About me

I am interested in the causes and consequences of reproductive challenges, i.e. threats to the conception and development of healthy offspring. My research covers aspects across the spectrum from pre-conception through pregnancy and up to delivery. The vast majority of my work is collaborative, whether involving individual experts or working in teams and larger networks.

Research description

Reproduction is the beginning of life, and the time we spend in utero inarguably the most important developmental period of our lives. Disruptions or insults during this critical time could, through direct or down-stream effects, impair offspring health both in the short and long-term. My research spans across the whole the range of sensitive periods, from pre-conception through pregnancy up to labour and delivery, and concerns the health of both mother and offspring.

Early life origins of later health and disease

To make meaningful inference from observational data, and ultimately identify modifiable risk factors, it is vital to understand and address threats to study validity. In my thesis work I used twins to exclude the potentially confounding influence of shared genetic and environmental factors on well-established associations between birth weight and adult health outcomes (cardiovascular disease and breast cancer). Extending this work I also explored whether twins’ health differs from singletons’ (which could be expected on account of a strained intrauterine experience, sharing space and supply line), by contrasting twins and singletons of twin families, and singletons of twin and non-twin families respectively. Continued investigations of early life factors and later health are currently mainly focused on offspring neurodevelopment, through collaboration with Indiana University.

Familial clustering of pregnancy complications

The unique information in Swedish population registers can be used to explore clustering of various pregnancy complications, to provide clues about underlying mechanisms and familial susceptibility. For postpartum hemorrhage, our finding of similar patterns of recurrence regardless of triggering mechanism (e.g. uterine atony, retained placenta, lacerations) suggests a common underlying liability to bleed. By considering different family clusters we have quantified the role of shared environment, maternal and fetal genetic factors for this liability, as well as for post-term birth. Familial clustering studies are currently focused on the liability for birth defects, while further studies are planned to advance our understanding of the causes and consequences of postpartum hemorrhage.

Infertility, fertility treatments in the Swedish population

Involuntary childlessness is prevalent and increasing in many countries, and the subsequent use of ART thus expected to continue to rise (with 5% of Nordic births currently due to ART). The effect this may have for offspring health is still not fully known, in part due to limited large-scale follow-up through childhood, adolescence, and early adulthood, but also lingering methodological challenges. Rigorous evaluation is required to establish whether potential adverse effects are due to the treatments (ART) or rather related to their indication (infertility). Further disentangling the extent risks are due to potentially unavoidable events, such as multiple and preterm birth, can also improve etiological insight and assist clinical decision-making both pre- and post-conception. After first evaluating the role of multiple births in fertility treatment influence on pregnancy complications, my main research effort now focuses on expanding this work to evaluate long-term outcomes, and ideally consider both common (asthma, ADHD) and more rare conditions (diabetes and depression).

Current supervision of students 

  • Chen Wang
  • Ayesha Sujan (co-advisor, PhD-student, Indiana University)
  • Kelsey Wiggs (co-advisor, PhD-student, Indiana University)
  • Eva Skärby (Medical student, Karolinska Institutet)
  • Mausumi Das (MPH-student, Harvard Chan)

Previous supervision of students

  • Rossana Calderon (MPH-student, Harvard Chan)
  • John Lowery ( MPH-student, Harvard Chan)
  • Davide Attebrant-Sbrzesny (Medical student, Karolinska Institutet)


I have received funding from the National Institutes of Health, FORTE, the Swedish Research Council (VR), Fulbright, Lennander’s stiftelse, Wallenius’ stiftelse, Karolinska Institutet and Iris.


Pregnancy complications following fertility treatment-disentangling the role of multiple gestation. Oberg AS, VanderWeele TJ, Almqvist C, Hernandez-Diaz S Int J Epidemiol 2018 08;47(4):1333-1342

Outcome-dependent associations between short interpregnancy interval and offspring psychological and educational problems: a population-based quasi-experimental study. Class QA, Rickert ME, Larsson H, Öberg AS, Sujan AC, Almqvist C, et al Int J Epidemiol 2018 08;47(4):1159-1168

Within-Family Analysis of Interpregnancy Interval and Adverse Birth Outcomes. Class QA, Rickert ME, Oberg AS, Sujan AC, Almqvist C, Larsson H, et al Obstet Gynecol 2017 12;130(6):1304-1311

A Family-Based Study of the Association Between Labor Induction and Offspring Attention-Deficit Hyperactivity Disorder and Low Academic Achievement. Wiggs KK, Rickert ME, Hernandez-Diaz S, Bateman BT, Almqvist C, Larsson H, et al Behav. Genet. 2017 07;47(4):383-393

Associations of Maternal Antidepressant Use During the First Trimester of Pregnancy With Preterm Birth, Small for Gestational Age, Autism Spectrum Disorder, and Attention-Deficit/Hyperactivity Disorder in Offspring. Sujan AC, Rickert ME, Öberg AS, Quinn PD, Hernández-Díaz S, Almqvist C, et al JAMA 2017 04;317(15):1553-1562

Association of Labor Induction With Offspring Risk of Autism Spectrum Disorders. Oberg AS, D'Onofrio BM, Rickert ME, Hernandez-Diaz S, Ecker JL, Almqvist C, et al JAMA Pediatr 2016 09;170(9):e160965

Carryover Effects in Sibling Comparison Designs. Sjölander A, Frisell T, Kuja-Halkola R, Öberg S, Zetterqvist J Epidemiology 2016 11;27(6):852-8

