Relationship between 17-alpha hydroxyprogesterone caproate concentration and spontaneous preterm birth

The dosing regimen for 17-hydroxyprogesterone caproate was suboptimal: lessons for future pharmacotherapy for pregnant women

BACKGROUND

Makena (17-hydroxyprogesterone caproate) was approved by the United States Food and Drug Administration for the prevention of recurrent spontaneous preterm birth in 2011 under the accelerated approval pathway, but fundamental pharmacokinetic or pharmacodynamic (Phase 1 and Phase 2) studies were not performed. At the time, there were no dose-response or concentration-response data. The therapeutic concentration was not known. The lack of such data brings into question the dosing regimen for 17-hydroxyprogesterone caproate and if it was optimized.

OBJECTIVE

The purpose of this study was to evaluate the dosing regimen for 17-hydroxyprogesterone by analyzing 3 data sets in which the 17-hydroxyprogesterone caproate pharmacology was evaluated, namely the Maternal-Fetal Medicine Omega 3 study, the Obstetric-Fetal Pharmacology Research Units study, and the Obstetrical-Fetal Pharmacology Research Centers study. If an inappropriate dosing regimen could be identified, such information could inform future studies of pharmacotherapy in pregnancy.

STUDY DESIGN

Data from the Omega 3 study were used to determine if plasma concentration was related to spontaneous preterm birth risk and if a threshold concentration could be identified. Data from the Obstetric-Fetal Pharmacology Research Units study were used to determine the half-life of 17-hydroxyprogesterone caproate and to develop a model to simulate drug concentrations with various dosing regimens. Data from the Obstetrical-Fetal Pharmacology Research Centers study were used to determine the relationship between dose and safety outcomes.

RESULTS

Analysis of the Omega 3 data set indicated that the risk for spontaneous preterm birth decreased as the log concentration of 17-hydroxyprogesterone caproate increased (odds ratio, 0.04; 95% confidence interval, 0.00-0.90). A steady state concentration of >9 ng/mL (equivalent to >8 ng/mL at 25-28 weeks) was associated with the lowest risk for spontaneous preterm birth (hazard ratio, 0.52; 95% confidence interval, 0.27-0.98; P=.04); this concentration was not achieved in 25% of subjects who received the 250 mg weekly dose. In the Obstetrical-Fetal Pharmacology Research Units study, the adjusted half-life (median and interquartile range) of 17-hydroxyprogesterone caproate was 14.0 (11.5-17.2) days. Simulations indicated that with the 250 mg weekly dose, >5 weekly injections were required to reach the 9 ng/mL target; however, those with the shortest half-life (corresponding to higher clearance), never reached the targeted 9 ng/mL concentration. In 75% of subjects, a loading dose of 500 mg weekly for 2 weeks followed by 250 mg weekly achieved and maintained the 9 ng/mL concentration within 2 weeks but in those 25% with the shortest half-life, concentrations exceeded the 9 ng/mL target for only 3 weeks. In the Obstetrical-Fetal Pharmacology Research Centers study, all 65 subjects who received a weekly dose of 500 mg exceeded the 9 ng/mL steady state.

CONCLUSION

The dosing regimen for 17-hydroxyprogesterone caproate was inadequate. There is a significant inverse relationship between drug concentration and spontaneous preterm birth. The risk was lowest when the concentration exceeded 9 ng/mL, but 25% of women who received the 250 mg weekly dose never reached or maintained this concentration. The drug's long half-life necessitates a loading dose to achieve therapeutic concentrations rapidly. The omission of basic pharmacologic studies to determine the proper dosing may have compromised the effectiveness of 17-hydroxyprogesterone caproate. Future pharmacotherapy trials in pregnancy must first complete fundamental pharmacology studies.

A Comparison of Vaginal and Intramuscular Progesterone for the Prevention of Recurrent Preterm Birth

OBJECTIVE

This study aimed to examine whether vaginal progesterone is noninferior to 17-α hydroxyprogesterone caproate (17OHP-C) in the prevention of recurrent preterm birth (PTB).

STUDY DESIGN

This retrospective cohort study included singleton pregnancies among women with a history of spontaneous PTB who received prenatal care at a single tertiary center from 2011 to 2016. Pregnancies were excluded if progesterone was not initiated prior to 24 weeks or the fetus had a major congenital anomaly. The primary outcome was PTB <37 weeks. A priori, noninferiority was to be established if the upper bound of the adjusted two-sided 90% confidence interval (CI) for the difference in PTB fell below 9%. Inverse probability of treatment weighting (IPTW) was used to carefully control for confounding associated with choice of treatment and PTB. Adjusted differences in PTB proportions were estimated via IPTW regression, with standard errors adjustment for multiple pregnancies per woman. Secondary outcomes included PTB <34 and <28 weeks, spontaneous PTB, neonatal intensive care unit admission, and gestational age at delivery.

RESULTS

Among 858 pregnancies, 41% (n = 353) received vaginal progesterone and 59% (n = 505) were given 17OHP-C. Vaginal progesterone use was more common later in the study period, and among women who established prenatal care later, had prior PTBs at later gestational ages, and whose race/ethnicity was neither non-Hispanic white nor non-Hispanic Black. Vaginal progesterone did not meet noninferiority criteria compared with 17-OHPC in examining PTB <37 weeks, with an IPTW adjusted difference of 3.4% (90% CI: -3.5, 10.3). For secondary outcomes, IPTW adjusted differences between treatment groups were generally small and CIs were wide.

CONCLUSION

We could not conclude noninferiority of vaginal progesterone to 17OHP-C; however, women and providers may be willing to accept a larger difference (>9%) when considering the cost and availability of vaginal progesterone versus 17OHP-C. A well-designed randomized trial is needed.

KEY POINTS

· Vaginal progesterone is not noninferior to 17OHP-C.. · PTB risk may be 10% higher with vaginal progesterone.. · Associations did not differ based on obesity status..

What now? A critical evaluation of over 20 years of clinical and research experience with 17-alpha hydroxyprogesterone caproate for recurrent preterm birth prevention

Spontaneous preterm birth is multifactorial, and underlying etiologies remain incompletely understood. Supplementation with progestogens, including 17-alpha hydroxyprogesterone caproate has been a mainstay of prematurity prevention strategies in the United States in the last 2 decades. Following a recent negative confirmatory trial, 17-alpha hydroxyprogesterone caproate was withdrawn from the US market and is currently available only through clinical research studies. This expert review summarized clinical and research data regarding the use of 17-alpha hydroxyprogesterone caproate in the United States from 2003 to 2023 for recurrent prematurity prevention. In 17-alpha hydroxyprogesterone caproate. The history of the use, mechanisms of action, clinical trial results, and efficacy by clinical and biologic criteria of 17-alpha hydroxyprogesterone caproate are presented. We report that disparate findings and conclusions between similarly designed rigorous studies may reflect differences in a priori risk and population incidence and extreme care should be taken in interpreting the studies and making decisions regarding efficacy of 17-alpha hydroxyprogesterone caproate for the prevention of preterm birth. The likelihood of improved obstetrical outcomes after receiving 17-alpha hydroxyprogesterone caproate may vary by clinical factors (eg, body mass index), plasma drug concentrations, and genetic factors, although the identification of individuals most likely to benefit remains imperfect. It is crucial for the medical community to recognize the importance of preserving the decades-long efforts invested in preventing recurrent preterm birth in the United States. Moreover, it is important that we thoroughly and thoughtfully evaluate 17-alpha hydroxyprogesterone caproate as a promising contender for future well-executed prematurity studies.

A Possible Mechanism of Action of 17α-Hydroxyprogesterone Caproate: Enhanced IL-10 Production

OBJECTIVE

The rate of recurrent spontaneous preterm birth (PTB) was reduced by 33% in the Maternal-Fetal Medicine Unit (MFMU) Network trial of 17α-hydroxyprogesterone caproate (17-OHPC), but the mechanism of action, 17 years later, remains elusive. The robustness of the interleukin-10 (IL-10) response to lipopolysaccharide (LPS) stimulation of leukocytes in pregnant women with a prior PTB correlates with gestational age at delivery. This study sought to determine if there is a relationship between the concentration of 17-OHPC and response to LPS stimulation.

STUDY DESIGN

We performed a secondary analysis of data from the Omega-3 MFMU trial which evaluated the effectiveness of omega-3 fatty acid supplementation in reducing recurrent PTB. We utilized previously characterized data from a subanalyses of the Omega-3 trial of IL-10 and tumor necrosis factor alpha (TNF-α) levels from peripheral blood mononuclear cells stimulated with LPS. Blood was obtained from enrolled women at 16 to 22 weeks' gestation (baseline) and 25 to 28 weeks' gestation (posttreatment). All women received 17-OHPC and plasma 17-OHPC concentrations were measured at 25 to 28 weeks' gestation. We analyzed these data to determine if there was a relationship between 17-OHPC concentration and cytokine production. We then performed an in vitro study to determine if 17-OHPC could directly alter cytokine production by THP-1-derived macrophages.

RESULTS

In the clinical samples, we found that 17-OHPC plasma concentrations were correlated with the quantity of the LPS-stimulated production of IL-10. TNF-α production after LPS stimulation was unrelated to 17-OHPC concentration. In the in vitro study, we demonstrate a 17-OHPC concentration dependent increase in IL-10 production.

CONCLUSION

In women receiving 17-OHPC for PTB prevention, we demonstrate a relationship between plasma 17-OHPC and LPS-stimulated IL-10 production by circulating leukocytes. We also demonstrate that, in vitro, 17-OHPC treatment affects IL-10 production by LPS-stimulated macrophages. Collectively, these findings support an immunomodulatory mechanism of action of 17-OHPC in the prevention of recurrent PTB.

