Which of the following is a known risk factor for preterm labor?

Polyhydramnios, which refers to an excessive accumulation of amniotic fluid in the uterus, is indeed a known risk factor for preterm labor. The presence of too much fluid can lead to increased uterine distension, which may trigger contractions and consequently result in premature delivery.

Conditions like polyhydramnios can also be associated with other complications, such as fetal abnormalities or maternal health issues, which may further increase the likelihood of preterm labor. Understanding the implications of polyhydramnios is important in prenatal care, as managing this condition may help mitigate the risk of going into labor prematurely.

In contrast, while dehydration and advanced maternal age can be associated with various complications in pregnancy, they are not as directly compelling as polyhydramnios concerning the specific mechanism leading to preterm labor. Cervical biopsy, while it may be indicated in certain circumstances, is not commonly recognized as a direct risk factor for preterm labor compared to polyhydramnios.