How does preeclampsia or HELLP develop?

This page describes the risk factors for preeclampsia or HELLP, and how this pregnancy complication develops.

Risk Factors for Preeclampsia or HELLP

At present, we do not know why some women develop preeclampsia or HELLP and others do not. However, there are certain risk factors that increase the chance. Underlying heart and kidney disease, high blood pressure, blood clotting disorders, a history of preeclampsia/HELLP or high blood pressure in the family, obesity, multiple pregnancy, diabetes, an advanced maternal age (>40 years) and fertility treatments can be such risk factors. This website lets you calculate your own risk of preeclampsia or HELLP (please always discuss this result with your doctor).

If one or more of the above risk factors apply to you, your doctor may decide for you to start taking aspirin at around 10 weeks into your pregnancy, to prevent preeclampsia or HELLP. Aspirin helps the placenta to form better, while also improving your vascular function. Taking aspirin is harmless for yourself and your child.

Please remember that it is still possible to develop preeclampsia or HELLP without having any of the above risk factors.

How does preeclampsia or HELLP develop?

Preeclampsia or HELLP occurs when, at the start of the pregnancy, development of the placenta is impaired. Because the placenta does not develop as it should, its blood supply decreases and your placenta passes less blood and oxygen on to your baby. This also explains why preeclampsia usually involves a growth delay in the baby.

But why is the placenta not developing well? It is probably due to the pregnant body putting a lot of stress on the vascular system. A pregnancy is more or less like a thorough stress test for the vascular system, and preeclampsia or HELLP occurs when your blood vessels do not adapt sufficiently to the pregnancy. Women with preeclampsia or HELLP also run an increased risk of cardiovascular disease later in life, which is why monitoring is extremely important, even after the delivery!


Any questions or physical issues that match the symptoms mentioned on the website?

Please make sure to always contact your attending physician.

Terminology explained


HELLP syndrome