A cohort evaluation on arterial stiffness and hypertensive disorders in pregnancy

Association between gestational weight gain and pregnancy outcomes in a Singaporean population: A prospective cohort study

OBJECTIVES

Inadequate or excessive gestational weight gain (GWG) is associated with adverse pregnancy outcomes. We aimed to study GWG in a Singaporean population and its association with pregnancy outcomes, including small for gestational age (SGA), macrosomia, and caesarean section secondary to failure to progress (FTP) or cephalopelvic disproportion (CPD).

STUDY DESIGN

926 women with low-risk singleton pregnancy were enrolled in a prospective cohort study from 2010 to 2014 in a Singapore tertiary maternity hospital. 704 patients without pre-existing diabetes or hypertension and had maternal weight information till term pregnancy were included in analyses. Participants were categorized according to their first antenatal visit body mass index (BMI) as underweight, normal weight, overweight and obese. Total GWG for each BMI group was calculated and compared to Institute of Medicine (IOM) 2009 GWG guidelines. Logistic regression analyses were performed to assess the association of GWG below or above IOM guidelines with pregnancy outcomes.

RESULTS

GWG below IOM guidelines was associated with an increased risk of SGA (adjusted OR: 2.97 [1.71, 5.15]; p < 0.0001). GWG above IOM guidelines significantly increased the risk of caesarean section due to FTP or CPD (adjusted OR: 2.10 [1.09, 4.01]; p = 0.0275). GWG above IOM guidelines was associated with an increased risk of macrosomia (adjusted odds ratio: 2.27 [1.43, 3.63]; p = 0.0006), while GWG below IOM guidelines was associated with a reduced risk of macrosomia (adjusted odds ratio: 0.18 [0.08, 0.39]; p < 0.0001).

CONCLUSIONS

GWG not achieving the IOM recommendations has been found to be associated with adverse pregnancy outcomes in Singaporean women. Inadequate GWG is associated with an increased risk of SGA whereas excessive GWG is associated with increased risks of macrosomia and caesarean section due to failure to progress or CPD. Results of the current study add to our understanding on the association of GWG with pregnancy outcomes in the South-East Asia and suggest that appropriate weight management during pregnancy is important.

Maternal blood pressure trajectories and associations with gestational age at birth: a functional data analytic approach

BACKGROUND

Research has revealed group-level differences in maternal blood pressure trajectories across pregnancy. These trajectories are typically constructed using clinical blood pressure data and multivariate statistical methods that are prone to bias and ignore the functional, dynamic process underlying a single blood pressure observation. The aim of this study was to use functional data analysis to explore blood pressure variation across pregnancy, and multivariate methods to examine whether trajectories are related to gestational age at birth.

METHODS

Clinical blood pressure observations were available from 370 women who participated in a longitudinal pregnancy cohort study conducted in Montreal, Quebec, Canada. Functional data analysis was used to smooth blood pressure data and then to conduct a functional principal component analysis to examine predominant modes of variation.

RESULTS

Three eigenfunctions explained greater than 95% of the total variance in blood pressure. The first accounted for approximately 80% of the variance and was characterized by a prolonged-decrease trajectory in blood pressure; the second explained 10% of the variance and captured a late-increase trajectory; and the third accounted for approximately 7% of the variance and captured a mid-decrease trajectory. The prolonged-decrease trajectory of blood pressure was associated with older, and late-increase with younger gestational age at birth.

CONCLUSION

Functional data analysis is a useful method to model repeated maternal blood pressure observations and many other time-related cardiovascular processes. Results add to previous research investigating blood pressure trajectories across pregnancy through identification of additional, potentially clinically important modes of variation that are associated with gestational age at birth.

The cardio-ankle vascular index as a predictor of adverse pregnancy outcomes

OBJECTIVE

To assess the association between maternal hemodynamic parameters; cardio-ankle vascular index (CAVI), representing arterial stiffness; mean arterial pressure (MAP), uterine artery pulsatility index (Ut-PI), and adverse pregnancy outcomes including preeclampsia (PE), fetal growth restriction (FGR), and gestational diabetes mellitus (GDM).

METHODS

A prospective cohort study was conducted on low-risk pregnancies. All were serially measured for the mean CAVI, MAP, and Ut-PI for four times at gestational age (GA) 11-14, 18-22, 28-32, and after 36 weeks. Also, the women were followed up for pregnancy outcomes, focusing on PE, FGR, and GDM.

