A nurse is implementing intrauterine resuscitation. Which interventions are appropriate? (Select all that apply)

Crowning occurs during the second stage of labor when the widest diameter of the fetal head stretches the vulvar ring. It signifies that delivery is imminent and the head no longer recedes between contractions. This stage requires the nurse to support the perineal body to minimize maternal tissue trauma.

A. Shoulder delivery: This occurs after the head has been born and the fetus undergoes external rotation to align the shoulders with the pelvic outlet. Crowning specifically refers to the cephalic portion of the fetus. Shoulder delivery is a subsequent step in the mechanism of labor.

B. Full dilation: While crowning only happens after the cervix is 10 centimeters dilated, the term "crowning" refers to a visible physical landmark rather than a cervical measurement. Full dilation is the start of the second stage, whereas crowning occurs at its conclusion.

C. Placenta delivery: The expulsion of the placenta is the defining event of the third stage of labor. Crowing is a second-stage phenomenon involving the fetus. Placental delivery follows the birth of the neonate and involves uterine contraction to shear the placenta from the wall.

D. Fetal head visible: Crowning is precisely defined as the point when the fetal scalp remains visible at the vaginal opening even after a contraction has subsided. It indicates that the pelvic floor is fully distended. This is the final stage before the expulsion of the fetal head.

Fetal viability is the gestational age at which a neonate has a reasonable chance of extrauterine survival with intensive medical support. This threshold is primarily determined by the pulmonary maturation and the development of the terminal air sacs for gas exchange. Survival rates increase significantly as the fetus approaches the third trimester.

A. Around 20-25 weeks: This range represents the current limit of viability where neonatal intensive care can occasionally support life outside the womb. Success depends heavily on the administration of antenatal corticosteroids and advanced ventilatory technology. It marks the transition from pre-viable to potentially viable status.

B. At term: Viability is reached much earlier than the 37-week definition of full term. While term infants have the highest survival rates and lowest morbidity, the viability threshold is a much earlier milestone in fetal development. Defining viability as term would ignore the capabilities of modern neonatology.

C. At 30 weeks: By 30 weeks, most fetuses are considered highly viable with a survival rate often exceeding 90%. However, this is not the point where viability "begins," as many infants survive if born several weeks earlier. This choice overlooks the critical window between 23 and 26 weeks.

D. Begins at 12 weeks: At this early stage, the lungs are in the pseudoglandular phase and are incapable of any gas exchange. The fetus lacks the skin integrity and organ maturity necessary to survive outside the intrauterine environment. Survival is physiologically impossible at this gestational age.