Prevention of recurrent preterm delivery by 17 alpha-hydroxyprogesterone caproate

Mechanisms of progesterone action in inhibiting prematurity

Progesterone is a steroid hormone that plays an integral role in each step of human pregnancy. In early pregnancy, 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 steroid hormone). The role of progesterone in later pregnancy, however, is less clear. It has been proposed that progesterone may be important in maintaining uterine quiescence in the latter half of pregnancy by limiting the production of stimulatory prostaglandins and inhabiting the expression of contraction-associated protein genes within the myometrium. Although systemic progesterone withdrawl may not correlate directly with the onset of labour in humans, there is increasing evidence to suggest that progesterone exerts its influence indirectly via a 'functional' withdrawl at the level of the uterus. The molecular mechanisms by which progesterone is able to maintain uterine quiescence and prevent preterm birth in some high-risk women are not clear. Six putative mechanisms have been proposed in the literature by both US and other investigators and are explored in this review.

Medical cost savings associated with 17 alpha-hydroxyprogesterone caproate

OBJECTIVE

This study was undertaken to assess the impact of 17 alpha hydroxyprogesterone caproate treatment on future medical costs for expectant mothers with a prior spontaneous preterm birth.

STUDY DESIGN

Data on the costs of preterm birth were combined with published data on the effectiveness of 17 alpha hydroxyprogesterone caproate to produce estimates of the effect of treatment on expected future direct medical costs. These estimates were compared with an estimate of the cost of a typical 17 alpha hydroxyprogesterone caproate treatment regimen to estimate the net savings per treated woman.

RESULTS

Treatment is estimated to reduce initial neonatal hospitalization costs by 3800 dollars per woman treated with 17 alpha hydroxyprogesterone caproate. Expected lifetime medical costs (discounted) of treated infants are estimated to decline 15,900 dollars.

CONCLUSIONS

Treating expectant mothers with a prior spontaneous preterm birth with 17 alpha hydroxyprogesterone caproate generates future medical cost savings that substantially exceed the cost of treatment. If this population were universally treated with 17 alpha hydroxyprogesterone caproate, discounted lifetime medical costs of their offspring could be reduced by more than 2.0 billion dollars annually.

Increased recurrence of preterm delivery with early cessation of 17-alpha-hydroxyprogesterone caproate

OBJECTIVE

The purpose of this study was to identify the effect of early cessation of 17-alpha-hydroxyprogesterone caproate (17P) on the incidence of spontaneous recurrent preterm delivery (PTD).

STUDY DESIGN

Retrospective analysis of data from women who were enrolled for outpatient 17P administration between January 2004 and May 2006 included women with previous PTD and current singleton pregnancy who were beginning weekly 17P injections (250 mg intramuscularly) at 16-20.9 weeks. The study group was comprised of patients who were electively terminating 17P at <32.0 weeks and who delivered >10 days from the last injection. The control group consisted of patients who received weekly 17P injections until PTD or 36.9 weeks of gestation. The primary study outcome was the rate of recurrent spontaneous PTD.

RESULTS

Study group patients were significantly more likely to have spontaneous recurrent PTD at <37 weeks of gestation (48.1% vs 33.3%; P = .011), at <35 weeks of gestation (30.9% vs 14.0%; P < .001), and at <32 weeks of gestation (16.0% vs 7.0%; P = .020).

CONCLUSION

Early cessation of 17P treatment is associated with an increased risk for spontaneous recurrent PTD.

Low birth weight in the United States

Pregnancy outcomes in the United States and other developed countries are considerably better than those in many developing countries. However, adverse pregnancy outcomes are generally more common in the United States than in other developed countries. Low-birth-weight infants, born after a preterm birth or secondary to intrauterine growth restriction, account for much of the increased morbidity, mortality, and cost. Wide disparities exist in both preterm birth and growth restriction among different population groups. Poor and black women, for example, have twice the preterm birth rate and higher rates of growth restriction than do most other women. Low birth weight in general is thought to place the infant at greater risk of later adult chronic medical conditions, such as diabetes, hypertension, and heart disease. Of interest, maternal thinness is a strong predictor of both preterm birth and fetal growth restriction. However, in the United States, several nutritional interventions, including high-protein diets, caloric supplementation, calcium and iron supplementation, and various other vitamin and mineral supplementations, have not generally reduced preterm birth or growth restriction. Bacterial intrauterine infections play an important role in the etiology of the earliest preterm births, but, at least to date, antibiotic treatment either before labor for risk factors such as bacterial vaginosis or during preterm labor have not consistently reduced the preterm birth rate. Most interventions have failed to reduce preterm birth or growth restriction. The substantial improvement in newborn survival in the United States over the past several decades is mostly due to better access to improved neonatal care for low-birth-weight infants.

Preterm Labour and Birth: A Survey of Clinical Practice Regarding Use of Tocolytics, Antenatal Corticosteroids, and Progesterone

OBJECTIVES

We wished to determine prescribing practices of obstetricians in Canada regarding tocolytics, antenatal corticosteroids, and progesterone for women at increased risk of preterm labour and birth, and to determine whether these practices changed between 1997-98 and 2004.

METHODS

Two cross-sectional surveys of Canadian obstetricians were conducted. The initial survey was in 1997-98 (N = 1313); the follow-up survey was in 2004 (N = 1508).

RESULTS

Response rates were 46.4% in 1997-98 and 43.3% in 2004. Most respondents reported that they prescribed tocolytics to women with signs and symptoms of preterm labour (97.4% in 1997-98; 92.2% in 2004; P < 0.001) but use had decreased. In 1997-98, 20.0% of respondents used tocolytics for > 48 hours during one course of treatment, whereas in 2004, only 9.6% did this (P = 0.06). The tocolytic prescribed most frequently was magnesium sulphate in 1997-98 (40.6% of respondents), whereas in 2004, it was indomethacin (47.5% of respondents). The use of repeat courses of antenatal corticosteroids decreased from 72.9% in 1997-98 to 18.7% in 2004 (P < 0.001). In 2004, only a few respondents (7.0%) prescribed progesterone for women at increased risk of preterm birth.

