Influence of Elevated Salivary Cortisol Levels and High Stress Scores on Preeclampsia during Pregnancy

Influence of Elevated Salivary Cortisol Levels and High Stress Scores on Preeclampsia during Pregnancy

Background:

Over 15% of all premature deaths in the United states are a result of preeclampsia (MOD 2017); this is equivalent to 3 out of 20 pregnancies nationally and 2 out of 8 in every 100 globally. Currently preeclampsia is detected and diagnosed through high blood pressure, elevated protein levels in urinalysis test and stress levels using the Perceived Stress Scale (PSS). There are many biological markers that result in preeclampsia for pregnant mothers, which include oxytocin, low platelet counts, impaired renal function and stress markers such as hormones. Stress is measured through cortisol levels in the blood. Cortisol is a hormone which secretes in the blood in response to high levels of stress and maintain blood pressure. Cortisol levels can be measured two ways: via urinary or salivary specimens respectively. High BMI and systolic and diastolic blood pressure (≥ 140 mm Hg and ≥ 90 mm Hg respectively) are equally responsible for the probability of developing preeclampsia (Hutcheon, 2011). Evidence has shown that renal function and stress markers play an important role on the development of preeclampsia in pregnant mothers. When it comes to preeclampsia, World Health Organization (WHO) recommends that pregnant mothers at risk of preeclampsia perform frequent ultrasounds to monitor the growth of the fetus. Ultrasound images allow the physician to be able to estimate the fetal weight and detect the accumulation of amniotic fluid in the uterus in order to promote optimal development and health.

Pregnant mothers during gestation period are advised to maintain a relatively healthy BMI level of 18.5-24.9. Healthy stress levels protects both mother and fetus against, high blood pressure, (HBP) which leads to elevated urinary cortisol levels as well as infections via the secretory IgA antibodies (Hutcheon, 2011). Excess weight gain and increased urinary cortisol levels can put expectant mothers at the risk of problems during pregnancy, which can result in high blood pressure, proteinuria, gestational diabetes, birth defects and even fetal death. Despite the recommendations and benefits of maintaining healthy recommended stress levels, only 34% of mothers in the U.S stayed within the range recommended by the American pregnancy organization. The CDC along with WHO launched the Saving Mothers, Giving Life Initiative (SMGL); a public health organization partnering with the national government, to implement strategies that rapidly reduce death through effective evidence-based interventions during delivery, labor and post-delivery.

The purpose of this project is to determine if salivary cortisol influences the bidirectionality of stress, oxytocin levels and proteinuria on preeclampsia in pregnant mothers. It is known that mothers suffering from preeclampsia will experience high blood pressure as a result of elevated cortisol levels in urine or saliva samples collected in the morning. Cortisol levels are generally highest early in the morning due to diurnal patterns; which acts on a positive feedback loops for daily activity patterns. Salivary cortisol Salivary cortisol reflects the quantity of cortisol that that  enters the body through tissues such as the salivary glands and is expressed in saliva (Sohlberg 2016). This fosters an increased risk of preeclampsia because it activates higher stressors in pregnant mothers which can cause complications during pregnancy and delivery. The reason for pursuing this project is to acknowledge the gaps in knowledge towards the relationship between the physiological factors that influence salivary cortisol levels and preeclampsia. This study will promote further studies and recommendations in regard to preeclampsia and stress-induced elevated salivary cortisol levels in different stages of the gestation period.