KEY POINTS

· 17-OHPC plasma concentrations and LPS-stimulated IL-10 levels correlate in clinical samples in women at risk for recurrent preterm birth.. · 17-OHPC can modulate the response of LPS-stimulated macrophages to increase IL-10 production.. · There was no relationship between TNF-α and plasma concentration of 17-OHPC in clinical samples or in vitro..

Relationship between plasma concentration of 17-hydroxyprogesterone caproate and gestational age at preterm delivery

BACKGROUND

The effectiveness of 17-hydroxyprogesterone caproate is unclear as trials have provided conflicting results. With the absence of fundamental pharmacologic studies addressing dosing or the relationship between drug concentration and gestational age at delivery, the effectiveness of the medication cannot be evaluated.

OBJECTIVE

This study aimed to evaluate the relationship between plasma concentrations of 17-hydroxyprogesterone caproate and preterm birth rates and gestational age at preterm delivery and to assess the safety of the 500-mg dose.

STUDY DESIGN

This study recruited 2 cohorts with previous spontaneous preterm birth; 1 cohort (n=143) was randomly assigned to either 250-mg or 500-mg 17-hydroxyprogesterone caproate, and the other cohort (n=16) was receiving the 250-mg dose for routine care. Steady-state trough plasma concentrations of 17-hydroxyprogesterone caproate obtained at 26 to 30 weeks of gestation were correlated to dose, spontaneous preterm birth rates, and measures of gestational length. Furthermore, maternal and neonatal safety outcomes were evaluated according to dose.

RESULTS

There was a dose proportional increase in trough plasma concentrations with the 250-mg (median, 8.6 ng/m; n=66) and 500-mg (median, 16.2 ng/mL; n=55) doses. In 116 compliant participants with blood samples, drug concentration was not related to the spontaneous preterm birth rate (odds ratio, 1.00; 95% confidence interval, 0.93-1.08). However, there was a significant relationship between drug concentration and both the interval from the first administration to delivery (interval A: coefficient, 1.11; 95% confidence interval, 0.00-2.23; P=.05) and the interval from the 26- to 30-week blood draw to delivery (interval B: coefficient, 1.56; 95% confidence interval, 0.25-2.87; P=.02). The spontaneous preterm birth rate or measures of gestational length were not related to dose. Postenrollment cerclage adversely affected all pharmacodynamic assessments because it was a powerful predictor of spontaneous preterm birth (odds ratio, 4.03; 95% confidence interval, 1.24-13.19; P=.021) and both measures of gestational length (interval A [coefficient, -14.9; 95% confidence interval, -26.3 to -3.4; P=.011] and interval B [coefficient, -15.9; 95% confidence interval, -25.8 to -5.9; P=.002]). Initial cervical length was significantly related to the risk of postenrollment cerclage (odds ratio, 0.80; 95% confidence interval, 0.70-0.92; P=.001). Maternal and neonatal safety outcomes were similar in both dosing groups.

CONCLUSION

In this pharmacodynamic study, trough plasma 17-hydroxyprogesterone caproate concentrations were significantly associated with gestational age at preterm birth but not with the preterm birth rate. Postenrollment cerclage was a powerful predictor of spontaneous preterm birth rate and gestational length. Initial cervical length predicted the risk of postenrollment cerclage. Adverse events were similar with the 500-mg and 250-mg doses of 17-hydroxyprogesterone caproate.

Drug development research in pregnant and lactating women

Pregnant and lactating women are considered "therapeutic orphans" because they generally have been excluded from clinical drug research and the drug development process owing to legal, ethical, and safety concerns. Most medications prescribed for pregnant and lactating women are used "off-label" because most of the clinical approved medications do not have appropriate drug labeling information for pregnant and lactating women. Medications that lack human safety data on use during pregnancy and lactation may pose potential risks for adverse effects in pregnant and lactating women as well as risks of teratogenic effects to their unborn and newborn babies. Federal policy requiring the inclusion of women in clinical research and trials led to considerable changes in research design and practice. Despite more women being included in clinical research and trials, the inclusion of pregnant and lactating women in drug research and clinical trials remains limited. A recent revision to the "Common Rule" that removed pregnant women from the classification as a "vulnerable" population may change the culture of drug research and drug development in pregnant and lactating women. This review article provides an overview of medications studied by the Obstetric-Fetal Pharmacology Research Units Network and Centers and describes the challenges in current obstetrical pharmacology research and alternative strategies for future research in precision therapeutics in pregnant and lactating women. Implementation of the recommendations of the Task Force on Research Specific to Pregnant Women and Lactating Women can provide legislative requirements and opportunities for research focused on pregnant and lactating women.

Cervical stitch (cerclage) in combination with other treatments for preventing spontaneous preterm birth in singleton pregnancies

BACKGROUND

Preterm birth (PTB) remains the foremost global cause of perinatal morbidity and mortality. Thus, the prevention of spontaneous PTB still remains of critical importance. In an attempt to prevent PTB in singleton pregnancies, cervical cerclage, in combination with other treatments, has been advocated. This is because, cervical cerclage is an intervention that is commonly recommended in women with a short cervix at high risk of preterm birth but, despite this, many women still deliver prematurely, as the biological mechanism is incompletely understood. Additionally, previous Cochrane Reviews have been published on the effectiveness of cervical cerclage in singleton and multiple pregnancies, however, none has evaluated the effectiveness of using cervical cerclage in combination with other treatments.

OBJECTIVES

To assess whether antibiotics administration, vaginal pessary, reinforcing or second cerclage placement, tocolytic, progesterone, or other interventions at the time of cervical cerclage placement prolong singleton gestation in women at high risk of pregnancy loss based on prior history and/or ultrasound finding of 'short cervix' and/or physical examination. History-indicated cerclage is defined as a cerclage placed usually between 12 and 15 weeks gestation based solely on poor prior obstetrical history, e.g. multiple second trimester losses due to painless dilatation. Ultrasound-indicated cerclage is defined as a cerclage placed usually between 16 and 23 weeks gestation for transvaginal ultrasound cervical length < 20 mm in a woman without cervical dilatation. Physical exam-indicated cerclage is defined as a cerclage placed usually between 16 and 23 weeks gestation because of cervical dilatation of one or more centimetres detected on physical (manual) examination.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (26 September 2019), and reference lists of retrieved studies.

SELECTION CRITERIA

We included published, unpublished or ongoing randomised controlled trial (RCTs). Studies using a cluster-RCT design were also eligible for inclusion in this review but none were identified. We excluded quasi-RCTs (e.g. those randomised by date of birth or hospital number) and studies using a cross-over design. We also excluded studies that specified addition of the combination therapy after cervical cerclage because the woman subsequently became symptomatic. We included studies comparing cervical cerclage in combination with one, two or more interventions with cervical cerclage alone in singleton pregnancies.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened titles and abstracts of all retrieved articles, selected studies for inclusion, extracted data, assessed risk of bias, and evaluated the certainty of the evidence for this review's main outcomes. Data were checked for accuracy. Standard Cochrane review methods were used throughout.

MAIN RESULTS

We identified two studies (involving a total of 73 women) comparing cervical cerclage alone to a different comparator. We also identified three ongoing studies (one investigating vaginal progesterone after cerclage, and two investigating cerclage plus pessary). One study (20 women), conducted in the UK, comparing cervical cerclage in combination with a tocolytic (salbutamol) with cervical cerclage alone in women with singleton pregnancy did not provide any useable data for this review. The other study (involving 53 women, with data from 50 women) took place in the USA and compared cervical cerclage in combination with a tocolytic (indomethacin) and antibiotics (cefazolin or clindamycin) versus cervical cerclage alone - this study did provide useable data for this review (and the study authors also provided additional data on request) but meta-analyses were not possible. This study was generally at a low risk of bias, apart from issues relating to blinding. We downgraded the certainty of evidence for serious risk of bias and imprecision (few participants, few events and wide 95% confidence intervals). Cervical cerclage in combination with an antibiotic and tocolytic versus cervical cerclage alone (one study, 50 women/babies) We are unclear about the effect of cervical cerclage in combination with antibiotics and a tocolytic compared with cervical cerclage alone on the risk of serious neonatal morbidity (RR 0.62, 95% CI 0.31 to 1.24; very low-certainty evidence); perinatal loss (data for miscarriage and stillbirth only - data not available for neonatal death) (RR 0.46, 95% CI 0.13 to 1.64; very low-certainty evidence) or preterm birth < 34 completed weeks of pregnancy (RR 0.78, 95% CI 0.44 to 1.40; very low-certainty evidence). There were no stillbirths (intrauterine death at 24 or more weeks). The trial authors did not report on the numbers of babies discharged home healthy (without obvious pathology) or on the risk of neonatal death.

AUTHORS' CONCLUSIONS

Currently, there is insufficient evidence to evaluate the effect of combining a tocolytic (indomethacin) and antibiotics (cefazolin/clindamycin) with cervical cerclage compared with cervical cerclage alone for preventing spontaneous PTB in women with singleton pregnancies. Future studies should recruit sufficient numbers of women to provide meaningful results and should measure neonatal death and numbers of babies discharged home healthy, as well as other important outcomes listed in this review. We did not identify any studies looking at other treatments in combination with cervical cerclage. Future research needs to focus on the role of other interventions such as vaginal support pessary, reinforcing or second cervical cerclage placement, 17-alpha-hydroxyprogesterone caproate or dydrogesterone or vaginal micronised progesterone, omega-3 long chain polyunsaturated fatty acid supplementation and bed rest.