CONCLUSIONS

Most Canadian obstetricians continue to use tocolytics for women in preterm labour, although use has decreased over time, and the most frequently prescribed tocolytic has changed from magnesium sulphate to indomethacin. The use of repeat courses of antenatal corticosteroids decreased substantially during this time, and in 2004, progesterone was not in frequent use.

Gestational age correlates to genotype in girls with CYP21 deficiency

CONTEXT

The mechanisms behind onset of labor and prolongation of pregnancy are not fully understood, but steroid hormones are thought to contribute. 17-Hydroxyprogesterone has been shown to prolong pregnancy in humans. Male fetuses have been reported to have longer gestation than females.

OBJECTIVE

The objective of the study was to investigate whether severity of 21-hydroxylase gene (CYP21) deficiency in fetuses with congenital adrenal hyperplasia (CAH) correlates with length of pregnancy.

DESIGN AND SUBJECTS

The gestational age (GA) of a cohort of CAH patients born between 1978 and 2004 was studied retrospectively. The GA was correlated to the severity of disease indicated by CYP21 genotype in 114 patients. The results were compared with respect to sex and the normal Swedish population data.

RESULTS

In female fetuses with CAH, we found a correlation between GA and CYP21 genotype. Females with the most severe form of the disease, null mutation, had the longest GA and differed significantly from the normal population. No difference between the sexes was detected for fetuses with CAH as a group. There were no significant differences between CYP21 genotype groups for males.

CONCLUSIONS

Female patients with severe CYP21 deficiency had longer GA than patients with the milder form of the disease, indicating that androgen excess, increased 17-hydroxyprogesterone levels, or cortisol deficiency or a combination of these factors is of importance for prolongation of pregnancy. The same correlation was not observed for male patients. The results of this study support the notion that steroid hormones affect the prolongation of pregnancy or onset of labor or both.

Human Homologs of the Putative G Protein-Coupled Membrane Progestin Receptors (mPRα, β, and γ) Localize to the Endoplasmic Reticulum and Are Not Activated by Progesterone

The steroid hormone progesterone exerts pleiotrophic functions in many cell types. Although progesterone controls transcriptional activation through binding to its nuclear receptors, it also initiates rapid nongenomic signaling events. Recently, three putative membrane progestin receptors (mPRα, β, and γ) with structural similarity to G protein-coupled receptors have been identified. These mPR isoforms are expressed in a tissue-specific manner and belong to the larger, highly conserved family of progestin and adiponectin receptors found in plants, eubacteria, and eukaryotes. The fish mPRα has been reported to mediate progesterone-dependent MAPK activation and inhibition of cAMP production through coupling to an inhibitory G protein. To functionally characterize the human homologs, we established human embryonic kidney 293 and MDA-MB-231 cell lines that stably express human mPRα, β, or γ. For comparison, we also established cell lines expressing the mPRα cloned from the spotted seatrout (Cynoscion nebulosus) and Japanese pufferfish (Takifugu rubripes). Surprisingly, we found no evidence that human or fish mPRs regulate cAMP production or MAPK (ERK1/2 or p38) activation upon progesterone stimulation. Furthermore, the mPRs did not couple to a highly promiscuous G protein subunit, Gαq5i, in transfection studies or provoke Ca2+ mobilization in response to progesterone. Finally, we demonstrate that transfected mPRs, as well as endogenous human mPRα, localize to the endoplasmic reticulum, and that their expression does not lead to increased progestin binding either in membrane preparations or in intact cells. Our results therefore do not support the concept that mPRs are plasma membrane receptors involved in transducing nongenomic progesterone actions.

Elective cesarean section and induction and their impact on late preterm births

At all gestational ages, the risks of continuing a pregnancy must be carefully balanced against the risks of delivery and the associates risk of prematurity. This concept is of increasing importance in late preterm pregnancy when medical or obstetric complications frequently warrant delivery and the risk of prematurity persists. Given that morbidity exists for infants born between 34 and 37 weeks gestations, efforts should be focused on minimizing the late preterm birth rate and at improving the outcome of these infants. Published guidelines outlining the appropriate timing of elective induction of labor and elective Cesarean section should be closely followed to avoid unintended iatrogenic prematurity. Research should continue to investigate the etiology of spontaneous preterm deliveries and aim to develop strategies of primary prevention. The incidence and etiology of iatrogenic late preterm birth should also be further investigated and alternative management strategies should be considered. To gain information about the impact of elective delivery on late preterm births, the data collected from birth records should reflect the changing obstetric practices in the United States and be revised to include specific information on elective deliveries.

Hormone Profiles and Treatments in the Late Pregnant Mare

Evaluation of hormone profiles in late pregnancy is one of the major determinants of fetoplacental compromise in equine clinical practice. Use of hormone therapies is subjective and reflects, to a large extent, our lack of understanding about the endocrine relations between the mare, placenta, and fetus. This article describes the normal endocrine events in late gestation, the abnormal hormone patterns associated with fetoplacental dysfunction, and the hormone interventions that are currently used or could be used to improve pregnancy outcome.

The impact of multiple gestations on late preterm (near-term) births

Multiple pregnancies currently account for 3% of all births in the United States but are disproportionately responsible for larger rates of prematurity and significant neonatal morbidity. The mean birth age for most multi-fetal pregnancies occurs during the late preterm period when both spontaneous preterm labor and iatrogenic premature birth because of obstetrical or maternal complications are common. Multiples pose numerous unique challenges, emphasizing the significant impact of plurality on late preterm births.

