Dermatology: Practical and Conceptual Original Article | Dermatol Pract Concept. 2024;14(4):e2024221 1 Impact of Psoriasis on Pregnancy Desire and Possible Consequences on Fertility Martina Burlando1, Ilaria Salvi1, Gabriele Poddine1, Emanuele Cozzani1, Aurora Parodi1 1 Section of Dermatology, DISSAL, University of Genoa, Ospedale-Policlinico San Martino, IRCCS, Genova, Italy Key words: psoriasis, dermatology, pregnancy, fertility Citation: Burlando M, Salvi I, Poddine G, Cozzani E, Parodi A. Impact of Psoriasis on Pregnancy Desire and Possible Consequences on Fertility. Dermatol Pract Concept. 2024;14(4):e2024221. DOI: https://doi.org/10.5826/dpc.1404a221 Accepted: June 28, 2024; Published: October 2024 Copyright: ©2024 Burlando et al. This is an open-access article distributed under the terms of the Creative Commons Attribution- NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing Interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding Author: Martina Burlando, Via A. Pastore 10, Genova, Italy, 161320105555761; Email: martina.burlando@unige.it Introduction: Approximately half of patients affected by psoriasis are women, and the management of female patients of childbearing age is an under-investigated topic. Some studies have shown a signif- icant decrease in births in psoriatic patients due to intimacy and pregnancy avoidance and to potential birth complications. Objectives: We sought to evaluate data on reproductive health in a cohort of female patients, to com- pare them with similar data in the general population and to assess the impact of psoriasis, especially genital psoriasis, on pregnancy desire and the prevalence of psoriasis in the children of patients with psoriasis. Methods: This retrospective observational study involved adult female patients with a diagnosis of psoriasis made during or before childbearing age. The enrolled patients were asked questions concern- ing fertility and previous pregnancies in relation to their dermatologic disease. Results: Of 100 women enrolled, 73 reported a history of pregnancy, for a total of 170 pregnancies. The average number of pregnancies to term and the average number of children per woman (1.2 ± 1) were lower than the national average. The percentage of miscarriages was 18.2%, higher than the national average; in particular, women with psoriatic arthritis had a greater percentage of miscar- riages (27.4%). During the pregnancies, psoriasis was mainly stable (36.1%) or improved (29.2%), even though most patients (91.5%) did not follow any treatment. Conclusions: Psoriasis impacts pregnancy desire and course. The management of psoriasis in women of childbearing age is crucial to minimize its burden on this vulnerable population. ABSTRACT 2 Original Article | Dermatol Pract Concept. 2024;14(4):e2024221 Introduction Psoriasis is a high-prevalence skin condition with a chronic course, multifactorial etiology, and immune-mediated patho- genesis [1]. Approximately half of the patients affected are women, who, even today, face limitations, especially thera- peutic ones, due to the changes that physiologically occur during different phases of their lives [2]. Moreover, the onset of signs and subsequent diagnosis in females is generally ear- lier than in males, leading to significant issues in the qual- ity of life, especially in younger patients [3]. Since women of childbearing age represent a significant percentage of psoriatic patients, the influence of psoriasis on fertility and pregnancy should be considered and adequately addressed. There is a lack of practical guidance available to help man- age the scenario when a patient with psoriasis plans to be- come pregnant or, since 50% of pregnancies are unplanned, is pregnant [4,5]. The impact on male and female fertility is unknown; how- ever, an American study shows a significant decrease in births in patients with psoriasis [6]. One possible reason that has been hypothesized is the avoidance of intimacy that stems from psoriasis, especially when genitals are involved, which can often cause pain, embarrassment, and discomfort [4]. Some studies suggest that there may be an increase in preterm and or low birth weight births and an increased number of spontaneous and induced abortions [7,8]. Other inflamma- tory and autoimmune diseases similar to psoriasis, such as rheumatoid arthritis and inflammatory bowel disease, have been associated with the same