Pharmacokinetics of 17 alpha hydroxyprogesterone caproate in singleton pregnancy and its influence of maternal body size measures

BACKGROUND

Reducing spontaneous preterm deliveries is a worldwide public health priority. Although many interventions have been studied, 1 of the most effective treatments to decrease recurrent preterm birth is the use of weekly 17 alpha hydroxy progesterone caproate. Previous studies on the influence of excessive adipose tissue and obesity on the use of 17 alpha hydroxyprogesterone caproate for the prevention of recurrent spontaneous preterm deliveries have shown conflicting findings.

OBJECTIVE

To estimate the pharmacokinetics of weekly17 alpha hydroxyprogesterone caproate in singleton and to evaluate the effect of maternal body size on the pharmacokinetics parameters.

STUDY DESIGN

A prospective, open-label, longitudinal design was implemented for this population pharmacokinetic study. Plasma samples and clinical variables were collected in pregnant women between 16 and 36 weeks' gestational age, carrying a singleton pregnancy and receiving 17 alpha hydroxyprogesterone caproate, 250 mg intramuscularly weekly for the prevention of recurrent spontaneous preterm birth. Pharmacokinetics parameters and significant clinical covariates were estimated using mixed effect modeling. Four body size indicators were used in the model to predict pharmacokinetics parameters: lean body weight, total body weight, body mass index, and body surface area.

RESULTS

A total of 56 pregnant women, aged 18-44 years with body mass index of 14.5-54.6 kg/m², provided 114 17 alpha hydroxyprogesterone caproate plasma samples concentration for analysis. A 1-compartment model with first-order absorption satisfactorily described 17 alpha hydroxyprogesterone caproate pharmacokinetics. Compared to other body size indicators, lean body weight best explained intersubject variability. Age, race, and gestational age did not influence 17 alpha hydroxyprogesterone caproate pharmacokinetics. Lean body weight was the best descriptor for the influence of body size on 17 alpha hydroxyprogesterone caproate apparent clearance. Simulations showed that administration of a standard fixed dose of 250 mg intramuscularly produced substantially lower 17 alpha hydroxyprogesterone caproate plasma concentrations in pregnant women with body mass index >30 kg/m² compared to those with body mass index <30 kg/m². Conversely, adjustment of the standard dose for differences in total body weight among women resulted in markedly higher 17 alpha hydroxyprogesterone caproate concentrations in women with body mass index >30 kg/m² compared to women with lower body mass index. Administration of doses adjusted for lean body weight produced nearly identical 117 alpha hydroxyprogesterone caproate plasma concentrations in both the low- and high-body mass index groups.

CONCLUSION

Population pharmacokinetics analysis indicates the clearance significantly increases with increasing lean body mass. Higher 17 alpha hydroxyprogesterone caproate doses, adjusted by maternal lean body mass, may be required in patients with a body mass index >30 to achieve equivalent plasma concentrations in pregnant women with a body mass index <30. Adjustment of 17 alpha hydroxyprogesterone caproate doses for lean body weight produces equivalent systemic 17 alpha hydroxyprogesterone caproate exposure in pregnant women regardless of body size.

A systematic review and meta-analysis of randomized controlled trials comparing 17-alpha-hydroxyprogesterone caproate versus placebo for the prevention of recurrent preterm birth

BACKGROUND

Preterm birth causes an increased risk for perinatal morbidity and mortality.

OBJECTIVE

To determine whether mid-trimester 17-alpha-hydroxyprogesterone caproate (17-OHPC) reduces the risk of recurrent preterm birth and adverse perinatal outcomes.

SEARCH STRATEGY

Systematic search to identify relevant studies published in different languages, registered after 2000, using appropriate MeSH terms.

SELECTION CRITERIA

Inclusion criteria were women between 16 and 26⁺⁶  weeks of pregnancy with history of preterm delivery in any pregnancy randomized to either 17-OHPC or placebo/no treatment.

DATA COLLECTION AND ANALYSIS

The number of preterm births and adverse outcomes in the 17-OHPC and placebo arms over the total number of patients in each randomized group were used to calculate the risk ratio (RR) by random-effects models using the Mantel-Haenszel method. Between-study heterogeneity was assessed using tau² , χ² (Cochrane Q), and I² statistics.

MAIN RESULTS

Four studies were included. There was a 29% (RR 0.71; 95% CI, 0.53-0.96; P=0.001), 26% (RR 0.74; 95% CI, 0.58-0.96; P=0.021), and 40% (RR 0.60; 95% CI, 0.42-0.85; P=0.004) reduction in recurrent preterm birth at <37, <35, and <32 weeks, respectively, in the 17-OHPC group compared with placebo. The reduction in neonatal death was 68% (RR 0.32; 95% CI, 0.15-0.66; P=0.002).

CONCLUSIONS

17-OHPC could reduce the risk of recurrent preterm birth at <37, <35, and <28 weeks and neonatal death.

PROSPERO

CDR42017082190.

Omega-3 fatty acid addition during pregnancy

BACKGROUND

Higher intakes of foods containing omega-3 long-chain polyunsaturated fatty acids (LCPUFA), such as fish, during pregnancy have been associated with longer gestations and improved perinatal outcomes. This is an update of a review that was first published in 2006.

OBJECTIVES

To assess the effects of omega-3 LCPUFA, as supplements or as dietary additions, during pregnancy on maternal, perinatal, and neonatal outcomes and longer-term outcomes for mother and child.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (16 August 2018), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing omega-3 fatty acids (as supplements or as foods, stand-alone interventions, or with a co-intervention) during pregnancy with placebo or no omega-3, and studies or study arms directly comparing omega-3 LCPUFA doses or types. Trials published in abstract form were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data, assessed risk of bias in trials and assessed quality of evidence for prespecified birth/infant, maternal, child/adult and health service outcomes using the GRADE approach.

MAIN RESULTS

In this update, we included 70 RCTs (involving 19,927 women at low, mixed or high risk of poor pregnancy outcomes) which compared omega-3 LCPUFA interventions (supplements and food) compared with placebo or no omega-3. Overall study-level risk of bias was mixed, with selection and performance bias mostly at low risk, but there was high risk of attrition bias in some trials. Most trials were conducted in upper-middle or high-income countries; and nearly half the trials included women at increased/high risk for factors which might increase the risk of adverse maternal and birth outcomes.Preterm birth < 37 weeks (13.4% versus 11.9%; risk ratio (RR) 0.89, 95% confidence interval (CI) 0.81 to 0.97; 26 RCTs, 10,304 participants; high-quality evidence) and early preterm birth < 34 weeks (4.6% versus 2.7%; RR 0.58, 95% CI 0.44 to 0.77; 9 RCTs, 5204 participants; high-quality evidence) were both lower in women who received omega-3 LCPUFA compared with no omega-3. Prolonged gestation > 42 weeks was probably increased from 1.6% to 2.6% in women who received omega-3 LCPUFA compared with no omega-3 (RR 1.61 95% CI 1.11 to 2.33; 5141 participants; 6 RCTs; moderate-quality evidence).For infants, there was a possibly reduced risk of perinatal death (RR 0.75, 95% CI 0.54 to 1.03; 10 RCTs, 7416 participants; moderate-quality evidence: 62/3715 versus 83/3701 infants) and possibly fewer neonatal care admissions (RR 0.92, 95% CI 0.83 to 1.03; 9 RCTs, 6920 participants; moderate-quality evidence - 483/3475 infants versus 519/3445 infants). There was a reduced risk of low birthweight (LBW) babies (15.6% versus 14%; RR 0.90, 95% CI 0.82 to 0.99; 15 trials, 8449 participants; high-quality evidence); but a possible small increase in large-for-gestational age (LGA) babies (RR 1.15, 95% CI 0.97 to 1.36; 6 RCTs, 3722 participants; moderate-quality evidence, for omega-3 LCPUFA compared with no omega-3. Little or no difference in small-for-gestational age or intrauterine growth restriction (RR 1.01, 95% CI 0.90 to 1.13; 8 RCTs, 6907 participants; moderate-quality evidence) was seen.For the maternal outcomes, there is insufficient evidence to determine the effects of omega-3 on induction post-term (average RR 0.82, 95% CI 0.22 to 2.98; 3 trials, 2900 participants; low-quality evidence), maternal serious adverse events (RR 1.04, 95% CI 0.40 to 2.72; 2 trials, 2690 participants; low-quality evidence), maternal admission to intensive care (RR 0.56, 95% CI 0.12 to 2.63; 2 trials, 2458 participants; low-quality evidence), or postnatal depression (average RR 0.99, 95% CI 0.56 to 1.77; 2 trials, 2431 participants; low-quality evidence). Mean gestational length was greater in women who received omega-3 LCPUFA (mean difference (MD) 1.67 days, 95% CI 0.95 to 2.39; 41 trials, 12,517 participants; moderate-quality evidence), and pre-eclampsia may possibly be reduced with omega-3 LCPUFA (RR 0.84, 95% CI 0.69 to 1.01; 20 trials, 8306 participants; low-quality evidence).For the child/adult outcomes, very few differences between antenatal omega-3 LCPUFA supplementation and no omega-3 were observed in cognition, IQ, vision, other neurodevelopment and growth outcomes, language and behaviour (mostly low-quality to very low-quality evidence). The effect of omega-3 LCPUFA on body mass index at 19 years (MD 0, 95% CI -0.83 to 0.83; 1 trial, 243 participants; very low-quality evidence) was uncertain. No data were reported for development of diabetes in the children of study participants.

