Salivary alpha-amylase during pregnancy: diurnal course and associations with obstetric history, maternal demographics, and mood

Characterizing and Evaluating Diurnal Salivary Uric Acid Across Pregnancy Among Healthy Women

Uric acid levels during pregnancy have been examined as a potential indicator of risk for gestational diabetes mellites, hypertension, and related adverse birth outcomes. However, evidence supporting the utility of serum uric acid levels in predicting poor maternal and fetal health has been mixed. The lack of consistent findings may be due to limitations inherent in serum-based biomeasure evaluations, such as minimal repeated assessments and variability in the timing of these assessments. To address these gaps, we examined repeated measurements of diurnal salivary uric acid (sUA) levels in a sample of 44 healthy women across early-mid and late pregnancy. We assessed potential covariates and confounds of sUA levels and diurnal trajectories, as well as associations between maternal weight gain and blood pressure during pregnancy and sUA concentrations. Using multilevel linear models, we found sUA increased across pregnancy and displayed a robust diurnal pattern with the highest concentrations at waking, a steep decline in the early morning, and decreasing levels across the day. Maternal pre-pregnancy BMI, age, prior-night sleep duration, and fetal sex were associated with sUA levels and/or diurnal slopes. Maternal blood pressure and gestational weight gain also showed significant associations with sUA levels across pregnancy. Our results expand upon those found with serum UA measurements. Further, they demonstrate the feasibility of using at-home, minimally-invasive saliva sampling procedures to track UA levels across pregnancy with potential applications for the long-term monitoring of maternal cardiometabolic risk.

Salivary Alpha-Amylase as a Biomarker of Stress in Behavioral Medicine

In recent years, research in behavioral medicine has become increasingly focused on understanding how chronic and acute exposure to stress impacts health outcomes. During stress, the body’s physiological stress systems are activated. These systems closely interact with the immune system and are, thus, importantly implicated in the onset and maintenance of disease states. While much of the research in behavioral medicine that has investigated the effects of stress on disease has focused on the role of the hypothalamic-pituitary-adrenal axis and its downstream biomarker, cortisol, it is evident that the autonomic nervous system (ANS) also plays a crucial role in both the biological stress process and the manifestation and maintenance of stress-related symptoms. In recent years salivary alpha-amylase (sAA) has emerged as a valid and reliable marker of ANS activity in stress research and is therefore an important biomarker to consider in behavioral medicine. In this commentary, we will highlight research relevant for behavioral medicine that has utilized sAA measurements, both basally, and in response to stress, to examine ANS function in clinical populations. We will additionally summarize findings from studies that have examined the effects of various targeted interventions on changes in sAA levels. Through this, our aim is to present evidence that sAA can serve as a feasible biomarker of ANS (dys)function in health and disease. To this end, we will also highlight important methodological considerations for readers to keep in mind when including sAA assessments in their own studies. The overarching goal of this brief commentary is to highlight how a multidimensional approach toward physiological stress measurement can allow researchers to develop a better understanding of physical health and disease states.

The biological underpinnings of perinatal depressive symptoms: A multi-systems approach

BACKGROUND

Well-established evidence exists of an association between depressive symptoms and alterations in the stress and inflammatory response systems; however, the picture is far less coherent during the perinatal period. This study combines the assessment of multiple stress and inflammatory biomarkers in late pregnancy and after delivery in order to investigate cross-sectional and prospective associations with perinatal depressive symptoms.

METHODS

One-hundred-ten healthy women were assessed in late pregnancy (mean gestational age=34.76; SD=1.12) and 89 were re-evaluated after delivery (mean hours after delivery=52.36; SD=19.70) for depressive and anxiety symptoms through the Edinburgh Postnatal Depression Scale and the State-Trait Anxiety Inventory. Serum Interleukin-6 (IL-6), C-Reactive Protein (CRP) and diurnal salivary cortisol levels were measured on both occasions, while diurnal salivary alpha amylase (sAA) levels were assessed in late pregnancy.

