**Core Concept**
The management of pain in pregnancy requires careful consideration of the potential risks and benefits of various medications. Nonsteroidal anti-inflammatory drugs (NSAIDs) are generally avoided due to the risk of premature closure of the ductus arteriosus and potential effects on fetal kidney function. However, some medications are considered safe for use in pregnancy, particularly in the context of acute pain management.

**Why the Correct Answer is Right**
One such medication is acetaminophen (paracetamol), which is considered safe for use in pregnancy. It is thought to act through the inhibition of cyclooxygenase enzymes (COX-1 and COX-2), leading to a reduction in prostaglandin synthesis and subsequent pain relief. Acetaminophen does not have the same risk of NSAID-induced fetal complications, such as premature ductal closure or renal impairment.

**Why Each Wrong Option is Incorrect**
* **Option A:** Ibuprofen is an NSAID, which carries a risk of fetal complications and is generally avoided in pregnancy.
* **Option B:** Aspirin is also an NSAID and is typically avoided in pregnancy due to its potential effects on fetal kidney function and ductal closure.
* **Option C:** Codeine is an opioid, which may be used in pregnancy for pain relief; however, it carries a risk of fetal respiratory depression and is not considered the first-line option.

**Clinical Pearl / High-Yield Fact**
When managing pain in pregnancy, it is essential to consider the gestational age and potential risks of various medications. Acetaminophen is a safe and effective option for acute pain management, but its use should be balanced with the need for ongoing fetal monitoring.

**Correct Answer:** D.