The preterm parturition syndrome

The implicit paradigm that has governed the study and clinical management of preterm labour is that term and preterm parturition are the same processes, except for the gestational age at which they occur. Indeed, both share a common pathway composed of uterine contractility, cervical dilatation and activation of the membranes/decidua. This review explores the concept that while term labour results from physiological activation of the components of the common pathway, preterm labour arises from pathological signalling and activation of one or more components of the common pathway of parturition. The term "great obstetrical syndromes" has been coined to reframe the concept of obstetrical disease. Such syndromes are characterised by: (1) multiple aetiology; (2) long preclinical stage; (3) frequent fetal involvement; (4) clinical manifestations that are often adaptive in nature; and (5) gene-environment interactions that may predispose to the syndromes. This article reviews the evidence indicating that the pathological processes implicated in the preterm parturition syndrome include: (1) intrauterine infection/inflammation; (2) uterine ischaemia; (3) uterine overdistension; (4) abnormal allograft reaction; (5) allergy; (6) cervical insufficiency; and (7) hormonal disorders (progesterone related and corticotrophin-releasing factor related). The implications of this conceptual framework for the prevention, diagnosis, and treatment of preterm labour are discussed.

Diagnosis and Treatment of Equine Placentitis

Equine placentitis is a complex disease that has devastating consequences for horse owners. Placentitis is a significant cause of foal loss annually. Prompt diagnosis and treatment of the disease are paramount for survival of the affected neonate. This article discusses current information on pathogenesis of the disease as well as diagnostic and therapeutic options.

Progesterone for the prevention of preterm birth: A critical evaluation of evidence

A systematic review of the literature identified nine randomised trials that evaluated the effects of progestational agents in the prevention of preterm delivery. These studies were of variable quality. Meta-analyses showed reductions in delivery rates before 37 weeks (OR 0.42, 95% CI 0.31-0.57) and 34 weeks (OR 0.51, 95% CI 0.34-0.77) as well as in respiratory distress syndrome (OR 0.55, 95% CI 0.31-0.96) with progestational agents. A cumulative meta-analysis showed that the treatment benefit for the outcome of delivery before 37 weeks exceeded the conventional level of statistical significance in 1975 (p<0.01); by 1985, the p-value was <0.001, and by 2003, it was <0.0001. Another cumulative meta-analysis in which the studies were added to the pooled analysis by decreasing quality score showed significant benefit even when the analysis was limited to just the highest quality trials (OR 0.47, 95% CI 0.33, 0.66, p<0.0001). An exploration of the applicability of the effects across various baseline risks using a L'abbe plot found that the benefit was consistent across a range of risks. A comprehensive review of both trial and observational data on harm did not show any demonstrable evidence of harm to mother and baby. Women at high risk of preterm birth should be recommended progestational agent therapy.

Feto-placental communication system with the myometrium inpregnancy and parturition: the role of hormones, neurohormones, inflammatory mediators, and locally active factors

Pregnancy is a unique condition in which the conceptus is allowed to implant, survive, develop, and reach a considerable organ growth and maturation within the maternal body despite the fact that it is half genetically different from the mother. Moreover, it deeply influences the overall endocrine, metabolic, and immunological functions of the recipient mother. These objectives are accomplished through the establishment of several communication systems in which a large array of substances produced by the feto-placental unit reach specific maternal target organs and/or systems and modulate their function. The myometrium is a fundamental reproductive tissue involved in pregnancy maintenance as well as in labor onset and progression and is a potential target organ for such a communication system. An appropriate regulation of myometrial function is a key condition required for pregnancy to develop physiologically until full term is reached and for labor to start. Emerging experimental and clinical evidence suggests that a very complex feto-placental biomolecular communication system exists with the myometrium and is actively operative in the control of myometrial contractility in pregnancy and parturition through the production of a continuously increasing number of substances with endocrine, paracrine, and immunoregulatory actions.

Tumor necrosis factor-alpha and interleukin-1beta regulate interleukin-8 expression in third trimester decidual cells: implications for the genesis of chorioamnionitis

Chorioamnionitis is associated with intense neutrophil infiltration of the decidua. We therefore determined whether chorioamnionitis enhances decidual interleukin-8 (IL-8) expression and examined cytokine-regulated decidual IL-8 expression. Decidua from chorioamnionitis-complicated pregnancies, but not term controls, displayed marked IL-8 immunohistochemical staining and a dense neutrophil infiltrate. Reverse transcriptase-polymerase chain reaction of microdissected decidual cells identified IL-8 mRNA, confirming decidual synthesis of IL-8. Confluent leukocyte-free term decidual cells were primed with 10(-8) mol/L estradiol (E2) or E2 + 10(-7) mol/L medroxyprogesterone acetate to mimic the steroidal milieu of pregnancy. Compared with cultures maintained in E2 alone, E2 + medroxyprogesterone acetate neither significantly affected IL-8 levels nor altered the response to the cytokines. The addition of 1.0 ng/ml tumor necrosis factor-alpha (TNF-alpha) or interleukin-1 beta (IL-1beta) increased IL-8 secretion levels by 236.6 +/- 51.4- and 1062.6 +/- 254.3-fold, respectively (n = 8, mean +/- SEM, P < 0.05), as measured by enzyme-linked immunosorbent assay. Concentration-response studies revealed that 0.01 ng/ml TNF-alpha and IL-1beta elevated IL-8 output by 10- and 100-fold, respectively. Western blotting confirmed these results, and quantitative reverse transcriptase-polymerase chain reaction demonstrated parallel changes in mRNA levels. In conclusion, IL-8 is strongly expressed in term decidua during chorioamnionitis, and TNF-alpha and IL-1beta enhance IL-8 expression in term decidual cells, suggesting that these cytokines are important regulators of chorioamnionitis-related decidual neutrophil infiltration.

Anti-inflammatory interventions in pregnancy: now and the future

A growing body of evidence implicates inflammatory pathways in adverse reproductive outcomes. This expanding evidence suggests that anti-inflammatory interventions may hold promise in reducing the maternal and neonatal morbidities and mortalities associated with these obstetrical complications. Preterm birth, preeclampsia, pregnancy loss and adverse neonatal outcomes have all been associated with the activation of inflammatory pathways during pregnancy. Because of the number of observational human studies, as well as animal models of preterm birth, the mechanisms by which inflammation may promote preterm parturition and adverse effects on the fetus are beginning to be elucidated. Although the future use of anti-inflammatory interventions in this context holds significant promise, much research is still warranted. Only when the pathogenesis of obstetrical complications is more fully understood can meaningful therapeutic interventions become a realistic goal.

