However, these odds are based on research done in 1983. We have to take into account more recent research. According to Science Daily, a study published in 2006 in Springer's journal Naturwissenschaften, (http://www.sciencedaily.com/releases/2006/10/061012184355.htm):
Neuhäuser and Krackow reviewed and analysed data from 1953 and 1972 (before abortion was widespread). They found that other factors, besides the mother's increasing age, were linked to the number of Down Syndrome cases. Down Syndrome rates were significantly higher in older mothers in their first pregnancy than in older mothers who had already had children. Only late first pregnancies were more likely to produce a Down Syndrome baby, not late second or third pregnancies. In addition, the larger the gap between pregnancies, the higher the rates of Down Syndrome.
Note, "Only late first pregnancies were more likely to produce a Down Syndrome baby, not late second or third pregnancies." This was Sarah Palin's fifth pregnancy. This suggests that the first stated statistics from the 1983 article are invalid in this case, since they do not take into account the number of previous pregnancies. We are actually not sure if Sarah Palin was 25 times more likely than Bristol Palin to produce a Down Syndrome baby.The changes may have been only slightly greater, if at all.
Please note also the last statement, "the larger the gap between pregnancies, the higher the rates of Down Syndrome." This might suggest that the six year gap between her last two children increased Sarah Palin's chance for a baby with Down Syndrome. However, we do not know how much the gap increased the risk. It may have been 1% or 200%. We also do not know if the gap between children the scientitsts are talking about is six years or twenty years? Therefore we cannot see this as a relevant factor in the case.
There is also another interesting study reported at Wiley Interscience from 1999 (click here that suggests that a mother not completing high school and a father's low occupation may be significant factors increasing risk in Down Syndrome. This would suggest that Bristol and Levi would be at higher risk than Sarah and Todd.
Conclusion: We cannot say with certainty that Sarah Palin had a significantly greater chance than Bristol Palin of giving birth to a Down Syndrome child. If this was her fifth child and not her first, Palin may not have had a much greater risk than Bristol, as is commonly supposed.
