Failure of exogenous prostacyclin to change placental and fetal blood flow in preeclampsia

Epoprostenol Exposure During Pregnancy

Institutional policies restricting pregnant providers from caring for patients receiving inhaled epoprostenol exist across the nation based on little to no data to substantiate this practice. Over the last 2 decades, the use of inhaled pulmonary vasodilators has expanded in patients with cardiac and respiratory disease providing more evidence for the safety of these medications in obstetrical patients. We propose a thoughtful consideration and review of the literature to remove this restriction to reduce the need to reveal early pregnancy status to employers, to alleviate undue stress for pregnant caregivers who are exposed to patients receiving epoprostenol, and to ensure safe, equal employment, and learning opportunities for pregnant providers.

Efficacy evaluation of low-dose aspirin in IVF/ICSI patients evidence from 13 RCTs: A systematic review and meta-analysis

BACKGROUND

We conducted a systematic review and meta-analysis of existing literature to evaluate the different outcomes of low-dose aspirin on patients undergoing in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI), including clinical pregnancy rate, implantation rate, live birth rate, miscarriage rate, fertilization rate, number of oocytes retrieved, and so forth.

METHODS

Electronic databases including PubMed, MEDLINE, and Embase were searched between 1997 and March 2016 to identity eligible studies. The following comparisons between treatment groups were included: aspirin versus placebo; aspirin versus control group; aspirin versus aspirin + prednisolone + control.

RESULTS

Thirteen randomized controlled trials which included 3104 participants were selected. There were no significant differences in implantation rate (RR = 1.15; 95% CI = 0.78-1.70), live birth rate (RR = 1.06; 95% CI = 0.93-1.21), miscarriage rate (RR = 1.28; 95% CI = 0.93-1.77), fertilization rate (RR = 0.91; 95% CI = 0.75-1.11), and endometrial thickness (WMD = 0.15; 95% CI = -0.38-0.67). But the research showed that aspirin treatment may improve the clinical pregnancy rate (RR = 1.16; 95% CI = 1.04-1.28) compared to placebo or no treatment, and reduce the number of oocytes retrieved (WMD = -0.68; 95% CI = -0.91-0.46).

CONCLUSIONS

Our findings suggest that low-dose aspirin may improve the pregnancy rate in IVF/ICSI, with the recommended clinical use dose of 100 mg/day. Considering the limitation of included studies, further well-designed large-scaled RCTs are necessary to clarify whether aspirin may improve assisted reproduction outcomes in IVF/ICSI patients.

Effect of Low-Dose Aspirin on Midluteal Phase Uterine Artery Blood Flow in Patients With Recurrent Pregnancy Loss

OBJECTIVES

The purpose of this study was to evaluate differences in uterine artery blood flow parameters and pregnancy outcomes, if any. An investigation was conducted to determine the effects of low-dose aspirin on uterine artery blood flow indices in patients with recurrent pregnancy loss.

METHODS

This observational study included 353 Chinese women with a history of recurrent pregnancy loss and 85 women without a history of recurrent pregnancy loss (control group) from Ren Ji Hospital. All patients were scanned transvaginally with transvaginal Doppler sonography 6 to 8 days after ovulation to measure the pulsatility index (PI), resistive index (RI), and systolic-to-diastolic ratio (S/D) of the left and right main uterine arteries. Low-dose aspirin at a dose of 50 mg/d was administered orally in patients with recurrent pregnancy loss for 2 months, and the blood flow indices were measured subsequently. The Student t test was used for analysis of the results, P < .05 was considered significant.

RESULTS

The mean PI and S/D of the uterine arteries in the recurrent pregnancy loss group were significantly higher than in the control group. Although not statistically significant, the RI was higher in the recurrent pregnancy loss group than the control group. Moreover, the PI and S/D increased as the number of pregnancy losses increased. Significant enhancements of the PI and S/D were observed in patients with 4 or more consecutive abortions. After low-dose aspirin supplementation, patients with recurrent pregnancy loss showed a highly significant reduction in the PI and S/D.

CONCLUSIONS

Uterine blood flow decreased during the luteal phase in patients with recurrent pregnancy loss. Low-dose aspirin induced a reversible increase in uterine blood flow and may be of therapeutic value.

Aspirin for in vitro fertilisation

BACKGROUND

Aspirin is used with the aim of optimising the chance of live birth in women undergoing assisted reproductive technology (ART), despite inconsistent evidence of its efficacy and safety (in terms of intraoperative bleeding during oocyte retrieval and risk of miscarriage). The most appropriate time to commence aspirin therapy and the length of treatment required are also still to be determined. This is the second update of the review first published in 2007.

