Abhilasha Nursing Home

stages of pregnancy week by week

Stages of fetal development by week: stages of pregnancy week by week

Pregnancy is an incredible journey marked by the remarkable growth and development of the fetus inside the womb. Understanding the stages of fetal development by week provides expectant parents with insight into the intricate process of pregnancy. In this comprehensive guide, we’ll explore when pregnancy starts, how long it lasts, and the stages of pregnancy week by week. 

When Does Pregnancy Start, and How Long Does it Last? 

Pregnancy officially begins with the fertilization of an egg by sperm, forming a zygote. This typically occurs during ovulation, when a mature egg is released from the ovary and travels down the Fallopian tube, where it may encounter sperm. Once fertilization occurs, the zygote begins to divide and develop into an embryo, eventually implanting itself into the lining of the uterus. From this point, pregnancy is measured in weeks, with the average gestation period lasting approximately 40 weeks (about 9 months) from the first day of the last menstrual period (LMP). 

Stages of Pregnancy Week-by-week 

1. Weeks 1-4: During the first four weeks of pregnancy, the fertilized egg undergoes rapid cell division to form a blastocyst. The blastocyst implants itself into the uterine lining, and the placenta begins to develop. Basic structures such as the neural tube, which will later become the brain and spinal cord, start to form. 

2. Weeks 5-8: By the fifth week, the embryo has grown, and the heart begins to beat. Limb buds appear, and essential organs such as the brain, lungs, liver, and kidneys start to form. Facial features become more defined, and the embryo is now referred to as a fetus. 

3. Weeks 9-12: During the ninth to twelfth weeks, the fetus undergoes significant growth and development. External genitalia begin to differentiate, and fingers and toes become distinct. Facial features continue to develop, and the fetus may begin to move spontaneously, although the mother does not yet feel these movements. 

4. Weeks 13-16: By the thirteenth week, the fetus has grown, and its movements become more coordinated. Fine hair, known as lanugo, begins to cover the skin, and the fetus may start to suck its thumb. The digestive system and urinary tract continue to mature, and the fetus is now capable of swallowing and excreting urine. 

5. Weeks 17-20: During the seventeenth to twentieth weeks, the fetus experiences rapid growth, and its proportions become more human-like. Vernix, a protective substance, forms on the skin, and the fetus begins to produce meconium, the first stool. Gender may be identifiable through ultrasound imaging. 

6. Weeks 21-24: In the twenty-first to twenty-fourth weeks, the fetus continues to mature, and its organs become more functional. Lung development accelerates, and the fetus may exhibit regular sleep-wake cycles. Survival outside the womb becomes increasingly possible with advanced medical care. 

7. Weeks 25-28: By the twenty-fifth week, the fetus’s sensory organs, such as hearing and vision, continue to develop. Rapid brain growth occurs, and the fetus may respond to external stimuli, such as sound and light. The lungs continue to mature in preparation for breathing air. 

8. Weeks 29-32: During the twenty-ninth to thirty-second weeks, the fetus gains weight rapidly, and its movements become more pronounced. The immune system strengthens as the fetus receives antibodies from the mother. Fetal position may change in preparation for birth, with the head moving downward into the pelvis. 

9. Weeks 33-36: In the thirty-third to thirty-sixth weeks, the fetus continues to grow and develop, primarily gaining weight and accumulating fat stores. Lung development nears completion, and the fetus may practice breathing movements. The fetus may settle into a head-down position in readiness for birth. 

10. Weeks 37-40: By the thirty-seventh week, the fetus is considered full-term and ready for birth. The lungs are fully mature, and the fetus’s organs are prepared for life outside the womb. During the final weeks of pregnancy, the fetus may descend further into the pelvis, and the mother may experience signs of impending labor, such as Braxton Hicks contractions and the release of the mucus plug. 


Pregnancy is a miraculous journey characterized by the continuous growth and development of the fetus from conception to birth. Understanding the stages of fetal development by week provides expectant parents with valuable insight into the remarkable process of pregnancy, fostering a deeper connection with their growing baby. As the journey unfolds, prenatal care and support from healthcare providers play a crucial role in ensuring a healthy pregnancy and childbirth experience.