AUTHORS' CONCLUSIONS

In the overall analysis, preterm birth < 37 weeks and early preterm birth < 34 weeks were reduced in women receiving omega-3 LCPUFA compared with no omega-3. There was a possibly reduced risk of perinatal death and of neonatal care admission, a reduced risk of LBW babies; and possibly a small increased risk of LGA babies with omega-3 LCPUFA.For our GRADE quality assessments, we assessed most of the important perinatal outcomes as high-quality (e.g. preterm birth) or moderate-quality evidence (e.g. perinatal death). For the other outcome domains (maternal, child/adult and health service outcomes) GRADE ratings ranged from moderate to very low, with over half rated as low. Reasons for downgrading across the domain were mostly due to design limitations and imprecision.Omega-3 LCPUFA supplementation during pregnancy is an effective strategy for reducing the incidence of preterm birth, although it probably increases the incidence of post-term pregnancies. More studies comparing omega-3 LCPUFA and placebo (to establish causality in relation to preterm birth) are not needed at this stage. A further 23 ongoing trials are still to report on over 5000 women, so no more RCTs are needed that compare omega-3 LCPUFA against placebo or no intervention. However, further follow-up of completed trials is needed to assess longer-term outcomes for mother and child, to improve understanding of metabolic, growth and neurodevelopment pathways in particular, and to establish if, and how, outcomes vary by different types of omega-3 LCPUFA, timing and doses; or by characteristics of women.

Prevention of Prematurity: Advances and Opportunities

Preterm birth (PTB) rate varies widely and has significant racial and ethnic disparities. Although causal mechanisms are ill understood, socioenvironment, phenotype, and genotype provide insight into pathways for preventing PTB. Data suggest varied response to current medical interventions is explicable Approved by underlying pharmacogenomics. Currently, prevention focuses on minimizing iatrogenic PTB and risk reduction especially in those with prior PTB using proven medical and public health strategies. In the future, preventive approaches will be based on better understanding of sociodemography, nutrition, lifestyles, and underlying individual genetic and epigenetic variation. Statistical approaches and "big-data" models are critical in future study.

Epigenetic Regulation of the Nitric Oxide Pathway, 17-α Hydroxyprogesterone Caproate, and Recurrent Preterm Birth

OBJECTIVE

We sought to evaluate nitric oxide pathway placental gene expression and the epigenome (CpG methylation) among women receiving 17-α hydroxyprogesterone caproate (17-OHPC) with and without recurrent preterm birth (PTB).

STUDY DESIGN

This was a case-control study. We prospectively recruited women with ≥ 1 prior singleton spontaneous PTB <34 weeks receiving 17-OHPC. DNA and RNA were isolated from placentas. RNA abundance (gene expression) and the methylome were analyzed for 84 genes in nitric oxide pathways. Women with recurrent PTB <34 weeks (cases) were compared with those delivering at term (controls). Statistical analysis included multivariable models with Bonferroni's corrected p-values.

RESULTS

In this study, 17 women met inclusion criteria; 7 preterm cases (delivered at 22.6 ± 2.9 weeks) and 10 term controls (delivered at 38.5 ± 0.8 weeks). Groups had similar PTB history, race/ethnicity, and socioeconomic risk factors for PTB. Twenty-seven nitric oxide genes displayed differential expression (p < 0.05 and q < 0.10) when comparing placentas from preterm cases and term controls; all were downregulated in preterm cases. Eight hundred sixty corresponding CpG sites were differentially methylated between the preterm cases and term controls (Bonferroni's p-value <0.05).

CONCLUSION

CpG methylation and gene expression patterns in nitric oxide pathway genes differ among placentas from recurrent PTB compared with term birth following 17-OHPC exposure.

Impact of Pregnancy History and 17-Hydroxyprogesterone Caproate on Cervical Cytokines and Matrix Metalloproteinases

OBJECTIVE

 The objective of this study was to evaluate the impact of pregnancy history and 17-hydroxyprogesterone caproate (17-OHPC) treatment on cervical fluid cytokines and matrix metalloproteinases (MMPs).

STUDY DESIGN

 Cervical fluid was obtained between 160/7 and 246/7 weeks from women with only prior term births (controls, n = 26), women with one or more prior spontaneous preterm births (SPTBs) choosing to receive 17-OHPC (17-OHPC, n = 24), or to not receive 17-OHPC (refusers, n = 12). Cervical fluid collections were repeated 2, 4, and 8 weeks after the first sample and concentrations of MMPs and cytokines were measured by multiplex immune assay.

RESULTS

 Among women whose earliest prior delivery occurred between 16 and 23 weeks, cervical fluid concentration of interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-α at baseline were significantly elevated when compared with cervical cytokines of women whose earliest delivery occurred between 32 and 36 weeks (relative risk ratio was 3.37 for IL-6 [95% confidence interval, CI, 1.08-10.53, p < 0.05], 2.81 for IL-10 [95% CI, 1.39-5.70, p < 0.05], and 6.34 for TNF-α [95% CI, 2.19-18.68, p < 0.001]). Treatment with 17-OHPC had no significant impact on these cytokines.

CONCLUSION

 The cervical fluid of women with a history of an early prior SPTB is characterized by inflammation that is unaffected by 17-OHPC.

Pharmacokinetics of Hydroxyprogesterone Caproate and its Primary Metabolites during Pregnancy

Objective  To measure pharmacokinetics of hydroxyprogesterone caproate (OHPC) and its major metabolites throughout pregnancy. Study Design  Thirty women were prescribed OHPC for recurrent preterm birth prevention. Three cohorts of subjects had blood drawn for 7 consecutive days at one of three times: cohort 1 ( n  = 6) after the first dose (weeks 16-20), cohort 2 ( n  = 8) between weeks 24 and 28, and cohort 3 ( n  = 16) between weeks 32 and 36. We measured serum trough levels after week 1 in cohort 1 or after two consecutive weekly doses in cohorts 2 and 3. In 10 subjects, we estimated OHPC terminal half-life at 28 days after their last dose. Results  In cohorts 1, 2, and 3, the areas under curve (ng × h/mL) for OHPC were 571.4 ± 195.2, 1,269.6 ± 285.0, and 1,268.0 ± 511.6, respectively. Maximum OHPC levels (ng/mL) were 5.0 ± 1.5, 12.5 ± 3.9, and 12.3 ± 4.9, respectively. The areas under the curve for mono-hydroxylated metabolites were 208.5 ± 92.4, 157.1 ± 64.6, and 211.2 ± 113.1, and maximum concentrations were 1.9 ± 0.7, 1.5 ± 0.7, and 1.8 ± 1.0, respectively. Di-hydroxylated metabolite levels were significantly lower than mono-hydroxylated metabolites. Estimated terminal half-life of OHPC was 16.3 ± 3.6 days and 19.7 ± 6.2 days for the mono-hydroxylated metabolites. Conclusion  After the first injection, OHPC maximum serum level was approximately half steady-state level. Measurable metabolites of unknown activity were detected.

In an in-vitro model using human fetal membranes, 17-α hydroxyprogesterone caproate is not an optimal progestogen for inhibition of fetal membrane weakening

BACKGROUND

The progestogen 17-α hydroxyprogesterone caproate (17-OHPC) is 1 of only 2 agents recommended for clinical use in the prevention of spontaneous preterm delivery, and studies of its efficacy have been conflicting. We have developed an in-vitro model to study the fetal membrane weakening process that leads to rupture in preterm premature rupture of the fetal membranes (pPROM). Inflammation/infection associated with tumor necrosis factor-α (TNF-α) induction and decidual bleeding/abruption associated thrombin release are leading causes of preterm premature rupture of the fetal membranes. Both agents (TNF-α and thrombin) cause fetal membrane weakening in the model system. Furthermore, granulocyte-macrophage colony-stimulating factor (GM-CSF) is a critical intermediate for both TNF-α and thrombin-induced fetal membrane weakening. In a previous report, we demonstrated that 3 progestogens, progesterone, 17-alpha hydroxyprogesterone (17-OHP), and medroxyprogesterone acetate (MPA), each inhibit both TNF-α- and thrombin-induced fetal membrane weakening at 2 distinct points of the fetal membrane weakening pathway. Each block both the production of and the downstream action of the critical intermediate granulocyte-macrophage colony-stimulating factor.

OBJECTIVE

The objective of the study was to characterize the inhibitory effects of 17-OHPC on TNF-α- and thrombin-induced fetal membrane weakening in vitro.

STUDY DESIGN

Full-thickness human fetal membrane fragments from uncomplicated term repeat cesarean deliveries were mounted in 2.5 cm Transwell inserts and cultured with/without 17-alpha hydroxyprogesterone caproate (10^-9 to 10^-7 M). After 24 hours, medium (supernatant) was removed and replaced with/without the addition of tumor necrosis factor-alpha (20 ng/mL) or thrombin (10 U/mL) or granulocyte-macrophage colony-stimulating factor (200 ng/mL). After 48 hours of culture, medium from the maternal side compartment of the model was assayed for granulocyte-macrophage colony-stimulating factor and the fetal membrane fragments were rupture strength tested.

RESULTS

Tumor necrosis factor-alpha and thrombin both weakened fetal membranes (43% and 62%, respectively) and increased granulocyte-macrophage colony-stimulating factor levels (3.7- and 5.9-fold, respectively). Pretreatment with 17-alpha hydroxyprogesterone caproate inhibited both tumor necrosis factor-alpha- and thrombin-induced fetal membrane weakening and concomitantly inhibited the induced increase in granulocyte-macrophage colony-stimulating factor in a concentration-dependent manner. However, contrary to our prior reports regarding progesterone and other progestogens, 17-alpha hydroxyprogesterone caproate did not also inhibit granulocyte-macrophage colony-stimulating factor-induced fetal membrane weakening.

