Adherence to prescription medication during pregnancy: Do pregnant women use pharmacological treatment as prescribed?

AIMS: Pregnant women are hypothesized to have low adherence to prescribed medication, because of concerns about harmful effects on the unborn child. However, very little is known about the actual adherence to prescribed medication during pregnancy. We determined to what extent women follow treatment recommendations regarding prescribed medication use in mid-pregnancy. METHODS: Dutch women participating in the PRIDE Study completed a 6-week diary on medication use. Additionally, pharmacy records were obtained. For each medication dispensed, we determined 3 measures of adherence: (i) whether use was reported in the diary (actual use); (ii) difference between dispensing date and date of first reported use (initiation time); and (iii) proportion of days with at least the correct number of doses taken (implementation adherence). RESULTS: During the 6-week study period, 235 of 816 women (29%) were dispensed medication. Actual use was highest for medications used for chronic conditions (88%; 95% confidence interval [95% CI] 81-93), followed by medication for pregnancy-related conditions (79%; 95% CI 71-86) and medication for occasional and short-time use (69%; 95% CI 60-77). We observed a ≥1-day delay in treatment initiation for 42% of medications dispensed for the first time in the study period. Mean implementation adherence was 74.2% (95% CI 69.3-79.2) for medications that were actually used. CONCLUSION: Although actual use of medications dispensed was high, many pregnant women did not adhere to treatment recommendations. This nonadherence may impact maternal and child health and lead to overestimation of medication use in studies in perinatal pharmacoepidemiology relying on administrative databases.

Associations between maternal awakening salivary cortisol levels in mid-pregnancy and adverse birth outcomes.

PURPOSE: Elevated levels of maternal cortisol have been hypothesized as the intermediate process between symptoms of depression and psychosocial stress during pregnancy and adverse birth outcomes. Therefore, we examined associations between cortisol levels in the second trimester of pregnancy and risks of three common birth outcomes in a nested case-control study. METHODS: This study was embedded in the PRIDE Study (n = 3,019), from which we selected all cases with preterm birth (n = 64), low birth weight (n = 49), and small-for-gestational age (SGA; n = 65), and 260 randomly selected controls, among the participants who provided a single awakening saliva sample in approximately gestational week 19 in 2012-2016. Multivariable linear and logistic regression was performed to assess the associations between continuous and categorized cortisol levels and the selected outcomes. RESULTS: We did not observe any associations between maternal cortisol levels and preterm birth and low birth weight. However, high cortisol levels (≥ 90th percentile) seemed to be associated with SGA (adjusted odds ratio 2.1, 95% confidence interval 0.9-4.8), in particular among girls (adjusted odds ratio 3.7, 95% confidence interval 1.1-11.9, based on eight exposed cases) in an exploratory analysis. CONCLUSION: The results of this study showed no suggestions of associations between maternal awakening cortisol levels in mid-pregnancy and adverse birth outcomes, except for an increased risk of SGA.

The PRIDE Study: Evaluation of online methods of data collection.

BACKGROUND: Large birth cohort studies are extremely valuable in assessing associations between early life exposures and long-term outcomes. Establishing new birth cohorts is challenging due to declining participation rates. Online methods of data collection may increase feasibility, but have not been evaluated thoroughly. OBJECTIVE: The primary objective of the ongoing PRegnancy and Infant DEvelopment (PRIDE) Study is to identify exposures during pregnancy and in early life that may affect short-term or long-term health of mother and/or child. In this manuscript, we aimed to evaluate methods of recruitment and online data collection applied. POPULATION: Dutch women aged ≥18 years in early pregnancy. DESIGN: Prospective cohort study. METHODS: Initially, only prenatal care providers recruited participants, but alternative recruitment methods were added as a result of disappointing participation rates, including collaboration with "Moeders voor Moeders" (organisation that visits women in early pregnancy) and Facebook advertisements. Data on demographic characteristics, obstetric history, maternal health, life style factors, occupational exposures, nutrition, pregnancy complications, and infant outcomes are primarily collected through Web-based questionnaires at multiple time points during and after pregnancy. Additional data collection components include paternal questionnaires, blood and saliva sampling, and linkage to medical records. PRELIMINARY RESULTS: By September 2019, 9573 women were included in the PRIDE Study, of which 1.3% completed paper-based questionnaires. Mean age of the women analysed was 30.6 years, 71.1% had a high level of education, 57.2% were primiparae, and mean gestational age at enrolment was 9.9 (range 3, 37) weeks, with slight differences between recruitment methods. Pregnancy outcome was known for 89.8%. Retention rate at 6 months after the estimated date of delivery was estimated at 70%. Multiple validation studies conducted within the PRIDE Study indicated high data quality. CONCLUSION(S): Although challenging and time-consuming, online methods for recruitment and data collection may enable the establishment of new birth cohort studies.

