Objective: To study the impact of maternal health and obstetric complications on the risk for sudden intrauterine unexplained death.
Methods: All 76 cases of sudden intrauterine unexplained death and 165 explained stillbirths among singletons in Oslo, Norway (1986-1995) were compared with 582 controls. Information on maternal health was registered from antenatal health cards and the Medical Birth Registry of Norway. The effect of pregnancy duration was studied before logistic regression analysis corrected for pregnancy duration was performed.
Results: Urinary tract colonization or infection in pregnancy was associated with a reduced risk for subsequent sudden intrauterine unexplained death (odds ratio [OR] 0.29 [0.12-0.74]), whereas insufficient physiologic hemodilution during pregnancy (lowest hemoglobin greater than 13 g/mL) increased the risk for sudden intrauterine unexplained death (OR 9.50 [1.30-69.3]). However, the risk for sudden intrauterine unexplained death remained unaffected by the total number of indicators of impaired maternal health during pregnancy, in contrast to significant impact on other stillbirths.
Conclusion: Urinary tract colonization or infection may offer protection against sudden intrauterine unexplained death. We hypothesize that the subsequent maternal immune response offers transplacental protection against lethal fetal infections by common pathogens of urinary tract infections. Other health indicators have little impact on sudden intrauterine unexplained death.