CONCLUSION

17-Alpha hydroxyprogesterone caproate blocks tumor necrosis factor-alpha- and thrombin-induced fetal membrane weakening by inhibiting the production of granulocyte-macrophage colony-stimulating factor. However, 17-alpha hydroxyprogesterone caproate did not also inhibit granulocyte-macrophage colony-stimulating factor-induced weakening. We speculate that progestogens other than 17-alpha hydroxyprogesterone caproate may be more efficacious in preventing preterm premature rupture of the fetal membranes-related spontaneous preterm birth.

17-alpha hydroxyprogesterone caproate for preterm birth prevention: Where have we been, how did we get here, and where are we going?

Prematurity is a major public health problem in the United States and worldwide. Women with a history of a previous preterm birth are at high risk for recurrence. Progesterone is a key hormone involved in pregnancy maintenance. In general, progesterone is thought to maintain pregnancy through several closely linked mechanisms: (1) promotion of uterine quiescence, (2) inhibition of pro-inflammatory cells, and (3) immunosuppressive action. 17-Alpha hydroxyprogesterone caproate is currently the only medication approved to prevent recurrent preterm birth. The purpose of this review is to discuss the history of 17-alpha hydroxyprogesterone caproate use for recurrent preterm birth prevention, the rationale behind 17-alpha hydroxyprogesterone caproate administration, and current evidence-based indications for 17-alpha hydroxyprogesterone caproate use.

The association among cytochrome P450 3A, progesterone receptor polymorphisms, plasma 17-alpha hydroxyprogesterone caproate concentrations, and spontaneous preterm birth

BACKGROUND

Infants born <37 weeks' gestation are of public health concern since complications associated with preterm birth are the leading cause of mortality in children <5 years of age and a major cause of morbidity and lifelong disability. The administration of 17-alpha hydroxyprogesterone caproate reduces preterm birth by 33% in women with history of spontaneous preterm birth. We demonstrated previously that plasma concentrations of 17-alpha hydroxyprogesterone caproate vary widely among pregnant women and that women with 17-alpha hydroxyprogesterone caproate plasma concentrations in the lowest quartile had spontaneous preterm birth rates of 40% vs rates of 25% in those women with higher concentrations. Thus, plasma concentrations are an important factor in determining drug efficacy but the reason 17-alpha hydroxyprogesterone caproate plasma concentrations vary so much is unclear. Predominantly, 17-alpha hydroxyprogesterone caproate is metabolized by CYP3A4 and CYP3A5 enzymes.

OBJECTIVE

We sought to: (1) determine the relation between 17-alpha hydroxyprogesterone caproate plasma concentrations and single nucleotide polymorphisms in CYP3A4 and CYP3A5; (2) test the association between progesterone receptor single nucleotide polymorphisms and spontaneous preterm birth; and (3) test whether the association between plasma concentrations of 17-alpha hydroxyprogesterone caproate and spontaneous preterm birth varied by progesterone receptor single nucleotide polymorphisms.

STUDY DESIGN

In this secondary analysis, we evaluated genetic polymorphism in 268 pregnant women treated with 17-alpha hydroxyprogesterone caproate, who participated in a placebo-controlled trial to evaluate the benefit of omega-3 supplementation in women with history of spontaneous preterm birth. Trough plasma concentrations of 17-alpha hydroxyprogesterone caproate were measured between 25-28 weeks of gestation after a minimum of 5 injections of 17-alpha hydroxyprogesterone caproate. We extracted DNA from maternal blood samples and genotyped the samples using TaqMan (Applied Biosystems, Foster City, CA) single nucleotide polymorphism genotyping assays for the following single nucleotide polymorphisms: CYP3A4*1B, CYP3A4*1G, CYP3A4*22, and CYP3A5*3; and rs578029, rs471767, rs666553, rs503362, and rs500760 for progesteronereceptor. We adjusted for prepregnancy body mass index, race, and treatment group in a multivariable analysis. Differences in the plasma concentrations of 17-alpha hydroxyprogesterone caproate by genotype were evaluated for each CYP single nucleotide polymorphism using general linear models. The association between progesterone receptor single nucleotide polymorphisms and frequency of spontaneous preterm birth was tested using logistic regression. A logistic model also tested interaction between 17-alpha hydroxyprogesterone caproate concentrations with each progesterone receptor single nucleotide polymorphism for the outcome of spontaneous preterm birth.

RESULTS

The association between CYP single nucleotide polymorphisms *22, *1G, *1B, and *3 and trough plasma concentrations of 17-alpha hydroxyprogesterone caproate was not statistically significant (P = .68, .44, .08, and .44, respectively). In an adjusted logistic regression model, progesterone receptor single nucleotide polymorphisms rs578029, rs471767, rs666553, rs503362, and rs500760 were not associated with the frequency of spontaneous preterm birth (P = .29, .10, .76, .09, and .43, respectively). Low trough plasma concentrations of 17-alpha hydroxyprogesterone caproate were statistically associated with a higher frequency of spontaneous preterm birth (odds ratio, 0.78; 95% confidence ratio, 0.61-0.99; P = .04 for trend across quartiles), however no significant interaction with the progesterone receptor single nucleotide polymorphisms rs578029, rs471767, rs666553, rs503362, and rs500760 was observed (P = .13, .08, .10, .08, and .13, respectively).

CONCLUSION

The frequency of recurrent spontaneous preterm birth appears to be associated with trough 17-alpha hydroxyprogesterone caproate plasma concentrations. However, the wide variation in trough 17-alpha hydroxyprogesterone caproate plasma concentrations is not attributable to polymorphisms in CYP3A4 and CYP3A5 genes. Progesterone receptor polymorphisms do not predict efficacy of 17-alpha hydroxyprogesterone caproate. The limitations of this secondary analysis include that we had a relative small sample size (n = 268) and race was self-reported by the patients.

Gestational age at initiation of 17-alpha hydroxyprogesterone caproate and recurrent preterm birth

BACKGROUND

Preterm birth is the leading cause of neonatal morbidity and mortality in nonanomalous neonates in the United States. Women with a previous early spontaneous preterm birth are at highest risk for recurrence. Weekly intramuscular 17-alpha hydroxyprogesterone caproate reduces the risk of recurrent prematurity. Although current guidelines recommend 17-alpha hydroxyprogesterone caproate initiation between 16 and 20 weeks, in clinical practice, 17-alpha hydroxyprogesterone caproate is started across a spectrum of gestational ages.

OBJECTIVE

The objective of the study was to examine the relationship between the gestational age at 17-alpha hydroxyprogesterone caproate initiation and recurrent preterm birth among women with a prior spontaneous preterm birth 16-28 weeks' gestation.

STUDY DESIGN

This was a retrospective cohort study of women from a single tertiary care center, 2005-2016. All women with ≥1 singleton preterm births because of a spontaneous onset of contractions, preterm prelabor rupture of membranes, or painless cervical dilation between 16 and 28 weeks followed by a subsequent singleton pregnancy treated with 17-alpha hydroxyprogesterone caproate were included. Women were grouped based on quartiles of gestational age of 17-alpha hydroxyprogesterone caproate initiation (quartile 1, 14^0/7 to 16^1/7; quartile 2, 16^2/7 to 17^0/7; quartile 3, 17^1/7 to 18^6/7; and quartile 4, 19^0/7 to 27^5/7). Women with a gestational age of 17-alpha hydroxyprogesterone caproate initiation in quartiles 1 and 2 were considered to have early-start 17-alpha hydroxyprogesterone caproate; those in quartiles 3 and 4 were considered to have late-start 17-alpha hydroxyprogesterone caproate. The primary outcome was recurrent preterm birth <37 weeks' gestation. Secondary outcomes included recurrent preterm birth <34 and <28 weeks' gestation and composite major neonatal morbidity (diagnosis of grade III or IV intraventricular hemorrhage, periventricular leukomalacia, bronchopulmonary dysplasia, necrotizing enterocolitis stage II or III, or death). Gestational age at delivery was compared by quartile of 17-alpha hydroxyprogesterone caproate initiation using Kaplan-Meier survival curves and the log-rank test. Logistic regression models estimated odds ratios for the association between gestational age at 17-alpha hydroxyprogesterone caproate initiation and preterm birth <37 weeks' gestation, adjusting for demographics, prior pregnancy and antenatal characteristics.

RESULTS

A total of 132 women met inclusion criteria; 52 (39.6%) experienced recurrent preterm birth <37 weeks in the studied pregnancy. 17-Alpha hydroxyprogesterone caproate was initiated at a mean 17^6/7 ± 2.5 weeks. Demographic and baseline characteristics were similar between women with early-start 17-alpha hydroxyprogesterone caproate (quartiles 1 and 2) compared with those with late-start 17-alpha hydroxyprogesterone caproate (quartiles 3 and 4). Women with early-start 17-alpha hydroxyprogesterone caproate trended toward lower rates of recurrent preterm birth <37 weeks compared with those with late-start 17-alpha hydroxyprogesterone caproate (41.3% vs 57.7%, P = .065). Delivery gestational age was inversely proportional to gestational age at 17-alpha hydroxyprogesterone caproate initiation (quartile 1, 37^4/7 weeks vs quartile 2, 36^5/7 vs quartile 3, 36^1/7 weeks vs quartile 4, 34^0/7, P = .007). In Kaplan-Meier survival analyses, these differences in delivery gestational age by 17-alpha hydroxyprogesterone caproate initiation quartile persisted across pregnancy (log-rank P < .001). In regression models, later initiation of 17-alpha hydroxyprogesterone caproate was significantly associated with increased odds of preterm birth <37 weeks. Women with early 17-alpha hydroxyprogesterone caproate initiation also had lower rates of major neonatal morbidity than those with later 17-alpha hydroxyprogesterone caproate initiation (1.5% vs 14.3%, P = .005).