Google AdWords and Facebook Ads for Recruitment of Pregnant Women into a Prospective Cohort Study With Long-Term Follow-Up.

Objectives Several types of epidemiologic studies suffer from decreasing participation rates, resulting in potential selection bias and delay or termination of studies. We aimed to determine the feasibility of online methods for recruitment of pregnant women into a prospective cohort study. Methods In addition to traditional recruitment through prenatal care providers, we advertized participation in the PRegnancy and Infant DEvelopment (PRIDE) Study, an ongoing prospective cohort study with long-term follow-up in The Netherlands enrolling women in early pregnancy, through Google AdWords (30 days) and Facebook Ads (31 and 27 days) campaigns between September 2016 and January 2017. We calculated costs per eligible participant and compared demographics, health-related characteristics, and follow-up rates between participants recruited through online methods and prenatal care providers. Results During the study period, we recruited six women through AdWords (€54.28 per participant), 59 through Facebook (€10.17 per participant), and 327 through prenatal care providers (no valid cost estimate available). Facebook participants seemed to be younger (29.0 vs. 30.7 years), to have a higher body mass-index and/or low/intermediate education (27.0 vs. 24.0 kg/m2 and 41 vs. 25%, respectively), and to start prenatal care in secondary care more often (12 vs. 5%) than participants recruited through prenatal care providers. Item non-response and loss to follow-up rates were higher among women recruited online than among those recruited through prenatal care providers. Conclusion Google AdWords did not contribute substantially, but Facebook Ads may complement traditional recruitment methods of pregnant women into prospective cohort studies, despite challenges that may threaten internal validity.

Using Web-Based Questionnaires to Assess Medication Use During Pregnancy: A Validation Study in 2 Prospectively Enrolled Cohorts.

Medication use is often underreported in paper-based questionnaires or interviews. Web-based questionnaires may improve recall of medication use, but data on their validity are currently lacking. Participants in the Pregnancy and Infant Development (PRIDE) Study (2014-2016; n = 557) and the Pregnancy Drug Registry (pREGnant) (2015-2016; n = 169) completed a 6-week paper-based medication diary during gestational weeks 19-24 or 26-31. In week 34, they completed a Web-based questionnaire with questions on medication names, time period and frequency of use, and quantity taken. To assess the degree of underreporting, we calculated the questionnaire's sensitivity using the medication diary as the reference standard. Sensitivity was high for many medication groups, including antiepileptic medication (sensitivity (Sn) = 0.96, 95% confidence interval (CI): 0.89, 1.00), antacids (Sn = 0.89, 95% CI: 0.86, 0.93), and iron preparations (Sn = 0.81, 95% CI: 0.64, 0.98). However, medications for short-term use were underreported more frequently, with sensitivities of 0.54 (95% CI: 0.35, 0.72) for antihistamines, 0.63 (95% CI: 0.57, 0.69) for analgesic and antipyretic agents, and 0.57 (95% CI: 0.51, 0.64) for acetaminophen. Shortening the period of time between exposure and questionnaire administration increased sensitivity substantially. In conclusion, underreporting in Web-based questionnaires is limited for many medication groups. In prospective studies, underreporting of medications for short-term use may be reduced by decreasing the interval between consecutive questionnaires.

Using Web-Based Questionnaires and Obstetric Records to Assess General Health Characteristics Among Pregnant Women: A Validation Study.

