I am an epidemiologist with a multidisciplinary background. I have been focusing on examining women and their children?s health determinants, which are embedded over the lifecourse and across generations. I am especially motivated to build scientific evidence that can inform clinical and social policies that reduce health inequalities.

Professional Education

  • Master of Science, Stockholm University (2012)
  • Doctor of Philosophy, Karolinska Institutet (2017)
  • Bachelor of Medicine, Fudan University (2008)
  • MB, Fudan University, Medicine (2008)
  • MSc, Stockholm University, Population Health (2012)
  • PhD, Karolinska Institutet, Medicine (2017)

Stanford Advisors


All Publications

  • Antidepressant Use around Conception, Prepregnancy Depression, and Risk of Ectopic Pregnancy. Canadian journal of psychiatry. Revue canadienne de psychiatrie Wall-Wieler, E., Robakis, T. K., Cesta, C. E., Masarwa, R., Lyell, D. J., Liu, C., Platt, R. W., Carmichael, S. L. 2020: 706743720927829


    OBJECTIVE: To compare the risk of ectopic pregnancy among women with and women without antidepressant prescriptions around conception and examine whether this risk differs by prepregnancy depression status.METHODS: We conducted a cohort study of all pregnancies between November 1, 2008, and September 30, 2015, identified in the nationwide (American) IBM MarketScan Databases. At least one day's supply of antidepressants in the 3 weeks after a woman's last menstrual period defined active antidepressant use around conception. At least one depression diagnosis in the year before the last menstrual period defined prepregnancy depression. Relative risk (RR) of ectopic pregnancy was estimated using unadjusted and inverse probability of treatment (IPT)-weighted log-binomial models.RESULTS: Of the 1,703,245 pregnancies, 106,788 (6.3%) women had a prepregnancy depression diagnosis. Among women with a depression diagnosis, 40,287 (37.7%) had an active antidepressant prescription around conception; the IPT-weighted risk of ectopic pregnancy was similar among women who did and did not fill an antidepressant prescription around conception (IPT-weighted RR = 1.01; 95% CI, 0.93 to 1.10). Overall, the risk of ectopic pregnancy was higher among women who had a prepregnancy depression diagnosis than women who did not have a prepregnancy depression diagnosis (IPT-weighted RR = 1.09; 95% CI, 1.04 to 1.15).CONCLUSIONS: This study's findings suggest that women who have a prepregnancy depression diagnosis are at a slightly increased risk of ectopic pregnancy, and among women who have a prepregnancy depression diagnosis, the use of antidepressants around conception does not increase the risk of ectopic pregnancy.

    View details for DOI 10.1177/0706743720927829

    View details for PubMedID 32436752

  • Preterm birth, unplanned hospital contact, and mortality in infants born to teenage mothers in five countries: An administrative data cohort study PAEDIATRIC AND PERINATAL EPIDEMIOLOGY Harron, K., Verfuerden, M., Ibiebele, I., Liu, C., Kopp, A., Guttmann, A., Ford, J., van der Meulen, J., Hjern, A., Gilbert, R. 2020


    Young maternal age is associated with lower birthweight and higher rates of preterm birth and childhood hospitalisations. Internationally, teen pregnancy rates vary widely, reflecting differences in social, welfare, and health care factors in different cultural contexts.To determine whether the increased risk of adverse infant outcomes among teenage mothers varies by country, reflecting different national teenage birth rates and country-specific social/welfare policies, in Scotland (higher teenage pregnancy rates), England, New South Wales (NSW; Australia), Ontario (Canada), and Sweden (lower rates).We used administrative hospital data capturing 3 002 749 singleton births surviving to postnatal discharge between 2010 and 2014 (2008-2012 for Sweden). We compared preterm birth (24-36 weeks' gestation), mortality within 12 months of postnatal discharge, unplanned hospital admissions, and emergency department visits within 12 months of postnatal discharge, for infants born to mothers aged 15-19, 20-24, 25-29, and 30-34 years.Compared to births to women aged 30-34 years, risks of adverse outcomes among teenage mothers were higher in all countries, but the magnitude of effects was not related to country-specific rates of teenage births. Teenage mothers had between 1.2% (95% confidence interval [CI] 0.7, 1.7, Sweden) and 2.0% (95% CI 1.4, 2.5, NSW) more preterm births, and between 9.8 (95% CI 7.2, 12.4, England) and 19.7 (95% CI 8.7, 30.6, Scotland) more deaths per 10 000 infants, compared with mothers aged 30-34. Between 6.4% (95% CI 5.5, 7.4, NSW) and 25.4% (95% CI 24.7, 26.1, Ontario), more infants born to teenage mothers had unplanned hospital contacts compared with those born to mothers aged 30-34.Regardless of country, infants born to teenage mothers had universally worse outcomes than those born to older mothers. This excess risk did not vary by national rates of livebirths to teenage mothers. Current mechanisms to support teenage mothers have not eliminated maternal age-related disparities in infant outcomes; further strategies to mitigate excess risk in all countries are needed.