OBJECTIVES

To evaluate the effectiveness and safety of aspirin in women undergoing ART.

SEARCH METHODS

We searched the Cochrane Gynaecology and Fertility Group Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 4) in the Cochrane Library (searched 9 May 2016); the databases MEDLINE (1946 to 9 May 2016) and Embase (1974 to 9 May 2016); and trial registers (ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform search portal). We also examined the reference lists of all known primary studies and review articles, citation lists of relevant publications and abstracts of major scientific meetings, combined with the Cochrane Gynaecology and Fertility Group's search strategy.

SELECTION CRITERIA

Randomised controlled trials on aspirin for women undergoing ART.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility and risk of bias and extracted the data. The primary review outcome was live birth. Secondary outcomes included clinical pregnancy, ongoing pregnancy, multiple pregnancy, miscarriage, and other complications associated with IVF/ICSI or with pregnancy and birth. We combined data to calculate risk ratios (RRs) (for dichotomous data) and mean differences (MDs) (for continuous data) and 95% confidence intervals (CIs). Statistical heterogeneity was assessed using the I² statistic. We assessed the overall quality of the evidence for the main comparisons using GRADE methods.

MAIN RESULTS

The search identified 13 trials as eligible for inclusion in the review, including a total of 2653 participants with a mean age of 35 years. Ten studies used a dose of 100 mg and three used 80 mg of aspirin per day. In most of them, aspirin was commenced immediately at the start of down-regulation, while the duration of treatment varied widely. Eight studies provided a placebo for the control group.There was no evidence of a difference between the aspirin group and the group receiving no treatment or placebo in rates of live birth (RR 0.91, 95% CI 0.72 to 1.15, 3 RCTs, n = 1053, I² = 15%, moderate-quality evidence). In addition, clinical pregnancy rates were also similar for the two groups (RR 1.03, 95% CI 0.91 to 1.17, 10 RCTs, n = 2142, I² = 27%, moderate-quality evidence); sensitivity analysis, excluding studies at high risk of bias, did not change the effect estimate. There was no evidence of a difference between groups in terms of multiple pregnancy as confirmed by ultrasound (RR 0.67, 95% CI 0.37 to 1.25, 2 RCTs, n = 656, I² = 0%, low-quality evidence), miscarriage (RR 1.10, 95% CI 0.68 to 1.77, 5 RCTs, n = 1497, I² = 0%, low-quality evidence), ectopic pregnancy (RR 1.86, 95% CI 0.75 to 4.63, 3 RCTs, n = 1135, I² = 0%, very low quality evidence) or vaginal bleeding (RR 1.01, 95% CI 0.14 to 7.13, 1 RCT, n = 487, very low quality evidence). Data were lacking on other adverse effects.The overall quality of the evidence ranged from very low to moderate; limitations were poor reporting of study methods and suspected publication bias.

AUTHORS' CONCLUSIONS

Currently there is no evidence in favour of routine use of aspirin in order to improve pregnancy rates for a general IVF population. This is based on available data from randomised controlled trials, where there is currently no evidence of an effect of aspirin on women undergoing ART, as there is no single outcome measure demonstrating a benefit with its use. Furthermore, current evidence does not exclude the possibility of adverse effects.

Aspirin for in vitro fertilisation

BACKGROUND

Aspirin is used to improve the outcome in women undergoing in vitro fertilisation despite inconsistent evidence of its efficacy. The most appropriate time to commence aspirin therapy and the length of treatment required are also still to be determined. This is an update of the review first published in 2007.

OBJECTIVES

To determine the effectiveness and safety of aspirin for improving the outcome of in vitro fertilisation and intracytoplasmic sperm injection treatment cycles.

SEARCH STRATEGY

We searched the Cochrane Menstrual Disorders and Subfertility Group Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library January 2011), MEDLINE (1966 to January 2011) and EMBASE (1980 to January 2011) databases. We used the research terms: "(aspirin OR acetylsalicylic acid) AND (in-vitro fertilisation OR intracytoplasmic sperm injection)", combined with the Cochrane Menstrual Disorders and Subfertility Group's search strategy, in order to identify randomised controlled trials on aspirin for women undergoing in vitro fertilisation.

SELECTION CRITERIA

Randomised controlled trials.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies to include in the review, extracted data and assessed trial quality.