BACKGROUND: Self-reported medical history information is included in many studies. However, data on the validity of Web-based questionnaires assessing medical history are scarce. If proven to be valid, Web-based questionnaires may provide researchers with an efficient means to collect data on this parameter in large populations. OBJECTIVE: The aim of this study was to assess the validity of a Web-based questionnaire on chronic medical conditions, allergies, and blood pressure readings against obstetric records and data from general practitioners. METHODS: Self-reported questionnaire data were compared with obstetric records for 519 pregnant women participating in the Dutch PRegnancy and Infant DEvelopment (PRIDE) Study from July 2011 through November 2012. These women completed Web-based questionnaires around their first prenatal care visit and in gestational weeks 17 and 34. We calculated kappa statistics (κ) and the observed proportions of positive and negative agreement between the baseline questionnaire and obstetric records for chronic conditions and allergies. In case of inconsistencies between these 2 data sources, medical records from the woman's general practitioner were consulted as the reference standard. For systolic and diastolic blood pressure, intraclass correlation coefficients (ICCs) were calculated for multiple data points. RESULTS: Agreement between the baseline questionnaire and the obstetric record was substantial (κ=.61) for any chronic condition and moderate for any allergy (κ=.51). For specific conditions, we found high observed proportions of negative agreement (range 0.88-1.00) and on average moderate observed proportions of positive agreement with a wide range (range 0.19-0.90). Using the reference standard, the sensitivity of the Web-based questionnaire for chronic conditions and allergies was comparable to or even better than the sensitivity of the obstetric records, in particular for migraine (0.90 vs 0.40, P=.02), asthma (0.86 vs 0.61, P=.04), inhalation allergies (0.92 vs 0.74, P=.003), hay fever (0.90 vs 0.64, P=.001), and allergies to animals (0.89 vs 0.53, P=.01). However, some overreporting of allergies was observed in the questionnaire and for some nonsomatic conditions sensitivity of both measurement instruments was low. The ICCs for blood pressure readings ranged between 0.72 and 0.92 with very small mean differences between the 2 methods of data collection. CONCLUSIONS: Web-based questionnaires can be used to validly collect data on many chronic disorders, allergies, and blood pressure readings among pregnant women.

Intimate partner violence is related to future alcohol use among a nationwide sample of LGBTQIA+ people: Results from The PRIDE Study.

BACKGROUND: Lesbian, gay, bisexual, transgender, queer, intersex, aromantic and asexual (LGBTQIA+) communities in the United States experience higher rates of alcohol use than the general population. While experiencing intimate partner violence (IPV) is thought to lead to increased alcohol use in LGBTQIA+ people, little research has investigated the temporal relationship between IPV and alcohol use in this population. METHODS: Data from two annual questionnaires of The Population Research in Identity and Disparities for Equality Study (The PRIDE Study) longitudinal cohort (n=3,783) were included. Overall IPV and three sub-types (physical, sexual, and emotional) - measured in 2021 using the extended Hurt, Insult, Threaten, Scream (E-HITS) screening tool - was examined as a predictor of Alcohol Use Disorders Identification Test (AUDIT) score in 2022 using multivariable linear regression to assess linear and quadratic associations. Models were adjusted for sociodemographic characteristics and history of alcohol use. RESULTS: One-quarter (24.7%) of respondents reported experiencing past-year IPV in 2021. The mean AUDIT score in 2022 was 3.52 (SD = 4.13). In adjusted models, both linear (B: 0.26, 95% CI: 0.14, 0.38) and quadratic (B: -0.03, 95% CI: -0.04, -0.01) terms for overall IPV were significantly associated with next-year AUDIT score. These patterns were mirrored in each IPV sub-type, were not attenuated when accounting for relationship characteristics, and were heterogeneous across gender identity groups. CONCLUSIONS: These results provide evidence of a temporal relationship between IPV and alcohol use in LGBTQIA+ communities, suggesting that efforts to prevent and mitigate IPV may help reduce alcohol use disparities in this population.

Associations of periconceptional oral contraceptive use with pregnancy complications and adverse birth outcomes.

BACKGROUND: Periconceptional use of oral contraceptives (OCs) has been reported to increase risks of pregnancy complications and adverse birth outcomes, but risks are suggested to differ depending on the timing of discontinuation, amount of oestrogen and progestin content. METHODS: Prospective cohort study among 6470 pregnancies included in the PRegnancy and Infant DEvelopment (PRIDE) Study in 2012-19. Exposure was defined as any reported use of OCs within 12 months pre-pregnancy or after conception. Outcomes of interest were gestational diabetes, gestational hypertension, pre-eclampsia, pre-term birth, low birthweight and small for gestational age (SGA). Multivariable Poisson regression using stabilized inverse probability weighting estimated relative risks (RRs) with 95% CIs. RESULTS: Any periconceptional OC use was associated with increased risks of pre-eclampsia (RR 1.38, 95% CI 0.99-1.93), pre-term birth (RR 1.38, 95% CI 1.09-1.75) and low birthweight (RR 1.45, 95% CI 1.10-1.92), but not with gestational hypertension (RR 1.09, 95% CI 0.91-1.31), gestational diabetes (RR 1.02, 95% CI 0.77-1.36) and SGA (RR 0.96, 95% CI 0.75-1.21). Associations with pre-eclampsia were strongest for discontinuation 0-3 months pre-pregnancy, for OCs containing ≥30 µg oestrogen and for first- or second-generation OCs. Pre-term birth and low birthweight were more likely to occur when OCs were discontinued 0-3 months pre-pregnancy, when using OCs containing <30 µg oestrogen and when using third-generation OCs. Associations with SGA were observed for OCs containing <30 µg oestrogen and for third- or fourth-generation OCs. CONCLUSIONS: Periconceptional OC use, particularly those containing oestrogen, was associated with increased risks of pre-eclampsia, pre-term birth, low birthweight and SGA.