    View details for DOI 10.1111/ppe.12685

    View details for Web of Science ID 000528902300001

    View details for PubMedID 32343005

  • Paternal violent criminality and preterm birth: a Swedish national cohort study. BMC pregnancy and childbirth Liu, C., Långström, N., Ekéus, C., Frisell, T., Cnattingius, S., Hjern, A. 2020; 20 (1): 307


    Fathers may affect expectant mothers' daily living situations, which in turn might influence pregnancy outcomes. We investigated the association between paternal violent criminality and risk of preterm birth (?36?weeks).We conducted a register-based study with all live singleton births in the Swedish Medical Birth Register from 1992 to 2012, linked with records of paternal violent crime convictions from the National Crime Register from 1973 to 2012.Paternal violent criminality was associated with increased risk of preterm birth and lower gestational age. The association was especially pronounced among infants of reoffenders: men convicted of three or more violent crimes (adjusted odds ratio [aOR] 1.23 [95% CI 1.17, 1.29]). Maternal half sibling-comparisons, an analytic approach controlling for maternal factors stable across pregnancies, also suggested increased risk of preterm birth and lower gestational age when exposed to a violently reoffending father compared to a father without violent criminal convictions (aOR 1.30 [0.99, 1.72], adjusted mean difference?-?1.07 [-?1.78, -?0.36]).Persistent paternal violent criminality was associated with increased risk of preterm birth, even after controlling for maternal characteristics that did not change between pregnancies.

    View details for DOI 10.1186/s12884-020-02964-2

    View details for PubMedID 32429861

  • Perinatal health of refugee and asylum-seeking women in Sweden 2014-17: a register-based cohort study EUROPEAN JOURNAL OF PUBLIC HEALTH Liu, C., Ahlberg, M., Hjern, A., Stephansson, O. 2019; 29 (6): 1048?55


    An increasing number of migrants have fled armed conflict, persecution and deteriorating living conditions, many of whom have also endured risky migration journeys to reach Europe. Despite this, little is known about the perinatal health of migrant women who are particularly vulnerable, such as refugees, asylum-seekers, and undocumented migrants, and their access to perinatal care in the host country.Using the Swedish Pregnancy Register, we analyzed indicators of perinatal health and health care usage in 31 897 migrant women from the top five refugee countries of origin between 2014 and 2017. We also compared them to native-born Swedish women.Compared to Swedish-born women, migrant women from Syria, Iraq, Somali, Eritrea and Afghanistan had higher risks of poor self-rated health, gestational diabetes, stillbirth and infants with low birthweight. Within the migrant population, asylum-seekers and undocumented migrants had a higher risk of poor maternal self-rated health than refugee women with residency, with an adjusted risk ratio (RR) of 1.84 and 95% confidence interval (95% CI) of 1.72-1.97. They also had a higher risk of preterm birth (RR 1.47, 95% CI 1.21-1.79), inadequate antenatal care (RR 2.56, 95% CI 2.27-2.89) and missed postpartum care visits (RR 1.15, 95% CI 1.10-1.22).Refugee, asylum-seeking and undocumented migrant women were vulnerable during pregnancy and childbirth. Living without residence permits negatively affected self-rated health, pregnancy and birth outcomes in asylum-seekers and undocumented migrants. Pregnant migrant women's special needs should be addressed by those involved in the asylum reception process and by health care providers.

    View details for DOI 10.1093/eurpub/ckz120

    View details for Web of Science ID 000506803600010

    View details for PubMedID 31274154

    View details for PubMedCentralID PMC6896976

  • Severe maternal morbidity and postpartum mental health-related outcomes in Sweden: a population-based matched-cohort study ARCHIVES OF WOMENS MENTAL HEALTH Wall-Wieler, E., Carmichael, S. L., Urquia, M. L., Liu, C., Hjern, A. 2019; 22 (4): 519?26
  • The Effect of Rotavirus Vaccine on Socioeconomic Differentials of Paediatric Care Due to Gastroenteritis in Swedish Infants INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH Ask, L., Liu, C., Gauffin, K., Hjern, A. 2019; 16 (7)


