The new research is in the journal Epidemiology. Chocolate, especially dark, is rich in a chemical called theobromine, which stimulates the heart, relaxes smooth muscle and dilates blood vessels. The theory is theobromine could improve circulation within the placenta while blocking oxidative stress.
Chocolate has been used to treat chest pain, high blood pressure and hardening of the arteries.
Researchers say preeclampsia in which blood pressure spikes during pregnancy has many features in common with heart disease.
Scientists say the results of their study warrants others to confirm the results.