A 23-year-old woman, gravida 2 para 1, with poorly controlled type 1 diabetes and hypothyroidism comes to the hospital with preterm, premature rupture of membrane at 30 weeks' gestation. Her medications include prenatal vitamins and insulin. Vital signs are normal and examination shows clear vaginal discharge. The patient's cervix is closed and she has no uterine contractions. Laboratory results are as follows: Which of the following medications has the greatest positive impact on fetal survival?

Question

A 23-year-old woman, gravida 2 para 1, with poorly controlled type 1 diabetes and hypothyroidism comes to the hospital with preterm, premature rupture of membrane at 30 weeks' gestation.  Her medications include prenatal vitamins and insulin.  Vital signs are normal and examination shows clear vaginal discharge.  The patient's cervix is closed and she has no uterine contractions.  Laboratory results are as follows:  Which of the following medications has the greatest positive impact on fetal survival?

Quizplus · Accepted Answer

In the terminal saccular stage of lung development, the type II pneumocytes produce pulmonary surfactant, a lipoprotein complex rich in phospholipids, most notably dipalmitoylphosphatidylcholine (DPPC, a type of lecithin). This surfactant decreases alveolar surface tension by creating a lipid-rich monolayer that separates alveolar gas from the underlying aqueous fluid. The phenomenon prevents atelectasis and end-expiratory collapse and increases pulmonary compliance. In a fetus, efflux of lung fluid into amniotic fluid enables testing of markers of lung maturity. Until 33 weeks gestation, the lecithin and sphingomyelin levels are about equal. After 33 weeks, the lecithin levels rise dramatically compared to sphingomyelin. A lecithin-to-sphingomyelin ratio >1.9 is indicative of mature fetal lungs. Premature infants born at <32 weeks gestation are at significant risk of surfactant deficiency. Corticosteroids (eg, betamethasone, dexamethasone) have the greatest effect on increasing surfactant production by accelerating maturation of type II pneumocytes. They are administered to patients at risk for preterm labor (eg, preterm premature rupture of membranes) to decrease the risk of respiratory distress syndrome and mortality. (Choice B) Uncontrolled maternal hyperglycemia causes fetal hyperinsulinemia and inhibits the maturational effects of cortisol and the production of surfactant proteins. Infants of these mothers can develop respiratory distress syndrome. Although corticosteroids cause temporary hyperglycemia, the beneficial effects of maternal steroid administration on surfactant production and eventual reduction of mortality far outweigh this side effect. (Choice C) In pregnancies at risk for preterm delivery, antenatal administration of magnesium sulfate has been shown to decrease the risk for cerebral palsy. While cerebral palsy can result in permanent neurologic disability, impaired lung function is a more common cause of death in premature infants. (Choices D and E) Nifedipine and terbutaline are medications used for inhibition of preterm labor (tocolysis). Nifedipine is a calcium channel blocker and results in myometrial relaxation by inhibition of myosin light-chain kinase-mediated phosphorylation. Terbutaline is a β-sympathomimetic that increases intracellular cAMP formation in myometrial cells. This inhibits myosin light-chain kinase and relaxes the smooth muscle. Neither drug directly affects fetal lung maturity. Educational objective: Both maternal and fetal cortisol help to accelerate fetal lung maturation by stimulating surfactant production. Betamethasone or dexamethasone is administered to pregnant women at risk of premature delivery to prevent neonatal respiratory distress syndrome. __________ References: Prevention of preterm delivery. (http://www.ncbi.nlm.nih.gov/pubmed/17671256) Antenatal corticosteroids for accelerating fetal lung maturation for women at risk of preterm birth. (http://www.ncbi.nlm.nih.gov/pubmed/16856047)

A 23-Year-Old Woman, Gravida 2 Para 1, with Poorly Controlled