**Core Concept**
Ortolani's test is a physical examination technique used to assess for developmental dysplasia of the hip (DDH) in infants. This test involves gently abducting and then applying gentle pressure to the femoral head to assess for any instability or dislocation of the hip joint.

**Why the Correct Answer is Right**
The Ortolani test is specifically performed in infants between 4-12 weeks of age, when the femoral head is still relatively large and can be easily palpated. This age range allows for the detection of hip instability or dislocation, which is a common issue in infants with DDH. The test is performed with the infant lying on their back, and the examiner gently abducts the hip joint while applying gentle pressure to the femoral head.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Ortolani's test is not typically performed in preterm infants, as their hip joints are still developing and may not be amenable to this examination.
**Option B:** This option is incorrect because Ortolani's test is not a diagnostic test for hip fractures, which require imaging studies such as X-rays or CT scans for diagnosis.
**Option C:** This option is incorrect because Ortolani's test is not a screening test for hip conditions in adults, who typically have fully developed hip joints and may require different diagnostic approaches.

**Clinical Pearl / High-Yield Fact**
A key clinical pearl is that Ortolani's test should only be performed by a qualified healthcare provider, as improper technique can lead to false-negative results or even dislocation of the hip joint.

**Correct Answer: C. In infants between 4-12 weeks of age.**