complications due to immune dysfunction, inflammatory cytokine storm, and effects on en- dothelial cells, with subsequent systemic and placental vascu- lopathy [6,9]. However, not all studies are concordant; some do not detect a significantly increased risk of infertility, con- genital disabilities, and other maternal complications [6,7]. Objectives Our aims were to evaluate data on reproductive health in a cohort of female patients followed at the Dermatology Clinic of IRCCS San Martino Polyclinic Hospital, to compare them with similar data in the general population, and to assess both the impact of psoriasis, especially genital psoriasis, on pregnancy desire and the prevalence of psoriasis in the chil- dren of patients with psoriasis. Methods Study Design This retrospective observational descriptive, single-center study was conducted at the IRCCS San Martino Polyclinic Hospital Dermatology Clinic from November 2021 to May 2022. Study Population Patients diagnosed with psoriasis followed on an outpatient basis at the Dermatology Clinic of the IRCCS San Martino Polyclinic Hospital were enrolled according to the following criteria: • Female sex • Age older than 18 years • Diagnosis of psoriasis made at or before childbearing age • Undergoing topical or systemic therapy, either traditional or biologic • Acquisition of informed consent. Data Collection One hundred patients were contacted to participate in an interview, conducted in person or by telephone, related to psoriasis and reproductive health. Sixty-one (61%) patients were interviewed in person during the outpatient follow-up, and 39 (39%) were contacted by telephone. After acquiring informed consent, the patients were asked 19 questions. The questions regarded the age of onset of psoriasis and current therapy, the presence of concomitant rheumatologic disease, the possible presence of genital psoriasis, pregnancy and the possible presence of children, course of pregnancy and health of children, and course of psoriasis during pregnancy. The questionnaire was structured in two parts: a first set of seven questions administered to all patients and a second set with the last 12 questions, administered only to women with a pregnancy history. The second part thoroughly investigated the course of the pregnancy by researching the type of de- livery, the presence of voluntary interruptions of pregnancy (IVG) and/or miscarriages, any history of complications of the pregnancy, and the treatment carried out during the said period. Information on live-born children was also gath- ered, with questions regarding the presence of noteworthy diseases, including, first and foremost, psoriasis. Statistical Analyses An initial analysis was performed using descriptive statisti- cal analysis through frequencies and appropriate measures of dispersion. Continuous variables were compared using the Mann-Whitney U test to reveal any differences between the three groups (presence/absence of arthritis or presence/ absence of genital psoriasis). P-values less than 0.05 were considered significant. Results Sample Description A total of 100 women were enrolled; 96 patients (96%) were of Caucasian ethnicity, three (3%) of Hispanic ethnicity, and Original Article | Dermatol Pract Concept. 2024;14(4):e2024221 3 one (1%) of Asian ethnicity. The mean age was 49.26±19 years (IQR: 19; 39-58), with a minimum value of 18 and a maximum of 82. The mean age at disease onset was 21.85 years (IQR: 16; 14-30), with a minimum value of one and a maximum value of 50. All patients enrolled (100%) at the time of the interview were on specific biologic drugs for the treatment of psoriasis. Eighteen patients (18%) were on therapy with secukinumab, 15 (15%) with ixekizumab, 13 (13%) with tildrakizumab, 13 (13%) with adalimumab, 12 (12%) with ustekinumab, 9 (9%) with guselkumab, nine (9%) with risankizumab, six (6%) with brodalumab, three (3%) with certolizumab, and two (2%) with etanercept (Table 1). Thirty-six patients (36%), in addition to skin involve- ment, had psoriatic arthropathy, diagnosed by a rheumatol- ogist. Forty-seven patients (47%) had a history of genital psoriasis. Seventy-three out of 100 patients (73%) had a history of previous pregnancy and were therefore selected for the study. In this subgroup, the mean age was 53.6 ± 12.23 years, with a mean age at disease onset of 23.26 ± 12.10 years. Survey Results Regarding the women with reported