MAIN RESULTS

The searches identified 13 trials which were eligible for inclusion in the review, including a total of 2653 participants. No significant differences were found between the treatment and control groups for any of the outcomes assessed. No significant differences were found in the meta-analysis of studies investigating the effect of aspirin compared with control on live birth rate (RR 0.91, 95% CI 0.72 to 1.15; three studies and 1053 participants), clinical pregnancy rate (RR 1.03, 95% CI 0.91 to 1.17; 10 studies and 2142 participants), ectopic and miscarriage rates (RR 1.86, 95% CI 0.75 to 4.63; RR 1.10, 95% CI 0.68 to 1.77) respectively (three and five studies involving 1135 and 1497 participants).

AUTHORS' CONCLUSIONS

Use of aspirin for women undergoing in vitro fertilisation cannot be recommended due to lack of evidence from the current trial data. Adequately powered trials are needed. It was proposed in the initial version of this review that a sample size of 350 women in each group would be required in order to demonstrate a 10% improvement from the use of aspirin, with 80% power at the 5% significance level. Until such evidence is available, this treatment can not be recommended.

Effects of acute L-arginine infusion on non-stress test in hypertensive pregnant women

OBJECTIVE

The present report evaluates the effect of acute L-arginine administration on fetal heart variables by a computerized non-stress test (NST) analysis.

METHODS

Fifteen pregnant women at 30-34 weeks of gestational age affected by mild to moderate gestational hypertension were enrolled in the study. The study was performed in the second and third days of hospitalization. Each woman received both active (Arg) or placebo treatment (Placebo), in a double-blind, randomized, cross-over design. Women received saline infusion for 40 min, then they were infused with either placebo (saline infusion prepared by Damor Pharmaceutics and labeled as Arg-B) or Arg (L-Arg 20 g/500 ml labeled as Arg-A).

RESULTS

Multiple analysis of variance (MANOVA) indicated that both placebo and Arg infusion were unable to affect cardiac variables and fetal movements. As far as maternal blood pressure changes were concerned, MANOVA indicated that active treatment showed an acute hypotensive effect on both systolic (F=8.98, p<0.001) and diastolic values (F=15.78, p>0.001). Conversely, placebo infusion does not seems to have induced any change. Considering each time of infusion we observed that Arg treatment was able to lower systolic and diastolic blood pressure after the 40 min of infusion, with this effect persisting for 20 min.

CONCLUSIONS

These data indicate that the acute, intravenous administration of high-dose L-arginine does not induce significant changes in fetal heart rate (FHR), whereas it lowers maternal blood pressure. Such conclusions are reinforced by the observation that saline administration in the same pregnant women was neutral for both FHR and maternal blood pressure values. According to previous studies, it seems conceivable that maternal L-arginine treatment enters the fetal circulation by crossing the placenta. The lack of changes in FHR, however, suggests that no significant hemodynamic changes were induced by the treatment. Contrary to what happens in the mother, this may possibly be due to a low, if any, conversion of L-arginine to nitric oxide in the fetus.

Low-dose aspirin for in vitro fertilisation

BACKGROUND

Low-dose aspirin is sometimes used to improve the outcome in women undergoing in vitro fertilisation, despite inconsistent evidence of efficacy and the potential risk of significant side affects. The most appropriate time to commence aspirin therapy and length of treatment required is also still to be determined.

OBJECTIVES

To determine the effectiveness of low-dose aspirin for improving the outcome of in vitro fertilisation and intracytoplasmic sperm injection treatment cycles.

SEARCH STRATEGY

We searched the Cochrane Menstrual Disorders and Subfertility Group Trials Register, Cochrane Central Register of Controlled Trials (April 2007), MEDLINE (1966 to March 2007) and EMBASE (1980 to March 2007) databases using the following research terms: "(aspirin OR acetylsalicylic acid) AND (in-vitro fertilisation OR intracytoplasmic sperm injection)" combined with the Cochrane Menstrual Disorders and Subfertility Group's search strategy for identifying randomised controlled trials for reports which appeared to describe randomised controlled trials of low-dose aspirin for women undergoing in vitro fertilisation.

SELECTION CRITERIA

Prospective randomised controlled trials, published or unpublished, which addressed the objectives of the review. Quasi-randomised trials were excluded.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies to include in the review, extracted data and assessed trial quality.

MAIN RESULTS

The searches identified nine trials which were eligible for inclusion in the review, including a total of 1449 participants. No significant differences were found between the treatment and control groups for any of the outcomes assessed. Only two studies (involving 401 participants) investigated the effect of low-dose aspirin on live birth rate, and no significant difference was found between the treatment and control groups (RR 0.94, 95% CI 0.63 to 1.39). No significant difference was found in clinical pregnancy rate between treatment and control groups, based on results from 1240 participants in seven studies (RR 1.09, 95% CI 0.83 to 1.43). No data were reported on adverse events related to aspirin treatment in any of the included studies.

