Nineteen genetic variants have been linked to the onset of pre-eclampsia or high blood pressure during pregnancy. While further research is required, this could lead to genetic risk scores that gauge an individual鈥檚 risk of developing either condition.
So-called gestational hypertension and pre-eclampsia are both defined as high blood pressure during pregnancy. The latter is also diagnosed by looking for protein in the urine, which can be a sign of kidney damage.
Some people have high blood pressure before they become pregnant, while others develop it during pregnancy. Why this occurs isn鈥檛 entirely understood. Pre-eclampsia is thought to be caused by the placenta not developing properly due to a problem with its blood vessels.
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Both conditions can result in a premature birth or a fetus not growing as expected. Symptoms are usually mild for the pregnant person, but in severe cases they can experience seizures and organ damage. Someone with either condition must be monitored closely and may be offered medication to lower their blood pressure or have an induced labour.
To better understand the role of genetics in the onset of these conditions, at Massachusetts General Hospital and his colleagues used genome sequences from global biobanks to study the genetics of 17,150 pregnant women who had been diagnosed with pre-eclampsia, 8961 who had been diagnosed with gestational hypertension and 451,241 pregnant women who had been medically certified by their doctor as having neither condition or who self-reported having normal blood pressure.
The results suggest 12 genetic variants are linked with pre-eclampsia. A further seven variants are linked with gestational hypertension.
The researchers then used this information to develop risk scores for both conditions. They tested these against genetic samples from 33,433 pregnant women in Norway and the US, some of whom had been diagnosed with pre-eclampsia or gestational hypertension.
When they assessed this group using clinical risk factors for these conditions, such as age and body mass index, they identified 17 per cent of the pregnant women who had been diagnosed with either gestational hypertension or pre-eclampsia. When these factors were combined with the genetic risk scores, that rose to 30 per cent.
Further research is required to increase the accuracy of the genetic risk scores, says at the University of Exeter Medical School, UK. However, these could one day improve our ability to identify those who are most at risk of certain pregnancy complications, she says.
Honingberg and his colleagues also hope the genetic risk scores could be used to gauge who may benefit from a low dose of aspirin during pregnancy, which is sometimes offered to reduce the risk of pre-eclampsia.
Both assessing just clinical risk factors and combining this with genetic risk scores led to the identification of supposed gestational hypertension and pre-eclampsia cases that turned out to be false positives, however, Honigberg says the proportion of correctly identified cases exceeded the mistaken incidences.
鈥淟ow-dose aspirin is a relatively low-risk intervention so we鈥檙e ok with treating some women who wouldn鈥檛 have gotten preeclampsia,鈥� he says.
According to at the University of Aberdeen, UK, using genetic risk scores to guide aspirin use may be difficult to apply in practice
鈥淎 lot of modelling would need to be done to try and quantify the degree of benefit and risk which would be accrued from offering enhanced monitoring to certain women at the expense of others,鈥� she says.
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