RESULTS

Of 335 recruited cases meeting the inclusion criteria, 16 cases developed PE, 24 cases had FGR, and 83 cases had GDM. Compared to the non-PE group, women developing PE had a significant increase in CAVI at 18-22, 28-32, and after 36 weeks (P-value = 0.021, 0.003, and <0.001, respectively), a significant increase in MAP at all of the four periods (P-value < 0.001, for all periods), and a significant increase in Ut-PI during GA 18-22 weeks (P-value = 0.021). In pregnancies with FGR, there was a significant increase of CAVI at GA 18-22, 28-32 and after 36 weeks (P-value = 0.012, 0.015, and 0.004, respectively), an increase in Ut-PI in all gestational periods (P-value < 0.05) but no changes of MAP throughout pregnancy. In GDM, the three parameters were not significantly different from those in the non-GDM group in all of the four periods. CAVI could predict PE and FGR with AUC of 0.655-0.835 and 0.673-0.760, respectively. CAVI added predictive values when combined with MAP or Ut-PI.

CONCLUSION

Increased CAVI, like MAP and Ut-PI, can be used as a predictor of PE and FGR but not GDM. Also, it has an added predictive value when combined with MAP or Ut-PI.

Risk factors for pregnancy-associated venous thromboembolism in Singapore

OBJECTIVES

Pregnancy-associated venous thromboembolism (VTE), including deep venous thrombosis (DVT) and pulmonary embolism (PE), is associated with increased risk of maternal mortality and morbidity. This study aimed to assess potential risk factors for pregnancy-associated VTE.

METHODS

In this case-control study, women with pregnancy-associated VTE were identified via International Classification of Diseases codes and included if they had been objectively diagnosed with VTE during pregnancy or within six weeks postpartum, from 2004 to 2016, at KK Women's and Children's Hospital or Singapore General Hospital in Singapore. Controls, i.e. pregnant women without VTE, were selected from a prospective longitudinal study. The odds ratio (OR) for VTE was computed for a range of maternal and obstetric factors.

RESULTS AND CONCLUSIONS

From 2004 to 2016, 89 cases of pregnancy-associated VTE and 926 controls were identifed and analysed using logistic regression. The most significant risk factors for pregnancy-associated VTE were smoking (OR 5.44, p=0.0002) and preterm delivery (OR 5.06, p=0.023). Malay race, multiparity, non-O blood group and caesarean section, were also identified to be of higher risk. These risk factors should be useful in the development of thromboprophylaxis strategies for pregnancy and the postpartum period, especially in Singapore.

Predictive models of hypertensive disorders in pregnancy based on support vector machine algorithm

BACKGROUND

The risk factors of hypertensive disorders in pregnancy (HDP) could be summarized into three categories: clinical epidemiological factors, hemodynamic factors and biochemical factors.

OBJECTIVE

To establish models for early prediction and intervention of HDP.

METHODS

This study used the three types of risk factors and support vector machine (SVM) to establish prediction models of HDP at different gestational weeks.

RESULTS

The average accuracy of the model was gradually increased when the pregnancy progressed, especially in the late pregnancy 28-34 weeks and ⩾ 35 weeks, it reached more than 92%.

CONCLUSION

Multi-risk factors combined with dynamic gestational weeks' prediction of HDP based on machine learning was superior to static and single-class conventional prediction methods. Multiple continuous tests could be performed from early pregnancy to late pregnancy.

Trajectories of antenatal maternal psychological stress and their association with gestational age and neonatal anthropometry: A prospective cohort study of multi-ethnic Asian women in an urban setting

PURPOSE

To determine common temporal change patterns (i.e., trajectories) of perceived antenatal psychological stress throughout the pregnancy, and to examine associations between these identified trajectories and neonatal birth outcomes.

METHODS

926 participants from a prospective cohort study of multi-ethnic Asian women from an urban setting with uncomplicated singleton pregnancies completed the Perceived Stress Scale in their first, second, and third trimesters, and just prior to parturition. Gestational age, neonatal weight, length, and head circumference were recorded at birth. Longitudinal trajectories of antenatal psychological stress were characterized with group-based trajectory modelling; associations between trajectories and neonatal outcomes were assessed with analyses of covariance and covariate-adjusted linear regressions.