Progesterone reduces lipopolysaccharide induced interleukin-6 secretion in fetoplacental chorionic arteries, fractionated cord blood, and maternal mononuclear cells

OBJECTIVE

The purpose of this study was to characterize effect of progesterone (P4) on interleukin-6 (IL-6) production by fetoplacental artery explants, fetal granulocytes, and fetal and maternal mononuclear cells.

STUDY DESIGN

Arteries and cord blood were obtained from 5 term pregnancies undergoing repeat cesarean section. Maternal blood was obtained from another 6 women at 16 to 20 weeks' gestation. Tissues were fractionated by dissection or Histopaque gradient. Specimens were incubated in physiologic media then exposed to lipopolysaccharide (LPS) or P4 alone, or pretreated with P4 and then exposed to LPS. Samples were evaluated for IL-6 by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Arteries and fetal and maternal mononuclear cells exposed to LPS increased IL-6 secretion by 9-, 27-, and 29-fold, respectively. P4 pretreatment blocked LPS induction of IL-6. Fetal granulocytes did not increase IL-6 production in response to LPS exposure.

CONCLUSION

LPS induces IL-6 in arteries and fetal and maternal mononuclear cells. P4 pretreatment significantly blocks this effect in these cell populations, suggesting possible targets for anti-inflammatory actions of P4 in prevention of preterm birth.

Impact of the recent randomized trials on the use of progesterone to prevent preterm birth: a 2005 follow-up survey

OBJECTIVE

The purpose of this study was to determine whether current attitudes regarding the use of progesterone to prevent preterm birth have changed since our last survey in 2003.

STUDY DESIGN

We mailed a 20 question survey to 1264 board certified Maternal-Fetal Medicine specialists in the United States between February and March of 2005 asking about their use and attitudes regarding progesterone to prevent preterm birth.

RESULTS

Five hundred and seventy-two surveys were returned (response rate of 45%). In 2005, 67% of respondents used progesterone to prevent SPTB, compared to 38% in 2003 (P < .001). Among users, 38% recommended progesterone for indications other than previous SPTB. Users were more concerned about lack of insurance coverage compared to nonusers but nonusers were more concerned about safety, efficacy, need for more data, and long-term neonatal effects.

CONCLUSION

Although the use of progesterone to prevent PTB has increased significantly since our last survey, there remain a substantial number of nonusers. Among users, many are using it for indications not yet proven in clinical trials. Current nonusers have higher levels of concerns compared to nonusers in the first survey and their major concern is the need for more data.

17-Hydroxyprogesterone caproate reverses induced vasoconstriction of the fetoplacental arteries by the thromboxane mimetic U46619

OBJECTIVE

This study was undertaken to determine whether 17-hydroxyprogesterone caproate (17P) has a vasoactive effect on fetoplacental vasculature.

STUDY DESIGN

Two cotyledons were obtained from each of 5 placentas. Baseline perfusion was established with Hanks-based solution. One cotyledon from each pair was then infused with perfusate to which U46619 a thromboxane sympathomimetic had been added. After 30 minutes, a dose of 17P was then administered to each cotyledon. Finally, a vasoconstricting dose of angiotensin II was administered to each cotyledon. Perfusion pressures were recorded throughout. Statistical analysis of pressure change for a single cotyledon was performed by using a paired t test. Statistical analysis of mean perfusion pressure difference between U46619 exposed and nonexposed cotyledons was analyzed by using a students t test.

RESULTS

17P did not significantly alter the perfusion pressure of the control cotyledon. (30.6 +/- 8.3 mm Hg vs 30.1 +/- 7.8 mm Hg P = .48). 17P administration significantly lowered the perfusion pressure of the U46619 preconstricted vessels in comparison with preadministration. (60.1 +/- 13 mm Hg vs 27.3 +/- 7.1 mm Hg P = .03). Both groups of cotyledons responded with vasoconstriction to angiotension II with no difference in response between groups (38.3 +/- 12 mm Hg vs 45.8 +/- 8.2 mm Hg P = .63).

CONCLUSION

17P reverses induced vasoconstriction by U46619 in fetoplacental arteries.

Characterization of progesterone receptor isoform expression in fetal membranes

OBJECTIVE

To quantify expression of progesterone receptor (PR) messenger RNA (mRNA) isoforms in fetal membranes, and to determine whether these levels change in culture.

STUDY DESIGN

Placentas from women undergoing term cesarean delivery before labor were collected. Layers of amnion, chorion, and decidua were separated manually, enzymatically digested, and separated further with the use of a density gradient. RNA was extracted immediately and after culture for 48 hours, then analyzed by quantitative reverse transcription polymerase chain reaction for PR-A, PR-B, and beta-2 microglobulin mRNA expression. Separation of cell types was confirmed by immunohistochemistry.

RESULTS

PR isoform expression was identified in fetal membranes, with levels highest in decidua and below the limits of detection in amnion. The ratio of PR-A/PR-B mRNA was not significantly different between cell layers. PR mRNA isoform levels did not differ significantly in fresh versus cultured cells.

CONCLUSION

Quantitative reverse transcription polymerase chain reaction was used to quantitate expression of PR mRNA isoforms in cells of fetal membranes and to validate systems for further study of PR with respect to inflammation, infection, and preterm delivery.

The use of progestational agents for preterm birth: lessons from a mouse model

OBJECTIVE

On the basis of the recent Maternal Fetal Medicine Unit Networks clinical trial, the American College of Obstetricians and Gynecologists supports the administration of 17-alpha hydroxyprogesterone caproate to high-risk patients. Because inflammation/infection is believed to be a contributing factor in many cases of preterm birth, it is imperative to understand the effect of 17-alpha hydroxyprogesterone caproate treatment in this clinical situation.