There are two aims in this study. The first aim is to evaluate the role of salivary cortisol levels as a response to increased stress/ stressors during pregnancy at different periods during gestation. To do this, the PSS will be gathered and analyzed at different periods of gestation; 16 weeks, 26 weeks, 36 weeks, and 40 weeks. The accepted PSS score is 0 to13 for considerably low stress. Salivary cortisol levels will be collected three time periods, 4-hour time intervals during the day ( morning,mid-afternoon and night). This is important to analyze at which time does stress affect the increase in cortisol surfactants in saliva during period of gestation listed above as well. The salivary analysis will be used as the standardized assessment protocol along with the PSS because both contribute to the investigation of the relationship between cortisol level and stress/stressors on preeclampsia. Normally, salivary cortisol is measured around 15.5nmol/L in the morning  and 3.9nmol/L at night. The PSS will serve in creating two groups of pregnant mothers (stressed or non-stressed). It is important to evaluate preeclampsia symptoms on a continuum. This will allow for the determination of whether the cortisol can be associated with volatile or brief symptoms as well as, present additional assessment of whether the stress level and cortisol levels of pregnant mothers can clinically confirm preeclampsia. From this aim, we expect to discover lower probabilities of preeclampsia, depending on when stress and salivary cortisol levels are managed and maintained to a certain criterion.  The second aim is a plan to conduct a prospective study on pregnant mothers with symptoms of preeclampsia and pregnant mothers with no symptoms and history of preeclampsia to assess the impact of elevated salivary cortisol levels and high stress scores on the initiation and successful cessation of the diagnosis. This will provide results on the difference between stressed and non-stressed pregnant mothers, especially when it comes the influence of salivary cortisol levels and the difference of stress/stressors and BMI levels on preeclampsia. From here a comparison of PSS between the two types of categories of pregnant mothers will be evaluated. The expected finding from this aim is to show a direct correlation with an increase in elevated stress levels and a higher BMI than recommended leading into 20 weeks of gestation for pregnant mothers resulting in higher probability of developing preeclampsia. This relationship can also be seen in the reverse with lower stress levels and an average to lower BMI scores for pregnant mothers entering 20 weeks of gestation will result in a lower probability of developing preeclampsia

Significance

Preeclampsia is a disorder related to perinatal health of both mother and fetus, which may lead to fetal and maternal morbidity and mortality. Preeclampsia; a pregnancy-specific syndrome, that occurs exactly after 20 weeks’ gestation. It is believed that early PPS use during the first trimester of a pregnancy, is predictive of early onset preeclampsia. Evidence has shown that salivary cortisol influences the bidirectionality of stress, oxytocin levels and proteinuria on preeclampsia in pregnant mothers, which means a decrease in stress and BMI levels will result in lower rates of preeclampsia. Studies have indicated that women with high PPS scores (≥20) were more likely to experience difficulties with HBP and more susceptible to preeclampsia. preeclampsia manifests a negative effect of the physiological development of the fetus and cognitive dissonance with the mother (Wang et., al, 2016). Preeclampsia is associated with elevated stress levels and proteinuria, which has the ability to negatively impact a mother’s long-term cognitive health (Haavaldsen, 2019). Given that preeclampsia has a late onset (≥20 weeks), the accumulation of proteinuria and elevated BMI levels can be correlated. Controlled stress levels within the 2nd trimester of pregnancy are essential for not only the fetus but the mother as well. With the current rate of salivary cortisol/stress levels and the prevalence of preeclampsia, the CDC along with WHO launched the Saving Mothers, Giving Life Initiative (SMGL); a public health partnership public-private implemented strategy to rapidly reduce death through effective evidence-based interventions during delivery, labor and post-delivery. SMGL promotes reducing maternal and perinatal deaths (WHO, 2019).

Innovation

There are numerous gaps in this field of study. First, the single use of the SMGL techniques in the first few months of pregnancy were unable to distinguish between common pregnancy sickness symptoms and true preeclampsia complications (Wang 2016). This gap will be addressed through scheduled PSS testing to distinguish whether mothers suffering from preeclampsia experience more stress or less stress which factors into higher salivary cortisol levels. In this study, the control group will be women with no prior history of preeclampsia and show normal cortisol levels during pregnancy to address this gap. Third, most studies included women who self-reported preeclampsia. The PSS scores from 16, 26, 36, 40 weeks will be evaluated. If the score is indicative of preeclampsia, cases will be sent to a physician for a clinical diagnosis. Finally, women with history of stress during pregnancy were not included. For this study, it will still be used to categorize stress induced and non-stress induced pregnant mothers. They will be included because evidence has shown a negative association between salivary cortisol/stress throughout pregnancy.

