The changing role of progesterone in preterm labour

Sex hormone-mediated change on muscle activation deactivation dynamics in young eumenorrheic women

The goal of the study was to characterize muscle activation/deactivation dynamics across the menstrual cycle in healthy young women. Twenty-two healthy eumenorrheic women (age: 27.0 ± 4.4 years; mean ± SD) were tested every other day for one menstrual cycle. Serum estradiol and progesterone were quantified at the time of testing. Peak torque (PT), time to peak torque (TPT), and half relaxation time (HRT) of soleus muscle twitch were measured. Muscle twitch was elicited by delivering 1 ms width electrical pulses to the tibial nerve at an intensity that generated a maximum motor response (S-100) and at supramaximal intensity (S-120; 1.2 × S-100). The analyses were performed for each menstrual cycle phase: 1) the follicular phase to analyze the effect of estradiol while the progesterone concentrations remained at low concentrations; 2) the luteal phase to analyze the effect of progesterone with background estradiol concentrations. In the follicular phase, there was no association of estradiol for PT, TPT, and HRT. In the luteal phase, while estradiol had no association on PT, TPT, and HRT, progesterone expressed a significant association with HRT reduction but no association on PT or TPT. Also, there was a significant estradiol and progesterone interaction for HRT. However, the regression parameters are nearly zero, suggesting that the change in HRT may not have an impact on muscle performance across the menstrual cycle but implications on other women's health conditions with elevated sex hormone concentrations, such as pregnancy, may prove critical.

Harmful and beneficial effects of inflammatory response on reproduction: sterile and pathogen-associated inflammation

In reproduction, inflammatory processes play important roles in the development of many pregnancy complications such as preterm labor/birth, recurrent pregnancy loss, recurrent implantation failure, and preeclampsia. Inflammation can be initiated by both microbial and non-microbial causes. Bacterial infection in the feto-maternal interface and uterus can provoke preterm labor/birth, miscarriage, and chronic endometritis. By contrast, inflammation without infection, or 'sterile inflammation,' can also lead to many kinds of complications, such as preterm labor/birth, miscarriage, or preeclampsia. Aberrant inflammation is facilitated by immune cells such as macrophages, dendritic cells, natural killer cells, and invariant natural killer T cells. In addition, cytokines, chemokines, and several kinds of inflammatory mediators are involved. On the other hand, appropriate inflammation is required for a successful offspring during the progression of the entire pregnancy. Herein, we discuss the relation between pregnancy and inflammation with immunological alterations. Understanding the role of inflammation in complications during pregnancy may establish new perspectives of the progress of normal pregnancy as well as treatments during pregnancy complications.

Association between serum progesterone concentration in early pregnancy and duration of pregnancy: a cohort study

Objective: To examine the association between progesterone concentration in early pregnancy and duration of pregnancy and risk of preterm delivery.Methods: Women enrolled in the Born in Guangzhou Cohort Study from 2013-2014, with a singleton pregnancy, who had serum progesterone measured at least one time between 4 and 10 weeks of gestation were included. The association between progesterone concentration both continuous and as categorical variable (quartile) and the risk of preterm delivery was assessed with Cox proportional hazards regression. Differences of length of gestation in four progesterone concentration quartiles were assessed using the Log-rank test.Results: We studied 1860 mother-newborn pairs. The mean overall progesterone concentration was 65.7 ± 21.3 nmol/L, with mean progesterone concentrations in the four quartiles of 42.4 ± 6.2 nmol/L (n = 463), 56.2 ± 3.3 nmol/L (n = 462), 68.9 ± 4.5 nmol/L (n = 470), and 95.1 ± 15.3 nmol/L (n = 465). There was no significantly difference in duration of gestation in four progesterone concentration groups (p=.511). There was no relation between progesterone level and preterm delivery (adjusted hazard ratio (HR) per 10 nmol/l progesterone level 1.00 (95% confidence interval (CI) 0.90, 1.11)). After adjusting for potential confounders, the HR of any preterm delivery for quartiles 1, 2 and 3 versus the highest quartile of progesterone level (> 77.3 nmol/L) was 1.04 (95% CI 0.52, 2.07), 1.17 (95% CI 0.60, 2.28), and 1.46 (95% CI 0.76, 2.78), respectively. When analysis was done for spontaneous preterm delivery only, also no association with first trimester progesterone was found.Conclusion: Lower first trimester serum progesterone concentration is not associated with reduction of length of gestation or increased risk of preterm delivery.