STUDY DESIGN

Using a mouse model of localized intrauterine inflammation, we investigated the ability of progestational agents to prevent preterm birth. On gestational day 15 (E15), dams were assigned randomly to treatment with 17-alpha hydroxyprogesterone caproate, medroxyprogesterone acetate, or vehicle before intrauterine infusion of lipopolysaccharide. All dams were monitored for morbidity and preterm birth. Three separate sets of experiments were performed to assess different outcomes at 6, 24, and 96 hours. At 6 and 24 hours, C-reactive protein, interleukin-6, and interleukin-10 levels were measured in maternal serum by enzyme-linked immunosorbent assay.

RESULTS

Pretreatment with 17-alpha hydroxyprogesterone caproate or medroxyprogesterone acetate before intrauterine lipopolysaccharide treatment significantly decreased the preterm birth rate, compared with lipopolysaccharide treatment alone. Medroxyprogesterone acetate treatment was more effective than 17-alpha hydroxyprogesterone caproate treatment in the prevention of preterm birth and resulted in live pups at term. Treatment with 17-alpha hydroxyprogesterone caproate was associated with significant maternal morbidity.

CONCLUSION

In the setting of intrauterine inflammation, progestational agents decrease the preterm birth rate but can result in maternal morbidity. 17-Alpha hydroxyprogesterone caproate should not be used in patients who are suspected of having subclinical infection and/or acute preterm labor. The mechanisms by which progestational agents inhibit preterm birth warrants further investigations so that the use of this drug to appropriate populations could be pursued without undue fetal or maternal harm.

The many faces of progesterone: a role in adult and developing male brain

In addition to its well documented action in female-typical behaviors, progesterone exerts an influence on the brain and behavior of males. This review will discuss the role of progesterone and its receptor in male-typical reproductive behaviors in adulthood and the role of progesterone and its receptor in neural development, in both sexual differentiation of the brain as well as in the development of "non-reproductive" functions. The seemingly inconsistent and contradictory results on progesterone in males that exist in the literature illustrate the complexity of progesterone's actions and illuminate the need for further research in this area. As progestin-containing contraceptives in men are currently being tested and progesterone administration to pregnant women and premature newborns increases, a better understanding of the role of this hormone in behavior and brain development becomes essential.

Uterine transcriptomes of bacteria-induced and ovariectomy-induced preterm labor in mice are characterized by differential expression of arachidonate metabolism genes

OBJECTIVE

The purpose of this study was to identify changes in gene expression that are associated with preterm labor induced by either bacteria or ovariectomy.

STUDY DESIGN

Pregnant mice (14.5 days of gestation) were allocated to: (1) intrauterine injection of heat-inactivated Escherichia coli; (2) media alone; (3) ovariectomy; or (4) sham operation. The uterine transcriptome was studied with photolithographic, very short oligonucleotide-based microarrays, and arachidonate metabolism genes were assayed with quantitative reverse transcriptase-polymerase chain reaction. Significance was determined by analysis of variance.

RESULTS

Microarray-based gene expression changes in the arachidonate metabolism pathway are associated globally with bacteria-induced preterm labor (P < or = .0031) and ovariectomy-induced preterm labor (P < or = .00036). Quantitative real-time reverse transcriptase-polymerase chain reaction measurements demonstrated that bacteria-induced preterm labor substantially increased the expression of genes involved in prostaglandin synthesis. In contrast, ovariectomy-induced preterm labor increased the expression of genes involved in lipoxin, leukotriene, and hydroxyeicosatetraenoic acid synthesis.

CONCLUSION

Bacteria-induced and ovariectomy-induced preterm labor each express a different balance of genes that are required for the synthesis of prostaglandins, lipoxins, leukotrienes, and hydroxyeicosatetraenoic acids.

17α-hydroxyprogesterone Caproate for the Prevention of Preterm Delivery

OBJECTIVE

To evaluate whether the use of 17alpha-hydroxyprogesterone caproate for the prevention of recurrent preterm deliveries is cost-effective.

METHODS

Using decision-analysis modeling, we compared the cost-effectiveness of using 17alpha-hydroxyprogesterone caproate in four subgroups: 1) Prior preterm deliveries less than 32 weeks; 2) prior preterm deliveries 32-37 weeks; 3) prior term delivery; and 4) no prior delivery. Each subgroup was compared with a "no treatment" group. Costs included those for 17alpha-hydroxyprogesterone caproate, hospital admissions, and complications from preterm deliveries. The main outcome measures include cost per quality-adjusted life-year gained and the number of preterm deliveries prevented. Secondary outcomes include neonatal complications prevented. One-way and multiway sensitivity analyses were performed.

RESULTS

The use of 17alpha-hydroxyprogesterone caproate for the prevention of preterm deliveries result in cost-savings in women with prior preterm deliveries less than 32 weeks and 32-37 weeks. The sensitivity analyses revealed the model to be robust over a wide range of values for evaluated variables.

CONCLUSION

Within our baseline assumptions, 17alpha-hydroxyprogesterone caproate was associated with cost-savings when used for the prevention of preterm deliveries in women with prior preterm deliveries.

Recurrence of spontaneous versus medically indicated preterm birth

OBJECTIVE

Despite the increased tendency of preterm birth to recur, little is known with regard to recurrence risks for spontaneous and medically indicated preterm birth as well as recurrence risks in relation to severity of preterm birth. We examined the recurrence of spontaneous and medically indicated preterm birth.

STUDY DESIGN

A population-based, retrospective cohort study of births in Missouri (1989 to 1997) was carried out with analyses restricted to women who delivered their first 2 consecutive singleton live births (n = 154,809). Women who experienced spontaneous onset of labor and subsequently delivered preterm (less than 35 weeks) were classified as spontaneous preterm birth. Medically indicated preterm birth included women who delivered preterm through a labor induction or a prelabor cesarean delivery. Risk and odds ratio of preterm birth recurrence were derived from fitting multivariate conditional logistic regression models after adjusting for potential confounders.

