving 23 pregnant women with FGR was included. We assessed the certainty of the evidence as low. The effect on the primary outcomes is not estimable due to no events in women participating in both groups. AUTHORS' CONCLUSIONS: Interventions affecting the nitric oxide pathway probably do not seem to influence all-cause (fetal and neonatal) mortality in pregnant women carrying a baby with FGR, although more evidence is needed. The certainty of this evidence is moderate for sildenafil and low for tadalafil and nitroglycerin. For sildenafil a fair amount of data are available from randomised clinical trials, but with low numbers of participants. Therefore, the certainty of evidence is moderate. For the other interventions investigated in this review there are insufficient data, meaning we do not know whether these interventions improve perinatal and maternal outcomes in pregnant women with FGR.