RESULTS

Using Hierarchical Linear Models, higher depressive symptoms were found to be associated with higher IL-6 levels, lower morning cortisol levels and a flatter cortisol diurnal slope during pregnancy, while adjusting for potential confounders. No significant associations were found after delivery or with change in biomarker levels from pre- to post-partum. Furthermore, preliminary evidence of a positive association between inflammation and stress markers in women with higher antenatal depressive symptoms was found.

LIMITATIONS

The sample was relatively small and highly selected, thus limiting generalizability of the findings.

CONCLUSIONS

Results emphasize the need for an integrated multi-systems approach to the understanding of the biological underpinnings of perinatal depression and suggest that the stress-immune interactions represent a promising avenue for future endeavor.

Ambulatory Blood Pressure Trajectory and Perceived Stress in Relation to Birth Outcomes in Healthy Pregnant Adolescents

OBJECTIVE

An early decline in resting blood pressure (BP), followed by an upward climb, is well documented and indicative of a healthy pregnancy course. Although BP is considered both an effector of stress and a clinically meaningful measurement in pregnancy, little is known about its trajectory in association with birth outcomes compared with other stress effectors. The current prospective longitudinal study examined BP trajectory and perceived stress in association with birth outcomes (gestational age (GA) at birth and birth weight (BW) percentile corrected for GA) in pregnant adolescents, a group at risk for stress-associated poor birth outcomes.

METHODS

Healthy pregnant nulliparous adolescents (n = 139) were followed from early pregnancy through birth. At three time points (13-16, 24-27, and 34-37 gestational weeks ±1 week), the Perceived Stress Scale was collected along with 24-hour ambulatory BP (systolic and diastolic) and electronic diary reporting of posture. GA at birth and BW were abstracted from medical records.

RESULTS

After adjustment for posture and pre-pregnancy body mass index, hierarchical mixed-model linear regression showed the expected early decline (B = -0.18, p = .023) and then increase (B = 0.01, p < .001) of diastolic BP approximating a U-shape; however, systolic BP displayed only an increase (B = 0.01, p = .010). In addition, the models indicated a stronger systolic and diastolic BP U-shape for early GA at birth and lower BW percentile and an inverted U-shape for late GA at birth and higher BW percentile. No effects of perceived stress were observed.

CONCLUSIONS

These results replicate the pregnancy BP trajectory from previous studies of adults and indicate that the degree to which the trajectory emerges in adolescence may be associated with variation in birth outcomes, with a moderate U-shape indicating the healthiest outcomes.

Anxiety and depressive symptoms, and stress biomarkers in pregnant women after in vitro fertilization: a prospective cohort study

STUDY QUESTION

Does in vitro fertilization (IVF) affect the course of anxiety and depressive symptoms as well as physiological stress from pregnancy to postpartum period?

SUMMARY ANSWER

IVF mothers have more anxiety symptoms and higher stress biomarker levels but fewer depression symptoms than natural conception mothers at the third trimester of pregnancy, but these differences are negligible during postpartum period.

WHAT IS KNOWN ALREADY

Cross-sectional studies have found an association between IVF and high stress levels during the prenatal period. There is, however, no follow-up study about the IVF effect on the mental health status from pregnancy to postpartum, adopting simultaneous measurement of self-reported symptoms and stress biomarkers.

STUDY DESIGN, SIZE, DURATION

This is a prospective cohort study. A total of 243 eligible women were recruited during the third trimester of pregnancy (60 women after successful IVF and 183 who conceived naturally). The recruitment was performed during a 12-month period, and the follow-up was carried out until 3 months after delivery.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study was performed in the Division of Obstetrics in a regional referral center. The State scale of the State-Trait Anxiety Inventory (STAI-S) and the Beck Depression Inventory-Sort Form (BDI/SF) were used as anxiety and depression indicators, respectively; salivary cortisol and α-amylase levels as stress biomarkers. Anxiety, depression and stress biomarkers were measured at the third trimester of pregnancy (T1), at 48 h after birth (T2) and at 3 months after birth (T3). Associations with IVF were assessed using ordinal mixed models for anxiety and depressive symptoms and linear quantile models for stress biomarkers.

