Question

What is the approximate pH of amniotic fluid?

• A. 6.7-6.9
• B. 6.9-7.0
• C. 7.1-7.2
• D. 7.4-7.5

Hint:

Amniotic fluid is mildly alkaline, about 7.2, which is why it turns nitrazine paper blue.

Answer 1

The Correct Option is C

Step 1: Understanding the Question.
We need the normal, approximate pH value of amniotic fluid, the fluid that surrounds the baby inside the uterus.

Step 2: Key Concept or Approach.
Amniotic fluid is mildly alkaline, standard obstetric references, including Williams Obstetrics, give its pH as being around 7.2, in contrast to normal vaginal secretions, which sit in an acidic range of about 3.8 to 4.5. This pH difference is the basis for a simple bedside test, the nitrazine test, used to check whether a woman's membranes have ruptured.

Step 3: Detailed Explanation.
On nitrazine paper, an acidic fluid such as normal vaginal secretion keeps the paper yellow, while an alkaline fluid such as amniotic fluid turns the paper blue, because amniotic fluid pH is well above 6.5.
Among the ranges given, 6.7 to 6.9 and 6.9 to 7.0 sit below the accepted value of about 7.2, and 7.4 to 7.5 sits a bit above it, closer to plasma pH. The range 7.1 to 7.2 sits closest to the textbook figure of 7.2.

Step 4: Final Answer.
The approximate pH of amniotic fluid is best represented by the range 7.1 to 7.2.
\[ \boxed{7.1-7.2} \]