The vast majority of pregnancies are uncomplicated, with healthy moms and healthy babies. But one of the more common pregnancy complications when one occurs is pre-eclampsia.
Pre-eclampsia is a pregnancy complication in which a woman experiences high blood pressure and protein in her urine.
The condition can become life-threatening without medical care. However, the only cure for pre-eclampsia is for the woman to have her baby.
A recent study found that mild pre-eclampsia rates in the US have dropped over the past 30 years, but severe pre-eclampsia has increased.
Two factors that appear related to the increase are increases in obese mothers and decreases in smoking during pregnancy, but they're not the sole reasons.
This study, led by Cande V. Ananth, of the Department of Obstetrics and Gynecology at Columbia University in New York, looked at the rates of pre-eclampsia across the US.
According to Andre Hall, MD, an OBGYN at Birth and Women's Care, PA in Fayetteville, NC, pre-eclampsia is also called "toxemia" and refers to having both of the following specific symptoms:
- a systolic (top number) blood pressure of 140 or higher, or diastolic (bottom number) blood pressure of 90 or higher
- protein in the urine in excess of 300 mg in a 24 hour period.
"He said the exact cause of pre-eclampsia is not known, but it is believed to be related to changes in blood flow in the body," Dr. Hall said.
In this study, the researchers examined data from national hospital discharge surveys from 1980 through 2010 in the US.
Together, the data sets from the discharge surveys included about 120 million women who had been admitted to US hospitals to deliver their babies.
Overall, the researchers found that about 3.4 percent of pregnant women experienced pre-eclampsia in 1980, which rose to 3.8 percent in 2010.
Much of this increase included increases in severe pre-eclampsia, which more than tripled over the three decades, from 0.3 percent in 1980 to 1.4 percent in 2010.
Meanwhile, mild pre-eclampsia slightly decreased from 3.1 percent in 1980 to 2.5 percent in 2010.
The peak of severe pre-eclampsia rates occurred in 2003: Women giving birth in 2003 were nearly seven times more likely to have severe pre-eclampsia compared to women giving birth in 1980.
After 2003, however, these rates declined slightly. Overall, women born in the 1970s appeared to have the highest risk for pre-eclampsia.
For example, a woman born in 1970 was approximately 20 percent more likely to have severe pre-eclampsia than a woman born in 1955.
Overall, mild pre-eclampsia particularly declined among mothers under 30 years old but increased among mothers aged 30 to 34.
The researchers also found some links between pre-eclampsia and both women's weight and women's smoking rates.
Obesity is linked to an increased risk of pre-eclampsia while smoking during pregnancy is actually related to a decreased risk.
However, despite the fact that increasing obesity and decreasing smoking rates might influence pre-eclampsia rates, these two trends alone could not explain the shifts seen in overall pre-eclampsia rates.
It's also possible that changes in how pre-eclampsia is diagnosed were also a part of the increase in the rates, the researchers wrote.
The researchers summarized their study as presenting four important findings:
- Some part of the increase in pre-eclampsia appeared simply related to the decade in which a pregnant woman was born.
- The rate of pre-eclampsia in general increased across all ages of pregnant women.
- Yet the very youngest and the oldest mothers particularly saw larger increases in the rates.
- The decrease in smoking across the US has likely had some effect on the rates of mild and severe pre-eclampsia.
Dr. Hall said that one possible cause of pre-eclampsia that has been suggested relates to poor diets.
"The take away message from this study is to realize that pre-eclampsia may not be able to be prevented but certain life choices (including healthier diets and exercise) clearly reduces the risk of developing this condition during pregnancy," he said.
This study was published November 7 in the journal BMJ. Study funding information was unavailable, but the authors declared no conflicts of interest.