Management of preterm labour

Nanomedicine strategies to improve therapeutic agents for the prevention and treatment of preterm birth and future directions

The World Health Organisation (WHO) estimates 15 million babies worldwide are born preterm each year, with 1 million infant mortalities and long-term morbidity in survivors. Whilst the past 40 years have provided some understanding in the causes of preterm birth, along with development of a range of therapeutic options, notably prophylactic use of progesterone or uterine contraction suppressants (tocolytics), the number of preterm births continues to rise. Existing therapeutics used to control uterine contractions are restricted in their clinical use due to pharmacological drawbacks such as poor potency, transfer of drugs to the fetus across the placenta and maternal side effects from activity in other maternal systems. This review focuses on addressing the urgent need for the development of alternative therapeutic systems with improved efficacy and safety for the treatment of preterm birth. We discuss the application of nanomedicine as a viable opportunity to engineer pre-existing tocolytic agents and progestogens into nanoformulations, to improve their efficacy and address current drawbacks to their use. We review different nanomedicines including liposomes, lipid-based carriers, polymers and nanosuspensions highlighting where possible, where these technologies have already been exploited e.g. liposomes, and their significance in improving the properties of pre-existing therapeutic agents within the field of obstetrics. We also highlight where active pharmaceutical agents (APIs) with tocolytic properties have been used for other clinical indications and how these could inform the design of future therapeutics or be repurposed to diversify their application such as for use in preterm birth. Finally we outline and discuss the future challenges.

Inhibition of Uterine Contractility by Thalidomide Analogs via Phosphodiesterase-4 Inhibition and Calcium Entry Blockade

Uterine relaxation is crucial during preterm labor. Phosphodiesterase-4 (PDE-4) inhibitors have been proposed as tocolytics. Some thalidomide analogs are PDE-4 inhibitors. The aim of this study was to assess the uterus-relaxant properties of two thalidomide analogs, methyl 3-(4-nitrophthalimido)-3-(3,4-dimethoxyphenyl)-propanoate (4NO2PDPMe) and methyl 3-(4-aminophthalimido)-3-(3,4-dimethoxyphenyl)-propanoate (4APDPMe) and were compared to rolipram in functional studies of spontaneous phasic, K⁺-induced tonic, and Ca²⁺-induced contractions in isolated pregnant human myometrial tissues. The accumulation of cAMP was quantified in HeLa cells. The presence of PDE-4B2 and phosphorylated myosin light-chain (pMLC), in addition to the effect of thalidomide analogs on oxytocin-induced pMLC, were assessed in human uterine myometrial cells (UtSMCs). Thalidomide analogs had concentration-dependent inhibitory effects on spontaneous and tonic contractions and inhibited Ca²⁺-induced responses. Tonic contraction was equipotently inhibited by 4APDPMe and rolipram (IC₅₀ = 125 ± 13.72 and 98.45 ± 8.86 µM, respectively). Rolipram and the thalidomide analogs inhibited spontaneous and tonic contractions equieffectively. Both analogs increased cAMP accumulation in a concentration-dependent manner (p < 0.05) and induced changes in the subcellular localization of oxytocin-induced pMLC in UtSMCs. The inhibitory effects of thalidomide analogs on the contractions of pregnant human myometrium tissue may be due to their PDE-4 inhibitory effect and novel mechanism as calcium-channel blockers.

Rates of preterm birth following antenatal maternal exposure to severe life events: a population-based cohort study

BACKGROUND

Preterm birth and other pregnancy complications have been linked to maternal stress during pregnancy. We investigated the association between maternal exposure to severe life events and risk of preterm birth.

METHODS

Mothers of all singleton live births (n = 1.35 million births) in Denmark between 1 January 1979 and 31 December 2002 were linked to data on their children, parents, siblings and partners. We defined exposure as death or serious illness in close relatives in the first or second trimesters or in the 6 months before conception. Log-linear binomial regression was used to estimate the effect of exposure on preterm birth, very preterm birth and extremely preterm birth.

RESULTS

There were 58 626 (4.34%) preterm births (<37 weeks), 11 732 (0.87%) very preterm births and 3288 (0.24%) extremely preterm births in the study cohort. Severe life events in close relatives in the 6 months before conception increased the risk of preterm birth by 16% (relative risk, RR = 1.16, [95% CI: 1.08-1.23]). Severe life events in older children in the 6 months before conception increased the risk of preterm birth by 23% (RR = 1.23, [95% CI: 1.02-1.49]) and the risk of very preterm birth by 59% (RR = 1.59, [95% CI: 1.08-2.35]).

CONCLUSIONS

Our population-based cohort study suggests that maternal exposure to severe life events, particularly in the 6 months before pregnancy, may increase the risk of preterm and very preterm birth.

Changes in neonatology: comparison of two cohorts of very preterm infants (gestational age <32 weeks): the Project On Preterm and Small for Gestational Age Infants 1983 and the Leiden Follow-Up Project on Prematurity 1996-1997

OBJECTIVE

To determine changes in peri- and neonatal care concerning neonatal mortality and morbidity by comparing 2 cohorts of very prematurely born infants (gestational age [GA] <32 weeks), 1 from the 1980s and 1 from the 1990s.

