**Core Concept**
The presence of risk factors is crucial in identifying patients susceptible to preterm delivery. Preterm birth is a significant cause of neonatal morbidity and mortality, making it essential to recognize and manage potential risk factors. Fetal fibronectin (fFN) is a protein that helps maintain the bond between the fetal sac and the uterine lining.

**Why the Correct Answer is Right**
The absence of fetal fibronectin at less than 37 weeks of gestation is not a risk factor for preterm delivery. In fact, the presence of fFN in vaginal secretions between 24 and 34 weeks of gestation is a well-established risk factor for preterm labor. Its presence suggests that the fetal sac has separated from the uterine lining, increasing the likelihood of preterm birth. Conversely, the absence of fFN indicates a lower risk of preterm labor.

**Why Each Wrong Option is Incorrect**
**Option B:** A previous history of preterm baby is indeed a significant risk factor for preterm delivery. Women who have had a previous preterm birth are at increased risk of experiencing another preterm birth, making this option an incorrect distractor.

**Option C:** Asymptomatic cervical dilatation is a risk factor for preterm delivery. Cervical dilatation is a sign of cervical insufficiency, which can lead to preterm labor.

**Option D:** Chlamydial infection of the genital tract is a risk factor for preterm delivery. Chlamydia infection can cause inflammation and damage to the cervix, increasing the risk of preterm labor.

**Clinical Pearl / High-Yield Fact**
Chlamydial infection of the genital tract is a common cause of preterm labor, emphasizing the importance of screening for chlamydia in pregnant women and treating any infections promptly.

**Correct Answer Line**
✓ Correct Answer: A. Absence of fetal fibronectin at < 37 weeks