Nutrition for the third trimester
Congratulations, you are on the home stretch. The third trimester is weeks 28 to 40
The third trimester is one of the most nutritionally demanding periods of pregnancy and what you eat during these final weeks has a direct impact on your baby's growth, brain development, and preparation for life outside the womb. During the third trimester of pregnancy, your baby gains approximately 50% of their birth weight, making adequate calorie intake, quality protein, and key micronutrients more important than ever. Iron-rich foods are essential during this stage, as your baby is building their own iron stores to last through the first six months of life
Omega-3 fatty acids, particularly DHA, support rapid brain and eye development in the final trimester and are found in abundance in oily fish like salmon, as well as in walnuts and flaxseed. Calcium and vitamin D work together to support your baby's bone and teeth development during the third trimester, with dairy products, fortified plant milks, and eggs among the most accessible sources
Folate remains important throughout all trimesters of pregnancy but is particularly valuable in supporting neural development, while magnesium found in nuts, seeds, and wholegrains helps manage the leg cramps and sleep disruption that commonly affect women in late pregnancy
Staying well hydrated is equally critical in the third trimester, as your blood volume is at its peak and your kidneys are working harder than ever. If you're finding it difficult to eat large meals due to the pressure your growing baby places on your stomach, focus on smaller, more frequent meals that are dense in third trimester nutrition prioritising protein, healthy fats, and complex carbohydrates at every sitting
Read on for 5 nutritional considerations for the third trimester
1. Maintain a good intake of iron and protein
Both nutrients are crucial to assist with the rapid growth that occurs in baby during the third trimester, plus to support and increase in blood volume and a healthy placenta. It is recommended women consume 27mg of iron daily throughout pregnancy, up from 18mg/day in non-pregnant women (National Health and Medical Research Council [NHMRC], 2006). Iron is available through food in 2 main forms: Heme iron, which is found in meat, seafood, and chicken; and non-heme iron, which is found in plants, such as lentils, quinoa, beans, tomato puree, asparagus, and spinach. Heme iron has higher bioavailability, meaning your body will be able to absorb more, so it is a good idea to include in your diet regularly. You can still obtain iron if you are following a plant-based diet, however you will need to set your overall intake 1.8x higher to meet pregnancy needs.
The amino acids found in protein are the building blocks for our body, including new tissue we grow during pregnancy, such as skin, uterine, placental and breast tissue. In Australia, it is recommended women consume 60g of protein per day (about 1g/kg body weight) (NHMRC, 2006), however research suggests this might be underestimated and for the third trimester and should be closer to 1.52g/kg body weight daily (Stephens, et al., 2015). Aim for at least 1 serve of animal protein per day (about the size of your palm), which is also a good source of heme iron, such as fish, beef, lamb, eggs, chicken or good quality organ meats. For plant-based mamas, you want to include complete proteins, such as quinoa, buckwheat and chia seeds, as well as other protein rich-plant foods like legumes and organic soy (eg: tofu or tempeh).
2. Consider including fermented foods or a probiotic
There are so many benefits to probiotics / fermented food, but the big one for me in the 3rd trimester is the influence of the maternal microbiome on the developing infant microbiome and future health outcomes. Whilst some inoculation is thought to occur in utero, the majority of bacteria transfer from mother to baby occurs during birth, as the baby passes through the vaginal canal and then continues with skin to skin and breastfeeding (Dunlop, et al. 2015). Consuming probiotic-rich foods during pregnancy is one way to boost your microbiome. I recommend adding in one good food source daily, such as Greek yoghurt, coconut yoghurt, sauerkraut, kimchi, tempeh or miso. You might also like to consider a probiotic supplement, however not all are equal so I would seek advice from a healthcare practitioner.
3. Boost your intake of DHA:
Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid that is found in large proportions in the human brain. During the third trimester, DHA accumulation in the fetal brain occurs at a rapid rate and continues for the first 2 years of life (Lauritzen et al, 2016). Maternal DHA levels may impact infant cognitive development, with one study finding a significantly higher score in eye and hand coordination amongst children whose mothers received 2.2g of DHA and 1.1g EPA from 20 weeks gestation until delivery (Dunstan et al, 2008). Additionally, DHA supplementation during pregnancy and breastfeeding may reduce risk of eczema or food allergy in baby’s first year (Gunaratne, 2015). If choosing to supplement, you want to look for high quality, naturally occurring forms from small fish such as sardines or anchovies, with no synthetic vitamin A added. Rich food sources include fatty fish such as salmon, sardines, tuna + trout. Marine algae (Schizochytrium) is the only plant-based source of DHA for those who don't eat fish.
4. Consume choline-rich foods:
Choline not only helps prevent neural tube defects in the 1st trimester, but it also plays a role in baby's brain development in the 3rd trimester. It is estimated that around half of Australian women are meeting the adequate intake for choline in late pregnancy (Probst, et al., 2022). While research on the benefits of choline in humans is still novel, evidence is mounting for the role it plays in supporting general brain development and enhancing neural and cognitive functioning (Derbyshire, E., 2020). Newer prenatal supplements to the market are beginning to incorporate choline into their formulations, which is great news for supporting women’s levels, but it is still a great idea to include some good quality food sources daily. Two large eggs will provide more than half your daily needs, followed by other moderate sources such as salmon, Brussel sprouts, beef, lamb, chicken, pork, beans, lentils and dairy products.
5. Up your vitamin D + calcium:
By the third trimester baby's bones are increasing in density (you probably don't need to be told this, since you can tell by the amount of kicks to your insides!), so it is important to continue to support bone development through calcium and vitamin D rich foods. The good news is the two often come hand in hand in nature, for example in fatty fish with small bones, such as salmon, sardines, mackerel and trout. Other calcium-rich foods include chia seeds, leafy greens, almonds, white beans and broccoli. We also obtain a lot of vitamin D from the sun, so aim for 15-20mins daily of safe sun exposure (ideally on large surfaces such as the belly and thighs) and especially during the winter months.
Lastly, these slow final weeks are a great time to prepare and ponder life with a newborn. However, instead of focusing so much on what the baby needs (which really isn’t much in the beginning), I like to recommend women plan for how they are going to be supported during their postpartum. For example, can you start preparing meals for the freezer, can you have someone organise a meal train for you, or book yourself a cleaner for those early weeks to minimise time spent on your feet doing chores. Looking after yourself is so critical throughout motherhood, because we can’t pour from an empty cup.
Kelly Benton – Pregnancy & Baby Nutritionist
Kelly Benton is a Nutritionist specialising in maternal and baby nutrition. She is a mother of two little ones, right there in the thick of it with you. After experiencing maternal nutrient depletion through her first pregnancy and postpartum period, Kelly saw a need to educate and empower other women to proactively take health into their hands so they can have a more positive experience. Kelly is available for 1:1 consults, to book please visit her website or Instagram page
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