CONCLUSION

Rates of recurrent preterm birth among women with a prior spontaneous preterm birth 16-28 weeks are high. Women beginning 17-alpha hydroxyprogesterone caproate early deliver later and have improved neonatal outcomes. Clinicians should make every effort to facilitate 17-alpha hydroxyprogesterone caproate initiation at 16 weeks.

Vaginal progesterone to reduce preterm birth among HIV-infected pregnant women in Zambia: a feasibility study protocol

Background

Women infected with HIV have a risk of preterm birth (PTB) that is twice that among uninfected women, and treatment with antiretroviral therapy (ART) may further increase this risk. Progesterone supplementation reduces the risk of preterm delivery in women who have a shortened cervix in the midtrimester. We propose to study the feasibility of a trial of vaginal progesterone (VP) to prevent PTB among HIV-infected women receiving ART in pregnancy. Given low adherence among women self-administering vaginal study product in recent microbicide trials, we plan to investigate whether adequate adherence to VP can be achieved prior to launching a full-scale efficacy trial.

Methods and design

One hundred forty HIV-infected pregnant women in Lusaka, Zambia, will be randomly allocated to daily self-administration of either VP or matched placebo, starting between 20 and 24 gestational weeks. The primary outcome will be adherence, defined as the proportion of participants who achieve at least 80% use of study product, assessed objectively with a validated dye stain assay that confirms vaginal insertion of returned single-use applicators. Secondary outcomes will be study uptake, retention, and preliminary efficacy. We will concurrently perform semi-structured interviews with participants enrolled in the study and with women who decline enrollment to assess the acceptability of VP to prevent PTB and of enrollment to a randomized controlled trial.

Discussion

We hypothesize that VP could prevent PTB among women receiving ART in pregnancy. In preparation for a trial to test this hypothesis, we plan to assess whether participants will be adherent to study product and protocol.

Trial registration

ClinicalTrial.gov, NCT02970552.

17-alpha Hydroxyprogesterone caproate did not reduce the rate of recurrent preterm birth in a prospective cohort study

BACKGROUND

17-alpha Hydroxyprogesterone caproate for prevention of recurrent preterm birth is recommended for use in the United States.

OBJECTIVE

We sought to assess the clinical effectiveness of 17-alpha hydroxyprogesterone caproate to prevent recurrent preterm birth ≤35 weeks compared to similar births in our obstetric population prior to the implementation of 17-alpha hydroxyprogesterone caproate.

STUDY DESIGN

This was a prospective cohort study of 17-alpha hydroxyprogesterone caproate in our obstetric population. The primary outcome was the recurrence of birth ≤35 weeks for the entire study cohort compared to a historical referent rate of 16.8% of recurrent preterm birth in our population. There were 3 secondary outcomes. First, did 17-alpha hydroxyprogesterone caproate modify a woman's history of preterm birth when taking into account her prior number and sequence of preterm and term births? Second, was recurrence of preterm birth related to 17-alpha hydroxyprogesterone caproate plasma concentration? Third, was duration of pregnancy modified by 17-alpha hydroxyprogesterone caproate treatment compared to a prior preterm birth?

RESULTS

From January 2012 through March 2016, 430 consecutive women with prior births ≤35 weeks were treated with 17-alpha hydroxyprogesterone caproate. Nearly two thirds of the women (N = 267) began injections ≤18 weeks and 394 (92%) received a scheduled weekly injection within 10 days of reaching 35 weeks or delivery. The overall rate of recurrent preterm birth was 25% (N = 106) for the entire cohort compared to the 16.8% expected rate (P = 1.0). The 3 secondary outcomes were also negative. First, 17-alpha hydroxyprogesterone caproate did not significantly reduce the rates of recurrence regardless of prior preterm birth number or sequence. Second, plasma concentrations of 17-alpha hydroxyprogesterone caproate were not different (P = .17 at 24 weeks; P = .38 at 32 weeks) between women delivered ≤35 weeks and those delivered later in pregnancy. Third, the mean (±SD) interval in weeks of recurrent preterm birth before 17-alpha hydroxyprogesterone caproate use was 0.4 ± 5.3 weeks and the interval of recurrent preterm birth after 17-alpha hydroxyprogesterone caproate treatment was 0.1 ± 4.7 weeks (P = .63). A side effect of weekly 17-alpha hydroxyprogesterone caproate injections was an increase in gestational diabetes. Specifically, the rate of gestational diabetes was 13.4% in 17-alpha hydroxyprogesterone caproate-treated women compared to 8% in case-matched controls (P = .001).

CONCLUSION

17-alpha Hydroxyprogesterone caproate was ineffective for prevention of recurrent preterm birth and was associated with an increased rate of gestational diabetes.

17-α Hydroxyprogesterone Caproate for the Prevention of Recurrent Preterm Birth: One Size May Not Fit All

Spontaneous preterm birth is a syndrome with many causes and thus unresponsive to a single intervention. It logically follows that patients with a prior spontaneous preterm birth are a heterogeneous group unlikely to respond equally to a single preventive intervention such as 17-α hydroxyprogesterone caproate. Further confounding this issue is our fundamental lack of knowledge about the mechanism(s) by which 17-α hydroxyprogesterone caproate reduces preterm birth. Recently, studies demonstrating that responders and nonresponders can be identified based on obstetric history, genotype, physical characteristics, and behavioral factors have begun to provide clues into both 17-α hydroxyprogesterone caproate's mechanism and the pathophysiology of recurrent preterm birth and may allow for more targeted therapy. These studies lend support to speculation that inflammation or nitric oxide metabolism may be common threads between 17-α hydroxyprogesterone caproate's mechanism and preterm birth prevention. It will remain critically important to avoid the temptation to regard prior spontaneous preterm birth as a single disease entity amenable to a single treatment.

Benefits and Risks of Antiretroviral Therapy for Perinatal HIV Prevention

BACKGROUND

Randomized-trial data on the risks and benefits of antiretroviral therapy (ART) as compared with zidovudine and single-dose nevirapine to prevent transmission of the human immunodeficiency virus (HIV) in HIV-infected pregnant women with high CD4 counts are lacking.

METHODS

We randomly assigned HIV-infected women at 14 or more weeks of gestation with CD4 counts of at least 350 cells per cubic millimeter to zidovudine and single-dose nevirapine plus a 1-to-2-week postpartum "tail" of tenofovir and emtricitabine (zidovudine alone); zidovudine, lamivudine, and lopinavir-ritonavir (zidovudine-based ART); or tenofovir, emtricitabine, and lopinavir-ritonavir (tenofovir-based ART). The primary outcomes were HIV transmission at 1 week of age in the infant and maternal and infant safety.

RESULTS

The median CD4 count was 530 cells per cubic millimeter among 3490 primarily black African HIV-infected women enrolled at a median of 26 weeks of gestation (interquartile range, 21 to 30). The rate of transmission was significantly lower with ART than with zidovudine alone (0.5% in the combined ART groups vs. 1.8%; difference, -1.3 percentage points; repeated confidence interval, -2.1 to -0.4). However, the rate of maternal grade 2 to 4 adverse events was significantly higher with zidovudine-based ART than with zidovudine alone (21.1% vs. 17.3%, P=0.008), and the rate of grade 2 to 4 abnormal blood chemical values was higher with tenofovir-based ART than with zidovudine alone (2.9% vs. 0.8%, P=0.03). Adverse events did not differ significantly between the ART groups (P>0.99). A birth weight of less than 2500 g was more frequent with zidovudine-based ART than with zidovudine alone (23.0% vs. 12.0%, P<0.001) and was more frequent with tenofovir-based ART than with zidovudine alone (16.9% vs. 8.9%, P=0.004); preterm delivery before 37 weeks was more frequent with zidovudine-based ART than with zidovudine alone (20.5% vs. 13.1%, P<0.001). Tenofovir-based ART was associated with higher rates than zidovudine-based ART of very preterm delivery before 34 weeks (6.0% vs. 2.6%, P=0.04) and early infant death (4.4% vs. 0.6%, P=0.001), but there were no significant differences between tenofovir-based ART and zidovudine alone (P=0.10 and P=0.43). The rate of HIV-free survival was highest among infants whose mothers received zidovudine-based ART.

CONCLUSIONS

Antenatal ART resulted in significantly lower rates of early HIV transmission than zidovudine alone but a higher risk of adverse maternal and neonatal outcomes. (Funded by the National Institutes of Health; PROMISE ClinicalTrials.gov numbers, NCT01061151 and NCT01253538 .).