Progestogen for treating threatened miscarriage

BACKGROUND

Miscarriage is a common complication encountered during pregnancy. It is defined as spontaneous pregnancy loss before 20 weeks' gestation. Progesterone's physiological role is to prepare the uterus for the implantation of the embryo, enhance uterine quiescence and suppress uterine contractions, hence, it may play a role in preventing rejection of the embryo. Inadequate secretion of progesterone in early pregnancy has been linked to the aetiology of miscarriage and progesterone supplementation has been used as a treatment for threatened miscarriage to prevent spontaneous pregnancy loss. This update of the Cochrane Review first published in 2007, and previously updated in 2011, investigates the evidence base for this practice.

OBJECTIVES

To determine the efficacy and the safety of progestogens in the treatment of threatened miscarriage.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (8 August 2017) and reference lists of retrieved trials.

SELECTION CRITERIA

Randomised, quasi-randomised or cluster-randomised controlled trials, that compared progestogen with placebo, no treatment or any other treatment for the treatment of threatened miscarriage in women carrying singleton pregnancy.

DATA COLLECTION AND ANALYSIS

At least two review authors assessed the trials for inclusion in the review, assessed trial quality and extracted the data and graded the body of evidence.

MAIN RESULTS

We included seven trials (involving 696 participants) in this update of the review. The included trials were conducted in different countries, covering the full spectrum of the World Bank's economic classification, which enhances the applicability of evidence drawn from this review. Two trials were conducted in Germany and Italy which are high-income countries, while four trials were conducted in upper-middle income countries; two in Iran, one in Malaysia and the fourth in Turkey, and the seventh trial was conducted in Jordan, which is a lower-middle income country. In six trials all the participants met the inclusion criteria and in the seventh study, we included in the meta-analysis only the subgroup of participants who met the inclusion criteria. We assessed the body of evidence for the main outcomes using the GRADE tool and the quality of the evidence ranged from very low to moderate. Downgrading of evidence was based on the high risk of bias in six of the seven included trials and a small number of events and wide confidence intervals for some outcomes.Treatment of miscarriage with progestogens compared to placebo or no treatment probably reduces the risk of miscarriage; (risk ratio (RR) 0.64, 95% confidence interval (CI) 0.47 to 0.87; 7 trials; 696 women; moderate-quality evidence). Treatment with oral progestogen compared to no treatment also probably reduces the miscarriage rate (RR 0.57, 95% CI 0.38 to 0.85; 3 trials; 408 women; moderate-quality evidence). However treatment with vaginal progesterone compared to placebo, probably has little or no effect in reducing the miscarriage rate (RR 0.75, 95% CI 0.47 to 1.21; 4 trials; 288 women; moderate-quality evidence). The subgroup interaction test indicated no difference according to route of administration between the oral and vaginal subgroups of progesterone.Treatment of preterm birth with the use of progestogens compared to placebo or no treatment may have little or no effect in reducing the rate of preterm birth (RR 0.86, 95% CI 0.52 to 1.44; 5 trials; 588 women; low-quality evidence).We are uncertain if treatment of threatened miscarriage with progestogens compared to placebo or no treatment has any effect on the rate of congenital abnormalities because the quality of the evidence is very low (RR 0.70, 95% CI 0.10 to 4.82; 2 trials; 337 infants; very-low quality evidence).

AUTHORS' CONCLUSIONS

The results of this Cochrane Review suggest that progestogens are probably effective in the treatment of threatened miscarriage but may have little or no effect in the rate of preterm birth. The evidence on congenital abnormalities is uncertain, because the quality of the evidence for this outcome was based on only two small trials with very few events and was found to be of very low quality.

Progesterone in normal and pathological pregnancy

Progesterone is an essential hormone in the process of reproduction. It is involved in the menstrual cycle, implantation and is essential for pregnancy maintenance. It has been proposed and extensively used in the treatment of different gynecological pathologies as well as in assisted reproductive technologies and in the maintenance of pregnancy. Called "the pregnancy hormone", natural progesterone is essential before pregnancy and has a crucial role in its maintenance based on different mechanisms such as: modulation of maternal immune response and suppression of inflammatory response (the presence of progesterone and its interaction with progesterone receptors at the decidua level appears to play a major role in the maternal defense strategy), reduction of uterine contractility (adequate progesterone concentrations in myometrium are able to counteract prostaglandin stimulatory activity as well as oxytocin), improvement of utero-placental circulation and luteal phase support (it has been demonstrated that progesterone may promote the invasion of extravillous trophoblasts to the decidua by inhibiting apoptosis of extravillous trophoblasts). Once the therapeutic need of progesterone is established, the key factor is the decision of the best route to administer the hormone and the optimal dosage determination. Progesterone can be administered by many different routes, but the most utilized are oral, the vaginal and intramuscular administration. The main uses of progesterone are represented by: threatened miscarriage, recurrent miscarriage and preterm birth (in the prevention strategy, as a tocolytic agent and also in the maintenance of uterine quiescence).

