Pregnancy/Morning Sickness

When to start taking prenatal vitamins

by Nikki Warren on Aug 08, 2023

When to start taking prenatal vitamins

In the first trimester from conception to 12 weeks, you might feel a range of emotions due to hormonal changes. It causes you to feel moody, irritable, and tired, which are actually normal.

Many changes happen to your body as it prepares and helps nourish and protect your baby. In this stage, the baby’s growth is at a critical point, and getting the right nutrients is crucial. While you might eating nutritious foods, taking prenatal vitamins is important for the baby’s development. 

Not all pregnancies are planned so at the time you discover you’re pregnant, you should start as soon as possible. But optimally, 4 months prior to conception

What are the most important nutrients in pregnancy, especially in the first trimester

  • Folate - This is the naturally occurring form of vitamin B9. Folate reduces the risk of birth defects. Specifically in the spine and brain development - spina bifida and anencephaly - by 50% or more.
  • It may also lower the risk of miscarriage, especially in women with high homocysteine levels. An amino acid that contributes to blood clotting.
  • Vitamin B12 and folate are equally important because of their shared functions. They also play a role in DNA synthesis, which is essential for cell growth and replication.  A recent study suggests that providing women with vitamin B12 supplements during pregnancy and shortly after giving birth could potentially enhance the cognitive development of their children. Vitamin B12 deficiency in the beginning stages of pregnancy may increase the risk of birth defects, such as neural tube defects. 
  • Choline is particularly important during pregnancy for optimal foetal development, during breastfeeding, and in the first two years of life. It has long been recognised that it is important in early brain development.  A choline-deficient diet during pregnancy may negatively affect the baby's memory function for life. Some studies suggest 440 mg of choline per day may protect your baby against neural tube defects.
  • Iodine - During the initial trimester of pregnancy, the baby's thyroid becomes active. Relying solely on the mother as its source of thyroid hormone. These hormones are essential for promoting healthy brain function and development. Therefore, it is vital for the mother to supplement her diet with iodine to prevent any deficiencies in this nutrient. The recommended daily intake from diet and supplements in pregnancy is 220mcg daily. Therefore supplementation of at least 150mcg daily is recommended.

Iron supplementation is known to aggravate the symptoms of morning sickness. Ideally, your iron stores will be high, from completing a preconception care plan. This is so you won’t need iron in the first trimester. 


The Need For Nutrients Increases In the Second Trimester


One of the key nutrients needed is iron, as it is used by your body to make the extra blood that you and your foetus need during pregnancy. 

In the second trimester, a normal physiological change of an increase in plasma volume doubles from week 16 onwards. While the red blood cell mass of pregnant women increases, plasma volume increases disproportionately, causing anaemia of pregnancy or haemodilution. The reason why many pregnant women lack the sufficient amount of iron needed for the second and third trimesters.  

Mild anaemia is normal during pregnancy due to said phenomena. However, more severe anaemia, can put your baby at higher risk for iron deficiency later in infancy. In addition, if you are significantly anaemic during your first two trimesters, you are at greater risk of having a pre-term delivery or low-birth-weight baby.

Being anaemic also burdens the mother by increasing the risk of blood loss during labour. It also impacts the immune system, making it more difficult to fight infections. 

So this is the time when your need for iron also increases, you can begin iron supplementation at a dose of 24 mg/day. When a woman is not pregnant, her recommended daily intake (RDI) of iron is 18 mg daily, but for pregnant women, the RDI is 27 mg per day

Your healthcare provider will give you a blood test at your first prenatal appointment to check whether or not you’re iron deficient. 


Consuming omega-3 fatty acid is critical to the healthy development of the eyes, nervous system, and brain. A study suggests that DHA may improve mood during late pregnancy and early postpartum. Some of the food sources of DHA are anchovies, sardines, and eggs.


This is a key mineral that aids in the development of vital structures like the skeleton. You also need more calcium for the formation of your baby’s bones and teeth. Foods like milk, dairy, salmon, and sesame seeds are calcium packed.

You can get the recommended 1,000 milligrams per day through a well-balanced diet. When taking calcium as a supplement, it is important that it also contains the co-factors. The cofactors include magnesium, vitamin D3 and vitamin K2. Vitamin K2 helps push the calcium into the bones where it’s needed, rather than build up in the arteries.


Magnesium is involved in over 300 enzyme reactions in the body, so taking 350 milligrams of magnesium every day is recommended. Magnesium supports nerve and muscle function and helps to maintain normal blood pressure. It also helps your baby build strong teeth and bones and assists in healthy bone development.

Vitamin D 

It is important to get enough vitamin D during pregnancy. The best way of getting vitamin D is to get a few minutes of midday sun on your chest. 

The RDI of vitamin D2 in pregnancy is 200iu. This also supports calcium absorption in bones. A diet deficient in calcium can lead to osteoporosis in later life.

Vitamin K2 

Vitamin K2 ensures that calcium is deposited in body parts such as bone and cartilage. Instead of accumulating where it shouldn't – like blood vessels. In pregnancy, achieving optimal calcium deposition is crucial for the proper development of the foetus. Including the formation of dental arches, teeth, and the structure of the face and jaw. 

Vitamin C

The RDI of vitamin C during pregnancy is 85 milligrams daily. Its core role is for tissue repair and wound healing (think prevention of stretch marks!). It also supports the body's production of collagen and helps boost immunity. Vitamin C also assists iron absorption. 

Can prenatal vitamins cause black stool? 

Black stools is one of the side effects of taking poor quality iron. Occasionally, your body is not able to absorb iron, causing the stool to be black or tarry. It can also be attributed to your diet, dehydration and constipation. 

To avoid black stool during pregnancy, it is important that you’re taking a quality iron supplementation that ensures optimal absorption. Or you can consume more iron-rich foods. 

Do you need prenatal vitamins in the third trimester

The third trimester will surely be one of the most exciting months of your life as you await the arrival of your bub. In this period, a lot of development is still incomplete until the last few weeks of pregnancy. This also means that as a mama, you're also more than happy to provide your child with the necessary nutrients.

The nutritional needs of a baby reach the maximum during this stage. There’s an increased call in the amount of iron due to increased blood volume. Research shows more than 90% of pregnancy anaemia cases develop in the third trimester. 

Protein is much needed for the growth and cellular development of your baby and a healthy placenta.

Essential fatty acids like omega-3 have a significant role in the third trimester of brain development. Consuming more omega-3, specifically EPA in late pregnancy lowers the risk of postpartum depression. Healthy fats help create a protective layer and also aid in building up maternal stores in anticipation of breastfeeding.

Now that you’re also in the home stretch of your pregnancy, an additional 340 calories a day is recommended starting in the second trimester and increasing slightly in the third trimester.

Taking prenatal vitamins while breastfeeding

It’s important to keep taking prenatal vitamins while breastfeeding. Breastfeeding requires extra nutrients to support both the mother's health and the production of breast milk. For instance, there’s an increased need for iodine and choline. It is recommended that lactating mothers should consume 270 mcg of iodine and 550mg of choline daily throughout the first year postpartum.