Smoking, 17 Alpha-Hydroxyprogesterone Caproate, and Preterm Birth

Objective The objective of this study was to determine if maternal smoking modifies the effectiveness of 17 α-hydroxyprogesterone caproate (17OHP-C). Study Design Secondary analysis of the Maternal-Fetal Medicine Units Network trial of 17OHP-C. The prevalence of preterm birth (PTB) by smoking status and treatment group was compared by chi-squared analysis and analysis of variance was used to compare gestational age (GA) at birth. Multivariable modeling was used to estimate the effect of smoking on 17OHP-C treatment. Results In this study, 459 women were included. Maternal smoking significantly modified the effectiveness of 17OHP-C treatment. In smokers, 17OHP-C significantly reduced the prevalence of multiple outcomes (PTB < 37 and < 35 weeks, spontaneous PTB < 37 and < 35 weeks), while in nonsmokers, only PTB < 37 weeks was reduced. Delivery GA was later in 17OHP-C versus placebo treated smokers (36.4 vs. 34.3 weeks, p = 0.041) but not nonsmokers (36.3 vs. 35.5 weeks, p = nonsignificant). In multivariable modeling, 17OHP-C was more effective in smokers than nonsmokers as measured by multiple outcomes (PTB < 37 weeks [p = 0.041] and < 35 weeks [p = 0.036] and spontaneous PTB < 37 weeks [p = 0.029]). Conclusion In this cohort of women with a prior PTB, maternal smoking status significantly modified the effectiveness of 17OHP-C treatment.

What we have learned about the role of 17-alpha-hydroxyprogesterone caproate in the prevention of preterm birth

Despite major advances in neonatal care, the burden of preterm birth remains high. This is not unexpected since strategies to identify and treat risk factors in early pregnancy have not been very effective in reducing the preterm birth rate. Initial studies suggested a potential benefit for 17-alpha-hydroxyprogesterone caproate (17-OHPC) in decreasing the risk of recurrent preterm birth women with a singleton gestation. However, the use of 17-OHPC has not conferred benefit for other categories of women at high risk for preterm delivery (twins, triplets, and short cervical length). The increasing body of evidence suggests that preterm birth is a complex condition with variable mechanisms of disease and significant individual heterogeneity. This review will examine the plausibility of 17-OHPC in preventing preterm birth and the investigation of its clinical efficacy. We will also highlight factors to explain variations in clinical trial outcomes and outline the trajectory needed for future investigations.

Population pharmacokinetics of 17α-hydroxyprogesterone caproate in singleton gestation

AIMS

17α-hydroxyprogesterone caproate (17-OHPC) reduces the rate of preterm birth in women with a prior preterm birth. Limited data exist on the pharmacokinetics (PK) of 17-OHPC or the plasma concentrations achieved during therapy. In this study, we evaluated the population PK of 17-OHPC in pregnant subjects with singleton gestation and also evaluated intrinsic and extrinsic factors that may potentially affect 17-OHPC PK in this patient population.

METHODS

Sixty-one women with singleton pregnancies participated in this trial. Subjects received weekly intramuscular injections of 250 mg 17-OHPC in 1 ml castor oil from the time of enrolment (16 0/7 weeks - 20 6/7 weeks) up to 35 weeks gestation or until delivery. Blood samples were obtained between 24 and 28 weeks, between 32 and 35 weeks and over a 28-day period beyond the last injection. Maternal and/or cord blood were obtained at delivery. Data analysis was performed by nonlinear mixed effects modelling (NONMEM(®) ).

RESULTS

The 17-OHPC PK were best described by a model with one maternal compartment and one fetal compartment, with first-order absorption and elimination from the maternal compartment. Maternal body weight was a significant covariate for both clearance (CL/F) and volume of distribution (Vmaternal /F). The final population mean estimates were: CL/F 1797 l/d, Vmaternal /F 32 610 l and mother to cord rate constant 0.005 day(-1) . This report describes for the first time the population PK of 17-OHPC in singleton pregnancy.

CONCLUSIONS

The population PK study reported here represents the initial steps in understanding and optimizing 17-OHPC therapy for preventing preterm birth.

Prevention of preterm birth with vaginal progesterone or 17-alpha-hydroxyprogesterone caproate: a critical examination of efficacy and safety

Progestogens are the first drugs to demonstrate reproducibly a reduction in the rate of early preterm birth. The efficacy and safety of progestogens are related to individual pharmacologic properties of each drug within this class of medication and characteristics of the population that is treated. The synthetic 17-hydroxyprogesterone caproate and natural progesterone have been studied with the use of a prophylactic strategy in women with a history of preterm birth and in women with a multiple gestation. Evidence from a single large comparative efficacy trial suggests that vaginal natural progesterone is superior to 17-hydroxyprogesterone caproate as a prophylactic treatment in women with a history of mid-trimester preterm birth. Progestogen therapy is indicated for women with this highest risk profile based on evidence from 2 trials. A therapeutic approach based on the identification of a sonographic short cervix has been studied in several phase III trials. Independent phase III trials and an individual patient metaanalysis suggest that vaginal progesterone is efficacious and safe in women with a singleton and a short cervix. Two trials that tested 17-hydroxyprogesterone caproate in women with a short cervix showed no benefit. No consistent benefit for the prophylactic or therapeutic use of progestogens has been demonstrated in larger trials of women whose pregnancies were complicated by a multiple gestation (twins or triplets), preterm labor, or preterm rupture of membranes. Unfortunately, several large randomized trials in multiple gestations have identified harm related to 17-hydroxyprogesterone caproate exposure, and the synthetic drug is contraindicated in this population. The current body of evidence is evaluated by the Grading of Recommendations Assessment, Development, and Evaluation guidelines to derive the strength of recommendation in each of these populations. A large confirmatory trial that is testing 17-hydroxyprogesterone caproate exposure in women with a singleton pregnancy and a history of preterm birth is near completion. Additional study of the efficacy and safety of progestogens is suggested in well-selected populations based on the presence of biomarkers.

17-Hydroxyprogesterone caproate in triplet pregnancy: an individual patient data meta-analysis

BACKGROUND

Preterm birth complicates almost all triplet pregnancies and no preventive strategy has proven effective.

OBJECTIVE

To determine, using individual patient data (IPD) meta-analysis, whether the outcome of triplet pregnancy is affected by prophylactic administration of 17-hydroxyprogesterone caproate (17OHPc).

SEARCH STRATEGY

We searched literature databases, trial registries and references in published articles.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of progestogens versus control that included women with triplet pregnancies.

DATA COLLECTION AND ANALYSIS

Investigators from identified RCTs collaborated on the protocol and contributed their IPD. The primary outcome was a composite measure of adverse perinatal outcome. The secondary outcome was the rate of birth before 32 weeks of gestation. Other pre-specified outcomes included randomisation-to-delivery interval and rates of birth at <24, <28 and <34 weeks of gestation.

MAIN RESULTS

Three RCTs of 17OHPc versus placebo included 232 mothers with triplet pregnancies and their 696 offspring. Risk-of-bias scores and between-study heterogeneity were low. Baseline characteristics were comparable between 17OHPc and placebo groups. The rate of the composite adverse perinatal outcome was similar among those treated with 17OHPc and those treated with placebo (34 and 35%, respectively; risk ratio [RR] 0.98, 95% confidence interval [95% CI] 0.79-1.2). The rate of birth at <32 weeks was also similar in the two groups (35 and 38%, respectively; RR 0.92, 95% CI 0.55-1.56). There were no significant between-group differences in perinatal mortality rate, randomisation-to-delivery interval, or other specified outcomes.

CONCLUSION

Prophylactic 17OHPc given to mothers with triplet pregnancies had no significant impact on perinatal outcome or pregnancy duration.

TWEETABLE ABSTRACT

17-Hydroxyprogesterone caproate had no significant impact on the outcome or duration of triplet pregnancy.

Does 17-alpha hydroxyprogesterone caproate prevent recurrent preterm birth in obese women?

OBJECTIVE

We sought to determine if maternal weight or body mass index (BMI) modifies the effectiveness of 17-alpha hydroxyprogesterone caproate (17OHP-C).

STUDY DESIGN

We performed a secondary analysis of the Maternal-Fetal Medicine Units Network Trial for the Prevention of Recurrent Preterm Delivery by 17-Alpha Hydroxyprogesterone Caproate. Binomial regression models were estimated to determine the relative risk (RR) of preterm birth (PTB) in women randomized to 17OHP-C vs placebo according to BMI category and maternal weight. Adjusted models considered inclusion of potential confounders.

RESULTS

In all, 443 women with complete data were included. 17OHP-C is effective in preventing PTB <37 weeks only in women with prepregnancy BMI <30 kg/m(2) (RR, 0.54; 95% confidence interval, 0.43-0.68). Above this BMI threshold there is a nonsignificant trend toward an increased risk of PTB (RR, 1.55; 95% confidence interval, 0.83-2.89) with 17OHP-C treatment. When analyzing by maternal weight, a similar threshold is observed at 165 lb, above which 17OHP-C is no longer effective.

CONCLUSION

The effectiveness of 17OHP-C is modified by maternal weight and BMI, and treatment does not appear to reduce the rate of PTB in women who are obese or have a weight >165 lb. This finding may be due to subtherapeutic serum levels in women with increased BMI or weight. Studies of adjusted-dose 17OHP-C in women who are obese or who weigh >165 lb are warranted, and current recommendations regarding the uniform use of 17OHP-C regardless of maternal BMI and weight may deserve reassessment.

Pharmacogenomics of preterm birth prevention and treatment

Pharmacogenomics and personalised medicine incorporate genetic factors, historical data, and environmental exposures to predict individual variation in response to medications. The study of pharmacology and pharmacogenomics is challenging in obstetrics, and our knowledge in this area lags behind other disciplines of medicine. Some preliminary data, however, suggest that some of the interindividual variation seen in response to medications given for the prevention (progesterone) and the treatment (nifedipine, terbutaline, and others) of preterm labour may be caused by pharmacogenomic effects. A comprehensive approach, integrating clinical data, environmental factors, including concomitant medications and genotype, to optimise the prevention and treatment strategies for preterm birth, is urgently needed.