Prevention of preterm birth: a randomized trial of vaginal compared with intramuscular progesterone

OBJECTIVE

To assess efficacy and tolerability of vaginal compared with intramuscular progesterone in reducing the rate of recurrent preterm birth before 34 weeks of gestation.

DESIGN

Prospective randomized study.

SETTING

Obstetrics and Gynecology Department, Armed Forces Hospital Southern Region, Kingdom of Saudi Arabia.

SAMPLE

Five-hundred and eighteen women with a prior history of preterm birth.

METHODS

Women were randomized to receive either 90 mg of vaginal progesterone gel once daily or 250 mg of intramuscular progesterone weekly. Treatment began between 14 and 18 weeks of gestation and continued until 36 complete weeks of gestation, delivery or the occurrence of premature rupture of membranes.

MAIN OUTCOME MEASURES

The primary outcome measure was delivery before 34 weeks of gestation. The secondary outcome measures were PTB between 34 and 37 weeks of gestation and neonatal outcomes including birthweight, neonatal death, and the need for admission to the neonatal intensive care unit.

RESULTS

The baseline characteristics of the study participants were similar. Two-hundred and thirty-eight (94.1%) patients in the vaginal group and 226 (90.8%) patients in the intramuscular group were compliant with their medications. Vaginal progesterone was associated with a lower percentage of deliveries before 34 weeks of gestation than the intramuscular preparation (p= 0.02). This association was also observed at 28 and 32 weeks of gestation (p= 0.04). Adverse effects were reported in 14.1% of patients in the intramuscular group, but in only 7.5% of patients in the vaginal group (p= 0.017).

CONCLUSIONS

Vaginal progesterone was more effective than intramuscular progesterone for the prevention of preterm birth and had fewer adverse effects.

Prevention of preterm delivery after successful tocolysis in preterm labor by 17 alpha-hydroxyprogesterone caproate: a randomized controlled trial

OBJECTIVE

The objective of the study was to evaluate the use of 17 alpha-hydroxyprogesterone caproate (17P) to reduce preterm delivery.

STUDY DESIGN

This open-label, multicenter, randomized controlled trial included women with singleton pregnancies admitted at 24-31 weeks' gestation and cervical length less than 25 mm for preterm labor successfully arrested by tocolytic treatment. Randomization assigned them to receive (or not) 500 mg of intramuscular 17P after tocolysis ended, repeated semiweekly until 36 weeks or preterm delivery. The primary outcome was the time from randomization to delivery.

RESULTS

Outcome data were available for 184 of 188 women randomized. The 17P and control groups (similar for most baseline characteristics) did not differ significantly for median [interquartile range] time to delivery (64 [42-79] and 67 [46-83] days, respectively) or rates of delivery before 37, 34, or 32 weeks of gestation or adverse perinatal outcomes.

CONCLUSION

Semiweekly injections of 17P did not prolong pregnancy significantly in women with tocolysis-arrested preterm labor.

Progestogen for treating threatened miscarriage

BACKGROUND

Miscarriage is a common complication encountered during pregnancy. The role of progesterone in preparing the uterus for the implantation of the embryo and its role in maintaining the pregnancy have been known for a long time. Inadequate secretion of progesterone in early pregnancy has been linked to the aetiology of miscarriage and progesterone supplementation has been used as a treatment for threatened miscarriage to prevent spontaneous pregnancy loss.

OBJECTIVES

To determine the efficacy and the safety of progestogens in the treatment of threatened miscarriage.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2011) and bibliographies of all located articles for any additional studies.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials that compare progestogen with placebo, no treatment or any other treatment given in an effort to treat threatened miscarriage.

DATA COLLECTION AND ANALYSIS

At least two authors assessed the trials for inclusion in the review, assessed trial quality and extracted the data. Data were checked for accuracy.

