It is not known whether schizophrenic women have increased incidence of complications during pregnancy and delivery. Data from the Danish Medical Birth Register were used to compare 2212 births to 1537 schizophrenic women in Denmark with a random sample of all deliveries in Denmark during 1973–1993 (122931 births to 72742 women). The schizophrenic women had fewer antenatal care visits.
They were at lower risk of pre-eclampsia, but tended to have lower Apgar scores. There were no other differences in the incidence of specific complications such as placenta previa, placental abruption, and abnormal fetal presentation. Schizophrenic women were at increased risk of interventions such as Cesarean section, vaginal assisted delivery, amniotomy, and pharmacological stimulation of labor.
There were no important differences between the deliveries to schizophrenic women who gave birth before and after their first admission to a psychiatric department. These results show no evidence that schizophrenic women have a greater frequency of specific obstetric complications than non-schizophrenic women. Nevertheless, they are at increased risk for interventions during delivery.
Maternal obstetric complications are widely regarded as environmental contributors to schizophrenia risk, although the evidence is still inconclusive. While meta-analyses of a number of case-control studies suggest that significant associations exist between adult schizophrenia and exposure to obstetric complications, several population-based investigations have failed to demonstrate excess occurrence of obstetric complications in individuals who developed schizophrenia compared to those who did not. The sources of discrepant findings are likely to include different definitions of obstetric complications, the use of retrospective maternal recall versus prospectively collected obstetric data, differences between rating scales, and variation in sample size and selection. A more fundamental problem may be the confounding of observed associations between maternal obstetric complications and schizophrenia by heterogeneity in the degree of maternal genetic risk within samples ascertained through an individual with schizophrenia. Since genetic susceptibility to schizophrenia may be associated with a heightened sensitivity of the developing brain to obstetric insults, varying degrees of transmitted parental genetic risk might result in variable thresholds for the effects of obstetric complications, dependent on their timing, severity, and points of impact. It is, therefore, important to reduce heterogeneity with regard to variables such as genetic risk, severity, and type of obstetric complications.
In this respect, a research focus on obstetric complications in mothers with schizophrenia and their offspring, termed “strategic populations” by Rosenthal, offers a vantage point by being more homogeneous for genetic risk transmitted to the offspring. Children of women with schizophrenia have an eight- to 10-fold higher risk of developing the disorder compared to the general population, and individuals who develop schizophrenia are more likely to have a mother, rather than a father, with schizophrenia. Examination of the following could help clarify whether obstetric complications are a covariant effect of the genetic predisposition to schizophrenia or a concomitant of severe mental illness:
1. The incidence of obstetric complications in mothers with schizophrenia relative to comparison samples of mothers without psychiatric disorder
2. The frequency of obstetric complications in pregnancies before and after the onset of overt psychotic illness
3. The association of obstetric complications with maternal risk factors, such as age, parity, and lifestyle exposures, including smoking, socioeconomic status, and availability of social support
4. The occurrence of obstetric complications that are specific to women with schizophrenia compared to obstetric complications in women with other psychiatric disorders
Early studies of pregnancy outcomes in women with schizophrenia showed an increased incidence of perinatal deaths and malformations among their newborns. The samples tended to be small, and the studies differed with regard to the selection of cases and comparison subjects, the definitions of obstetric complications, and the methods of assessment. A meta-analysis by Sacker et al. of 14 such studies conducted before 1990 concluded that compared to births in the general population, a small but statistically significant excess could be demonstrated for obstetric complications, low birth weight, stillbirths, and fetal or neonatal deaths among the offspring of mothers (but not fathers) suffering from schizophrenia. Several recent, population-based studies of large samples have produced more clearcut evidence. Bennedsen et al. found a significantly increased relative risk for preterm births, low birth weight and small-for-gestation babies, as well as postneonatal deaths among children born to women with schizophrenia. Nilsson et al. reported significantly increased risks of low birth weight and stillbirths, particularly high in women who developed schizophrenic episodes during pregnancy.
It appears likely, therefore, that women with schizophrenia are at an increased risk for adverse reproductive outcomes. However, the extent to which such adverse outcomes are intrinsically related to schizophrenia, rather than to a nonspecific “continuum of reproductive casualty” associated with severe maternal mental illness, remains unclear. Few studies to date have addressed the occurrence of obstetric complications in women with affective disorders, and the findings are inconsistent.
We report results from a population-based study with record linkage across several morbidity case registers and databases in Western Australia. The aims of the study were to determine the frequency, nature, and severity of obstetric complications experienced by women with schizophrenia compared to women with affective disorders and women without a diagnosed psychiatric disorder, to investigate the temporal relationship between pregnancies and the onset of maternal psychiatric illness, and to explore a range of pregnancy outcomes in relation to maternal risk factors.
B.E Bennedsena, P.B Mortensen, A.V Olesen, T.B Henriksen, M Frydenberg
Department of Psychiatric Demography, Institute for Basic Psychiatric Research, Psychiatric Hospital in Aarhus, Aarhus University Hospital, Aarhus, Denmark
Perinatal Epidemiological Research Unit, Department of Obstetrics and Gynaecology, Aarhus University Hospital, Aarhus, Denmark
Department of Biostatistics, University of Aarhus, Aarhus, Denmark