AUTHORS' CONCLUSIONS

Use of low-dose aspirin for women undergoing in vitro fertilisation cannot currently be recommended due to lack of adequate trial data. There is a need for randomised controlled trials investigating the use of low-dose aspirin for different patient groups undergoing in vitro fertilisation. We used control group data from the largest trial included in this review to determine that a sample size of 350 women in each group would be required in order to demonstrate a 10% improvement from the use of aspirin with 80% power at the 5% significance level. Until evidence from appropriately powered trials is available, this treatment can not be recommended.

Nitric oxide dysfunction in the pathophysiology of preeclampsia

Researchers disagree as to the importance of nitric oxide (NO) in preeclampsia. Many researchers have alluded to NO's possible primary or secondary role in the development of preeclampsia, but few have correlated the dysfunction of nitric oxide production with the other metabolic derangements seen in this condition. This paper will review the evidence that the primary dysfunction in preeclampsia is a relative deficiency of available NO (secondary to oxidative degradation) and an excess of peroxynitrite (ONOO(-)). The combination of a deficiency of NO and an increase in ONOO(-) can directly or indirectly initiate the vast majority of physiological and serological changes associated with preeclampsia, such as blood pressure, increased glomerular filtration rate, proteinuria, platelet dysfunction, increased thromboxane and endothelin, and a decrease in prostacyclin. Understanding the complex role of nitric oxide in this condition may explain why previous interventions have been unsuccessful and suggest possible strategies for prevention and treatment in the future.

Low-dose aspirin treatment improves ovarian responsiveness, uterine and ovarian blood flow velocity, implantation, and pregnancy rates in patients undergoing in vitro fertilization: a prospective, randomized, double-blind placebo-controlled assay

OBJECTIVE

To determine the effects of low-dose aspirin on ovarian response, uterine and ovarian blood flow velocity, and implantation and pregnancy rates in patients undergoing IVF.

DESIGN

Prospective, randomized, double-blind placebo-controlled assay.

SETTING

Department of Reproductive Medicine, CER Medical Institute, Buenos Aires, Argentina.

PATIENT(S)

Two hundred ninety-eight infertile patients (mean [+/- SDI age, 35.6+/-4.09 years) undergoing IVF cycles.

INTERVENTION(S)

In the treatment group, 149 patients underwent controlled ovarian hyperstimulation and received a daily dose of 100 mg of aspirin. In the control group, 149 patients underwent controlled ovarian hyperstimulation in association with placebo.

MAIN OUTCOME MEASURE(S)

Number of follicles, number of oocytes retrieved, serum E2 levels, uterine and ovarian pulsatility index, cancellation rate, number of embryos transferred, and implantation and pregnancy rates.

RESULT(S)

There were statistically significant differences between the treatment group and the control group, respectively, in the number of follicles (19.8+/-7.2 versus 10.2+/-5.3), number of oocytes retrieved (16.2+/-6.7 versus 8.6+/-4.6), serum E2 levels (2,923.8+/-1,023.4 versus 1,614.3+/-791.7 pg/mL), uterine pulsatility index (1.22+/-0.34 versus 1.96+/-0.58), ovarian pulsatility index (1.18+/-0.31 versus 1.99+/-0.56), pregnancy rate (45% versus 28%), and implantation rate (17.8% versus 9.2%).

CONCLUSION(S)

Low-dose aspirin treatment significantly improves ovarian responsiveness, uterine and ovarian blood flow velocity, and implantation and pregnancy rates in IVF patients.

Effects of drugs on uteroplacental blood flow and the health of the foetus

1. The placental vascular bed is normally fully dilated. Therefore, changes in vascular resistance elsewhere in the body can affect uteroplacental blood flow (UBF). For example, antihypertensive drugs, such as diazoxide, hydralazine and the angiotensin-converting enzyme inhibitor captopril, cause falls in arterial pressure and, hence, in UBF. 2. Angiotensin II (AngII), prostacyclin and nitric oxide (NO) all influence uteroplacental vascular tone. Angiotensin II in a pharmacological dose (62.5 micrograms/h) had a biphasic effect on UBF in the sheep. Initially, there was a rise in UBF as pressure rose; however, by 16-24 h, UBF had fallen. The AngII-induced fall in UBF caused severe foetal hypoxia and hypercapnia. 3. Prostacyclin may protect the uteroplacental circulation from vasoconstrictors such as AngII, as the vasoconstrictor effect of AngII in the uteroplacental circulation is enhanced following indomethacin. 4. Oestrogen-induced uterine artery vasodilation is nitrergic dependent. As well, nitrergic nerves alter the responsiveness of pregnant uterine arteries to noradrenaline. 5. Thus, both systemic and local factors are important in the control of UBF and in promoting foetal health and growth.