    Background: Previous Swedish studies have shown a social gradient on paediatric care for viral gastroenteritis. Aim: To study the effect of a free rotavirus vaccine programme on hospital care for viral gastroenteritis. Method: A register-based national cohort study of paediatric in- and outpatient care for viral gastroenteritis in children <2 years old in two Swedish counties in 2014?2017, with the rest of the country as comparison. Adjusted hazard ratios were estimated by the differences-in-differences (DiD) estimator in Cox regression in the entire cohort and by social indicators. Results: Reductions of 37% and 24% for inpatient care, and 11 % and 21% for outpatient care for viral gastroenteritis were found in the Stockholm and Jönköping counties, respectively, after adjusting for time trends and social indicators. For inpatient care, the change was similar over social groups in both counties. In the larger county of Stockholm, smaller reductions in outpatient care were detected for children in socially disadvantaged families. Conclusions: A free rotavirus vaccination programme moderately reduced paediatric care for viral gastroenteritis. There were indications of an increase in socioeconomic differences in paediatric outpatient care for viral gastroenteritis, but further studies are needed to confirm this result in a broader health care perspective.

    View details for DOI 10.3390/ijerph16071095

    View details for Web of Science ID 000465595800008

    View details for PubMedID 30934717

    View details for PubMedCentralID PMC6479834

  • Severe maternal morbidity and postpartum mental health-related outcomes in Sweden: a population-based matched-cohort study. Archives of women's mental health Wall-Wieler, E., Carmichael, S. L., Urquia, M. L., Liu, C., Hjern, A. 2018


    We examined whether women experiencing severe maternal morbidity (SMM) are more likely to be treated for a psychiatric illness or be prescribed psychotropic medications in the postpartum year than mothers who did not experience SMM. We also examine the relationship between SMM and specific mental health-related outcomes, and the relationship between specific SMM diagnoses/procedures and postpartum mental-health-related outcomes. The national registers in Sweden were used to create a population-based matched cohort. Every delivery with SMM between July 1, 2006, and December 31, 2012 (n=8558), was matched with two deliveries without SMM (n=17,116). Conditional logistic regression models assessed the relationship between SMM and postpartum mental health-related outcomes. Women who experienced SMM had significantly greater odds of being treated for a psychiatric disorder (aOR 1.22; 95% CI 1.03-1.45) and being prescribed psychotropic medications (aOR 1.40; 95% CI 1.24-1.58) in the postpartum year. Specifically, they had significantly greater odds of being treated for neuroses (aOR 1.35; 95% CI 1.09-1.69) and having a prescription for anxiolytics/hypnotics (aOR 1.36; 95% CI 1.18-1.58) or antidepressants (aOR 1.35; 95% CI 1.17-1.55). Women who were diagnosed with shock or uterine rupture/obstetric laparotomy during delivery had the greatest odds of postpartum mental health-related outcomes. This study identified mothers with SMM as a group at high risk for postpartum mental illness. Postpartum mental health services should be provided to ensure the well-being of these high-risk mothers.

    View details for PubMedID 30334101

  • Out-of-Home Care and Subsequent Preterm Delivery: An Intergenerational Cohort Study PEDIATRICS Liu, C., Vinnerljung, B., Ostberg, V., Gauffin, K., Juarez, S., Cnattingius, S., Hjern, A. 2018; 142 (2)


    Adverse early-life experience may affect preterm delivery later in life through priming of stress response. We aim to investigate the links between out-of-home care (OHC) experience in childhood, as a proxy of severe adversities, on subsequent risk of preterm delivery.A register-based national cohort of all women born in Sweden between 1973 and 1977 (N = 175?821) was crosslinked with information on these women's subsequent deliveries as recorded in the Swedish medical birth register. During 1986-2012, 343?828 livebirths of these women were identified. The associations between women's OHC experience and her risk of preterm delivery were analyzed through logistic regression models, adjusting for women's own preterm birth, intrauterine growth, and childhood socioeconomic situation.Compared with women that never entered OHC, women with OHC experience up to and after age 10 were both associated with increased risks of preterm delivery (adjusted odds ratio [aOR] = 1.23 [95% confidence interval 1.08-1.40] and aOR = 1.29 [1.13-1.48], respectively). Women who experienced OHC before or at 10 years of age had increased risk of both spontaneous and medically indicated preterm delivery (aOR = 1.19 [1.03-1.38] and aOR = 1.27 [1.02-1.59], respectively). Women who experienced OHC after age 10 had a more pronounced risk of medically indicated preterm delivery (aOR = 1.76 [1.44-2.16]) than for spontaneous preterm delivery (aOR = 1.08 [0.92-1.27]).Women who were placed in OHC in childhood had increased risk of preterm delivery independent from their own perinatal history. Stress response, as 1 consequence of early life adversities, may take its toll on women's reproductive health and their offspring, calling for integrative efforts in preventing early life adversity.

