Week 4 Development

It’s the 4th week of your pregnancy. You’ve been pregnant for one whole month. Normally, it is the time for next menstrual period, but your pregnancy will trigger some hormonal secretions that will prevent this from happening. During this period, more advanced development of your baby will take place.

Everything looks normal from the outside, but your body is undergoing great changes inside to accommodate growing baby in your womb. During this stage, fetus is at high risk for abnormalities, as the brain, heart, head, spinal cord, bones, muscles, tissues, and teeth of baby are developing. By the fourth week, blastocyst is firmly embedded in your uterus.

Body changes during 4th Week of pregnancy-

  • Now, your body is producing the pregnancy hormone HCG (human chorionic gonadotrophin). This hormone can cause anxiety, vomiting, fainting, dizziness, nausea, light-headedness and mood swings.
  • Your breasts will become increasingly tender and sore. You may also experience tingling sensation in your breasts.
  • Your basal body temperature will be high.
  • You may notice some mild cramping.
  • There will be an increase in vaginal discharge.
  • You may experience spotting.
  • Your sense of smell may become sharp.

Fetal development during 4th Week of pregnancy-
The blastocyst is now a tiny group of embryonic cells. Blastocyst would have already made the journey from your fallopian tube into your uterus. Now, implantation will occur and blastocyst will develop into an embryo.

Placenta may become fully functional by the end of this week. But in the beginning, it will not be able to provide nutrients to developing foetus. During this period, yolk sac delivers nutrients to the foetus.

Placenta will produce hormones like human chorionic gonadotropin (hCG) to alert your ovaries to stop releasing eggs and increase the production of estrogen and progesterone.

The embryo is about 2 mm long, now. It has three layers:

  • Outer layer- The outer layer is known as ectoderm. It will develop into the nervous system, skin, hair, nails, eyes and teeth of baby.
  • Middle layer- The middle layer is known as mesoderm. It will develop into the circulatory system, heart, sex organs, skeleton, connective tissues and muscles of baby.
  • Endoderm- The inner layer is known as endoderm. It will develop into the lungs, lining of gastrointestinal tract, liver, pancreas and thyroid gland of baby.

Arm and leg buds may also begin their development during this period. Rudimentary blood begins to move through the main vessels.