Endothelial dysfunction in preeclampsia. Part II: Reducing the adverse consequences of endothelial cell dysfunction in preeclampsia; therapeutic perspectives

Next to low-dose Aspirin there appear to be several new and promising pharmacologie approaches for reducing the adverse consequences of endothelial cell dysfunction in preeclampsia. Among these are selective thromboxane-A2 synthetase and/or thromboxane-A2 receptor antagonists, stable prostacyclin analogues, selective S(erotonin)2-receptor blockers, nitrovasodilators, glycoprotein IIb/IIIa antagonists, hirudin, and ticlopidine. Early-onset preeclampsia appears to be associated with certain disorders that are likely to provoke an arterial thrombotic process by impairing the normal endothelial cell-platelet interactions. Especially heterozygous hyperhomocysteinemia, protein S deficiency and anticardiolipin antibodies appear to be fairly common. The management of these 3 separate disease entities will be discussed.

Plasma prostacyclin and thromboxane concentrations in 160 normotensive, hypotensive, and preeclamptic patients during pregnancy, delivery, and the post partum period

Plasma concentrations of 6-keto-prostaglandin F1 alpha, a stable metabolite of prostacyclin, and TxB2 were measured in 160 women during pregnancy (n = 106), delivery (n = 40), and in the postpartum period (n = 14). Fifty nine patients had normal blood pressure, 10 had mild and 9 severe preeclampsia while 38 patients were hypotensive. Normotensive patients were grouped according to their gestational age: 22-26 weeks (n = 22), 27-31 weeks (n = 22), and 32-38 weeks (n = 15). 20 patients were in early first stage of delivery (cervical dilatation < or = 5 cm), 20 patients in late first stage (cervical dilatation > or = 6 cm). The concentration (mean value +/- SEM) of the PGI2 metabolite tended to increase during pregnancy without reaching significance (218 +/- 11; 225 +/- 10; 250 +/- 15 pg/ml). At the same time, TxB2 showed a decrease, which was most pronounced at 27-31 weeks (65 +/- 15; 40 +/- 2; 48 +/- 4 pg/ml; p < 0.001). The ratio of PGI2/TxA2 increased in parallel (4.9 +/- 0.4; 6 +/- 0.4; 4 +/- 0.5). There was no difference in plasma concentrations of PGI2 (figure 4) and TxA2 in patients with normal blood pressure, mild preeclampsia and hypotension, whereas in severe preeclampsia, the plasma concentration of PGI2 was significantly lower (p < 0.001) and of TxA2 significantly higher (p < 0.001). The ratio of PGI2/TxA2 shifted significantly to vasoconstriction in patients with severe preeclampsia (p < 0.0001) and to vasodilatation in those with hypotension (p < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of prostaglandins in obstetrical disorders

All pregnancy-associated tissues are capable of producing prostaglandins including PGI2 and TXA2. In normal pregnancy there is a dominance of PGI2 over TXA2 which may contribute to the maternal circulatory adaptation to pregnancy. Furthermore, both fetoplacental PGI2 and TXA2 production are important regulators of the fetal blood supply. It has been clearly established that in pre-eclampsia PGI2 production decreases in the fetoplacental tissues and quite probably also in the maternal tissues. The effect of this change may be further exaggerated by the simultaneous stimulation in pre-eclampsia of TXA2 production. The reason for PGI2 deficiency is not known. Other vasoactive agents, such as endothelin, may act in concert with prostaglandins. Relative PGI2 deficiency is likely to exist also in IUGR and lupus anticoagulant syndrome of pregnancy. In the latter, lupus anticoagulant may directly inhibit the synthesis of PGI2. One study suggests PGI2 deficiency also in early pregnancies of women with a history of repeated abortions. Prostaglandin production increases during full-term labour, and similar but smaller changes also occur in preterm labour. A silent bacterial infection may trigger the onset of preterm labour through cytokine-stimulated increase of prostaglandin production. No data were found on prostaglandin production in post-term pregnancies. That oligo-polyhydramnios is possibly prostaglandin mediated is suggested by the control of polyhydramnios by indomethacin treatment. Smoking decreases the production of PGI2 and possibly increases that of TXA2, which may lead to decreased blood flow and IUGR. Which constituent of cigarette smoke exerts this effect is not known. Ethanol consumption causes aberrations in prostaglandin metabolism which cannot be directly connected with fetal alcohol effects.