Table 1: Perceived stress scale questionnaire for analysis of pregnant mothers to revel stress indicator(s).

In order to fully address these gaps, this study will evaluate role of elevated salivary cortisol and BMI levels during pregnancy at different periods during gestation. This is because each provides a different approach to investigative the relationship between cortisol/stress level on preeclampsia. The PSS will serve in creating two groups of pregnant mothers (stressed or non-stressed). It is important to evaluate preeclampsia symptoms on a continuum. This will allow for the determination of whether the salivary cortisol can be associated with volatile or brief symptoms as well as, present additional assessment of whether the stress level and BMI levels of pregnant mothers can clinically confirm preeclampsia. Overall findings will establish the difference in preeclampsia between stressed induced and non-stressed pregnant mothers and the outcomes will enable the implementation of the type of association in regard to salivary cortisol levels on preeclampsia.

Table 2: Scoring chart for variables to determine which variable(s) is most responsible for inducing preeclampsia in pregnant mothers.

Analytic Plan:

Figure 1: The eligibility diagnostic criteria for prevalence of preeclampsia in pregnant women

Ineligible Criteria:

PSS questionnaire, miscarriage, (<20-week gestation)

The study design for this experiment will be a prospective cohort study. This design was chosen because it uses a hypothesis to observe for outcomes and the development of diseases (i.e., preeclampsia) over a time period. Prospective cohort studies are efficient for estimating the relative risk or incidence rate of an outcome. With a prospective cohort study, you can obtain the levels of salivary cortisol and PSS score in real time and then follow up the cohort members during the time after exposure to measure the occurrence of preeclampsia in pregnant mothers.   To begin, first identify the group of pregnant mothers diagnosed with preeclampsia and the comparison group ( pregnant mothers not diagnosed with preeclampsia). Next, analyze from the group of interest and comparison groups, which had the exposure of interest (i.e., preeclampsia), and evaluate the frequency of preeclampsia against both groups.

The study population will be pregnant mothers at 20 weeks of gestation, who have been diagnosed with preeclamptic conditions or have not by a physician. The inclusion criteria for participating in this study will be women who show elevated salivary cortisol levels throughout the day and have a history of HBP or have recorded HBP within two prenatal appointments (systole ≥ 140 mm Hg and diastole  ≥ 90 mm Hg respectively). The prenatal characteristics to be included in the case groups are: age, age distribution (<30 and≥30), education (High school education, below higher education, or secondary level), marriage status (married or non-married), gestation period (≥20 weeks), BMI levels around 20 weeks of gestation ((<20 and≥20), salivary cortisol levels (≥15.5nnmol/L). These characteristics will be evaluated across stressed and non-stressed pregnant mothers using the PSS scale. The exclusion criteria will be not completing the PSS questionnaire, and having a miscarriage (<20 weeks of gestaion). Potential problems may arise with all prospective studies; some areas of concern are its propensity to be prone to biases such as recall, selection and observer bias. In addition, prospective cohort study may be difficult with large sample sizes, time consumption, a surplus of funding as confounding variables can become a  larger problem within the study.

Furthermore, with prospective study, there are limits to analyzing only one outcome. First, there will be a long period of time for analysis of symptoms in order to address the incidence of preeclampsia given that there is a long onset period. Due to the probability of bias affecting the study, selection bias will be limited by having the participants selected for the study represent their respective population of interest. In regard to observer bias, all observers will be properly trained, and all behaviors and physiological responses/ emotions are clearly defined. For recall bias, times between surveys will be shortened, and periodically accounting for all baseline data collected since the study duration is 16-20 weeks.

