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Pregnancy week 4
Pregnancy Week 4

Pregnancy Week 4

Baby Development

By this week, your baby will be tiny and the size of a poppy seed. The baby has developed two cellular layers called hypoblast and epiblast, which will develop into the baby’s organs and body parts in the coming weeks. Usually, the first ultrasound happens in week 6; however, an ultrasound in week 4 has a good chance to let you know if you are having twins.

Three cell layers are present in the embryo: endoderm, mesoderm, and ectoderm. The inner layer (endoderm) will become the baby’s digestive system, liver, and lungs. In contrast, the middle layer ( mesoderm ) will become the baby’s heart, reproductive organ, kidney, muscles, and skeletal system. The outer layer (ectoderm)  will turn into nerves, eyes, skin, and hair.

A yolk sac is visible on the mother’s body for some time, supplying food to the embryo and producing blood. This yolk sac disappears after the placenta forms in the baby’s digestive tract. The placenta acts as a baby’s lifeline, connecting the mother’s body to the baby till delivery. The placenta is formed from the division of the embryo into the baby and placenta. The placenta is responsible for transporting nutrients and waste between the mother and the baby.

Changes in mother

Few mothers would start experiencing early pregnancy symptoms like cramps, mood swings, bloats, etc., while many wouldn’t experience anything. These symptoms are unreliable pregnancy tests, and it’s too early to confirm whether the woman is pregnant. Pregnancy hormone or the hCG would start to begin production now. This makes the corpus luteum that produces the yolk sac stick around, along with the production of estrogen and progesterone.

Pregnancy Due Date Calculator

Pregnancy Due Date Calculator

Note: This calculation is based on Naegele's rule.

Pregnancy Week 4 Symptoms

  1. Implantation bleeding:- light pink, red, or brown bleeding happens before your regular period. It’s perfectly normal, and there is no need to worry.
  2. Breast Growth:- Your Breast might feel tender and seems to have grown. However, Breasts will continue to grow more in the coming weeks.

Important Tips

What to do

  1. Add healthy fats containing DHA to your diet, as it’s essential for a baby’s development. You can add fish, eggs, or flaxseed to your diet as they are rich in DHA.
  2. Find your due date and plan your schedule according to it. The most common delivery occurs in the 38-42 weeks of pregnancy
  3. Get enough Vitamin D from the sun, sardines, egg yolk, and milk.

What to avoid

  1. Avoid active and passive smoking.
  2. Avoid any food items that trigger any aversion. Look for alternate foods that will provide the nutrients while being palatable.

When to Consult a Doctor

  1. Gear up for a visit to your doctor to talk about prenatal care.


At four weeks, your baby has just started growing. The mother is unsure of pregnancy as there are no reliable tests yet, and the mother might experience some symptoms or none. Expected mothers should find comfort food and take enough vitamin D and healthy fats while avoiding secondhand smoke.

  1. N H S
  2. Healthdirect Australia
  3. The Cleveland Clinic
    Fetal Development 
  4. The Mayo Clinic
    Fetal development
  5. Women Health
    Pregnancy: Stages of pregnancy


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