Post-term pregnancy is the pregnancy which continues beyond:
**Core Concept**
Post-term pregnancy is a condition where the gestational age exceeds the normal duration of pregnancy, typically beyond 42 weeks of gestation. This condition is also known as postdate pregnancy. The exact cause of post-term pregnancy is often unknown, but it is believed to be related to hormonal and genetic factors.
**Why the Correct Answer is Right**
The correct answer is **42 weeks** because this is the standard definition of post-term pregnancy. After 42 weeks, the risk of complications increases, including fetal distress, meconium aspiration, and stillbirth. The placenta undergoes changes after 42 weeks, which can lead to a decrease in fetal growth and an increase in fetal stress.
**Why Each Wrong Option is Incorrect**
**Option A:** _40 weeks_ is the standard definition of full-term pregnancy, not post-term.
**Option B:** _38 weeks_ is considered early term, and pregnancies before 39 weeks are generally not considered post-term.
**Option C:** _45 weeks_ is not a standard definition of post-term pregnancy; it is actually considered postdate or post-term, but not the correct answer.
**Clinical Pearl / High-Yield Fact**
It is essential to note that post-term pregnancies are associated with an increased risk of stillbirth, and delivery should be considered between 41 and 42 weeks to minimize this risk.
**Correct Answer: D. 42 weeks**