MAIN RESULTS AND THE ROLE OF CHANCE

Relative to natural conception mothers, IVF mothers had higher STAI-S scores at T1 (P = 0.016, odds ratio (OR) = 2.46), and this difference remained steady from T1 to T2 (P = 0.37, OR = 0.70) and from T2 to T3 (P = 0.36, OR = 0.69). In the case of depressive symptoms, the IVF group obtained lower BDI/SF scores at T1 (P < 0.001, OR = 0.192). This difference was apparently reduced from T1 to T2 (P = 0.072, OR = 2.21) and remained constant from T2 to T3 (P = 0.107, OR = 2.09). It is important to note that whereas the mean BDI/SF score was not clinically significant for any group (it was lower than the cut-off 4), the mean STAI-S score of the IVF group at T1 was so (it was higher than the cut-off 19). As for stress biomarkers, IVF mothers had higher cortisol levels at T1 (P = 0.043, Δlog(cortisol) = 0.88) compared to natural conceptions. From T1 to T2 cortisol levels of both groups increased at the relatively same rate (P = 0.81, Δlog(cortisol) = -0.16). However, the progressions tended to be different from T2 to T3, with IVF mothers exhibiting a sharp decrease in cortisol levels (P = 0.059, Δlog(cortisol) = -0.94), while natural conceptions value remained steady. In the case of α-amylase, there were no statistically significant differences between both groups at T1 (P = 0.7, Δlog(α-amylase) = -0.095). On the contrary, while IVF mothers showed sustained α-amylase levels across the time, the progression was different in the natural conception group, who showed a decrease in α-amylase levels from T1 to T2 (P = 0.049, Δlog(α-amylase) = 0.596) and a non-significant increase from T2 to T3 (P = 0.53, Δlog(α-amylase) = -0.283).

LIMITATIONS REASON FOR CAUTION

Since this follow-up study has been carried out from the third trimester of pregnancy, the findings cannot be generalized to extremely preterm births.

WIDER IMPLICATIONS OF THE FINDINGS

IVF women may have lower depressive symptoms for being pregnant. However, due to the potential pregnancy complications associated with IVF, they may have higher physiological stress and clinically significant anxiety at the third trimester of pregnancy but not during postpartum. Taking into account that both prenatal high maternal cortisol levels and prenatal clinically significant anxiety increase the risk of disturbance in the fetal neurodevelopment, psychological therapy should be extended during pregnancy in IVF women.

STUDY FUNDING/COMPETING INTEREST(S)

MV funded by FIS PI17/0131 grant from the Instituto de Salud Carlos III (ISCIII) and RETICS funded by the PN 2018-2011, and the European Regional Development Fund, reference RD16/0022/0001; AG-B funded by a 'Juan Rodés' Grant (JR17/00003) from the ISCIII. CC-P funded by a 'Miguel Servet I' Grant (CP16/00082) from the ISCIII. Authors declare no competing interests.

Beyond the HPA-axis: Exploring maternal prenatal influences on birth outcomes and stress reactivity

Accumulating evidence suggests that antenatal maternal stress is associated with altered behavioral and physiological outcomes in the offspring, however, whether this association is causal and the underlying biological mechanisms remain largely unknown. While the most studied mediator of maternal stress influences on the fetus has generally been cortisol, alternative novel markers of stress or inflammation warrant further consideration. The current investigation explored the influence of variations in self-reported symptoms of distress, stress hormones and inflammatory markers on infant birth outcomes and early stress regulation. The sample consisted of 104 pregnant women (mean gestational age = 34.76; SD = 1.12) and their healthy newborns. Maternal self-reported symptoms of depression and anxiety were evaluated through the Edinburgh Postnatal Depression Scale and the State-Trait Anxiety Inventory and levels of serum Interleukine-6 (IL-6), C-Reactive Protein (CRP), salivary cortisol and alpha amylase (sAA) were measured in late pregnancy. Newborns' cortisol and behavioral response to the heel-stick was assessed 48-72 hours after birth. The associations between maternal stress measures and infant birth outcomes and stress reactivity, adjusted for potential confounders, were examined through hierarchical linear regressions and hierarchical linear models. Higher maternal IL-6 levels were associated with smaller head circumference at birth, while diurnal sAA levels were positively associated with birthweight. Maternal diurnal cortisol was related to newborn's stress reactivity: a flatter infant cortisol response to the heel-stick was associated with greater maternal cortisol increases after awakening during pregnancy, while greater infant behavioural reactivity was related to a flatter maternal diurnal cortisol profile. The observational nature of these data does not allow for causal inferences but the current findings illustrate that antenatal factors related to alterations in maternal stress and immune response systems are associated with fetal growth and neonatal stress reactivity. This may have implications for later health and psychological outcomes.

