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4-weeks pregnant: baby development and diet advice

Almost one month already! There are lots of things happening inside you this week.

3 mins to read Dec 13, 2021


Your baby is starting the process of splitting into the embryo and placenta, and their neural tube – the beginning of their spine and brain, is already formed! This week is also an important milestone in their embryonic development: the beginning of what is called organogenesis: the outlines of many internal organs are starting to form, as is their bloodstream. At the end of the fourth week, your baby is 4-6 mm in length (around the size of a pea), and the fetal-placental circulation is set up and running. Amazingly, since their conception, their weight has multiplied by 10,000! 


A big wave of hormones is being produced. Hormones are essential for ensuring your baby has  all they need to grow. Those hormones will prevent you from having a period again while you’re pregnant. And they also help form the placenta. What does the placenta do? It supplies baby with oxygen and nutrients and serves to protect them against many germs and pollutants. But not all – if you smoke and haven’t given up smoking yet, now’s the time to do it! (Dads too!)


Everyone says to “eat healthily” while pregnant but that can sometimes seem a tall, unspecific order. A great rule of thumb is to focus on food quality– it will help you build good habits early in your pregnancy. Focus on taking special care in preparing your food to avoid the risk of food poisoning, both for you and baby. Thoroughly cook your meat: steak tartare, sushi, and undercooked meats are no-noes! Wash your hands thoroughly after gardening or feeding pets and before cooking, and make sure you wash fruits and vegetables  well. Avoid eating leftovers that were not immediately stored and cooled in the refrigerator in which bacteria might have had a chance to grow. A little caution can go a long way to keeping you and your baby feeling good!


Is it a good idea to take a prenatal multivitamin while pregnant?
Experts recommend women eat a diet of folate-rich foods and take a multivitamin with at least 0.4 mg of folic acid, and iron, every day starting at least 3 months before pregnancy, and then continued throughout pregnancy and for 4 to 6 weeks postpartum and throughout breastfeeding. 
Pregnant women have a higher dietary requirements for many nutrients, including folic acid, proteiiron, zinc, and docosahexaenoic acid (DHA – a healthy fat found in fish and some animal foods)to name a few.  Taking a prenatal multivitamin that also includes with DHA can help fill some nutrient gaps. Talk to your doctor if you have questions about which prenatal multivitamin is best for you.

By the way, have you seen your healthcare practitioner yet?  Your doctor may order a blood test for early pregnancy and schedule your first ultrasound, which may take place around the 12th week. They may also refer you to an Obstetrician to care for you during your pregnancy.


  • Health Canada. Food safety for pregnant women. 2019. Food safety for pregnant women - Accessed August 2021.

  • SOGC. Pre-conception Folic Acid and Multivitamin Supplementation for the Primary and Secondary Prevention of Neural Tube Defects and Other Folic Acid-Sensitive Congenital Anomalies. SOGC Clinical Practice Guideline, No. 324. JOGC. 2015;37(6):534-549.


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