Pregnancy and birth complications (PBCs) in general are detrimental to the health of the developing fetus - especially its neurodevelopment: thus many studies have examined whether PBCs increase the risk of schizophrenia. Overall, most but not all studies, using various sources of data and various scoring methods, have supported an association between PBCs and an increased risk of schizophrenia - possibly reflecting a common underlying hypoxia.
Some caveats
PBCs lack specificity and have a small effect size.
There is some but not conclusive evidence relating obstetric complications to brain structure in schizophrenia
Methodological problems (eg measurement issues such as relying on maternal recall and/or case records)
PBCs may be related to subtypes of schizophrenia. Eg there is mixed evidence of whether PBCs are more common or less common among cases without a family history.
Obstetric complications may not adequately reflect complex developmental processes so that the direction of causality may be unclear. For example, a neurodevelopmental abnormality and/or genetic predisposition may directly or indirectly the cause of the increase rates of PBCs. But there are arguments against this in schizophrenia. Other indicators of prenatal developmental delay or disruption are low or high birthweight and diminished head circumference
Low birthweight has been associated with schizophrenia; but it is unclear whether this relationship is accounted for by prematurity and/or retarded intrauterine growth. Also one study found that higher birthweight by body length increased the risk for schizophrenia.
Diminished head circumference, independent of gestational age, has also been found to increase the risk for schizophrenia.
These findings again suggest that a disruption of orderly brain growth in utero may predispose individuals to schizophrenia.