pregnancy, only four (5.5%) saw their psoriasis as a limitation in pregnancy seek- ing. In contrast, 69 patients (94.5%) did not experience this problem. Thirty-three patients (45.2%) reported that they had suffered or still suffered from genital psoriasis. The to- tal number of pregnancies for the whole sample was 170, with an average per woman of 1.7±1.40. One hundred and twenty-one (71.2%) were carried to term with an average rate of pregnancy to term of 1.2±1 (Figure 1). Among the 73 patients with a history of pregnancy, for a total number of 170 pregnancies, the number of those ter- minated through spontaneous abortions and voluntary in- terruptions of pregnancy (IVGs) was 49/170 (28.8%). The number of spontaneous abortions was 31/170 (18.2%) and the number of IVGs was 18/170 (10.6%). Among patients with psoriatic arthropathy, the rate of spontaneous abor- tions was 17/62 (27.4%). The number of patients who reported at least one miscarriage was 19/73 (26%) in the whole population and 9/25 (36%) the subgroup of patients with psoriatic arthritis. Joint involvement in psoriasis pres- ents a correlation with the prevalence of miscarriages, IRR 2.11 (1.12-3.99), P<0.05. Regarding the type of delivery, out of 121 pregnancies carried to term, 77 (63.6%) were vagi- nal deliveries, while cesarean delivery was performed in 44 pregnancies (36.4%). Only 11/170 (6.5%) pregnancies had complications, as shown in Table 2. The mean age during pregnancy (considering the mean age in women who had reported more than one pregnancy) was 28.9 ± 5.29 years, while the calculated mean age at first pregnancy was 27.0 ± 6.28 years. Regarding the course of psoriatic disease, psoriasis did not change during pregnancy in 26 patients (36.1%), im- provement was reported in 21 patients (29.2%), there was a worsening of the condition in 9 patients (12.5%), and Table 1. Current Treatments For Psoriasis. Adalimumab 13 (13%) Brodalumab 6 (6%) Certolizumab Pegol 3 (3%) Secukinumab 18 (18%) Etanercept 2 (2%) Guselkumab 9 (9%) Ixekizumab 15 (15%) Risankizumab 9 (9%) Tildrakizumab 13 (13%) Ustekinumab 12 (12%) Figure 1. Pregnancy outcomes. Table 2. Reported Complications During Pregnancy. Dystocia 1 (1%) Emergency C-section 1 (1%) Gestational diabetes 5 (5%) Pre-eclampsia 2 (2%) Cholestasis of pregnancy 1 (1%) Hyperemesis gravidarum 1 (1%) 4 Original Article | Dermatol Pract Concept. 2024;14(4):e2024221 overlooked [4]. Relative to maternal age, the survey found an average age of conception of 28.9 ± 5.29 years, which, compared to the average in the general population, does not present significant differences. Another significant finding from the study was that the percentage of miscarriages was 18.2% of the total number of pregnancies (95% CI: 13.2–24.7%). This data point, when compared with the general population, which over the years has had a miscarriage rate of about 10-14% [11], is higher. Moreover, of the 73 patients with a history of pregnancy, 26% also had a history of miscarriage, which is significantly higher than the available data in the general population (IRR: 1.86; 95% CI: 1.26–2.74; P = 0.005). This finding highlights that patients with psoriasis have more miscar- riages. The reasons that could explain this finding are the increase in inflammatory cytokines, and particularly TNF-α, which have been associated with an increased risk of mis- carriage [10]), the teratogenic effect of many drugs used to treat psoriasis [4)], and the increase in maternal age, which is associated with an increase in comorbidities including metabolic syndrome, anxiety or depression, alcohol abuse, and smoking, factors with a known detrimental effect on pregnancy [4]. The latter finding also agrees with recently published studies, thus favoring the condition’s link with in- creased miscarriages [12]. Furthermore, the rate of miscarriages in patients with psoriatic arthropathy was much higher than in patients with only cutaneous disease: 27.4% (95% CI: 17.9–39.6) vs 13% (95% CI: 17.9–20.6), respectively. The comparison between the two groups proved significant with IRR: 2.11 (1.12–3.99). This difference may be explained by the fact that patients with psoriatic arthritis present a disease with a more signifi- cant systemic impact, leading to increased comorbidities and aggravating the inflammatory condition [13]. In addition, patients with psoriatic arthritis often require special thera- pies, which