Magnesium is important for pregnant women as it plays an important role in various physiological processes that support both pregnant mother and fetal health.  This includes :

1. Muscle and nerves function: Magnesium is essential for muscle contraction and relaxation, including the muscles of the uterus.

2. Energy production: Magnesium is involved in energy metabolism, which is essential for the growth and development of the foetus and to support the increased energy demands of pregnancy.

3. Prevention of gestational diabetes: Magnesium plays a role in insulin action and glucose metabolism. Adequate magnesium intake may help reduce the risk of gestational diabetes; a condition characterized by high blood sugar levels during pregnancy.

4. Blood Pressure Regulation: Magnesium helps regulate blood pressure, which is crucial during pregnancy to prevent conditions like preeclampsia.

Based on U.S. National Institutes of Health (NIH), it is recommended to take 350-360mg of magnesium per day. However, the recommended dietary intake of magnesium can vary based on factors such as age, health status and individual needs.

Taking magnesium before pregnancy may be beneficial as it is an essential mineral involved in various physiological functions. However, it's important to approach any supplementation with careful consideration and consultation with a healthcare provider.

1.  General Health – Magnesium is involved in numerous bodily functions which includes muscle and nerve function, bone health, heart health and body metabolism.

2.  Muscle Function – Magnesium can help prevent muscle cramps and contractions.

3.  Menstrual Health – Magnesium may play a role in alleviating symptoms associated bloating and mood swings.

4.  Stress and Anxiety – Magnesium has been associated with relaxation and stress reduction. 

Magnesium deficiency occurs when the body doesn't have enough magnesium to function properly. This deficiency can arise due to various factors, including inadequate dietary intake, certain medical conditions, or medication. There are a few symptoms which may include:

1. Muscle cramps or spasms – Magnesium is essential for muscle function, and a deficiency may lead to muscle cramps, spasms, or weakness.

2. Fatigue and weakness – Inadequate magnesium levels can contribute to feelings of fatigue and weakness.

3. Nausea and vomiting – Magnesium deficiency may be associated with nausea and vomiting.

4. Loss of appetite – The desire to eat may be reduced.

5. Abnormal heart rhythms – Magnesium is involved in regulating heart rhythm, and a deficiency may lead to palpitations or irregular heartbeats.

Incorporating these magnesium-rich foods into your diet can help ensure you meet your daily magnesium needs. However, if you have concerns about your magnesium intake or suspect a deficiency, it's essential to consult with a healthcare professional for personalized advice. There are a few food sources that are rich in magnesium which includes:

1. Leafy green vegetables: Spinach, kale, Swiss chard. These vegetables are not only nutritious but also easy to prepare in salads, smoothies, stir-fries, and more.

2. Nuts and seeds: Almonds, sunflower seeds, pumpkin seeds. Snacking on nuts and seeds or adding them to salads or yoghurt will increase the magnesium intake.

3. Whole grains: Brown rice, quinoa, whole wheat. Choose whole grain products over refined grains to maximize your magnesium intake.

4. Legumes: Black beans, chickpeas, lentils. Add these legumes into soups, stews, salads, or as a side dish.

5. Dairy products: Milk, yogurt.

6. Fish: Mackerel, halibut. Add fish into your diet by grilling or broiling it as a healthy protein option.

7. Fruits: Bananas, avocados, and dried fruits. Add them in a portable snack or add them to smoothies, yogurt, or oatmeal.