RESULTS

If the first pregnancy resulted in a spontaneous preterm birth, then affected women were more likely to deliver preterm spontaneously (adjusted odds ratio 3.6, 95% confidence interval 3.2, 4.0) and also as a medically indicated preterm birth (odds ratio 2.5, 95% confidence interval 2.1, 3.0) in the second birth. Similarly, if the first pregnancy resulted in a medically indicated preterm birth, affected women were 10.6-fold (95% confidence interval 10.1, 12.4) more likely to deliver preterm because of medical indications in the second pregnancy as well as preterm spontaneously (odds ratio 1.6, 95% confidence interval 1.3, 2.1). The greatest risk of recurrence of preterm birth in the second pregnancy tended to occur around the same gestational age as preterm birth in the first pregnancy, regardless of the clinical subtype.

CONCLUSION

The observation that spontaneous preterm birth is not only associated with increased recurrence of spontaneous but also medically indicated preterm birth and vice versa, suggests that the 2 clinical subtypes may share common etiologies.

Do screening-preventative interventions in asymptomatic pregnancies reduce the risk of preterm delivery—A critical appraisal of the literature

Recent research has suggested that women who experience preterm delivery (PTD) may be identified earlier in pregnancy and before onset of symptoms. Interventions commenced at this earlier asymptomatic stage may offer an opportunity to prevent PTD or lengthen gestation sufficiently to reduce adverse perinatal outcome. Our objective was to examine the evidence that supports or refutes this approach to preventing PTD. We therefore conducted a systematic search and critical appraisal of the identified literature. We found evidence that introducing screening-preventative strategies for asymptomatic pregnancies may reduce the rate of PTD. Evidence for screening and selective treatment exists for: asymptomatic bacteriuria; bacterial vaginosis in low-risk population groups; elective cervical cerclage in high-risk pregnancies; indicated cervical cerclage in women with short cervical length on ultrasound; prophylactic progesterone supplementation in high-risk pregnancies, and smoking cessation. However, for most other strategies, such as increased antenatal attendance, or routine administration of prophylactic micronutrients, the evidence is inconsistent and conflicting. Information on neonatal outcomes apart from PTD (such as serious neonatal morbidity and mortality) was found to be lacking in most studies. It was therefore not possible to establish whether preventing PTD or prolonging gestation would correlate to improved perinatal outcome, and this lessened the potential clinical usefulness of any proposed preventative strategy. No studies were found that evaluated the effectiveness of combining screening-preventative strategies. The review concludes with a suggested an antenatal management plan designed to prevent PTD based on current practice and the evidence presented in this article.

Early mid-trimester serum relaxin, soluble CD163, and cervical length in women at high risk for preterm delivery

OBJECTIVE

The purpose of this study was to evaluate the relationship between serum concentrations of relaxin and soluble CD163 with cervical length and preterm delivery in women with previous spontaneous preterm delivery.

STUDY DESIGN

Sixty-one of 69 pregnant women with a previous spontaneous preterm had serum relaxin and soluble CD163 measured at week 16 (range, 12-25 weeks). End points were cervical length and gestational age at delivery.

RESULTS

Of the 61 women, 26% had >1 previous spontaneous preterm delivery; 84% were black; 87% were unmarried; 13% were smokers, and 39% were delivered before 37 weeks of gestation. Neither relaxin (median, 368 ng/L; range, 83-1493 ng/L) nor soluble CD163 (2.4 mg/L; range, 0.86-6.85 mg/L) correlated with cervical length or gestational age at delivery. Black women had higher relaxin levels (436 vs 205 ng/L; P = .002), but soluble CD163 levels were similar among racial groups.

CONCLUSION

Relaxin and soluble CD163 measured at 16 weeks of gestation are not clinically useful predictors of short cervical length or preterm delivery in women with a previous spontaneous preterm delivery.

Genetic variation associated with preterm birth: a HuGE review

Preterm birth (PTB) is a major public health concern because of its high prevalence, associated mortality and morbidity, and expense from both short-term hospitalization and long-term disability. In 2002, 11.9% of U.S. births occurred before 37 weeks gestation. Epidemiologic studies have identified many demographic, behavioral, and medical characteristics associated with PTB risk. In addition, recent evidence indicates a role for genetic susceptibility. We reviewed 18 studies published before June 1, 2004, that examined associations between polymorphisms in the maternal or fetal genome and PTB risk. Studies of a polymorphism in tumor necrosis factor-alpha, a proinflammatory cytokine, showed the most consistent increase in the risk of PTB. Environmental factors such as infection, stress, and obesity, which activate inflammatory pathways, have been associated with PTB, suggesting that environmental and genetic risk factors might operate and interact through related pathways. This review highlights maternal and fetal genetic susceptibilities to PTB, the potential relationships with environmental risk factors, and the need for additional well-designed studies of this critical public health problem.

Prenatal care initiation among very low-income women in the aftermath of welfare reform: does pre-pregnancy Medicaid coverage make a difference?

OBJECTIVES

To examine pre-pregnancy Medicaid coverage and initiation of prenatal care among women likely eligible for Medicaid coverage regardless of pregnancy.

METHODS

The Pregnancy Risk Assessment Monitoring System (PRAMS) was used to identify very low-income women with Medicaid payment for delivery. We then compared prenatal care initiation among women with (Non-GAP) and without (Medicaid GAP) pre-pregnancy Medicaid coverage.

RESULTS

Rates of first trimester prenatal care were 47.3% for women in the Medicaid GAP, 70.0% for women who were not. The adjusted odds ratio for being in the Medicaid GAP and delayed prenatal care was 2.7 (95% CI 1.2, 6.2), although this varied by race/ethnicity and education. The relationship was strongest among White and Hispanic women with less than a high school education: OR=13.8, (95% CI 3.0, 62.7) and OR=19.0 (95% CI 2.4, 149.2), respectively.

CONCLUSIONS

Pre-pregnancy Medicaid coverage appears to be associated with early initiation of prenatal care. Almost a decade after welfare reform, it is essential to preserve the Medicaid expansions for pregnant women, foster Medicaid family planning waivers, and promote access to primary care and early prenatal care, particularly for very low-income women.