A comparative study of the use of epoprostenol and dihydralazine in severe hypertension in pregnancy

OBJECTIVE

To compare the antihypertensive effects of epoprostenol sodium (prostacyclin) with that of dihydralazine in acute hypertensive crises of pregnancy.

DESIGN

A prospective randomized study. A minimum of 20 patients per group was considered statistically acceptable (alpha = 0.05, power = 0.9).

SETTING

A large urban tertiary hospital.

SUBJECTS

Forty-seven pregnant patients with diastolic blood pressures of > 100 mmHg were studied.

INTERVENTION

Lowering of high blood pressure with either dihydralazine (n = 25), the standard drug for this purpose, or epoprostenol (n = 22).

MAIN OUTCOME MEASURE

A significant drop in high blood pressure was regarded as a fall of 15 mmHg diastolic and 30 mmHg systolic blood pressure.

RESULTS

There were no statistically significant differences in the antihypertensive effects between the two treatment groups. Epoprostenol infusion caused less tachycardia; the mean pulse rate changed from 81.77 beats/min, before treatment to 88.36 at stabilization, compared with a change from 80.96 beats/min to 102.68 in the group treated with dihydralazine (P = 0.0024).

CONCLUSION

The place of epoprostenol in pregnancy might be in patients with severe hypertension and tachycardia and in those requiring acute control of severe hypertension on the operating table before general anaesthesia.

Doppler findings in the fetal and uteroplacental circulation: a promising guide to clinical decisions

The combination of real time and Doppler ultrasonic methods has opened up new possibilities for the study of fetal and uterine haemodynamics in humans particularly for the umbilical, uterine and fetal cerebral arteries. A pathological finding in blood velocity waveforms seems to be an early and consistent alteration which precedes other markers of chronic fetal distress. The challenges are to differentiate between fetal and uteroplacental aetiologies of chronic fetal asphyxia and to search for effective treatment of early fetal distress. Recent data on the practical value of haemodynamic studies in different perinatal complications is presented in this review.

Fetal vascular responses to prostacyclin

Prostacyclin is a potent vasodilator produced by both maternal and fetal tissues that dilates the umbilical placental vasculature in vitro. To test the hypothesis that prostacyclin dilates the fetal placental circulation in vivo, we measured blood flow by the radioactive microsphere technique in six unanesthetized near-term ovine fetuses before and during prostacyclin infusion. Fetal mean arterial pressure fell 15% from 35 +/- 3 to 31 +/- 3 mm Hg (p less than 0.05) during prostacyclin infusion, and heart rate increased from 182 +/- 6 to 208 +/- 19 beats/min (p less than 0.05). Placental blood flow changed from 240 +/- 58 to 191 +/- 46 ml.min-1.kg-1 fetal weight (p = 0.07), whereas vascular resistance was unchanged (0.16 +/- 0.04 to 0.18 +/- 0.06 mm Hg.ml-1.min.kg fetal weight). Fetal arterial pH decreased from 7.33 +/- 0.03 to 7.28 +/- 0.02 (p less than 0.05) during prostacyclin infusion, with a significant decrease in base excess from -1.2 +/- 1.4 to -3.1 +/- 1.6 (p less than 0.05) and a trend toward hypercarbia (p = 0.07). We conclude that in vivo administration of prostacyclin to the ovine fetus does not cause fetal placental vasodilation and does cause a significant fetal acidemia. The mechanism for these unexpected observations is likely shunting of blood away from the placenta to other organs in the face of systemic vasodilation.

Effect of exogenous prostacyclin on central and uterine hemodynamics in the chronically instrumented pregnant guinea pig before and after indomethacin administration

The effect of prostacyclin before and after pretreatment with indomethacin was studied in the chronically instrumented pregnant guinea pig. Twenty-six animals were studied between 45 and 65 days' gestation. Prostacyclin (6.25, 12.5, 25, 50, and 125 micrograms/kg/min) produced a dose-dependent decrease in arterial pressure (r = -0.915, p less than 0.0001) and uterine artery blood flow velocity, as measured by a miniaturized Doppler flow probe (r = -0.850, p = 0.0001), and an increase in heart rate (r = 0.745, p = 0.0335). Uterine resistance increased at each dose, with 125 micrograms/kg/min generating an increase greater than all others (p less than 0.02). The hypotensive effect of prostacyclin was blunted by indomethacin (p = 0.018). Rather than blunting the expected changes in the remaining parameters, pretreatment with indomethacin followed by prostacyclin significantly decreased uterine blood flow velocity further and increased uterine resistance. We conclude that prostacyclin infusion can have adverse effects on uterine blood flow and that these are altered by pretreatment with a prostaglandin synthetase inhibitor. Prostacyclin should be avoided in women with preeclampsia until further animal studies are available.