Trajectories of stress biomarkers and anxious-depressive symptoms from pregnancy to postpartum period in women with a trauma history

Background: Cross-sectional studies have found that a trauma history can be associated with anxious-depressive symptomatology and physiological stress dysregulation in pregnant women. Methods: This prospective study examines the trajectories of both anxiety and depressive symptoms and salivary cortisol and α-amylase biomarkers from women with (n = 42) and without (n = 59) a trauma history at (i) 38th week of gestation (T1), (ii) 48 hours after birth (T2), and (iii) three months after birth (T3). Results: The quantile regression model showed that trauma history was associated with higher cortisol levels at T1 and this difference was sustained along T2 and T3. Conversely, there were no significant differences in α-amylase levels between groups across the three time points and both groups showed an increase in α-amylase levels from T2 to T3. The ordinal mixed model showed that trauma history was associated with higher anxiety symptoms at T1 and this remained constant from T1 to T2 but was reversed from T2 to T3. In contrast, both groups showed similar depressive symptoms across the three time points. Conclusions: Whereas physiological stress dysregulation (in terms of higher cortisol levels) was maintained from pregnancy to postpartum period, pregnancy and childbirth were the most vulnerable stages for developing anxious symptoms in mothers with trauma history.

Associations between biological markers of prenatal stress and infant negative emotionality are specific to sex

PURPOSE

Fetal programming is the idea that environmental stimuli can alter the development of the fetus, which may have a long-term effect on the child. We have recently reported that maternal prenatal cortisol predicts infant negative emotionality in a sex-dependent manner: high prenatal cortisol was associated with increased negative emotionality in females, and decreased negative emotionality in males. This study aims to test for this sex-specific effect in a different cohort, and investigate whether sex differences in fetal programming may be specific to glucocorticoid mechanisms by also examining a maternal salivary alpha-amylase (sAA) by sex interaction.

METHODS

88 pregnant women (mean gestational age=27.4 weeks, SD=7.4) collected saliva samples at home over two working days to be assayed for the hormone cortisol (range=0.13-88.22nmol/l) and the enzyme alpha-amylase (range=4.57-554.8units/ml). Samples were collected at waking, 30-min post-waking and 12h post-waking. Two months after birth participants reported infant negative emotionality using the distress to limits subscale of the Infant Behavior Questionnaire.

RESULTS

The interaction between maternal prenatal cortisol and infant sex to predict distress to limits approached significance (p=0.067). In line with our previous finding there was a positive association between prenatal cortisol and negative emotionality in females, and a negative association in males. The interaction between sAA and sex to predict distress was significant (p=0.025), and the direction of effect was the same as for the cortisol data; high sAA associated with increased negative emotionality in females and reduced negative emotionality in males.

CONCLUSIONS

In line with our previous findings, this research adds to an emerging body of literature, which suggests that fetal programming mechanisms may be sex-dependent. This is the first study to demonstrate that maternal prenatal sAA may be an important biomarker for infant behavior, and the findings have implications for understanding sex differences in developmental psychopathology.

Hormonal and Neuromuscular Responses to Breastfeeding: A Pilot Study

OBJECTIVES

Difficult breastfeeding in the first weeks after birth may result in muscle tension in infants and activation of the maternal hypothalamic-pituitary-adrenal (HPA) axis and sympathetic nervous system (SNS). Our primary objective was to examine the feasibility of collecting neuroendocrine markers of maternal HPA axis and SNS activation (salivary cortisol and α-amylase [sAA]) and electromyographic (EMG) markers of infant distress during feeding in the first 2 weeks after birth. We also examined the relationships of these indices to each other and to mother-infant interactive behaviors during feeding.