RESULTS

Three distinct non-fluctuating trajectories of antenatal psychological stress were identified, with 43 % of women experiencing significant levels of stress throughout the pregnancy. Women in this persistently-higher stress trajectory delivered neonates who were 57.5 g lighter and with head circumferences of 20 mm less than their counterparts in the other trajectories. Each one-point increase on the Perceived Stress Scale was associated with a decrease of 5.64 g in birthweight and a decrease of 0.4 mm in head circumference.

CONCLUSIONS

This study delineated three meaningful trajectories of antenatal psychological stress. The persistently-higher antenatal psychological stress trajectory, experienced by two in five women, was associated with lower birthweight and possibly smaller head circumference. While further research is needed to better appreciate the clinical relevance of these findings, it highlights the importance of psychosocial support even for healthy pregnant women with uncomplicated pregnancies in Asian settings.

Identifying trajectories of antenatal depression in women and their associations with gestational age and neonatal anthropometry: A prospective cohort study

OBJECTIVE

The present study sought to determine the longitudinal trajectories of antenatal depression and examine their associations with birth outcomes.

METHOD

926 healthy women with uncomplicated singleton pregnancies within 14 weeks of gestation participated in this prospective cohort study. Women completed a sociodemographic and medical questionnaire and the locally-validated Edinburgh Postnatal Depression Scale (EPDS) in their first, second, and third trimesters, and prior to parturition. Gestational age and neonatal weight, length, and head circumference were recorded at birth. Group-based trajectory modelling characterized trajectories of antenatal depression. Analyses of covariance and covariate-adjusted linear regressions identified associations between trajectories and neonatal outcomes.

RESULTS

Four distinct non-fluctuating trajectories of depressive symptoms were identified, with 9% women suffering from probable clinical depression throughout the pregnancy. Women in this persistently-moderate depression trajectory delivered 2.48 days earlier than in other trajectories; a one-point increase in EPDS scores was associated with an adjusted reduction of 5.82 g in birthweight.

CONCLUSIONS

Although meaningful trajectories were identified, no clinically relevant associations between persistently-moderate depressive symptoms with neonatal outcomes were found. The stability of these trajectories, however, suggests the importance of screening for depressive symptoms early in pregnancy to identify women who may benefit from greater formal and informal support.

Central haemodynamics in normal pregnancy: a prospective longitudinal study

OBJECTIVE

To conduct a longitudinal evaluation of the central haemodynamic adaptations of normal pregnancy.

METHODS

This was a prospective longitudinal study involving healthy, normotensive women who were having an uncomplicated, singleton pregnancy. Brachial and central SBP, DBP, mean arterial pressure (MAP), brachial and central pulse pressure (PP), aorta-to-brachial pulse pressure amplification (AMPA-B), heart rate (HR), augmentation index adjusted for HR (AIx75), carotid-femoral pulse wave velocity (cfPWV) and cardiac output (CO) were measured at a mean gestational age of 14, 24 and 36 weeks.

RESULTS

One hundred women were followed prospectively throughout pregnancy. Brachial and central SBP, DBP and MAP decreased slightly in early gestation, followed by a significant increase in late gestation (P < 0.05). Brachial PP was lowest in the final trimester (P = 0.011) whereas central PP remained unchanged, resulting in a significant decrease in AMPA-B (P < 0.001). HR and AIx75 rose continuously throughout pregnancy (P < 0.001). A significant fall in cfPWV was observed mid-pregnancy, which remained significant after adjustment for MAP and HR (P < 0.05). CO rose mid-pregnancy, before returning to baseline values by week 36 of gestation (P < 0.05).

CONCLUSION

To our knowledge, this is the largest prospective study to evaluate several central haemodynamic parameters in normotensive pregnancies, including adjusted-AIx and the gold-standard cfPWV. These data are a necessary foundation for the establishment of pregnancy-specific reference values and provide reference data for future trial design.

Are women in Singapore gaining weight appropriately during pregnancy: a prospective cohort study

BACKGROUND

We aimed to study gestational weight gain (GWG) in a Singaporean population and compare it with Institute of Medicine (IOM) 2009 GWG guidelines.

METHODS

Nine hundred twenty-six women with low-risk singleton pregnancy were enrolled in a prospective cohort study from 2010 to 2014 in a Singapore tertiary maternity hospital. Seven hundred twenty-four patients had maternal weight information till term pregnancy and were included in analysis. Participants were categorized according to their first antenatal visit body mass index (BMI) as underweight, normal weight, overweight and obese. Total GWG for each BMI group was calculated. Multivariate logistic regression was performed to determine the predictors of total GWG above and below IOM guidelines.