Maternal depressive symptoms during pregnancy and infant wheezing up to 2 years of age.

PURPOSE: To determine whether maternal depressive symptoms at multiple time points during pregnancy are associated with infant wheezing in the first 2 years of life to assess etiologically relevant time windows. METHODS: We included Dutch women participating in the PRIDE Study with delivery in 2013-2019. Maternal depressive symptoms were assessed with the Hospital Anxiety and Depression Scale and Edinburgh Depression Scale at enrollment and in gestational weeks 17 and 34. The International Study of Asthma and Allergies in Childhood questionnaire was used to assess infant wheezing biannually postpartum. Adjusted risk ratios (RRs) and 95% confidence intervals (CIs) were estimated with modified Poisson regression. RESULTS: Among 5294 pregnancies included, maternal depressive symptoms in gestational weeks 15-22 was associated with any wheezing in the first 2 years of life (RR 1.36, 95% CI 1.04-1.78) and with current wheezing at 12 (RR 1.29, 95% CI 1.03-1.61) and 18 months (RR 1.33, 1.04-1.69). Depressive symptoms in gestational weeks 32-35 seemed to be associated with any wheezing reported at two years (RR 1.27, 95% CI 0.96-1.69) and current wheezing at 12 months (RR 1.28, 95% CI 1.02-1.60). Four trajectories of depressive symptoms were identified. Only the trajectory with increasing symptoms throughout pregnancy seemed to be associated with infant wheezing (RR 1.36, 95% CI 0.97-1.89). CONCLUSIONS: Maternal depressive symptoms in mid- and late pregnancy may be associated with development of infant wheezing, particularly those with onset in the second half of pregnancy. Research is needed to identify biological pathways and associations with more objective, long-term respiratory morbidity.

Associations Between Late-Onset Preeclampsia and the Use of Calcium-Based Antacids and Proton Pump Inhibitors During Pregnancy: A Prospective Cohort Study.

Purpose: Preeclampsia is a leading cause of maternal morbidity and mortality. Calcium-based antacids and proton pump inhibitors (PPIs) are commonly used during pregnancy to treat symptoms of gastroesophageal reflux disease. Both have been hypothesized to reduce the risk of preeclampsia. We determined associations of calcium-based antacid and PPI use during pregnancy with late-onset preeclampsia (≥34 weeks of gestation), taking into account dosage and timing of use. Patients and Methods: We included 9058 pregnant women participating in the PRIDE Study (2012-2019) or The Dutch Pregnancy Drug Register (2014-2019), two prospective cohorts in The Netherlands. Data were collected through web-based questionnaires and obstetric records. We estimated risk ratios (RRs) for late-onset preeclampsia for any use and trajectories of calcium-based antacid and PPI use before gestational day 238, and hazard ratios (HRs) for time-varying exposures after gestational day 237. Results: Late-onset preeclampsia was diagnosed in 2.6% of pregnancies. Any use of calcium-based antacids (RR 1.2 [95% CI 0.9-1.6]) or PPIs (RR 1.4 [95% CI 0.8-2.4]) before gestational day 238 was not associated with late-onset preeclampsia. Use of low-dose calcium-based antacids in gestational weeks 0-16 (<1 g/day; RR 1.8 [95% CI 1.1-2.9]) and any use of PPIs in gestational weeks 17-33 (RR 1.6 [95% CI 1.0-2.8]) seemed to increase risks of late-onset preeclampsia. We did not observe associations between late-onset preeclampsia and use of calcium-based antacids (HR 1.0 [95% CI 0.6-1.5]) and PPIs (HR 1.4 [95% CI 0.7-2.9]) after gestational day 237. Conclusion: In this prospective cohort study, use of calcium-based antacids and PPIs during pregnancy was not found to reduce the risk of late-onset preeclampsia.

