In a foetus, the insulin secretion begins by
**Core Concept**
Insulin secretion in the fetus is a critical aspect of glucose homeostasis, and understanding its onset is essential for fetal physiology.
**Why the Correct Answer is Right**
Insulin secretion in the fetus begins around 10-12 weeks of gestation due to the production of insulin by the fetal pancreas. This is triggered by the increase in fetal glucose levels, which stimulate the release of insulin from the beta cells of the islets of Langerhans. The fetal pancreas produces insulin in response to the high glucose levels, which helps to regulate fetal growth and development.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because insulin secretion does indeed begin in the fetus, and it's not related to the mother's diet or insulin levels.
**Option B:** This option is incorrect because insulin secretion in the fetus is not dependent on the mother's insulin levels, but rather on the fetal pancreas's ability to produce insulin in response to high glucose levels.
**Option C:** This option is incorrect because insulin secretion in the fetus begins before birth, not after birth.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that insulin secretion in the fetus is a critical aspect of fetal glucose homeostasis, and any disruption in this process can lead to fetal growth restriction or other complications.
**Correct Answer: C. Before birth.**