Urine formation usually begins towards end of ______and containes throughout fetal life:
A. 2-3 weeks
B. 11-12 weeks
C. 3-5 weeks
D. 21-22 weeks
Correct Answer: B. 11-12 weeks
Urine formation in the fetus usually begins towards the end of the first trimester and continues throughout fetal life.
Explanation:
Development of the urinary system occurs in stages from the intermediate mesoderm. Three kidney systems appear sequentially: pronephros, mesonephros, and metanephros. The pronephros is non-functional, and the mesonephros functions only briefly in early embryonic life. The metanephros, which becomes the permanent kidney, starts developing around the 5th week of gestation.
Although the metanephric kidneys begin forming earlier, they become functionally active by the end of the first trimester (around 10–12 weeks of gestation). At this time, fetal nephrons mature sufficiently to start urine production. From this point onward, urine formation continues throughout the rest of fetal life.
Fetal urine does not serve an excretory role like in postnatal life because waste products are removed via the placenta into the maternal circulation. Instead, fetal urine plays a crucial role in maintaining amniotic fluid volume, which is essential for normal lung development, fetal movement, and protection of the fetus.
As pregnancy advances, fetal urine becomes the major contributor to amniotic fluid, especially in the second and third trimesters. Therefore, normal urine formation is vital for healthy fetal growth and development.
Other Options Details
Urine formation in the fetus begins when the permanent kidneys (metanephros) become functional. Let us describe all the options clearly and then identify the correct one.
A. 2–3 weeks
At this very early stage of development, only the primitive kidney systems (pronephros) appear briefly. These structures are non-functional and do not produce urine. Therefore, urine formation does not begin at 2–3 weeks.
B. 11–12 weeks ✅ (Correct Answer)
By the end of 11–12 weeks, the metanephric kidneys are well developed and become functionally active. From this time onward, the fetus starts producing urine regularly. Fetal urine is passed into the amniotic cavity and contributes significantly to amniotic fluid throughout fetal life.
C. 3–5 weeks
During this period, the mesonephros functions temporarily. Although it has some excretory role, it does not contribute significantly to true urine formation that continues throughout fetal life. Hence, this option is incorrect.
D. 21–22 weeks
By this stage, fetal urine formation is already well established. Waiting until 21–22 weeks would be too late, as urine production has already been ongoing for many weeks.
✅ Conclusion
Urine formation usually begins towards the end of 11–12 weeks and continues throughout fetal life.
I hope that you liked this article.
Thanks!! 🙏 😊
Writer: Vandita Singh, Lucknow (GS India Nursing Group