Antenatal and intrapartum factors associated with sudden infant death syndrome in the New Zealand Cot Death Study.

OBJECTIVE

To describe the relationship between antenatal and intrapartum factors and sudden infant death syndrome (SIDS).

METHODOLOGY

The New Zealand Cot Death Study was a 3 year case-control study, with 485 infants who died from SIDS in the postneonatal period and 1800 randomly selected control infants. Data were obtained from obstetric records, parental interview and community nursing records.

RESULTS

This study confirms many of the antenatal and intrapartum risk factors for SIDS noted in studies from both the southern and northern hemispheres. After controlling for potential confounders, such as occupational group and marital status, significant inverse effects were noted for interpregnancy interval, birthweight and gestation. Other factors that retained a significantly increased risk of SIDS were: increasing parity, bacteriological evidence of urinary tract infection (UTI) (adjusted odds ratio 1.73, 95% CI 1.10-2.73); smoking antenatally (AdjOR 2.14, 95% CI 1.61-2.84); less than six antenatal checks attended (AdjOR 1.84, 95% CI 1.19-2.84); second stage of labour less than 16 min (AdjOR 2.06, 95% CI 1.35-3.14) and multiple birth (AdjOR 3.23, 95% CI 1.70-6.02). No interaction was observed between maternal haemoglobin and antenatal smoking. Interactions were tested for and not found between antenatal smoking and three antenatal risk factors (UTI, short second stage of labour and number of antenatal appointments). The only significant interaction between these three factors and three modifiable postnatal risk factors (prone sleeping, bed sharing and bottle feeding) was between bed sharing and fewer antenatal appointments. The risk of SIDS associated with bed sharing was greater among those whose mothers had fewer antenatal appointments.

CONCLUSIONS

Although many of the previously identified antenatal and intrapartum risk factors for SIDS are confirmed, the risks of SIDS associated with obstetric factors are in general considerably lower than the risks associated with the four modifiable postnatal risk factors.