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Dominika Modzelewska

Doctoral Student

Department of Obstetrics and
Visiting address
Journalvägen 6 kvinnoklin su/östra
41685 Göteborg
Postal address
Kvinnokliniken su östra
41685 Göteborg

About Dominika Modzelewska

Dominika Modzelewskas will defend her dissertation on 31 May.

Link to the dissertation

Here is a short summary of the results in the dissertation;

Methodological considerations in epidemiological studies in perinatal medicine

Epidemiological research on pregnancy outcomes is challenging due to the complexity of pregnancy. Pregnancy, like no other medical subject, includes two individuals, the fetus and mother. Perinatal outcomes are the results of the interplay of signals between them. The normal chain of reactions might be affected by multiple factors over the pregnancy. Furthermore, every next pregnancy might differ from the previous; primiparity alone is considered as a risk factor for preterm birth PTD

– The complexity of pregnancy gives rise to multiple questions on how to perform epidemiological research to obtain unbiased estimates. In her dissertation, she presents the results of the included studies in the perspective of two methodological puzzles observed in the field of obstetrics, called ‘birthweight paradox’ and ‘missing heritability’ in pregnancy duration. Both phenomena point at the importance of data summaries and interpretation. After having exact scientific question, methodology is crucial to obtain a desired answer, says Dominika Modzelewska, PhD researching in Biostatistics and Public Health.

Etiologic heterogeneity leading to spurious observations

The concept of ‘birthweight paradox’ is used to refer to studies which reported confusing relationships observed in the group of children born with birthweight smaller than expected (in medical terms, babies who are ‘small for gestational age’, SGA). It was repeatedly reported that SGA children had higher chance to survive if their mother was smoking. In other words, smoking during pregnancy seemed to be a life saver for children who were SGA. It was explained that counterintuitive association is not due to cause-effect relation but due to not accounting for diversity in the factors affecting baby’s birthweight.

– In the studies included in the thesis, they observed surprising associations of similar nature between maternal diet during pregnancy, baby’s size (whether, SGA or not), and baby’s health status in his first days of life as presented in ‘birthweight paradox’. Analogically, the observations could be explained by the diversity in the factors underlying baby’s birthweight.

Varying environmental conditions possibly contributing to the occurrence of ‘missing heritability’

In the field of genetics of pregnancy duration, we have dissonance between the findings of two different types of analyses based on the epidemiological and genetic data, phenomenon called ‘missing heritability’. Heritability analysis provides the evidence for genetic contribution to population variability and gives promises for successful genetic-variant identification. However, findings of genetic analyses do not provide a complete explanation for the etiologies of studied traits.

– In the second project, she presents the possible reason for the occurrence of missing heritability. Heritability is measured based on the association estimates between family members. In the studies, they show that those association estimates are affected by time-related changes like data handling or estimation methods. Given that heritability analysis assumes constant environmental contribution over time, the dependence of the association estimates might underly the problem of missing heritability.