    View details for DOI 10.1542/peds.2017-2729

    View details for Web of Science ID 000440459900005

    View details for PubMedID 30021856

  • Intergenerational transmission of out-of-home care in Sweden: A population-based cohort study. Child abuse & neglect Wall-Wieler, E., Almquist, Y., Liu, C., Vinnerljung, B., Hjern, A. 2018; 83: 42?51


    The objective of this study is to examine the intergenerational transmission of out-of-home care. This population-based study used data from the Swedish National Registers and included all children born in Sweden between 1990 and 2012 (followed for up to 13 years), whose parents were both born in Sweden between 1973 and 1980 (278 327 children; 145 935 mothers; 146 896 fathers). Cox regression models are used to obtain crude and adjusted hazard ratios (HR) of OHC placement among children based on parents' history of OHC. Compared with children whose parents both did not have a history of OHC, the risk of being placed in OHC was greater when both parents spent time in OHC (crude HR?=?48.70, 95% CI 41.46-57.21; adjusted HR?=?3.04, 95% CI?=?2.54-3.64), however, children who had only one parent who spent time in care were also at higher risk (mothers only adjusted HR?=?2.37, 95% CI?=?2.08-2.70; fathers only adjusted HR?=?1.33, 95% CI?=?1.13-1.55). The crude rate of placement in OHC was highest for children whose parents were placed in care during adolescence, but after adjusting for social and behavioral covariates, children whose parents were in care in early childhood were at greater risk of OHC than children whose parents were in care in adolescence. To reduce this intergenerational transmission of OHC, more supports should be provided to parents who spent time in OHC to ensure a successful transition to parenthood.

    View details for DOI 10.1016/j.chiabu.2018.07.007

    View details for PubMedID 30016744

  • Intergenerational involvement in out-of-home care and death by suicide in Sweden: A population-based cohort study. Journal of affective disorders Wall-Wieler, E., Bolton, J., Liu, C., Wilcox, H., Roos, L. L., Hjern, A. 2018; 238: 506?12


    Individuals involved in out-of-home care are at higher risk of death by suicide. We aimed to determine whether parents with two generations of involvement in out-of-home care (themselves as children, and their own children) are at increased risk of death by suicide than parents with no involvement or parents with one generation of involvement in out-of-home care.This population-based cohort study included all individuals born in Sweden between 1973 and 1980 who had at least one child between 1990 and 2012 (n?=?487,948). Women (n?=?259,275) and men (n?=?228,673) were examined separately.When compared with mothers with no involvement in out-of-home care, mothers with two generations of involvement were at more than five times greater risk of death by suicide (aHR?=?5.52; 95% CI 2.91-10.46); mothers with one generation of involvement were also at significantly higher risk of death by suicide (mothers were in care as children: aHR?=?2.35; 95% CI 1.27-4.35; child was placed in care: aHR?=?3.23; 95% CI 1.79-5.83). Involvement in out-of-home care (in either generation) did not affect risk of death by suicide for fathers.Reason for placement in out-of-home care is not known; these reasons could also be associated with risk of death by suicide Conclusion: Mothers with involvement in out-of-home care, either as children or when their child was placed in care, are at significantly higher risk of death by suicide. Mental health services should be provided to individuals involved in out-of-home care.

    View details for DOI 10.1016/j.jad.2018.06.022

    View details for PubMedID 29936388

  • Avoidable mortality among parents whose children were placed in care in Sweden: a population-based study. Journal of epidemiology and community health Wall-Wieler, E., Vinnerljung, B., Liu, C., Roos, L. L., Hjern, A. 2018


    Separation from one's child can have significant consequences for parental health and well-being. We aimed to investigate whether parents whose children were placed in care had higher rates of avoidable mortality.Data were obtained from the Swedish national registers. Mortality rates among parents whose children were placed in care between 1990 and 2012 (17 503 mothers, 18 298 fathers) were compared with a 1:5 matched cohort of parents whose children were not placed. We computed rate differences and HRs of all-cause and avoidable mortality.Among mothers, deaths due to preventable causes were 3.09 times greater (95%?CI 2.24 to 4.26) and deaths due to amenable causes were 3.04 times greater (95%?CI 2.03 to 4.57) for those whose children were placed in care. Among fathers, death due to preventable causes were 1.64 times greater (95%?CI 1.32 to 2.02) and deaths due to amenable causes were 1.84 times greater (95%?CI 1.33 to 2.55) for those whose children were placed in care. Avoidable mortality rates were higher among mothers whose children were young when placed in care and among parents whose children were all placed in care.Parents who had a child placed in out-of-home care are at higher risk of avoidable mortality. Interventions targeting mothers who had a child aged less than 13 placed in care, and parents whose children were all placed in care could have the greatest impact in reducing avoidable mortality in this population.