RESULTS

Obese women had a mean total GWG (9.1 kg) that exceeded the upper limit IOM guidelines (9 kg). In multivariate analysis of predictors of total GWG above IOM guidelines, being overweight (adjusted OR: 3.91 [95% CI, 2.60-5.88]; p < .0001) and obese (adjusted OR: 4.78 [95% CI, 2.80, 8.15]; p < .0001) significantly increased the risks of gaining weight above IOM guidelines during pregnancy, compared to being normal weight.

CONCLUSIONS

Overweight and obesity are independent significant risk factors for gaining excessive gestational weight. Appropriate weight management for overweight and obese Singaporean women prior to and during pregnancy is important.

I-ACT: Integrated study on effect of Activity on ComplicaTions in pregnancy: study protocol of a multiethnic prospective cohort study

INTRODUCTION

Physical activity (PA) during first 20 weeks of pregnancy may lower risks of gestational diabetes mellitus (GDM) and gestational hypertension (GH), though evidence of association remains inconclusive. Current studies rely heavily on subjective assessment of PA levels. Wearable activity trackers provide a convenient and objective surrogate index for PA validated by evidence-based steps/day categorisation along a physical inactivity/activity continuum. I-ACT primarily aims to examine objectively measured PA levels and patterns in first and second trimesters of pregnancy and the association with GDM and/or GH in Singapore, a multiethnic Asian population. Secondary aims include investigating the bio-socio-demographic factors associated with sedentary behaviour, and association of early pregnancy PA level with maternal weight at 6 weeks postdelivery. Results may facilitate identification of high-risk mothers-to-be and formulation of interventional strategies.

METHODS AND ANALYSIS

Prospective cohort study that will recruit 408 women at first antenatal visit at <12 weeks' gestation. Baseline bio-socio-demographic factors and PA levels assessed by participant characteristics form and the International Physical Activity Questionnaire (IPAQ), respectively. An activity tracker (Fitbit) will be provided to be worn daily from date of recruitment to end of 20 weeks' gestation. Tracker-recorded data will be synchronised with an application on participant's smartphone. Compliance will be reinforced with fortnightly reminders. After 20 weeks, a second IPAQ and a feedback form will be administered. GDM screened at 24-28 weeks' gestation. GH diagnosed after 20-weeks gestation. Maternal weight assessed at 6 weeks postdelivery. Appropriate statistical tests will be used to compare continuous and categorical PA measurements between first and second trimesters. Logistic regression will be used to analyse associations.

ETHICS AND DISSEMINATION

Ethical approval obtained from the Centralised Institutional Review Board of SingHealth (reference 2017/2836). Dissemination of results will be via peer-reviewed research publications both online and in print, conference presentations, posters and medical forums.

Changes of Arterial Pulse Waveform Characteristics with Gestational Age during Normal Pregnancy

Arterial pulse waveform analysis has been widely used to reflect physiological changes in the cardiovascular system. This study aimed to comprehensively investigate the changes of waveform characteristics of both photoplethysmographic (PPG) and radial pulses with gestational age during normal pregnancy. PPG and radial pulses were simultaneously recorded from 130 healthy pregnant women at seven gestational time points. After normalizing the arterial pulse waveforms, the abscissa of notch point, the total pulse area and the reflection index were extracted and compared between different measurement points and between the PPG and radial pulses using post-hoc multiple comparisons with Bonferrioni correction. The results showed that the effect of gestational age on all the three waveform characteristics was significant (all p < 0.001) after adjusting for maternal age, heart rate and blood pressures. All the three waveform characteristics demonstrated similar changing trends with gestational age, and they were all significantly different between the measurements from gestational week 12–15 and the others (all p < 0.05, except for the PPG total pulse area between the first and second measurement points). In conclusion, this study has comprehensively quantified similar changes of both PPG and radial pulse waveform characteristics with gestational age.

