Amy Merlino

Magnesium sulfate for preterm labor and preterm birth.

Approximately half of the more than 500,000 preterm births each year result from preterm labor. Tocolytic therapy continues to be the focus of treatment of these women. Although a variety of tocolytics are used in clinical practice, magnesium sulfate remains one of the most commonly used agents. Magnesium sulfate has also been the focus of recent research for its potential neuroprotective effects for neonates born preterm. Evaluation of 19 randomized clinical trials reveals that magnesium sulfate tocolysis does not reduce the frequencies of delivery within 48 hours, 7 days, or early/late preterm birth, and is not associated with improvements in newborn morbidities or mortality. No other tocolytic class resulted in improved newborn outcomes when compared with magnesium sulfate tocolysis. We conclude that it is appropriate to withhold tocolysis with magnesium sulfate or other agents from women presenting in preterm labor as newborn benefit has not been demonstrated with such treatment. If initiated to achieve time for antenatal corticosteroid administration, or for other acute reasons, treatment can be discontinued once these goals have been achieved or if labor subsides before then. Because brief pregnancy prolongation is unlikely to improve newborn outcomes after corticosteroid administration has been completed, it is appropriate to withhold magnesium sulfate tocolysis from women with recurrent preterm labor thereafter. If magnesium sulfate is given for neuroprotection, a protocol from one of the three major trials that have demonstrated benefits should be used.

Nuclear progesterone receptor expression in the human fetal membranes and decidua at term before and after labor

To explore how progesterone affects human pregnancy, we identified the progesterone target cells within the fetal membranes (amnion, chorion, and decidua) at term by assessing the extent of expression and localization of the nuclear progesterone receptors, progesterone receptor-A and progesterone receptor-B. Fetal membranes (separated into amnion and chorion—decidua) were obtained after term cesarean deliveries performed before (n = 7) and after (n = 7) labor onset. Nuclear progesterone receptor expression was determined by the abundance of nuclear progesterone receptor mRNAs (by quantitative reverse transcriptase—polymerase chain reaction) and proteins (by western blotting). Localization of nPRs was determined by immunohistochemistry. Progesterone receptor-A and progesterone receptor-B mRNA and protein levels were highest in the chorion—decidua and did not change in association with labor. Nuclear progesterone receptor mRNAs and proteins were barely detectable in amnion. Nuclear progesterone receptor immunostaining was detected only in the nucleus of decidual cells. These findings suggest that the decidua, and not the amnion and chorion, is a direct target for nuclear progesterone receptor—mediated progesterone actions during human pregnancy.