Data From Web-Based Questionnaires Were Valid for Gestational Diabetes and Preeclampsia, but Not Gestational Hypertension.

OBJECTIVES: We aimed to validate Web-based questionnaires for the common pregnancy complications gestational diabetes, gestational hypertension, and preeclampsia. STUDY DESIGN AND SETTING: We included 1,809 women participating in the PRegnancy and Infant DEvelopment (PRIDE) Study who delivered in 2012-2017, for whom relevant data were complete. Sensitivity, specificity, and positive and negative predictive values of self-reported diagnoses of gestational diabetes, gestational hypertension, and preeclampsia were determined using obstetric records as reference standard. Furthermore, we assessed whether maternal characteristics affected disagreement between questionnaires and obstetric record. RESULTS: For gestational diabetes and preeclampsia, we observed very few false-positive and false-negative reports, yielding sensitivities of 93% (95% confidence interval [CI] 86-100) and 88% (95% CI 79-98), respectively, and specificities of 100%. Depending on the definition of gestational hypertension, sensitivity and positive predictive values ranged from 62% to 89% and 53% to 64%, respectively. Disagreement on gestational hypertension was associated with prepregnancy overweight and multiparity. CONCLUSION: Self-reports of gestational diabetes and preeclampsia in Web-based questionnaires were valid, but the validity of gestational hypertension seemed to be lower because of relatively high numbers of false-positive reports. However, it is questionable whether an appropriate reference standard exists to validate this pregnancy complication.

Efficacy and safety of ranibizumab with or without panretinal laser photocoagulation versus laser photocoagulation alone in proliferative diabetic retinopathy - the PRIDE study.

PURPOSE: Panretinal photocoagulation (PRP) is the current standard of care in proliferative diabetic retinopathy (PDR). However, treatment with anti-vascular endothelial growth factor agents might offer better patient outcomes with fewer side-effects. The PRIDE study aimed to assess the efficacy and safety of ranibizumab with or without PRP compared with PRP alone in patients with PDR. METHODS: A total of 106 PDR patients without diabetic macular oedema were randomized to receive ranibizumab 0.5 mg monotherapy (n = 35), PRP (n = 35) or combined ranibizumab 0.5 mg/PRP (n = 36). The primary objective of this 12-month, multicentre, phase II study was to investigate the change in area of retinal neovascularization (NV). Complete regression of leakage and best-corrected visual acuity (BCVA) were key secondary end-points. RESULTS: At Month 12, there was a statistically significant difference of -2.83 mm² in the least square mean change in NV area between the ranibizumab monotherapy and PRP group, favouring ranibizumab (95% CI [-5.45; -0.21], p = 0.0344). At Month 3, 67%/0%/67% of the patients in the ranibizumab/PRP/combination groups, respectively, showed complete regression of leakage from NVs, while at Month 12, 28%/8%/18% showed complete regression of leakage from NVs. BCVA change was greater in the ranibizumab group compared with the PRP monotherapy group at Month 12 (+1.6 letters; 95% CI [-2.3; 5.5] versus -3.9 letters; 95% CI [-7.8; -0.1], p = 0.0495). CONCLUSIONS: Ranibizumab monotherapy is an alternative treatment option to laser treatment in patients with PDR. Ranibizumab showed stronger effects on NV leakage and area reduction while offering better visual acuity results than PRP alone.

Assessment of medication use during pregnancy by Web-based questionnaires, pharmacy records and serum screening.

OBJECTIVE: To compare assessment of early pregnancy medication exposure using three methods of data collection. METHODS: Serum samples were obtained from 752 women participating in the PRegnancy and Infant DEvelopment (PRIDE) Study before gestational week 17. For 52 women using medication at the date of blood sampling according to Web-based questionnaires or pharmacy records, we analysed serum samples using untargeted liquid chromatography time-of-flight spectrometry. RESULTS: Medication was detected in 18 serum samples (35%). Medications taken orally for chronic conditions reported in the questionnaire were detected in serum and vice versa. Pharmacy records did not identify additional exposed women, but missed exposure in 5 women mainly due to unavailability. We observed substantial discordance between the three methods for inhaled medication, dermatological preparations, and medications for short-term use, which went often undetected in serum. CONCLUSIONS: It remains challenging to assess medication use in large-scale studies as no 'gold standard' is currently available.