Prenatal care: limitations and opportunities

Prenatal care is a venerable tradition in the U.S. health care system and one that deserves critical examination. Inordinate amounts of public and personal resources are expended on a tradition of care that has not proven itself equal to current perinatal prevention challenges. In this article, the evolution of prenatal care is reviewed, its efficacy is critiqued, and efforts at restructuring the content and processes of care are examined. Three promising alternatives to the dominant medical model are described: the comprehensive prenatal care approach illustrated by many publicly funded prenatal clinics, the prenatal empowerment model as exemplified by midwifery care, and the prenatal group model as illustrated by CenteringPregnancy. Nurses are called upon to champion prenatal options for women.

Calcium channel blockers for tocolysis: A review of their role and safety following reports of serious adverse events

The use of nifedipine and other calcium channel blockers has become commonplace in the management of preterm labour. Several relatively small randomised trials have compared calcium channel blockers with beta-agonists and the meta-analyses of these studies have demonstrated superior or comparable efficacy and a superior adverse events profile. The safety of calcium channel blockers in pregnancy has not been rigorously evaluated and they remain unlicensed for use as tocolytics. Indeed, there is concern following a number of recent case studies that have reported serious adverse events after the administration of a calcium channel blocker as a tocolytic. In this article all these recently reported cases are critically reviewed and the pros and cons of tocolytic treatment options are discussed. Based on the findings of this review the following recommendations can be made with regard to tocolysis with calcium channel blockers: firstly, calcium channel blockers should not be combined with intravenous beta-agonists; secondly, intravenous nicardipine or high oral doses of nifedipine should not be used in cases where the mother is cardiovascular compromised or in cases of multiple gestation; finally, blood pressure should be monitored and cardiotocography recorded during the administration of immediate release tablets and patients should be advised to avoid chewing them. To truly establish the safety of tocolytics, all serious adverse effects of tocolytics should be reported to a central point and be critically reviewed.

Mifepristone-induced cervical ripening: structural, biomechanical, and molecular events

OBJECTIVE

The purpose of this study was to assess the structural, biomechanical, and biochemical effects of mifepristone-induced progesterone withdrawal on the rat cervix to identify possible mechanisms by which mifepristone incites cervical ripening.

STUDY DESIGN

After the administration of mifepristone, cervical tensile strength was determined by the cervical creep method. With polarized light microscopy and transmission electron microscopy, collagen organization and microstructure were quantified. Matrix metalloproteinase expression was assessed by Western Blot and Real-time reverse transcriptase-polymerase chain reaction.

RESULTS

Mifepristone induced a decrease in cervical tensile strength at mid gestation that was associated with a decrease in collagen organization. Additionally, mifepristone led to collagen fragmentation with a significant decrease in fibril length and diameter, although fibril bundling remained unaffected. Matrix metalloproteinase-2 expression increased after the administration of mifepristone.

CONCLUSION

Mifepristone-induced cervical ripening is associated with collagen degradation, and the collagenase activity of matrix metalloproteinase-2 may play a role in this process.

Maternal characteristics and cervical length in the prediction of spontaneous early preterm delivery in twins

OBJECTIVE

The purpose of this study was to examine the value of combining maternal characteristics and measurement of cervical length at 22 to 24 weeks in the prediction of spontaneous early preterm delivery.

STUDY DESIGN

Cervical length was measured by transvaginal sonography at 22 to 24 weeks in 1163 twin pregnancies attending for routine antenatal care. Logistic regression analysis was used to examine the effect of maternal demographic characteristics and cervical length on the risk of spontaneous early preterm delivery.

RESULTS

The rate of spontaneous delivery before 32 weeks was 6.5%. The rate of early delivery was inversely related to cervical length, and for a false-positive rate of 10%, the detection rate of early delivery was 65.3%. The respective detection rate for maternal characteristics and obstetric history was 26.4%. Logistic regression analysis demonstrated that the only significant independent predictor of spontaneous early delivery was cervical length.

CONCLUSION

In twins, the prediction of spontaneous early preterm delivery by measurement of cervical length at 22 to 24 weeks is not improved by maternal characteristics.

Progesterone for the prevention of preterm birth among women at increased risk: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

This study was undertaken to determine whether progestational agents, initiated in the second trimester of pregnancy, reduce the risk of delivery less than 37 weeks, among women at increased risk of spontaneous preterm birth.

STUDY DESIGN

Medline, pre-Medline, EMBASE, and Cochrane Central Register of Controlled Trials were searched. Randomized controlled trials with less than 20% lost to follow-up were included.

RESULTS

Three trials were eligible for inclusion. There was a significant reduction in risk of delivery less than 37 weeks with progestational agents (relative risk [95% CI] = 0.57 [0.36-0.90]). There was no significant effect on perinatal mortality or serious neonatal morbidity.

CONCLUSION

Progestational agents, initiated in the second trimester of pregnancy, may reduce the risk of delivery less than 37 weeks' gestation, among women at increased risk of spontaneous preterm birth, but the effect on neonatal outcome is uncertain. Larger randomized controlled trials are required to determine whether this treatment reduces perinatal mortality or serious neonatal morbidity.

A possible role for progesterone metabolites in human parturition

There has been a recent resurgence of interest in the role of progesterone in the maintenance of human pregnancy and the onset of labour, following recent reports of its use to prevent preterm labour in high-risk patients. One possible mechanism by which progesterone might contribute to uterine quiescence is through the actions of its metabolites. This article provides a brief overview of progesterone in human pregnancy and an outline of progesterone metabolism in the various reproductive tract tissues as well as the evidence for actions of progesterone metabolites in pregnancy.

