Ann Quinton

A Longitudinal Study Using Ultrasound to Assess Flow-Mediated Dilatation in Normal Human Pregnancy

Objective: To develop normal ranges of endothelial function in normal human pregnancy to use as a screening test for preeclampsia. Methods: In this longitudinal study, women were studied five times during pregnancy and once postpartum using flow-mediated dilatation (FMD). FMD is a noninvasive ultrasound technique used to assess endothelial function. Healthy nonpregnant women were controls. Results: FMD increased non-significantly in pregnancy until 32 weeks, when it decreased significantly at 36+ weeks (n = 47). Conclusion: The fall in FMD in the third trimester has not been previously reported. This indicates the importance of gestational age when assessing FMD as a screening test for preeclampsia.

The relationship between cigarette smoking, endothelial function and intrauterine growth restriction in human pregnancy

This study examined the relationship of cigarette smoking and endothelial function in pregnant women by comparing smokers with nonsmokers. Endothelial function was assessed at 28–32 weeks of gestation by flow‐mediated dilatation (FMD) using ultrasound of the brachial artery. The initial FMD was significantly different between the smoking group (n = 21) at 4.0 ± 2.3, indicating endothelial dysfunction, and the nonsmoking group (n = 20) at 9.7 ± 4.0 (P < 0.001). After smoking, this difference in the groups persisted. Babies who were growth restricted (<10th percentile) had mothers with a significantly lower FMD, that is endothelial dysfunction. This work demonstrates persistent endothelial dysfunction in smoking pregnant women.

Smaller fetal thymuses in pre‐eclampsia: a prospective cross‐sectional study

To determine whether the thymus is smaller in fetuses of pre‐eclamptic mothers than in those of normal controls.

Comparison of maternal abdominal subcutaneous fat thickness and body mass index as markers for pregnancy outcomes: A stratified cohort study.

Obesity in pregnancy is associated with a number of adverse outcomes. The effects of central versus general obesity in pregnancy have not been well established.

Impaired fetal thymic growth precedes clinical preeclampsia: a case–control study

In preeclampsia the maternal adaptive immune system undergoes specific changes, which are different from the physiological processes associated with healthy pregnancy. Whether preeclampsia also affects the fetal immune system is difficult to investigate, due to limited access to the fetus. We hypothesized that if preeclampsia affects the fetal adaptive immune system this might be associated with early changes in thymic growth. In this case-control study, 53 preeclamptic and 120 healthy control pregnancies were matched for maternal age, gestational age and smoking. Fetal thymus diameter was measured as the greatest width perpendicular to a line connecting sternum and spine based on ultrasound images taken at 17-21 weeks gestation. Independent of fetal and maternal anthropometric measures, thymuses were found to be smaller in preeclamptic pregnancies than healthy controls (16.2 mm versus 18.3 mm, respectively, mean difference=2.1 mm, 95% CI: 0.8-3.3, p<0.001), and the odds of developing preeclampsia was estimated to be 0.72 (95% CI: 0.60-0.86, p<0.001) lower for each 1 mm increase in thymus diameter. There was no correlation between the onset of preeclampsia and fetal thymus size. This is the first study to suggest that fetal thymus growth is reduced before the clinical onset of preeclampsia and precedes any described fetal anomalies or maternal immunological changes associated with preeclampsia. We propose that the fetal adaptive immune system is either passively affected by maternal processes preceding clinical preeclampsia or is actively involved in initiating preeclampsia in later pregnancy.

Maternal abdominal subcutaneous fat thickness as a predictor for adverse pregnancy outcome: a longitudinal cohort study

To assess maternal abdominal subcutaneous fat thickness (SFT) measured by ultrasound as an independent predictor of adverse pregnancy outcomes.