Translational Epidemiologic Approaches to Understanding the Consequences of Early-Life Exposures. D'Onofrio BM, Class QA, Rickert ME, Sujan AC, Larsson H, Kuja-Halkola R, et al Behav. Genet. 2016 05;46(3):315-28

A Genetically Informed Study of the Associations Between Maternal Age at Childbearing and Adverse Perinatal Outcomes. Sujan AC, Rickert ME, Class QA, Coyne CA, Lichtenstein P, Almqvist C, et al Behav. Genet. 2016 05;46(3):431-56

Cancer risks in twins and singletons from twin and non-twin families. Chen L, Cnattingius S, Nyman Iliadou A, Oberg AS Int. J. Cancer 2016 Mar;138(5):1102-10

Chronic hypertension in pregnancy and the risk of congenital malformations: a cohort study. Bateman BT, Huybrechts KF, Fischer MA, Seely EW, Ecker JL, Oberg AS, et al Am. J. Obstet. Gynecol. 2015 Mar;212(3):337.e1-14

Genetic contribution to postpartum haemorrhage in Swedish population: cohort study of 466,686 births. Oberg AS, Hernandéz-Diaź S, Frisell T, Greene MF, Almqvist C, Bateman BT BMJ 2014 Aug;349():g4984

The association between caesarean section and asthma or allergic disease continues to challenge. Almqvist C, Oberg AS Acta Paediatr. 2014 Apr;103(4):349-51

Are epidemiological approaches suitable to study risk/preventive factors for human birth defects? Hernandez-Diaz S, Oberg AS Curr Epidemiol Rep 2015 Mar;2(1):31-36

Patterns of recurrence of postpartum hemorrhage in a large population-based cohort. Oberg AS, Hernandez-Diaz S, Palmsten K, Almqvist C, Bateman BT Am. J. Obstet. Gynecol. 2014 Mar;210(3):229.e1-8

Breast cancer risk in opposite-sexed twins: influence of birth weight and co-twin birth weight. Hajiebrahimi M, Bahmanyar S, Öberg S, Iliadou AN, Cnattingius S J. Natl. Cancer Inst. 2013 Dec;105(23):1833-6

Maternal and fetal genetic contributions to postterm birth: familial clustering in a population-based sample of 475,429 Swedish births. Oberg AS, Frisell T, Svensson AC, Iliadou AN Am. J. Epidemiol. 2013 Mar;177(6):531-7

Birthweight discordant female twins and their offspring: is the intergenerational influence on birthweight due to genes or environment? Högberg L, Lundholm C, Cnattingius S, Oberg S, Iliadou AN Hum. Reprod. 2013 Feb;28(2):480-7

Low digit ratio predicts early age at menarche in Colombian schoolgirls. Oberg AS, Villamor E Paediatr Perinat Epidemiol 2012 Sep;26(5):448-55

Sibling comparison designs: bias from non-shared confounders and measurement error. Frisell T, Öberg S, Kuja-Halkola R, Sjölander A Epidemiology 2012 Sep;23(5):713-20

Sjölander A, Frisell T, Oberg S. Causal interpretation of between-within models for twin studies. Epidemiologic Methods 2012 Aug;1(1): 217–237.

Twinship influence on morbidity and mortality across the lifespan. Öberg S, Cnattingius S, Sandin S, Lichtenstein P, Morley R, Iliadou AN Int J Epidemiol 2012 Aug;41(4):1002-9

Familial aggregation of schizophrenia: the moderating effect of age at onset, parental immigration, paternal age and season of birth. Svensson AC, Lichtenstein P, Sandin S, Öberg S, Sullivan PF, Hultman CM Scand J Public Health 2012 Feb;40(1):43-50

Birth weight predicts risk of cardiovascular disease within dizygotic but not monozygotic twin pairs: a large population-based co-twin-control study. Oberg S, Cnattingius S, Sandin S, Lichtenstein P, Iliadou AN Circulation 2011 Jun;123(24):2792-8

Birth weight-breast cancer revisited: is the association confounded by familial factors? Oberg S, Cnattingius S, Sandin S, Lichtenstein P, Iliadou A Cancer Epidemiol. Biomarkers Prev. 2009 Sep;18(9):2447-52

Ethnic differences in the association of birth weight and blood pressure: the Georgia cardiovascular twin study. Oberg S, Ge D, Cnattingius S, Svensson A, Treiber FA, Snieder H, et al Am. J. Hypertens. 2007 Dec;20(12):1235-41

Letters / Responses to letters

Oberg AS, Bateman BT. Genetics and Postpartum Hemorrhage: Author’s response to Sholapurkar. BMJ 2014; 349:g6210


Oberg AS. Health Consequences of Adverse Fetal Growth – Studies in Twins. Doctoral Thesis Karolinska Institutet, 2011. IBAN: 978-91-7457-371-8.


MD (2002) Karolinska Institutet

PhD (2011) Karolinska Institutet

MPH (2009) Harvard T.H. Chan School of Public Health


Academic positions

Postdoc research fellow (2011-2016), Harvard T.H. Chan School of Public Health 

Curriculum fellow (2015-2016), Harvard T.H. Chan School of Public Health 

Assistant professor (2016-) Karolinska Institutet

Adjunct assistant professor (2016-), Harvard T.H. Chan School of Public Health

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