negatively impact conception and the physiolog- ical course of pregnancy [14]. Relative to the number of cesarean deliveries, the number of pregnancies carried out by surgical delivery in the sample was 44 (36.36%), which is aligned with the available data in the general population. Recent studies show that this per- centage is slightly higher in patients with psoriasis [12]. This is most likely due to more significant complications during delivery such as preeclampsia and abnormalities at the pla- cental level caused by the inflammatory vasculopathy and the different maternal-fetal relationship [10,12,15]. The survey also provided data on the prevalence of com- plications in pregnancy. The rate of serious complications was 6.5%, which is lower than the reference rate in the gen- eral population, (25.4%) [11]. This finding also does not appear to agree with the literature, which defines psoriasis psoriasis was still not present at the time of pregnancy in 16 patients (22.2%), exacerbating later in the postpar- tum period. Regarding therapy during pregnancy, 65 patients (91.5%) did not use psoriasis-specific therapy, while only six (8.5%) continued/initiated treatment. Regarding the presence of children, most patients car- ried at least one pregnancy to term. Seventy (95.9%) patients had at least one child, while only three (4.1%) did not carry to term any pregnancy. The average number of children per woman was 1.7 ± 0.72, with a minimum value of one and a maximum value of four. The survey also considered a possible correlation be- tween genital psoriasis and the number of pregnancies. Of the 47 patients with genital psoriasis, 33 (70.2%) had at least one pregnancy, compared to 40/53 (75.5%) patients without genital involvement. There was no signif- icant correlation between genital psoriasis and occurrence of pregnancy. Lastly, the study investigated the presence of significant diseases in the children of mothers with psoriasis. Fifteen pa- tients (21.4%) reported health issues in at least one of their children, while 55 patients (78.6%) reported having healthy children. Of the 15 patients with at least one affected child, nine (12.9%) reported a child with psoriasis. Discussion The study of reproductive health in psoriatic women is a hugely developing area of research. More and more scien- tific evidence correlates the skin condition with alterations in reproductive life. In particular, systemic inflammation, the increase in comorbidities, and the psychological impact of psoriasis have been studied. Psoriasis is a disease charac- terized by lesions of visible skin; since many of the patients affected are young women, this leads to a significant impact on their quality of life. The first objective of this study was to evaluate the avail- able data on the reproductive health of women with psoria- sis and to compare them with similar data from the general population. Data analysis showed a total number of 170 pregnancies, 121 of which carried to term. The average in- dex of pregnancies to term in the entire sample was 1.2 ± 1, which is lower than the reported national average over the past 50 years. Similarly, the average number of children per woman was 1.2 ±1, also lower than the national average. These results could be primarily due to the systemic inflam- matory condition, leading to a deficit in placental immune modulation and consequently more issues in pregnancy [10]. Additionally, the psychological condition of patients, who are often unwilling to have children or have difficul- ties in conception due to discomfort and pain, should not be Original Article | Dermatol Pract Concept. 2024;14(4):e2024221 5 reproductive life, even though the impact of this condition on sex life is known and described in the literature. The third and final objective of the study was to assess the prevalence of psoriasis in the children of patients with psoriasis. Considering the 121 pregnancies carried to term and twin births (122 children), nine (7.37%) children had the same condition as the mother. This figure can be defined as underestimated because some of the children in the sam- ple are still young and thus have a good chance of developing psoriasis in the future. This finding confirms sources in the literature, which show that children of patients with psori- asis are more likely to develop the disease [19]. It has been seen that psoriasis has a vital genetic component