Investigators in the UK have found that women who have an infant that dies from Sudden Infant Death Syndrome (SIDS) are more likely in their subsequent pregnancies to deliver infants who are born preterm or small for gestational age.
The researchers say that because these complications increase the risk of SIDS, the data helps explain why some women have more than one infant who dies from SIDS.
Although statistics show that women who have one baby who dies from SIDS are five times more likely than other women to have another SIDS occurrence, the reason underlying the increased risk of recurrence is not known.
To carry out their investigation Dr. Gordon C. S. Smith from Cambridge University and his team used Scottish databases to identify a group of women who had consecutive births between 1985 and 2001.
Among the 258,000 women, the first infant of 332 women and the second infant of 203 women died from SIDS, while one woman had two consecutive infants die with a diagnosis of SIDS.
It is suggested that women whose previous infant died were two to three times more likely to deliver an infant that was deemed small for gestational age or to have a preterm birth, both of which are associated with increased risk of SIDS.
A range of analysis showed that these associations were explained by maternal characteristics such as age, marital status and smoking, as well as obstetric complications.
The investigators say the findings provide direct evidence that the risk of SIDS after a given birth is not statistically independent on whether previous infants died.
The study is published int The Lancet December 17, 2005.