Multiple gestations and late preterm (near-term) deliveries

Multiple gestations present unique challenges to the modern obstetrician. Many twin and high-order multiple pregnancies are delivered between 34 and 37 weeks' gestation either secondary to preterm labor or obstetrical complications necessitating intervention. Recognizing the increasing prevalence of multiple gestations and the impact of late preterm deliveries in modern practice, this review analyzes the impact of multiple pregnancies on perinatal outcomes, reviews the strategies to prevent preterm labor, and summarizes potential indications for late preterm delivery. In this paper, "late preterm" has been used instead of "near-term," as the former was considered more appropriate to reflect this subgroup of preterm infants in a workshop on this topic held in July 2005, organized by the National Institute of Child Health and Human Development.

Hydroxyprogesterone caproate and progesterone increase tumor necrosis factor-alpha production in lipopolysaccharide stimulated whole blood from non-pregnant women

OBJECTIVE

Hydroxyprogesterone caproate (17-P) and progesterone have been shown to decrease the rate of preterm birth in high-risk pregnant women, but the mechanism of action is unknown. We hypothesized that 17-P or progesterone would reduce production of the pro-inflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), after lipopolysaccharide (LPS) stimulation of whole blood.

STUDY DESIGN

Whole blood collected from 10 non-pregnant women in the follicular phase was treated with LPS (1000 ng/mL) alone or with either 17-P or progesterone (125 ng/mL and 1250 ng/mL) and LPS. Supernatant collected after 24 h was tested for TNF-alpha by enzyme immunoassay. Results were compared using the Wilcoxon rank sum test.

RESULTS

Whole blood treated with 17-P or progesterone in addition to LPS produced significantly higher TNF-alpha concentrations than blood treated with LPS alone.

CONCLUSION

17-P and progesterone appear to have a pro-inflammatory effect during LPS stimulation of blood from non-pregnant women in vitro. Our data suggest that the reduction in pre-term birth in women treated with progesterone is not mediated through an anti-inflammatory effect on peripheral blood cells.

Examining the spatio-temporal expression of mRNA encoding the membrane-bound progesterone receptor-alpha isoform in human cervix and myometrium during pregnancy and labour

Human parturition is associated with a modification in the sensitivity of the myometrium to progesterone. The molecular basis for this change, however, remains unclear. It is well documented that progesterone can exert its effects through non-genomic mechanisms, including acting through membrane-bound progesterone receptors (mPRs). Recently, a novel membrane-bound PR, termed mPRalpha, was cloned. mPRalpha was unlike any other PR in the databases, but it was seen to have significant homology to G-protein-coupled receptors (GPCR). In this study, we examined the spatio-temporal expression of mPRalpha mRNA in human cervix and both lower and upper myometrial segments from non-pregnant (NP), pregnant (P) and spontaneously labouring (SL) women. We observed an incremental increase in mPRalpha mRNA expression in NP and P samples with the peak level being observed in SL tissues. No major differences were observed between upper or lower pregnant myometrial regions. Interestingly, levels of mPRalpha transcripts were substantially greater in labouring lower segment myometrium compared with labouring upper segment. Significantly, we failed to detect mPRalpha message in either unripe or ripe human cervices. These data suggest that mPRalpha protein function may play a role in regulating lower segment myometrial activity during labour. Whether it functions in the cervix, however, remains unclear.

Estimates of the cost and length of stay changes that can be attributed to one-week increases in gestational age for premature infants

OBJECTIVE

To estimate the potential savings, both in terms of costs and lengths of stay, of one-week increases in gestational age for premature infants. The purpose is to provide population-based data that can be used to assess the potential savings of interventions that delay premature delivery.

DATA

Cohort data for all births in California in 1998-2000 that linked vital records data with those from hospital discharge abstracts, including those of neonatal transport. All infants with a gestational age between 24 and 37 weeks were included. There were 193,167 infants in the sample after deleting cases with incomplete data or gestational age that was inconsistent with birth weight.

METHODS

Hospital costs were estimated by adjusting charges by hospital-specific costs-to-charges ratios. Data were aggregated across transport into episodes of care. Mean and median potential savings were calculated for increasing gestational age, in one-week intervals. The 25th and 75th percentiles were used to estimate ranges.

RESULTS

The results are presented in matrix format, for starting gestational ages of 24-34 weeks, with ending gestational ages of 25 to 37 weeks. Costs and lengths of stay decreased with gestational age from a median of $216,814 (92 days) at 24 weeks to $591 (2 days) at 37 weeks. The potential savings from delaying premature labor are quite large; the median savings for a 2 week increase in gestational age were between $28,870 and $64,021 for gestational ages below 33 weeks, with larger savings for longer delays in delivery. Delaying deliveries <29 weeks to term (37 weeks) resulted in savings of over $122,000 per case, with the savings being over $206,000 for deliveries <26 weeks.

CONCLUSIONS

These results provide population-based data that can be applied to clinical trials data to assess the impacts on costs and lengths of stay of interventions that delay premature labor. They show that the potential savings of delaying premature labor are quite large, especially for extremely premature deliveries.

Expression of sex-steroid receptors and steroidogenic enzymes in the carotid body of adult and newborn male rats

This study describes the localization and pattern of expression of estradiol and progesterone receptors as well as key enzymes for steroid synthesis (i.e. P450 side-chain-cleavage--P450scc, and P450 aromatase--P450Aro) in the carotid body (CB) and superior cervical ganglion (SCG) of adult, newborn and late fetal male rats, using immunohistochemistry, Western blot and real-time RT-PCR. Our results show a constitutive expression of the beta estradiol receptor (Erbeta) and the 80 kDa and 60 kDa progesterone receptors (PR-A and PR-C) isoforms in the CB, while in the SCG Eralpha, Erbeta, PR-A and PR-C are expressed. While P450Aro staining was negative, P450scc staining was strong both in the SCG and CB. In late fetal and newborn rats, Eralpha was not detected in the CB or SCG, but a slight staining appeared for P450 aromatase in the CB, and to a lesser extent in SCG. P450scc was strongly expressed in CB and SCG of late fetal and newborn rats. We conclude that the carotid body shows a constitutive expression of Erbeta and PR and may be able to synthesize steroids, including estradiol during late fetal life.