    View details for DOI 10.1136/jech-2018-210672

    View details for PubMedID 30077964

  • Prenatal parental depression and preterm birth: a national cohort study BJOG-AN INTERNATIONAL JOURNAL OF OBSTETRICS AND GYNAECOLOGY Liu, C., Cnattingius, S., Bergstrom, M., Ostberg, V., Hjern, A. 2016; 123 (12): 1973?82


    To investigate the effects of maternal and paternal depression on the risk for preterm birth.National cohort study.Medical Birth Register of Sweden, 2007-2012.A total of 366 499 singleton births with linked information for parents' filled drug prescriptions and hospital care.Prenatal depression was defined as having filled a prescription for an antidepressant drug or having been in outpatient or inpatient hospital care with a diagnosis of depression from 12 months before conception until 24 weeks after conception. An indication of depression after 12 months with no depression was defined as 'new depression', whereas all other cases were defined as 'recurrent depression'.Odds ratios (ORs) for very preterm (22-31 weeks of gestation) and moderately preterm (32-36 weeks of gestation) births were estimated using multinomial logistic regression models.After adjustment for maternal depression and sociodemographic covariates, new paternal prenatal depression was associated with very preterm birth [adjusted OR (aOR) 1.38, 95% confidence interval (95% CI) 1.04-1.83], whereas recurrent paternal depression was not associated with an increased risk of preterm birth. Both new and recurrent maternal prenatal depression were associated with an increased risk of moderately preterm birth (aOR 1.34, 95% CI 1.22-1.46, and aOR 1.42, 95% CI 1.32-1.53, respectively).New paternal and maternal prenatal depression are potential risk factors for preterm birth. Mental health problems in both parents should be addressed for the prevention of preterm birth.Depression in both mothers and fathers is associated with an increased risk of preterm birth.

    View details for DOI 10.1111/1471-0528.13891

    View details for Web of Science ID 000388314800015

    View details for PubMedID 26786413

    View details for PubMedCentralID PMC5096244

  • Birth Outcomes of Foreign-Born, Native-Born, and Mixed Couples in Sweden PAEDIATRIC AND PERINATAL EPIDEMIOLOGY Urquia, M. L., Qiao, Y., Ray, J. G., Liu, C., Hjern, A. 2015; 29 (2): 123?30


    Many births in industrialised countries are to immigrant parents, or to one immigrant and one domestically born parent. Their newborn outcomes have not been well studied.We conducted a study of 1,690,423 singleton infants born in Sweden between 1987 and 2008, including those of immigrants from East Asia, South Asia, Sub-Saharan Africa, and East Africa. Preterm delivery and small for gestational age (SGA) were assessed among infants of (i) immigrant parents from the same world region, (ii) an immigrant mother and a Swedish-born father, and (iii) a Swedish-born mother and an immigrant father; each compared to (iv) two Swedish-born parents. Log binomial regression analysis generated adjusted risk ratios (ARRs) and 95% confidence intervals (CIs) for preterm delivery and SGA.Compared with infants of two Swedish-born parents, infants born to immigrant mothers from East Asia, South Asia, and Sub-Saharan African were at higher risk of preterm delivery (ARR ranging from 1.2 to 1.9), irrespective of whether the father was from the same world region or Swedish-born, with the only exception of East African women, who had lower risk. Infants born to two foreign-born parents had the highest risks of SGA, particularly South Asians (ARR 4.69; 95% CI 4.29, 5.12). Mixed couples exhibited intermediate risks of SGA.Adverse birth outcomes differ according to a couple's ethnic composition. Having a Swedish-born partner is associated with lower risk of SGA among immigrant mothers and fathers, and with lower risk of preterm delivery among immigrant fathers but not mothers.

    View details for DOI 10.1111/ppe.12179

    View details for Web of Science ID 000350273800004

    View details for PubMedID 25683170

  • Migration and preterm birth in war refugees: a Swedish cohort study EUROPEAN JOURNAL OF EPIDEMIOLOGY Liu, C., Urquia, M., Cnattingius, S., Hjern, A. 2014; 29 (2): 141?43

    View details for DOI 10.1007/s10654-013-9877-9

    View details for Web of Science ID 000335230800007

    View details for PubMedID 24420703

    View details for PubMedCentralID PMC3955479

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