TWEETABLE ABSTRACT

Some of the variation to meds for prematurity prevention/treatment may arise from pharmacogenomic effects.

Progesterone inhibits in vitro fetal membrane weakening

OBJECTIVE

Inflammation/infection and abruption are leading causes of preterm premature rupture of the membranes. Recently, we identified granulocyte-macrophage colony-stimulating factor (GM-CSF) as a critical mediator of both tumor necrosis factor-α- (TNF; modeling inflammation) and thrombin-induced (modeling abruption) weakening of the fetal membranes. We found that (1) TNF and thrombin both induced GM-CSF in the choriodecidua, (2) blockade of GM-CSF action with neutralizing antibodies inhibited both TNF- and thrombin-induced fetal membrane weakening, and (3) GM-CSF alone induced fetal membrane weakening. GM-CSF is thus part of an overlap of the inflammation and abruption-induced fetal membrane weakening pathways. The effects of progesterone analogs on the pathways by which fetal membranes are weakened have not been investigated. We examined the effects of progesterone, medroxyprogesterone acetate (MPA) and 17α-hydroxyprogesterone (HP) on TNF- and thrombin-induced fetal membrane weakening.

STUDY DESIGN

Full-thickness fetal membranes from uncomplicated term repeat cesarean deliveries were mounted in Transwell inserts in Minimum Essential Medium alpha and incubated at 37°C in 5% CO2. The choriodecidua side of the fetal membrane fragments were preincubated with progesterone, MPA, HP, or vehicle for 24 hours. Fetal membranes were then exposed to TNF, thrombin, or GM-CSF on the choriodecidua side for an additional 48 hours. The fetal membrane tissues were then strength tested, and medium from the choriodecidua and amnion compartments was assayed for GM-CSF content.

RESULTS

TNF and thrombin both weakened fetal membranes and elevated media GM-CSF levels on the choriodecidua side of the fetal membrane. Pretreatment with progesterone, MPA, or HP inhibited both TNF- and thrombin-induced fetal membrane weakening and also inhibited the induced increase in GM-CSF. GM-CSF decreased fetal membrane rupture strength by 68%, which was inhibited by progestogen pretreatment with a potency order: progesterone <MPA <HP.

CONCLUSION

Progestogen pretreatment blocks TNF- and thrombin-induced fetal membrane weakening by inhibiting both the production and action of GM-CSF. These findings are consistent with the administration of progestogens in the prevention of preterm premature rupture of the membranes.

Relation of body mass index to frequency of recurrent preterm birth in women treated with 17-alpha hydroxyprogesterone caproate

OBJECTIVE

The standard weekly dose of 17-alpha hydroxyprogesterone caproate (17OHP-C; 250 mg/wk) to reduce the risk of recurrent preterm birth was adopted without regard to patient characteristics. We examined the relationship between prepregnancy body mass index (BMI) and gestational age at birth after 17OHP-C prophylaxis. We hypothesized that rates of births before 32, 35, and 37 weeks of gestation would be increased in women with a BMI of 25 kg/m(2) or greater.

STUDY DESIGN

A retrospective cohort study was conducted from a deidentified database of women treated with 17OHP-C for prior spontaneous preterm birth. The frequency of recurrent preterm delivery before 32, 35, and 37 weeks of gestation was investigated for women with a BMI less than 25 kg/m(2) compared with women with a BMI of 25 kg/m(2) or greater. The adjusted relative risk of preterm delivery was estimated through a modified Poisson regression approach.

RESULTS

Of 390 women who met inclusion criteria, 60 (15.4%) delivered before 32 weeks, 89 (22.8%) before 35 weeks, and 156 (40.0%) before 37 weeks. A total of 174 women had a BMI less than 25 kg/m(2) (mean [SD], 21.2 [2.5]) and 216 had a BMI of 25 kg/m(2) or greater (mean [SD], 33.5 [6.7]). Risk of birth before 32 weeks was 1.7 times higher on average (adjusted relative risk, 1.7; 95% confidence interval, 1.05-2.77) in overweight women than in women with a BMI less than 25 kg/m(2), adjusting for age, race, smoking, and short cervix. There was no difference in the risk of preterm birth before 35 or 37 weeks.

CONCLUSION

Among pregnant women receiving 17OHP-C prophylaxis for a prior preterm birth, recurrent preterm birth before 32 weeks was significantly more common in those women whose prepregnancy BMI was 25 kg/m(2) or greater than in women with BMI less than 25 kg/m(2). This observation is consistent with pharmacological studies suggesting that dosing regimens of 17OHP-C may affect efficacy.

Route of administration and formulation dependent pharmacokinetics of 17-hydroxyprogesterone caproate in rats

1. Weekly intramuscular injections of (250 mg/week) of 17-hydroxyprogesterone caproate (17-OHPC) are the only treatment option for prevention of preterm birth in women with a prior history of preterm delivery. 2. The objective of the current study was to evaluate the use of an alternate formulation and the feasibility of an alternate route of administration of this agent. 17-OHPC was administered to adult female SD rats, as marketed oily formulation intramuscularly, or as a solution IV, IM, or PO. 3. Plasma concentrations of 17-OHPC were measured by LC-MS-MS and pharmacokinetic parameters were calculated by non-compartmental analysis, using WinNonLin (Certara, St. Louis, MO). 4. After IV or IM administration as a solution, the mean half-life of 17-OHPC was around 11 h. The bioavailability was nearly 100% after IM administration, but was very low (<3%) after PO administration of a solution dosage form. 5. Intramuscular injection of the oily formulation resulted in low levels of 17-OHPC that were sustained for a prolonged time period with a projected bioavailability close to 100%. 6. The pharmacokinetics of 17-OHPC is dependent on the formulation and the route of administration. 7. The low bioavailability after oral administration indicates that oral administration of 17-OHPC may not be feasible with simple formulations of this drug.

17 alpha-hydroxyprogesterone caproate does not prolong pregnancy or reduce the rate of preterm birth in women at high risk for preterm delivery and a short cervix: a randomized controlled trial

OBJECTIVE

The objective of the study was to evaluate the efficacy of 17 alpha-hydroxyprogesterone caproate (17OHP-C) in prolonging gestation in patients with a short cervix and other risk factors for preterm delivery, such as previous preterm birth, cervical surgery, uterine anomalies, or prenatal diethylstilbestrol (DES) exposure.

STUDY DESIGN

This open-label, multicenter, randomized controlled trial included asymptomatic singleton pregnancies from 20(+0) through 31(+6) weeks of gestation with a cervical length less than 25 mm and a history of preterm delivery or cervical surgery or uterine malformation or prenatal DES exposure. Randomization assigned them to receive (or not) 500 mg of intramuscular 17OHP-C weekly until 36 weeks. The primary outcome was time from randomization to delivery.

RESULTS

After enrolling 105 patients, an interim analysis demonstrated the lack of efficacy of 17OHP-C in prolonging pregnancy. The study was discontinued because of futility. The groups were similar for maternal age, body mass index, parity, gestational age at inclusion, history of uterine anomalies, DES syndrome, previous preterm delivery or midtrimester abortion, and cervical length at randomization. The enrollment-to-delivery interval did not differ between patients allocated to 17OHP-C (n = 51) and those allocated to the control group (n = 54) (median [interquartile range] time to delivery: 77 [54-103] and 74 [52-99] days, respectively). The rate of preterm delivery less than 37 (45% vs 44%, P > .99), less than 34 (24% vs 30%, P = .51), or less than 32 (14% vs 20%, P = .44) weeks was similar in patients allocated to 17OHP-C and those in the control group.

CONCLUSION

17OHP-C did not prolong pregnancy in women with singleton gestations, a sonographic short cervix, and other risk factors of preterm delivery (prior history, uterine malformations, cervical surgery, or prenatal DES exposure).

Basic obstetric pharmacology

Pregnancy is associated with a variety of physiological changes that can alter the pharmacokinetics and pharmacodynamics of several drugs. However, limited data exists on the pharmacokinetics and pharmacodynamics of the majority of the medications used in pregnancy. In this article, we first describe basic concepts (drug absorption, bioavailability, distribution, metabolism, elimination, and transport) in pharmacokinetics. Then, we discuss several physiological changes that occur during pregnancy that theoretically affect absorption, distribution, metabolism, and elimination. Further, we provide a brief review of the literature on the clinical pharmacokinetic studies performed in pregnant women in recent years. In general, pregnancy increases the clearance of several drugs and correspondingly decreases drug exposure during pregnancy. Based on current drug exposure measurements during pregnancy, alterations in the dose or dosing regimen of certain drugs are essential during pregnancy. More pharmacological studies in pregnant women are needed to optimize drug therapy in pregnancy.

Prevention of preterm delivery with 17-hydroxyprogesterone caproate: pharmacologic considerations

Despite advances in neonatal care, the burden of preterm birth remains high. Preterm birth is a multifactorial problem, and strategies to identify and treat medical risk factors in early pregnancy have not been effective in reducing preterm birth rates. In a sentinel clinical trial, prophylactic therapy with 17-hydoxyprogesterone caproate (17-OHPC) reduced the risk of recurrent, spontaneous preterm birth in 34% of women. As a result, clinical practice changed and extensive research on 17-OHPC followed. The increasing body of evidence demonstrated a variable efficacy of the drug. This review will examine the plausibility, pharmacology, clinical efficacy, and safety of 17-OHPC when used in the setting of preterm birth prevention. We will also discuss pharmacokinetic and pharmacodynamics data to highlight drug metabolism and mechanism of action, which will help clarify the variability in clinical outcomes and efficacy.