MAIN RESULTS

We included four studies (421 participants) in the meta-analysis. In three studies all the participants met the inclusion criteria and in the fourth study, we included only the subgroup of participants who met the inclusion criteria in the meta-analysis. There was evidence of a reduction in the rate of spontaneous miscarriage with the use of progestogens compared to placebo or no treatment (risk ratio (RR) 0.53; 95% confidence interval (CI) 0.35 to 0.79). There was no increase in the rate of antepartum haemorrhage (RR 0.76; 95% CI 0.30 to 1.94), or pregnancy-induced hypertension (RR 1.00; 95% CI 0.54 to 1.88) for the mother. The rate of congenital abnormalities was no different between the newborns of the mothers who received progestogens and those who did not (RR 0.70; 95% CI 0.10 to 4.82).

AUTHORS' CONCLUSIONS

The data from this review suggest that the use of progestogens is effective in the treatment of threatened miscarriage with no evidence of increased rates of pregnancy-induced hypertension or antepartum haemorrhage as harmful effects to the mother, nor increased occurrence of congenital abnormalities on the newborn. However, the analysis was limited by the small number and the poor methodological quality of eligible studies (four studies) and the small number of the participants (421), which limit the power of the meta-analysis and hence of this conclusion.

Prevention of preterm labour: 2011 update on tocolysis

The aim of this paper is to review available data about drugs for preventing preterm labour. Tocolytic therapy includes β adrenergic receptor agonists, NO donors, magnesium sulphate, prostaglandin-synthase inhibitors, oxytocin receptor antagonists, calcium-channel blockers, progesterone, 17-α-hydroxyprogesterone caproate, and antibiotics. Their specific effects on myometrial contractility, their safety, their efficiency, and side effects profile for the mother and the fetus are presented. The main question of why and for what reasons tocolysis should be administrated is discussed.

Progesterone maintains amniotic tight junctions during midpregnancy in mice

The amniotic epithelium is in direct contact with the amniotic fluid and restricts fluid flux via the paracellular pathway by means of tight junctions (TJs). Several factors affect TJs to modulate the paracellular flux. Progesterone contributes to the antenatal formation and disappearance of TJs in uterine and mammary epithelial tissues. In this study, we investigated whether progesterone positively or negatively influences amniotic TJs. The administration of RU-486, a progesterone receptor (PR) antagonist, into pregnant mice adversely affects the localization and expression of claudin-3 and claudin-4 in the amniotic epithelium. RU-486 administration also increased the permeability of the amniotic membrane. In organ-cultured amniotic membranes, progesterone induced increases in claudin-3 and claudin-4 expression in a dose-dependent manner but did not influence their localization. PRs were also present in the amniotic epithelium during midpregnancy but they disappeared during late pregnancy. These results indicate that the progesterone/PR pathway maintains TJs in the amniotic epithelium during midpregnancy.

Progestogen for treating threatened miscarriage

BACKGROUND

Miscarriage is a common complication encountered during pregnancy. The role of progesterone in preparing the uterus for the implantation of the embryo and its role in maintaining the pregnancy have been known for a long time. Inadequate secretion of progesterone in early pregnancy has been linked to the aetiology of miscarriage and progesterone supplementation has been used as a treatment for threatened miscarriage to prevent spontaneous pregnancy loss.

OBJECTIVES

To determine the efficacy and the safety of progestogens in the treatment of threatened miscarriage.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (December 2009) and bibliographies of all located articles for any unidentified articles.

SELECTION CRITERIA

Randomized or quasi-randomized controlled trials that compare progestogen with placebo, no treatment or any other treatment given in an effort to treat threatened miscarriage.

DATA COLLECTION AND ANALYSIS

At least two authors assessed the trials for inclusion in the review and extracted the data.

MAIN RESULTS

Two studies (84 participants) were included in the meta-analysis. In one study, all the participants met the inclusion criteria and in the other study, only the subgroup of participants who met the inclusion criteria was included in the meta-analysis. There was no evidence of effectiveness with the use vaginal progesterone compared to placebo in reducing the risk of miscarriage (risk ratio 0.47; 95% confidence interval 0.17 to 1.30).

AUTHORS' CONCLUSIONS

Based on scarce data from two methodologically poor trials, there is no evidence to support the routine use of progestogens for the treatment of threatened miscarriage. Information about potential harms to the mother or child, or both, with the use of progestogens is lacking. Further, larger, randomized controlled trials on the effect of progestogens on the treatment of threatened miscarriage, which investigate potential harms as well as benefits, are needed.