For the study of a multivariable analysis, such as this one, a logistical regression modeling will be conducted to observe the association between preeclampsia and stress levels/ elevated BMI levels. The variable selected for analysis will be age, age distribution (<30 and≥30), education (High school education, below higher education, or secondary level), marriage status (married or non-married), gestation period (≥20 weeks), BMI levels around 20 weeks of gestation ((<20 and≥20), diagnosed case of proteinuria (≥20 weeks). These characteristics would be evaluated across stressed and non-stressed pregnant mothers using the PSS scale. odds ratio, and 95% confidence interval (CI), relative risk ratio, incidence rate, and risk difference, will be measured.

Standard odds ratio will be used to calculate the association between the outcome and exposure in the general population. Since the odds ratio first expresses the ratio of the odds of exposure among cases to the odds of exposure among controls, it seemingly only tells us about the relative difference in exposure between cases and controls, not about the relative risk or ratio of disease rates between exposure groups. Because a properly designed case control study, using incident cases and controls sampled from the at-risk source population, gives an accurate estimate of the rate ratio, and shows that the odds ratio estimates disease risk in exposed relative to. non-exposed. The relative risk expresses the impact of preeclampsia among the exposed (elevated stress/ salivary cortisol levels) relative to the impact among the unexposed. If the relative risk estimate is < 1.0 or >1.0, the exposure will appear to be protective of preeclampsia occurrence or a risk factor it respectively. If 95% Confidence Interval includes 1, it will suggest that relative risk is not statistically significant. The combination of the CI and risk ratio will determine the prevalence of stress and salivary cortisol level` as a risk factor for preeclampsia.

There are several different expected outcomes from this study. First, there should be a difference between preeclamptic and non-preeclamptic pregnant mothers. It is expected that preeclamptic pregnant mothers will have elevated levels of stress, higher salivary cortisol rates, increased BMI levels and abnormal renin levels. The accepted PSS score is 27-30 for high perceived stress and the accepted salivary cortisol average throughout the day when measured is 15nmol/L. For this study, a score of 26 or greater will be marked as major stress indicators and these participants will be referred to a psychologist and a specialist to address both psychological and physiological symptoms. It is hypothesized that pregnant mothers who are screened to have elevated salivary cortisol levels during when measured in the morning and mid-day, coupled with high stress scores will have increased chances of preeclampsia, as these moms most likely had higher HBP readings and showed significant levels of protein in their urinalysis. Non-preeclamptic mothers will report lower PSS scores, normal salivary cortisol reading during all time periods of the day, and normal metabolic functions. Furthermore, it is imperative that the time between PSS surveys are timely in order to reveal the onset of preeclampsia, because this will set the precedents for future studies on the prevalence of self-reported preeclamptic rates and clinically diagnosed preeclampsia. 

Public Health Significance

There are current numerous gaps when studying the association between stress, salivary cortisol levels and preeclampsia. One area of interest is the single use of urinalysis techniques in the first few months of pregnancy to diagnose preeclampsia complications. This gap will be addressed through scheduled PSS testing to distinguish whether  mothers suffering from preeclampsia experience more stress or less stress. This study is important in bridging these gaps by: (1) having scheduled urinalysis testing to determine preeclampsia, (2) evaluating the PSS scores from 20 and 40 weeks; if the scores show greater indication of stress, patients will be referred to psychologist and specialist for related conditions. Evidence shows that a negative association between stress and preeclampsia throughout pregnancy can cause congenital birth defects. Addressing these gaps in this study will allow for future studies to, address the link between preeclampsia during pregnancy and stress resulting in HBP. Future studies should focus on if urinary cortisol levels shows greater association in hypertensive pregnant mothers that causes elevated stress for the occurrence of preeclampsia. Furthermore, this study will not address the influence of the placenta abnormalities and the transfer of trophoblast tissue in initiating preeclampsia, therefore, future studies on determine preeclampsia induced pregnancies should include women in the study who are suffering from abnormal formation of the placenta. Lastly, future studies should examine fetal growth as a result of elevated BMI and stress levels in controlling for preeclampsia.

References

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