Preterm labour and delivery

Abstract

Preterm birth is a major cause of perinatal morbidity and mortality. It accounts for 5-10% of all births, and any treatment to prevent it could have a profound effect on neonatal outcome in both human and economic terms. The pathogenesis of both term and preterm birth remain poorly understood. Our ability to predict those at risk of preterm labour is also inaccurate, despite the creation of scoring systems, uterine activity monitoring, cervical ultrasound and several biochemical markers. Current drug therapies for preterm labour have not been shown in randomised controlled trials to significantly affect perinatal morbidity and mortality. Furthermore, most are associated with significant maternal or fetal side effects. Nitric oxide (NO) is a potent smooth muscle relaxant, produced when NO synthase acts on the amino acid L-arginine. Its presence has been demonstrated in human myometrium. We have conducted an observational study which has suggested that glyceryl trinitrate (GTN), and NO donor, may be effective in prolonging gestation. A randomised trial comparing GTN to intravenous ritodrine is currently recruiting patients; results will be available in the Spring of 1997. Few side effects have so far been encountered. Evidence suggests that GTN, an NO donor, should be a safe and effective tocolytic and early observations are encouraging; randomised trials currently underway should determine the significance of this breakthrough in the management of preterm labour.

Nitric oxide donors in pregnancy: fetomaternal hemodynamic effects induced in mild pre‐eclampsia and threatened preterm labor

“…In our study, we opted for sublingual administration of glyceryl trinitrate as a NO donor because of its rapid action, its short plasma half-life, and its known lack of adverse effects on the fetus. Furthermore, glyceryl trinitrate has tocolytic properties; the decreased synthesis of NO is associated with initiation of labor in animals 23 and the benefits of NO donors in the treatment of preterm labor have been demonstrated in recent studies [22][23][24] . In the present study we compared pregnancies complicated by threatened preterm labor to the preeclamptic groups, as approved by the ethical committee of our Center.…”

“…The effect of glyceryl trinitrate on maternal blood pressure in pre-eclamptic patients is known, but the ability of this drug to release NO into the placental circulation of preeclamptic patients appears to reflect the placental vascular reserve. The lack of NO in the pre-eclamptic state involves a reduction of the vasodilatory tone of the placental circulation [23][24][25][26][27][28][29] and this, initially, may reduce blood flow in some regions of the placenta. The subsequent and continuous poor perfusion of the placenta may cause irreversible vascular damage 14 .…”

Role of nitric oxide in the uterus and cervix: Implications for the management of labor

“…Although, it was concluded that this treatment can arrest preterm labor in women, it must be remembered that this study was small (n = 13), and observational in nature, lacking an appropriate control group. Based on this observational study, a multicenter, randomized, controlled trial was established at Kings College Hospital [3,4,31]. This randomized study covered the gestational range of 24-35 weeks and compared GTN with the conventional ß-mimetic therapy ritodrine.…”

Oxytocics reverse the tocolytic effect of glyceryl trinitrate on the human uterus

“…The drugs currently used in the treatment of preterm labour include magnesium sulphate, calcium channel blockers, beta‐adrenoceptor agonists and prostaglandin synthetase inhibitors. However, most of the available drugs lack uterine selectivity and have adverse side effects for the woman and the infant 1 . Glyceryl trinitrate (10 mg patches transdermally) in an uncontrolled study was reported to be effective in inhibiting preterm labour and prolonging gestation 2 .…”