Cyclooxygenase inhibition reduces placental transfer: reversal by carbacyclin

The effect of the cyclooxygenase inhibitors, indomethacin and ibuprofen, on diffusional transfer in the human placenta was assessed with the dual-perfused isolated placental lobe. Antipyrine, a freely diffusible substance, was used as an indicator of placental transfer efficiency. Each inhibitor (100 mumol/L) was perfused for 30 minutes after a baseline period, resulting in a significant reduction in antipyrine clearance. During a subsequent washout period, ibuprofen-inhibited antipyrine clearance returned to baseline values, whereas indomethacin-inhibited clearance remained reduced. An additional 30 minutes perfusion of 500 mumol/L of ibuprofen resulted in a further reduction in antipyrine clearance compared with 100 mumol/L of ibuprofen, suggesting a dosage-related effect. The perfusion of each inhibitor caused a reduced production of 6-keto-prostaglandin F1 alpha (the stable metabolite of prostacyclin) in the fetal circulation. The simultaneous perfusion of carbacyclin, a prostacyclin analogue, at 100 nmol/L and 1 mumol/L resulted in a dosage-dependent reversal of the effects of ibuprofen (500 mumol/L) on antipyrine clearance. The results indicate that the inhibition of cyclooxygenase activity reduces placental transfer and that the effects of these inhibitors are reversed by carbacyclin. This study suggests that the use of cyclooxygenase inhibitors during pregnancy could compromise the developing fetus by reducing placental transfer.

Urinary 6-keto-prostaglandin F1a in patients with gynaecological tumours

The production of the antiaggregatory and vasodilatory prostacyclin (PGI2) in patients with gynaecological tumours was studied by assaying urinary 6-keto-prostaglandin F1a (= 6-keto-PGF1a), a hydration product of PGI2), by radioimmunoassay following high performance liquid chromatography (HPLC) in 59 patients with gynaecological tumours and 12 non-tumourous control women. Urinary 6-keto-PGF1a excretion in patients with cervical cancer (28.3 +/- 3.6 pmol/mmol creatinine, mean +/- S.E., n = 12), endometrial cancer (22.8 +/- 3.7 pmol/mmol creatinine, n = 12, uterine fibroids (26.0 +/- 3.5 pmol/mmol creatinine, n = 12) benign ovarian cysts (22.4 +/- 1.8 pmol/mmol creatinine, n = 12) did not differ from that in the control women (29.9 +/- 3.6 pmol/mmol creatinine, n = 12). However, patients with ovarian cancer excreted increased amounts of 6-keto-PGF1a (55.4 +/- 10.4 pmol/mmol creatinine, n = 11, P less than 0.05), although this bore no relation to tumour histology, clinical stage or the outcome of the patients. Thus, ovarian cancer is accompanied by increased PGI2 production, perhaps in the kidneys and/or in the cancer tissue.

Vaginal and abdominal delivery increases maternal urinary 6-keto-prostaglandin F1 alpha excretion

To study the role of the antiaggregatory and vasodilatory prostacyclin (PGI2) during human delivery, serial urine samples collected from 13 women delivered vaginally and from eight delivered abdominally were assayed for 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha, a breakdown product of PGI2) by high-performance-liquid-chromatography and radioimmunoassay. In women delivered vaginally the mean urinary 6-keto-PGF1 alpha concentration was 41.9 (SE 8.3) ng/mmol creatinine, before the onset of labour and increased progressively to a maximum of 186.5 (SE 47.6) ng/mmol creatinine 2 h after delivery irrespective of the use of oxytocin and epidural analgesia. In women delivered by caesarean section under epidural anaesthesia, the urinary 6-keto-PGF1 alpha rose from 33.4 (SE 4.2) ng/mmol creatinine to 2153 (SE 314) ng/mmol creatinine 2 h after section. In both groups the increased levels had fallen by 24 h postpartum to levels below those found before delivery. In neonatal urine 6-keto-PGF1 alpha concentrations were some 12-30 times higher than those in postpartum urine. Thus, vaginal and abdominal delivery is accompanied by significant increases in maternal PGI2 release, perhaps in the myometrium and/or intrauterine tissues. This may be of significance in the regulation of fetoplacental blood flow and in the prevention of intra- and postpartum thrombosis.