Extracellular vesicles yield predictive pre-eclampsia biomarkers

Circulating extracellular vesicles (EVs) such as cholera toxin B chain (CTB)- or annexin V (AV)-binding EVs were previously shown to be rich sources of biomarkers. Here we test if previously identified pre-eclampsia (PE) candidate biomarkers, TIMP-1 in CTB-EVs (CTB-TIMP) and PAI-1 in AV-EVs (AV-PAI) complement plasma PlGF in predicting PE in a low-risk obstetric population. Eight hundred and forty-three prospectively banked plasma samples collected at 28 + 0 to 32 + 0 gestation weeks in the Neonatal and Obstetrics Risk Assessment (NORA) cohort study were assayed by sandwich ELISAs for plasma PlGF, CTB-TIMP1 and AV-PAI1. Nineteen patients subsequently developed PE 7.3 (±2.9) weeks later at a mean gestational age of 36.1 ± 3.5 weeks. The biomarkers were assessed for their predictive accuracy for PE using stepwise multivariate logistic regression analysis with Firth correction and Areas under the curve (AUC). To achieve 100% sensitivity in predicting PE, the cut-off for plasma PlGF, CTB-TIMP1 & AV-PAI1 were set at <1235, ≤300 or >1300 and <10,550 pg/mL plasma, respectively. The corresponding AUCs, specificity and PPV at a 95% confidence interval were 0.92, 52.1% and 4.7%; 0.72, 44.5% and 4.0%; and 0.69, 21.5% and 2.9%, respectively. At 100% sensitivity, the three biomarkers had a combined AUC of 0.96, specificity of 78.6%, and PPV of 9.9%.

This is the first large cohort validation of the utility of EV-associated analytes as disease biomarkers. Specifically, EV biomarkers enhanced the predictive robustness of an existing PE biomarker sufficiently to justify PE screening in a low-risk general obstetric population.

Gestational age-specific reference intervals for serum thyroid hormone levels in a multi-ethnic population

BACKGROUND

Thyroid disorders are common during pregnancy. To date, a limited number of studies have reported differences in serum thyroid hormone concentrations between different ethnic groups. We sought to establish gestational age-specific reference intervals for serum levels of thyroid hormones in a multi-ethnic population and investigate whether separate reference intervals should be used for different ethnic groups.

METHODS

A total of 926 pregnant women from multiple ethnic groups attended four separate study visits spanning the three trimesters. Venous blood samples were taken at 9 to 14 weeks, 18 to 22 weeks, 28 to 32 weeks, and 34 to 39 weeks of gestation. Serum concentrations of thyroid-stimulating hormone (TSH), free thyroxine (T4), free triiodothyronine (T3), total T4, total T3, thyroid peroxidase antibody and thyroglobulin antibody were measured using Abbott Architect immunoassays. A total of 562 women with singleton pregnancies were found to be negative for both thyroid autoantibodies at all four study visits and thus included in the reference sample group for the establishment of reference intervals (2.5th to 97.5th percentiles).

RESULTS

Reference intervals for serum thyroid hormones at 9-14 weeks of gestation derived from the combined group of pregnant women are as follows: TSH, 0.01-2.39 mIU/L; free T4, 11.4-19.5 pmol/L; free T3, 4.23-6.69 pmol/L; total T4, 77.8-182.4 nmol/L; total T3, 1.39-2.97 nmol/L. No differences in the five thyroid parameters' reference intervals are detectable among the ethnic groups except that at study visit 3 (28-32 weeks of gestation), the upper reference limit of total T3 in Malays (3.20 nmol/L; 90% CI, 2.99-3.76 nmol/L) is slightly higher than that in Chinese (2.86 nmol/L; 90% CI, 2.70-2.98 nmol/L).

CONCLUSIONS

The findings from this study on a multi-ethnic cohort highlight the importance of establishing locally derived and gestational age-specific reference intervals for the five thyroid hormone parameters.

[Estimation of central blood pressure and arterial stiffness in pregnant women with different forms of hypertension]

AIM

To estimate central (aortic) blood pressure (BP) and arterial stiffness and their prognostic value in the development of preeclampsia (PE) in pregnant women with different forms of hypertension.

SUBJECTS AND METHODS

The study included 106 patients with chronic hypertension, 21 with the latter concurrent with PE, 63 with gestational hypertension, 10 with PE, and 100 without hypertension. All the women underwent 24-hour BP monitoring by an oscillometric method to estimatecentral (aortic) BP and arterial stiffness at 16-22 weeks' gestation.

RESULTS

The highest average daily central systolic and diastolic BP was in the pregnant women with PE. ROC analysis showed that the average daily aortic systolic BP greater than 115 mm Hg was most significant for the prediction of PE. The highest values of arterial stiffness (augmentation index, stiffness, maximum rate of blood pressure rise) were detected in the pregnant women with PE in the presence of chronic hypertension.

CONCLUSION

24-four BP monitoring inpregnant women can provide additional characteristics that reflect the stiffness of the aorta and peripheral arteries, which may be used to predict PE.