and that children from two affected parents are 50% more likely to develop psoriasis. If, on the other hand, there is only one affected parent, the probability drops to 16% (still much higher than the general Italian population, among which the prevalence is about 3%) [19,20,21]. Conclusions Psoriasis is a chronic disease that can impact all phases of life, including conception and pregnancy. In our retrospective study, we found that women with psoriasis had fewer preg- nancies and a greater prevalence of miscarriages than the na- tional average. In particular, women with psoriatic arthritis had a significantly higher rate of miscarriages than women without joint involvement, which may be explained by the higher levels of systemic inflammation that accompany joint involvement in psoriasis. We also confirmed the current knowledge on the course of psoriasis during pregnancy and on the hereditary transmission of psoriasis in children con- ceived by affected mothers. Despite the availability of new effective and, in some cases, pregnancy-safe treatments, the management of psoriasis in women of childbearing age de- serves greater attention from specialists. References 1. Rendon A, Schäkel K. Psoriasis Pathogenesis and Treatment. Int J Mol Sci. 2019 Mar 23;20(6):1475. DOI: 10.3390/ijms20061475. PMID: 30909615; PMCID: PMC6471628. 2. Bucur Ș, Savu AP, Stănescu AMA, et al. Oversight and Management of Women with Psoriasis in Childbearing Age. Medicina (Kaunas). 2022 Jun 9;58(6):780. DOI: 10.3390 /medicina58060780. PMID: 35744043; PMCID: PMC9227010. 3. Cozzani E, Borrini V, Pennella A, et al. The quality of life in Italian psoriatic patients treated with biological drugs. G Ital Dermatol Venereol. 2010 Dec;145(6):709-12. PMID: 21139547. 4. Rademaker M, Agnew K, Andrews M, et al. Psoriasis in those planning a family, pregnant or breast-feeding. The Australasian Psoriasis Collaboration. Australas J Dermatol. 2018 May;59(2): 86–100. DOI: 10.1111/ajd.12641. Epub 2017 May 23. PMID: 28543445. as a possible causative/aggravating factor in pregnancy com- plications [15]. In the study, this result could be ascribable to the limited number of patients in the sample and to the fact that being a retrospective study, the accuracy of specific data may only be partially reliable. Regarding the course of psoriasis in pregnancy, the sur- vey found that psoriasis did not change during pregnancy in 26 patients (36.1%). In 21 patients (29.2%), improvement was reported; in nine patients (12.5%), there was a worsen- ing of the condition, and in 16 patients (22.2%), psoriasis was still not present at the time of pregnancy, exacerbating later in the postpartum period. These data agree with those in the literature, which reports that 55-56% of pregnant women with psoriasis reported improvement in pregnancy, 16-21% noticed no change, and only 23-24% worsened [16,17]. What may explain this slight difference, especially the higher percentage of patients in clinical stabilit is that the study is retrospective. The patients’ self-assessment of the lesions may therefore have been biased”, compared with an accurate specialist clinical evaluation. Regarding therapy during gestation, 65 patients (91.5%) did not use psoriasis-specific therapy, while only six (8.5%) continued/initiated treatment. This result might be due to the fear of the consequences that therapies might have during pregnancy. Moreover, because the disease frequently tends to improve during pregnancy, there often is no need to con- tinue with treatment. Nonetheless, a significant number of patients who experienced psoriasis worsening or stability during pregnancy still were not receiving treatment. How- ever, it must be noted that many of the reported pregnancies occurred in the pre-biologic era, when systemic treatments were not compatible with pregnancies. Currently, certoli- zumab pegol, a biologic drug suitable for psoriasis during pregnancy, is available and recommended for women who are planning to conceive. However, while anti-interleukins should be discontinued when planning pregnancy, new data suggest that exposure to most biologic drugs does not cause significant harm to the fetus [18]. This allows the dermatol- ogist to plan the most effective treatment in fertile female patients, with the possibility of switching to certolizumab in case of pregnancy diagnosis or desire. The second purpose of the study was to assess the im- pact of psoriasis, especially genital psoriasis, on the ideation of motherhood. Patients with an occurrence of pregnancy were selected, and a correlation between genital psoriasis and the number of pregnancies was studied. Of 73 patients, 33 reported pregnancy with genital psoriasis involvement, with a mean of 2.3±1.09. In contrast, there were 40 patients without genital psoriasis who reported at least one preg- nancy, with a mean of 2.4±1.14. The correlation does not show statistical significance (P 0.82), so it emerges from our study that genital involvement does not significantly impact 6 Original Article | Dermatol Pract Concept. 