Maternity Nursing Q 203
To prevent preterm labor from progressing, drugs are usually prescribed to halt the labor. The drugs commonly given are:
A. Magnesium sulfate and terbutaline
B. Prostaglandin and oxytocin
C. Progesterone and estrogen
D. Dexamethasone and prostaglandin
Correct Answer: A. Magnesium sulfate and terbutaline
Magnesium sulfate acts as a CNS depressant as well as a smooth muscle relaxant. Terbutaline is a drug that inhibits the uterine smooth muscles from contracting. On the other hand, oxytocin and prostaglandin stimulate the contraction of smooth muscles.
Option B: Prostaglandins act to mediate cervical ripening and to stimulate uterine contractions and indirectly to increase fundally dominant myometrial contractility by up-regulation of gap junctions, oxytocin, and arginine vasopressin receptors, and synchronizations of contractions. Oxytocin receptor antagonists (ORA), such as atosiban, have been specially developed for the treatment of preterm labor. ORA has been proposed as effective tocolytic agent for women in preterm labor to prolong pregnancy with fewer side effects than other tocolytic agents.
Option C: In the first trimester, progesterone produced by the corpus luteum is critical to the maintenance of early pregnancy until the placenta takes over this function at 7 to 9 weeks of gestation, hence its name (pro-gestational steroidal ketone). Indeed, removal of the source of progesterone (the corpus luteum) or administration of a progesterone receptor antagonist readily induces abortion before 7 weeks (49 days) of gestation. Estrogen is one of the key hormones of labor. As the labor comes closer, the high levels of estrogens stimulate many different processes necessary for delivery. As the levels of estrogen rise, an increase in oxytocin receptors in the uterus is stimulated, as well as prostaglandins in the cervix.
Option D: Dexamethasone accelerates maturation of fetal lungs, decreases the number of neonates with respiratory distress syndrome, and improves survival in preterm delivered neonates. Optimal gestational age for use of dexamethasone therapy is 31 to 34 weeks of gestation.