Plane identification in fetal ultrasound images using saliency maps and convolutional neural networks

Fetal development is noninvasively assessed by measuring the size of different structures in ultrasound (US) images. The reliability of these measurements is dependent upon the identification of the correct anatomical viewing plane, each of which contains different fetal structures. However, the automatic classification of the anatomical planes in fetal US images is challenging due to a number of factors, such as low signal-to-noise-ratios and the small size of the fetus. Current approaches for plane classification are limited to simpler subsets of the problem: only classifying planes within specific body regions or using temporal information from videos. In this paper, we propose a new general method for the classification of anatomical planes in fetal US images. Our method trains two convolutional neural networks to learn the best US and saliency features. The fusion of these features overcomes the challenges associated with US fetal imaging by emphasising the salient features within US images that best discriminate different planes. Our method achieved higher classification accuracy than a state-of-the-art baseline for 12 of the 13 different planes found in a clinical dataset of fetal US images.

The prediction of the small for gestational age fetus with the head circumference to abdominal circumference (HC/AC) ratio: a new look at an old measurement

The small for gestational age (SGA) fetus is at a higher risk of adverse events throughout life. Third trimester ultrasound measurements are poor at predicting SGA at delivery. We aimed to determine if ultrasound biometric growth parameters at 28–32 weeks of gestation could predict SGA, defined as birth weight below the 10th percentile.

Mid-gestational enlargement of fetal thalami in women exposed to methadone during pregnancy

Methadone maintenance therapy is the standard of care in many countries for opioid-dependent women who become pregnant. Despite recent evidence showing significant neurodevelopmental changes in children and adults exposed to both licit and illicit substances in utero, data on the effects of opioids in particular remains scarce. The purpose of this study was to examine the effects of opiate use, in particular methadone, on various fetal cortical and biometric growth parameters in utero using ultrasound measurements done at 18–22 weeks gestation. Head circumference (HC), bi-parietal diameter, lateral ventricle diameter, transcerebellar diameter, thalamic diameter, cisterna magna diameter, and femur length were compared between fetuses born to methadone-maintained mothers and non-substance using controls. A significantly larger thalamic diameter (0.05 cm, p = 0.01) was observed in the opiate-exposed group. Thalamic diameter/HC ratio was also significantly raised (0.03 mm, p = 0.01). We hypothesize here that the increase in thalamic diameter in opiate-exposed fetuses could potentially be explained by regional differences in opioid and serotonin receptor densities, an alteration in monoamine neurotransmitter systems, and an enhancement of the normal growth increase that occurs in the thalamus during mid-gestation.

Flow-mediated dilatation assessment in women with preeclampsia compared to women with gestational hypertension.

Objectives. To assess flow-mediated dilatation (FMD) in women with preeclampsia (PE) versus gestational hypertension (GH) and to determine if results of this ultrasound method vary with modifications to the technique. Methods. Pregnant women with hypertension (BP ≥ 140/90 mmHg) were recruited. Women were allocated to the PE group if they had proteinuria ≥300 mg/24 h. FMDo was calculated from the percentage difference in baseline and post-occlusion (PO) diameter at 45–60 s and FMDmax from baseline and maximum diameter between 45 and 90 s. FMDmax was adjusted for hematocrit and shear rate. Results. FMDo (m ± SD) was similar (p = 0.83) in the no medication GH (5.3 ± 3.2; n = 15) and the PE (6.5 ± 4.1; n = 13) groups. FMDo was reduced (p < 0.001) in the medication GH (3.7 ± 2.8; n = 23) versus the PE (8.8 ± 4.3; n = 25) groups. For FMDmax the interaction between group and medication was not significant (both p = 0.08) in unadjusted analysis or analysis adjusted for covariates hematocrit (p = 0.023) and shear rate (p = 0.007). Means averaged over medication are presented. FMDmax was reduced (p < 0.0001) in the GH (5.7 ± 4.0; n = 38) versus the PE group (9.2 ± 4.0; n = 38). Of the PE women, 79% (30/38) reached maximum dilatation by 90 s compared with 63% (24/38) of the GH women (chi-square, p = 0.16). Conclusions. The FMDmax analysis revealed reduced FMD in GH women compared with PE women. We therefore hypothesize that PE may be a different disease to GH. Our work demonstrates differing results in FMDo and FMDmax because of modifications in the technique. Previous work on PE and FMD may not be definitive due to this evolving technique.