METHODS

We recruited mothers in the postpartum unit of a teaching hospital and observed a feeding in the dyad's home. Cortisol and sAA were sampled before feeding, 10 min into feeding, at feeding end, and 20 min after feeding. Infant muscle activity was recorded continuously with an EMG data logger. We used the Nursing Child Assessment Feeding Scale to measure mother-infant interaction.

RESULTS

The 20 mothers reported no disruption to breastfeeding and no change in infant behavior due to collection measures. Mean cortisol levels decreased significantly; there was no significant change in sAA levels. Relationships were found between interactive behavior and trends in neuroendocrine biomarkers. Longer bursts of infant muscle activity were associated with higher levels of maternal cortisol during feeding but not mother-infant interactive behaviors.

CONCLUSIONS

Maternal salivary biomarkers and their association with feeding behaviors can be a useful tool for clinical longitudinal research beginning soon after birth. Infant EMG data may be useful for assessing maternal arousal.

Prenatal Depression Risk Factors, Developmental Effects and Interventions: A Review

This narrative review based on a literature search in PubMed and PsycInfo on the two terms prenatal and antenatal depression includes empirical studies, reviews and meta-analyses that have been published during the last 5 years on risk factors, developmental effects and interventions for prenatal depression. Risk factor studies that met criteria feature demographic measures (lower socioeconomic status, less education, non-marital status, non-employment, less social support and health locus of control, unintended pregnancy, partner violence and history of child abuse) and physiological variables (cortisol, amylase, and pro-inflammatory cytokines and intrauterine artery resistance). The negative effects include postpartum depression, paternal depression, and prematurity and low birth weight. Negative effects on infants include greater right frontal EEG, amygdala connectivity, cortical thinning and more difficult temperament. In childhood, externalizing and internalizing problems have been reported. The data on prenatal antidepressants (specifically SSRIs) reveal negative effects including internalizing problems as well as a greater risk for autism spectrum disorder. Prenatal interventions that have been effective include interpersonal psychotherapy, peer support, massage therapy, yoga, tai chi, and aerobic exercise. Potential underlying mechanisms are discussed as well as methodological limitations including homogeneity of samples and lack of randomization to intervention groups. Despite these limitations, the literature highlights the need for prenatal depression screening and intervention.

Symptoms of prenatal depression are associated with raised salivary alpha-amylase levels

PURPOSE

Prenatal depression increases risk for a number of adverse offspring outcomes, however the biological mechanisms underlying this association remain unclear. It has been suggested that maternal glucocorticoids may mediate this link, though supporting evidence has been mixed. An alternative mechanism of effect may be via depression-induced changes in maternal sympathetic nervous system (SNS) function. We examined this hypothesis by determining the relationship between symptoms of maternal prenatal depression and diurnal salivary alpha-amylase (sAA) levels.

METHODS

76 pregnant women were recruited during either the second or third trimester of pregnancy. Participants self-reported depressive symptoms using the Edinburgh postnatal depression scale. Saliva samples, to be assayed for alpha-amylase activity, were collected at home over two working days.

RESULTS

Participants with depressive symptoms in later pregnancy had elevated awakening sAA levels compared with non-depressed controls (t(73) = -2.737, p = 0.008), and continued to have raised sAA throughout the day (F(1) = 10.924, p = 0.002).

CONCLUSIONS

Our findings highlight that symptoms of depression during late pregnancy are associated with increased maternal SNS activity. Thus, changes in maternal SNS function, which may include increased vasoconstriction and reduced foetal blood flow, could, in part, mediate associations between prenatal depression and adverse offspring outcomes.

