Pre-eclampsia is a serious complication of pregnancy which can become life threatening to the mother and baby. High blood pressure and severe swelling of the lower legs and face are symptoms of pre-eclampsia. If the condition worsens it is called eclampsia and seizures may be the life threatening risk. The swelling can become severe enough that toxin removal by the kidneys is reduced.
What causes pre-eclampsia is not yet well understood. Providing IV solutions of magnesium sulfate just prior to delivery helps reduce risk of seizures and usually delivery of the baby causes the rest of the symptoms to resolve. However people who’ve experienced IVs of magnesium sulfate shared with me that it feels like fire running through their veins. Background information — magnesium is an electrically active mineral that during normal health is kept in a very narrow range within the blood and is largely found within the interior of cells and within the bones. Calcium is also electrically active and it is in higher concentration within the blood than within the interior of cells.
Skipping ahead, oxidative stress prenatally has been shown to be involved in pre-eclampsia and it causes an increase in calcium flow in the placenta. 
While looking for more information about pre-eclampsia I found a Celiac Sprue forum  that included questions and comments about whether anyone else with celiac gluten intolerance had also experienced pre-eclampsia or HELLP complications of pregnancy and if so any ideas why they might co-occur. HELLP is a blood coagulation problem which I didn’t look into but Celiac sprue and pre-eclampsia may be likely to co-occur because both involve oxidative stress:
Hi, I’m a dietitian with an autoimmune condition and previous work experience with prenatal health. I’ve been researching why the advice I gave when I was working helped so many women at the time worked – but isn’t in the mainstream medical treatment yet. Increasing magnesium rich foods such as beans, nuts, and seeds helped women that had a history of preeclampsia or high blood pressure to have a normal pregnancy.
In a nut shell – oxidative stress causes the placenta to increase flow of calcium. Too much calcium can cause other cellular reactions and fluid changes. And oxidative stress can be caused by gluten exposure when there is an underlying celiac autoimmune condition or probably other autoimmune conditions.
Re oxidative stress, and calcium channels in the placenta: Reactive Oxygen Species Inhibit Polycystin-2 (TRPP2) Cation Channel Activity In Term Human Syncytiotrophoblast 
Re Celiac Sprue and oxidative stress, “long chain omega 3 fatty acids, plant flavonoids and carotenoids” were suggested as antioxidants that may help reduce the “oxidative stress, gene expression & production of inflammatory mediators”: Celiac disease, inflammation and oxidative damage: a nutrigenetic approach. Carotenoids include beta-carotene from carrots. Orange, red and dark green fruits and vegetables are generally good sources of carotenoids and plant flavonoids are also found in a variety of colorful fruits and vegetables. Omega 3 fatty acids are found in fish oil supplements or salmon, tuna, sardines – limit as a mercury source however during pregnancy or child bearing years. Vegetarian sources of a precursor omega 3 fat include flax seed meal (ground is digestible, whole flax seeds aren’t really), walnuts, and hemp seed kernels.
Sesame seeds, or tahini, sesame paste, has been shown in sports research to help reduce oxidative stress. The trial subjects ate 2 tablespoons per day of the seeds. Effects of Sesame (Sesamum indicum L.) Supplementation on Creatine Kinase, Lactate Dehydrogenase, Oxidative Stress Markers, and Aerobic Capacity in Semi-Professional Soccer Players.
Dark chocolate has also been shown to be beneficial antioxidant source.
Best wishes to any Celiac sufferers – I avoid gluten due to intolerance, initially for fibromyalgia like symptoms, and later autoimmune thyroid antibodies were found but not antibodies for Celiac Sprue.
A dietitian can help work out more balanced diets when major food items have to be excluded for health purposes. A professional organization offers a search feature for helping to find a Registered Dietitian eatright.org/find-an-expert
One more link that didn’t make it into the comment, magnesium deficiency in combination with elevated calcium levels may be involved in increasing oxidative stress: Magnesium deficiency and oxidative stress: an update, 2016, 
Who am I? What is my purpose? I am a sick person, with professional health experience, who reads and writes about sickness for my own health and for other sick people — they are the ones who realize just how valuable health is and who may appreciate information whether it has a large price tag & an expensive office — or is shared freely out of love and concern. Pain hurts.
One more link because they’re so informative, the inflammatory system seems to be connected to both pain receptors and other nerve receptors so inflammation, (which leads to oxidative stress) activates pain receptors (nociceptors) – /speculation/ which could be part of the reason fibromyalgia and other inflammatory conditions cause pain – they may simply be causing pain receptors to be over-active due to inflammation: Neurogenic Inflammation – The Peripheral Nervous System’s Role in Host Defense and Immunopathology 
The inflammatory process causes oxidative stress: Chronic inflammation and oxidative stress as a major cause of age-related diseases and cancer. 
Adequate oxygen intake and flow to all the cells throughout the body is also necessary to prevent oxidative stress. Obesity can make it more difficult for oxygenated blood to reach all cells. 
Moderate exercise and deep breathing relaxation exercises may be helpful for improving oxygen intake and blood flow.
A previous article I wrote regarding magnesium and pre-eclampsia also includes information from a research hypothesis suggesting that intrauterine pressure itself may also be a trigger for worsening pre-eclampsia symptoms.  Not included in the hypothesis was why — which is likely to be due to the fact that physical (osmotic) pressure can cause TRP ion channels to open. TRP channels are a large group of specialized proteins which control flow of minerals such as calcium into the interior of cells. TRP channels include the ones that were shown to be dysregulated by oxidative stess in the placenta which allowed an increase of calcium to enter, which is described in the research article: Reactive Oxygen Species Inhibit Polycystin-2 (TRPP2) Cation Channel Activity In Term Human Syncytiotrophoblast 
Disclaimer: Opinions are my own and the information is provided for educational purposes within the guidelines of fair use. While I am a Registered Dietitian this information is not intended to provide individual health guidance. Please see a health professional for individual health care purposes.
- A.A. Zheltova, et al., Magnesium deficiency and oxidative stress: an update, Biomedicine (Taipei). 2016 Dec; 6(4): 20. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5112180/
- Isaac M. Chiu, et al., Neurogenic Inflammation – The Peripheral Nervous System’s Role in Host Defense and Immunopathology, Nat Neurosci. 2012 Jul 26; 15(8): 1063–1067.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3520068/
- Khansari N, Shakiba Y, Mahmoudi M., Chronic inflammation and oxidative stress as a major cause of age-related diseases and cancer. Recent Pat Inflamm Allergy Drug Discov. 2009 Jan;3(1):73-80. https://www.ncbi.nlm.nih.gov/pubmed/19149749
- N. Netzer, Hypoxia, Oxidative Stress and Fat., Biomolecules. 2015 Jun; 5(2): 1143–1150.