NEW YORK (Reuters Health) - Women carrying fetuses with trisomy 21 have an unexpectedly reduced risk of preeclampsia compared with women with normal fetuses, especially nulliparous women.
In the March issue of Epidemiology, Dr. Jun Zhang of the National Institute of Child Health and Human Development in Bethesda, Maryland and colleagues conducted a study designed to test the association between fetal trisomy 21 and pregnancy-related hypertension.
The authors explain that because women with preeclampsia have higher levels of cell-free fetal DNA, and because levels of cell-free fetal DNA are twice as high as normal when the fetus is affected with trisomy 21, they expected to find that the risk of preeclampsia was elevated in women with trisomic pregnancies.
However, in an evaluation of 7763 pregnancies with fetal trisomy 21 and 15,293 matched normal pregnancies, the investigators discovered that nulliparous women with affected fetuses had “a reduced, rather than increased” risk of pregnancy-associated hypertension, mainly because of a decreased risk of preeclampsia.
Specifically, women with trisomy 21 pregnancies had an adjusted relative risk for pregnancy-related hypertension of 0.67, and an adjusted relative risk of preeclampsia of 0.19.
The researchers could only speculate about the mechanisms behind their findings. Earlier studies have shown that placentas from women with preeclampsia have decreased superoxide dismutase activity and mRNA expression. In women with trisomy 21 pregnancies, however, placental expression and activity of copper/zinc superoxide dismutase is significantly higher, probably because the gene for this antioxidant enzyme is located on chromosome 21q22.1.
The authors hypothesize, therefore, that the “heightened expression and activity of copper/zinc superoxide dismutase in trisomy 21-affected placenta may have protective effects on preeclampsia.” They note, however, that their study was not designed to test this hypothesis.
Source: Epidemiology 2004;15:195-201. [ Google search on this article ]
Copyright © 2002 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.