Utilizing Consumer Technology (Apple's ResearchKit) for Medical Studies by Patients and Researchers: Proof of Concept of the Novel Platform REach.

Medical research suffers from declining response rates, hampering the quest for answers to clinically relevant research questions. Furthermore, objective data on a number of important study variables, such as physical activity, sleep, and nutrition, are difficult to collect with the traditional methods of data collection. Reassuringly, current technological developments could overcome these limitations. In addition, they may enable research being established by patients themselves provided that they have access to a user-friendly platform. Using the features of Apple's ResearchKit, an informed consent procedure, questionnaire, linkage with HealthKit data, and "active tasks" may be administered through a publicly available app. However, ResearchKit requires programming skills, which many patients and researchers lack. Therefore, we developed a platform (REach) with drag and drop functionalities producing a ready-to-use code that can be embedded in existing or new apps. Participants in the pilot study were very satisfied with data collection through REach and measurement error was minimal. In the era of declining participation rates in observational studies and patient involvement, new methods of data collection, such as REach, are essential to ensure that clinically relevant research questions are validly answered. Due to linkage with HealthKit and active tasks, objective health data that are impossible to collect with the traditional methods of data collection can easily be collected.

Web-based questionnaires to assess perinatal outcome proved to be valid.

OBJECTIVES: The objective of this study was to validate a Web-based questionnaire completed by the mother to assess perinatal outcome used in a prospective cohort study. STUDY DESIGN AND SETTING: For 882 women with an estimated date of delivery between February 2012 and February 2015 who participated in the PRegnancy and Infant DEvelopment (PRIDE) Study, we compared data on pregnancy outcome, including mode of delivery, plurality, gestational age, birth weight and length, head circumference, birth defects, and infant sex, from Web-based questionnaires administered to the mothers 2 months after delivery with data from obstetric records. For continuous variables, we calculated intraclass correlation coefficients (ICCs) with 95% confidence intervals (CIs), whereas sensitivity and specificity were determined for categorical variables. RESULTS: We observed only very small differences between the two methods of data collection for gestational age (ICC, 0.91; 95% CI, 0.90-0.92), birth weight (ICC, 0.96; 95% CI, 0.95-0.96), birth length (ICC, 0.90; 95% CI, 0.87-0.92), and head circumference (ICC, 0.88; 95% CI, 0.80-0.93). Agreement between the Web-based questionnaire and obstetric records was high as well, with sensitivity ranging between 0.86 (termination of pregnancy) and 1.00 (four outcomes) and specificity between 0.96 (term birth) and 1.00 (nine outcomes). CONCLUSION: Our study provides evidence that Web-based questionnaires could be considered as a valid complementary or alternative method of data collection.

Single awakening salivary measurements provide reliable estimates of morning cortisol levels in pregnant women.

Mood disorders during pregnancy have been associated with adverse effects on maternal as well as fetal health. Since mood, anxiety, and stress disorders are related with elevated cortisol levels, salivary cortisol may be a useful biomarker. Although multiple samples are generally recommended, a single measurement of awakening salivary cortisol could be a simpler and more cost-effective method to determine whether women have elevated morning cortisol levels during a specific period of pregnancy. Therefore, the aim of this validation study among 177 women in the PRIDE Study was to examine whether one awakening salivary cortisol measurement will suffice to classify pregnant women as having normal or elevated cortisol levels compared to awakening salivary cortisol measurements on three consecutive working days. We calculated intraclass correlation coefficients (ICC) and Cohen's kappa statistics (κ) overall as well as in sub-analyses within strata based on maternal age, level of education, net household income, pre-pregnancy BMI, parity, complications during pregnancy, caffeine consumption, gestational week of sampling, and awakening time. The mean cortisol concentrations were 8.98ng/ml (SD 5.32) for day one, 8.62ng/ml (SD 4.55) for day two, and 8.39ng/ml (SD 4.58) for day three. The overall ICC was 0.86 (95% CI 0.82-0.89) while the κ was 0.75 (95% CI 0.64-0.86). For the ICCs calculated within sub-analyses, a maximum difference of 0.11 was observed between the strata. For the κ statistics, most strata did not differ more than 0.12, except for pre-pregnancy BMI, severe nausea, and extreme fatigue with differences up to 0.22. In conclusion, one awakening salivary cortisol measurement is as reliable for the classification of pregnant women into normal and elevated morning cortisol levels as salivary cortisol measurements on three consecutive working days.