Labetalol does not alter the placental and fetal blood flow or maternal prostanoids in pre-eclampsia

The effect of intravenously administered labetalol (1 mg/kg) on placental and fetal blood flow was studied in 13 pre-eclamptic women. Although the maternal blood pressure decreased, no changes occurred in the blood flows in the intervillous space, the umbilical vein or the fetal descending aorta, nor did the indices of peripheral vascular resistance in the fetal aorta change, but the placental vascular resistance did decrease. Labetalol had no effect on prostacyclin or thromboxane A2 as measured by urinary 6-keto-prostaglandin F1 alpha and serum thromboxane B2 respectively. These findings are clinically relevant since they suggest that labetalol reduces maternal blood pressure without interfering with the placental or fetal blood flow.

Prostacyclin and thromboxane in gynecology and obstetrics

The gynecologic and obstetric implications of the smooth muscle-relaxing, antiaggregatory prostacyclin and its endogenous antagonist, thromboxane A2, are reviewed. In addition to the vascular wall and circulating platelets, which are primary sources for prostacyclin and thromboxane A2, respectively, reproductive tissues produce great amounts of these prostanoids, evidently for the regulation of the vascular tone and/or vascular platelet interaction. Several gynecologic and obstetric disorders are characterized by abnormalities in prostacyclin and/or thromboxane A2. In primary menorrhagia the uterine release of prostacyclin is increased, and consequently menstrual blood loss can be reduced with various prostaglandin synthesis inhibitors. Prostacyclin relaxes the nonpregnant myometrium in vitro and may also do so in vivo, although intravenous infusion of prostacyclin has no effect upon the uterine contractility in nonpregnant or pregnant subjects. Patients with pelvic endometriosis may have increased levels of prostacyclin and thromboxane A2 metabolites in the peritoneal fluid. The prostacyclin/thromboxane A2 balance shifts to thromboxane A2 dominance in patients with gynecologic cancer. During pregnancy the production of prostacyclin and thromboxane A2 increases in the mother and fetoplacental tissue. Preeclampsia and other chronic placental insufficiency syndromes are accompanied by prostacyclin deficiency in the mother and in fetomaternal tissues and by an overproduction of thromboxane A2, at least in the placenta. These changes may account for the vasoconstriction and platelet hyperactivity, which are pathognomonic for hypertensive pregnancies. By directing the prostacyclin/thromboxane A2 balance to prostacyclin dominance (by dietary manipulation, administration of prostacyclin and/or its analogues, drugs with prostacyclin-stimulating and/or thromboxane A2-inhibiting action), it may be possible to prevent and/or treat hypertensive pregnancy complications in the future.

Urinary 6-keto-prostaglandin F1 alpha during ovulation induction

To elucidate the role of the vasodilatory prostacyclin (PGI2) in human ovulation, urinary samples were collected from spontaneously ovulating women (n = 8) and from those undergoing ovulation induction with clomiphene (seven women, 9 cycles) and human gonadotropins (five women, 11 cycles). The samples were assayed for 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), a breakdown product of PGI2, employing high-pressure liquid chromatography and radioimmunoassay. The urinary 6-keto-PGF1 alpha was not consistently related to the menstrual cycle day at collection, the occurrence of spontaneous (n = 8) or induced (n = 11) ovulation, or the simultaneous concentration of estradiol in plasma. However, its concentrations both before and after the approximated time of ovulation during clomiphene (41.6 +/- 6.7 and 52.7 +/- 7.9 pmol/mmol creatinine, before/after, mean +/- standard error) or gonadotropin treatment (49.0 +/- 5.8 and 48.1 +/- 6.8 pmol/mmol creatinine) were higher (P less than 0.01) than those in spontaneously ovulating women (26.4 +/- 3.8 and 20.5 +/- 3.0 pmol/mmol creatinine, respectively). Multiple ovarian follicles, as assessed ultrasonographically, developed during four courses of the treatments with gonadotropins, and in three of them the urinary 6-keto-PGF1 alpha was high. The data suggest that treatment with clomiphene and gonadotropin is accompanied by increased production of PGI2, perhaps in the ovaries and/or in the kidneys. This may perhaps play a role in the etiopathogenesis of ovarian hyperstimulation syndrome.