Final answer:
The second stage of labor begins when the cervical canal has fully dilated to about 10 cm (3.9 in.) in width, allowing the baby to descend into the birth canal for delivery. The option (B) is correct.
Step-by-step explanation:
The beginning of the second stage of labor is marked by the completion of cervical dilation, which is when the cervical canal has dilated to about 10 cm (3.9 in.) in width. At this point, the baby descends (usually headfirst) through the now fully dilated cervix into the birth canal. The mother actively participates by bearing down during contractions, which aids in the expulsion of the newborn. This stage continues until the baby has fully exited the vagina.
There are solid indicators for each stage of labor. The first stage involves the thinning and dilation of the cervix, and the breaking of the amniotic sac may occur at any point during this stage or even before labor begins. However, it is the complete dilation of the cervix that signifies the transition to the second stage. The final stage involves the delivery of the afterbirth, which includes the placenta and associated fetal membranes, following the birth of the baby. Therefore, option (B) is correct.
This question is not complete, Here I am attaching the complete question:
What marks the beginning of the second stage of labor?
A. The baby's head moving through the cervix
B. The baby's descent from the uterus to the birth canal
C. The onset of contractions
D. The breaking of the amniotic sac