Emerging tocolytics: challenges in designing and testing drugs to delay preterm delivery and prolong pregnancy

The global rate of preterm delivery (before 37 completed weeks of pregnancy) is increasing and there are no effective means available to prevent this rise. Prematurity is the principal cause of neonatal mortality and a major cause of pediatric morbidity and long-term disability. Current strategies to prolong pregnancy are based on inhibiting the mechanisms that effect uterine smooth muscle (myometrium) contractions in women who are in preterm labor. Most drugs in this group were developed for other purposes. Newer strategies are designed to maintain a state of uterine quiescence and pregnancy, preventing the myometrium from initiating contractions and entering preterm labor. Again, it may be possible to use existing drugs for pregnancy maintenance. Several financial and practical barriers exist for developing completely new drugs to delay labor. Designing clinical trials to test tocolytics is complicated, as the health of two patients must be considered and the nature of preterm birth and its outcomes are different at early preterm labor (< 28 weeks) and late preterm labor (34 - 36 weeks).

Progesterone vaginal gel for the reduction of recurrent preterm birth: primary results from a randomized, double-blind, placebo-controlled trial

OBJECTIVE

Preterm birth is the leading cause of perinatal morbidity and mortality worldwide. Treatment of preterm labor with tocolysis has not been successful in improving infant outcome. The administration of progesterone and related compounds has been proposed as a strategy to prevent preterm birth. The objective of this trial was to determine whether prophylactic administration of vaginal progesterone reduces the risk of preterm birth in women with a history of spontaneous preterm birth.

METHODS

This randomized, double-blind, placebo- controlled, multinational trial enrolled and randomized 659 pregnant women with a history of spontaneous preterm birth. Between 18 + 0 and 22 + 6 weeks of gestation, patients were assigned randomly to once-daily treatment with either progesterone vaginal gel or placebo until either delivery, 37 weeks' gestation or development of preterm rupture of membranes. The primary outcome was preterm birth at </= 32 weeks of gestation. The trial was analyzed using an intent-to-treat strategy.

RESULTS

Baseline characteristics were similar in the two treatment groups. Progesterone did not decrease the frequency of preterm birth at </= 32 weeks. There was no difference between the groups with respect to the mean gestational age at delivery, infant morbidity or mortality or other maternal or neonatal outcome measures. Adverse events during the course of treatment were similar for the two groups.

CONCLUSION

Prophylactic treatment with vaginal progesterone did not reduce the frequency of recurrent preterm birth (</= 32 weeks) in women with a history of spontaneous preterm birth. The effect of progesterone administration in patients at high risk for preterm delivery as determined by methods other than history alone (e.g. sonographic cervical length) requires further investigation.

Progestogen for treating threatened miscarriage

BACKGROUND

Miscarriage is a common complication encountered during pregnancy. The role of progesterone in preparing the uterus for the implantation of the embryo and its role in maintaining the pregnancy have been known for a long time. Inadequate secretion of progesterone in early pregnancy has been linked to the aetiology of miscarriage and progesterone supplementation has been used as a treatment for threatened miscarriage to prevent spontaneous pregnancy loss.

OBJECTIVES

To determine the efficacy and the safety of progestogens in the treatment of threatened miscarriage.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (December 2006), the Cochrane Central Register of Controlled Trials (The Cochrane Library 2006, Issue 1), MEDLINE (January 1966 to April 2006), EMBASE (1980 to April 2006) and CINAHL (1982 to April 2006). We scanned bibliographies of all located articles for any unidentified articles.

SELECTION CRITERIA

Randomized or quasi-randomized controlled trials that compare progestogen with placebo, no treatment or any other treatment given in an effort to treat threatened miscarriage.

DATA COLLECTION AND ANALYSIS

At least two authors assessed the trials for inclusion in the review and extracted the data.

MAIN RESULTS

Two studies (84 participants) were included in the meta-analysis. In one study, all the participants met the inclusion criteria and in the other study, only the subgroup of participants who met the inclusion criteria was included in the meta-analysis. There was no evidence of effectiveness with the use vaginal progesterone compared to placebo in reducing the risk of miscarriage (relative risk 0.47; 95% confidence interval (CI) 0.17 to 1.30).

AUTHORS' CONCLUSIONS

Based on scarce data from two methodologically poor trials, there is no evidence to support the routine use of progestogens for the treatment of threatened miscarriage. Information about potential harms to the mother or child, or both, with the use of progestogens is lacking. Further, larger, randomized controlled trials on the effect of progestogens on the treatment of threatened miscarriage, which investigate potential harms as well as benefits, are needed.

