Pre-eclampsia, pregnancy-induced hypertension in association with significant amounts of protein in the urine, and eclampsia, convulsions during or after labor, kill an estimated 70,000 worldwide each year.

University of Nottingham researchers said if women give up smoking before or even during pregnancy they can significantly reduce those risks.

Study leader Fiona Broughton Pipkin studied 1,001 white European women with moderate to severe pre-eclampsia and their babies, and found smokers were five times more likely to develop eclampsia.

The study, published in the journal Hypertension, also found that the pregnant smokers were more likely than women who don't smoke to deliver prematurely -- before 34 weeks -- produce much lower birth weight babies, or have babies with adverse outcomes.

"The pre-eclampsia babies risk short-term breathing problems, potential brain damage and long-term cardiovascular disease," Broughton Pipkin said in a statement. "The deaths are the tip of an iceberg for hospital admissions and worry for mothers, babies and families."