Sexually dimorphic adaptations in basal maternal stress physiology during pregnancy and implications for fetal development

There is clear evidence of reciprocal exchange of information between the mother and fetus during pregnancy but the majority of research in this area has focussed on the fetus as a recipient of signals from the mother. Specifically, physiological signals produced by the maternal stress systems in response to the environment may carry valuable information about the state of the external world. Prenatal stress produces sex-specific adaptations within fetal physiology that have pervasive and long-lasting effects on development. Little is known, however, about the effects of sex-specific fetal signals on maternal adaptations to pregnancy. The current prospective study examined sexually dimorphic adaptations within maternal stress physiology, including the hypothalamic-adrenal-pituitary (HPA) axis and the autonomic nervous system (ANS) and associations with fetal growth. Using diurnal suites of saliva collected in early and late pregnancy, we demonstrate that basal cortisol and salivary alpha-amylase (sAA) differ by fetal sex. Women carrying female fetuses displayed greater autonomic arousal and flatter (but more elevated) diurnal cortisol patterns compared to women carrying males. Women with flatter daytime cortisol trajectories and more blunted sAA awakening responses also had infants with lower birth weight. These maternal adaptations are consistent with sexually dimorphic fetal developmental/evolutionary adaptation strategies that favor growth for males and conservation of resources for females. The findings provide new evidence to suggest that the fetus contributes to maternal HPA axis and ANS regulation during pregnancy and that these systems also contribute to the regulation of fetal growth.

Biomarkers of stress in behavioural medicine

PURPOSE OF REVIEW

In recent years, a growing interest has emerged in behavioural medicine to examine the role of acute and chronic stress as a predisposing and contributing factor to physical health and illness. For a deeper understanding of these associations, research is in need of biological markers for alterations in biological stress systems. This review will summarize a selection of important recent findings in this area of research.

RECENT FINDINGS

We will focus on essential peripheral stress-sensitive physiological systems, that is, the hypothalamic-pituitary-adrenal axis, the autonomic nervous system, and the immune system. We will present findings on commonly used stress biomarkers (cortisol, alpha-amylase, pro-inflammatory cytokines) regarding alterations in basal activity and stress-dependent reactivity in these systems, and discuss selected findings on intervention-induced changes of these biomarkers.

SUMMARY

This review will highlight new developments and guide readers in their choice of suitable study designs and outcomes in behavioural medicine. The reviewed studies included here encourage optimism that the employment of stress biomarkers in behavioural medicine has the potential to significantly improve our understanding of physical health and illness.

Salivary mental stress proteins

Of the major diagnostic specimen types, saliva is one of the most easily collected. Many studies have focused on the evaluation of salivary proteins secreted by healthy people and patients with various diseases during responses to acute mental stress. In particular, such studies have focused on cortisol, α-amylase, chromogranin A (CgA), and immunoglobulin A (IgA) as salivary stress markers. Each of these salivary stress markers has its own strengths and weaknesses as well as data gaps related to many factors including collection technique. In this review, we summarize the critical knowledge of the positive and negative attributes and data gaps pertaining to each salivary stress marker.

Increasing the quality of life from womb to grave: the importance of pregnancy and birth cohorts

Epigenetics is revealing how "nature is nurtured", with environmental factors such as nutrition, environmental neurotoxicants, and psychological stress influencing DNA expression. In this current opinion paper, we argue that understanding the dynamic interplay between the genome acquired at conception and environmental exposures throughout life requires pregnancy and birth cohorts, and that greater Canadian national commitment to the infrastructure needed for sustaining such cohorts is warranted. We present a framework that is now being implemented in Alberta.

The Alberta Pregnancy Outcomes and Nutrition (APrON) cohort study: rationale and methods

The Alberta Pregnancy Outcomes and Nutrition (APrON) study is an ongoing prospective cohort study that recruits pregnant women early in pregnancy and, as of 2012, is following up their infants to 3 years of age. It has currently enrolled approximately 5000 Canadians (2000 pregnant women, their offspring and many of their partners). The primary aims of the APrON study were to determine the relationships between maternal nutrient intake and status, before, during and after gestation, and (1) maternal mood; (2) birth and obstetric outcomes; and (3) infant neurodevelopment. We have collected comprehensive maternal nutrition, anthropometric, biological and mental health data at multiple points in the pregnancy and the post-partum period, as well as obstetrical, birth, health and neurodevelopmental outcomes of these pregnancies. The study continues to follow the infants through to 36 months of age. The current report describes the study design and methods, and findings of some pilot work. The APrON study is a significant resource with opportunities for collaboration.