METHODS

The Leiden Follow-Up Project on Prematurity (LFUPP-1996/97), a regional, prospective study, includes all infants who were born alive after a GA <32 weeks in 1996 and 1997 in the Dutch health regions Leiden, The Hague, and Delft. The Project On Preterm and Small for Gestational Age Infants (POPS-1983), a national, prospective study from the presurfactant era, includes all liveborn infants <32 weeks' GA and/or <1500 g from 1983 (n = 1338). For comparison, infants from the POPS-1983 cohort with a GA <32 weeks from the same Dutch health regions were selected (n = 102).

RESULTS

The absolute number of preterm births in the study region increased by 30%: 102 in 1983 to on average of 133 in 1996-1997. Centralization of perinatal care improved: the percentage of extrauterinely transported infants decreased from 61% in 1983 to 35% in 1996-1997. A total of 182 (73%) of the LFUPP-1996/97 infants were treated antenatally with glucocorticosteroids compared with 6 (6%) of the POPS-1983 infants. A total of 112 (42%) of the LFUPP-1996/97 infants received surfactant. In-hospital mortality decreased from 30% in the 1980s to 11% in the 1990s. Mortality of the extremely preterm infants (<27 weeks) decreased from 76% to 33%. The incidence of respiratory distress syndrome remained the same: approximately 60% in both groups. Mortality from respiratory distress syndrome, however, decreased from 29% to 8%. The incidence of bronchopulmonary dysplasia increased from 6% to 19%. For the surviving infants, the average length of stay in the hospital and the mean number of NICU days stayed approximately the same ( approximately 67 days total admission time and 44 NICU days in both groups); including the infants who died, the mean NICU admission time increased from 27 days in the 1980s to 41 days in the 1990s. Equal percentages of adverse outcome (dead or an abnormal general condition) at the moment of discharge from hospital were found (+/-40% in both groups).

CONCLUSIONS

An increase in the absolute number of very preterm births in this study region was found, leading to a greater burden on the regional NICUs. Improvements in peri- and neonatal care have led to an increased survival of especially extremely preterm infants. However, increased survival has resulted in more morbidity, mainly bronchopulmonary dysplasia, at the moment of discharge from the hospital.

O uso de medicamentos na gravidez

O uso de medicamentos na gravidez é cada vez mais intenso, enquanto a prática médica volta-se para a incorporação do conceito de risco. Embora a tragédia da talidomida tenha marcado o início da reflexão sobre a ocorrência de efeitos adversos de medicamentos usados durante a gestação, as percepções dos prescritores, no âmbito da terapêutica medicamentosa na gravidez, ainda oscilam entre a certeza de que tudo é nocivo e a relativa crença de que tudo é seguro até que se prove o contrário. Faz-se necessária a produção de evidências que substanciem as condutas clínicas. O ensaio clínico randomizado é considerado a pedra angular do paradigma da medicina baseada em evidências. Sugerem-se os contextos nos quais a aplicação dos diversos tipos de pesquisa clínica seriam apropriados na gestação e ainda o emprego ampliado da farmacoepidemiologia para a construção de evidências nessa população, por meio de estudos analíticos, em especial a coorte. Entende-se que estes estudos, desde que executados com rigor metodológico, possam oferecer informação balizada, geradora de hipóteses, essenciais para a prática clínica.

Cyclooxygenase-1-selective inhibition prolongs gestation in mice without adverse effects on the ductus arteriosus

Preterm delivery is the leading cause of neonatal mortality and contributes significantly to infant morbidity. Classical cyclooxygenase (COX) inhibitors, such as indomethacin, which inhibit both COX-1 and COX-2, are effective for delaying premature labor, but their use is limited by serious complications to the fetus and neonate, including adverse effects on the ductus arteriosus (DA). Using isoform-selective inhibitors, we characterized the roles of the COX isoforms in the initiation of labor and the regulation of fetal and neonatal DA closure in mice. Chronic inhibition of COX-2 during pregnancy (gestation days 15-18) significantly increased neonatal mortality by preventing closure of the DA after birth, whereas acute COX-2 inhibition near the end of term (gestation day 18) constricted the fetal DA. In contrast, the inhibition of COX-1 during pregnancy lacked these prenatal and postnatal adverse effects on the DA and effectively delayed the initiation of full-term labor and LPS-induced preterm labor. These findings suggest that premature fetal DA closure or neonatal patent DA observed following indomethacin tocolysis in women may result from the inhibition of COX-2. Therefore, COX-1-selective inhibitors may provide effective treatment to delay preterm labor with fewer adverse effects on fetal or neonatal health than nonselective or COX-2-selective inhibitors.

Phenotypes of the COX-deficient mice indicate physiological and pathophysiological roles for COX-1 and COX-2

The development of mice deficient in either cyclooxygenase-1 (COX-1) or COX-2, as well as mice deficient in both COX isoforms, has provided models to elucidate the physiological and pathophysiological roles of these enzymes. The findings obtained with the COX-deficient mice suggest that COX-2 may be more important than COX-1 for supplying prostaglandins (PGs) to maintain tissue homeostasis. Furthermore, both isoforms may be involved in the development of diseases, such as inflammation and cancer. Therefore, the contribution of each isoform to the prevention or development of disease is more complex than originally described. Studies with the COX-deficient mice suggest that in addition to COX-2-selective inhibition, therapeutic advances may also be achieved with COX-1-selective inhibitors which lack gastrointestinal side effects.