2024;14(4):e2024221 13. de Oliveira M de FSP, Rocha B de O, Duarte GV. Psoriasis: classical and emerging comorbidities. An Bras Dermatol. 2015 Jan-Feb;90(1):9-20. DOI: 10.1590/abd1806-4841.20153038. PMID: 25672294; PMCID: PMC4323693. 14. Kaushik SB, Lebwohl MG. Psoriasis: Which therapy for which patient. J Am Acad Dermatol. 2019 Jan;80(1):43–53. DOI: 10.1016/j.jaad.2018.06.056. Epub 2018 Jul 11. PMID: 30017706. 15. Xie W, Huang H, Ji L, Zhang Z. Maternal and neonatal out- comes in pregnant women with psoriasis and psoriatic arthri- tis: a systematic review and meta-analysis. Rheumatology. 2021 Sep;60(9):4018–28. DOI: 10.1093/rheumatology/keab357. PMID: 33878171. 16. Raychaudhuri SP, Navare T, Gross J, et al. Clinical course of pso- riasis during pregnancy. Int J Dermatol. 2003 Jul;42(7):518-20. DOI: 10.1046/j.1365-4362.2003.01760.x. 17. Murase JE, Chan KK, Garite TJ, et al. Hormonal effect on pso- riasis in pregnancy and post partum. Arch Dermatol. 2005 May;141(5):601–6. DOI: 10.1001/archderm.141.5.601. PMID: 15897382. 18. Owczarek W, Walecka I, Lesiak A, Czajkowski R, Reich A, Zerda I, Narbutt J. The use of biological drugs in psoriasis patients prior to pregnancy, during pregnancy and lactation: a review of current clinical guidelines. Postepy Dermatol Alergol. 2020 Dec;37(6):821-830. DOI: 10.5114/ada.2020.102089. Epub 2021 Jan 6. PMID: 33603597; PMCID: PMC7874874. 19. Gupta R, Debbaneh MG, Liao W. Genetic Epidemiology of Psori- asis. Curr Dermatol Rep. 2014 Mar;3(1):61–78. DOI: 10.1007/ s13671-013-0066-6. PMID: 25580373; PMCID: PMC4285384. 20. Prignano F, Rogai V, Cavallucci E, et al. Epidemiology of Pso- riasis and Psoriatic Arthritis in Italy-a Systematic Review. Curr Rheumatol Rep. 2018 May;20(7):43. DOI: 10.1007/s11926 -018-0753-1. PMID: 29846817. 21. Griffiths CE, Barker JN. Pathogenesis and clinical features of psoriasis. The Lancet. 2007 Jul;370(9583):263–71. DOI: 10.1016/S0140-6736(07)61128-3. PMID: 17658397. 5. Bardazzi F, Evangelista V, Ferrara F, et al. Does psoriasis influence female sexual dysfunction? A multicentric Italian case- control study. Ital J Dermatol Venerol. 2022 Oct;157(5):432-435. DOI: 10.23736/S2784-8671.21.07128-0. Epub 2021 Sep 21. PMID: 34545729. 6. Horn EJ, Chambers CD, Menter A, Kimball AB, International Psoriasis Council. Pregnancy outcomes in psoriasis: why do we know so little? J Am Acad Dermatol. 2009 Aug;61(2):e5-8. DOI: 10.1016/j.jaad.2009.05.004. PMID: 19615534. 7. Yang YW, Chen CS, Chen YH, et al. Psoriasis and pregnancy outcomes: a nationwide population-based study. J Am Acad Dermatol. 2011 Jan;64(1):71–7. DOI: 10.1016/j.jaad.2010.02 .005. PMID: 20970879. 8. Ryan C, Sadlier M, De Vol E, et al. Genital psoriasis is asso- ciated with significant impairment in quality of life and sexual functioning. J Am Acad Dermatol. 2015 Jun;72(6):978–83. DOI: 10.1016/j.jaad.2015.02.1127. Epub 2015 Mar 29. PMID: 25824273. 9. Cohen-Barak E, Nachum Z, Rozenman D, et al. Pregnancy outcomes in women with moderate-to-severe psoriasis. J Eur Acad Dermatol Venereol. 2011 Sep;25(9):1041–7. DOI: 10.1111 /j.1468-3083.2010.03917.x. Epub 2010 Nov 25. PMID: 21108670. 10. Romanowska-Próchnicka K, Felis-Giemza A, Olesińska M, et al. The Role of TNF-α and Anti-TNF-α Agents during Preconception, Pregnancy, and Breastfeeding. Int J Mol Sci. 2021 Mar;22(6):2922. DOI: 10.3390/ijms22062922. PMID: 33805757; PMCID: PMC7998738. 11. ISTAT (istituto nazionale di statistica). La salute riproduttiva della donna. [Last accessed: May 18 2023] Available from: https://www4.istat.it/it/archivio/209905 12. Bobotsis R, Gulliver WP, Monaghan K, et al. Psoriasis and ad- verse pregnancy outcomes: a systematic review of observational studies. Br J Dermatol. 2016 Sep;175(3):464–72. DOI: 10.1111/ bjd.14547. Epub 2016 Jul 24. PMID: 26991866.