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.

Preterm labour: update on prediction and prevention strategies

PURPOSE OF REVIEW

The incidence of preterm birth is increasing and continues to be a significant cause of neonatal mortality and morbidity. Techniques now exist that can accurately predict early birth. Prevention can therefore be targeted, although effective measures that improve outcome are yet to be established.

RECENT FINDINGS

Obtaining an accurate history is the first step in identifying high-risk women. Clinicians then rely on other predictors such as fetal fibronectin, cervical length assessment and biochemical markers. Research should focus on the combination of noninvasive markers targeted at high-risk women as a screening tool, determining not only appropriate diagnostic levels for positive tests, but also sufficiently large studies should be performed to determine the predictive values of these tests. Interventions to prevent delivery and improve neonatal outcome remain unsatisfactory, mainly comprising tocolysis, cerclage, progesterone and, in some cases, antibiotics. Women who would most benefit from these interventions are difficult to identify and an appreciation of the pathophysiology in an individual woman, such as the relevance of the inflammatory status of the endocervix, may be important in tailoring intervention.

SUMMARY

An improved understanding of the mechanisms underlying the pathological process in preterm birth will allow screening and interventions to be appropriately targeted.

Hormonal changes accompanying cigarette smoke-induced preterm births in a mouse model

Epidemiologic evidence indicates that maternal smoking increases the risk of preterm birth. While a number of plausible mechanisms for early delivery have been offered, the role of gestational hormones in this smoke-induced outcome is uncertain. Thus, a toxicologic study was performed to examine the effects and underlying hormonal mechanisms of mainstream cigarette smoke (MCS) exposure on gestational duration. Pregnant B6C3F1 mice were exposed by inhalation to MCS for 5 days/week (4 hrs/day) from Gestational Day (GD) 4 to parturition. Smoke-induced effects on gestational length, interpubic ligament length, maternal hormone secretion patterns (estradiol-17beta, progesterone, prolactin, and relaxin), body weight gain, postimplantation loss, litter size, and offspring sex ratio were examined. Dams exposed to MCS at a concentration equivalent to smoking less than one pack of cigarettes/day (carbon monoxide = 25 parts per million, total suspended particulates = 16 mg/m3) demonstrated a significant (P < 0.05) shortening of gestational duration (compared with pregnant, air-exposed mice). In addition, MCS-exposed mice sacrificed on GD 18 had significantly (P < 0.05) increased interpubic ligament length, elevated serum estrogen levels, and a reduced progesterone to estradiol-17beta ratio (compared with air-exposed controls); levels of progesterone and prolactin were only modestly decreased and increased, respectively, in the MCS-exposed mice. Smoke exposure had no significant effects on maternal relaxin levels, body weight gain, postimplantation loss, litter size, or sex ratio. Results of this study demonstrate that inhalation exposure of pregnant mice to a low dose of MCS shortens gestation and alters hormone secretory patterns, which are important for maintaining pregnancy and inducing parturition. These findings support the view that pregnant women who smoke (even modestly) may be at increased risk for preterm birth, and that early delivery may be related (at least partly) to MCS-induced.

Progesterone and pregnancy

PURPOSE OF REVIEW

Progesterone is an essential hormone in the process of reproduction. Although the pharmacokinetics and pharmacodynamics of progesterone have been well studied, its use in the pathophysiology of pregnancy remains controversial. One of these concerns is the way in which the hormone is administered.

RECENT FINDINGS

In obstetrics the most frequent uses of progesterone are in the treatment of threatened abortion, prevention of recurrent miscarriage, or in the support of the luteal phase in assisted reproduction programmes, and in threatened preterm labour. Randomized, controlled trials showed that women who received progesterone were statistically significantly less likely to have recurrent miscarriages before 34 weeks, to have an infant with birth weight of 2.5 kg or lower, or to have an infant diagnosed with intraventricular haemorrhage. There is currently, however, insufficient information to allow recommendations regarding the optimal dose, route and timing of administration of progesterone supplementation.

SUMMARY

Progesterone has shown to be efficacious when continuation of pregnancy is hampered by immunological factors, luteinic and neuroendocrine deficiencies and myometrial hypercontractility. This may explain the reduction in the incidence of preterm birth in high-risk pregnant women using high-dosage prophylactic progesterone.