Early and late preterm birth rates in participants adherent to randomly assigned high dose docosahexaenoic acid (DHA) supplementation in pregnancy.

BACKGROUND: Intention-to-treat analyses do not address adherence. Per protocol analyses treat nonadherence as a protocol deviation and assess if the intervention is effective if followed. OBJECTIVE: To determine the rate of early preterm birth (EPTB, <34 weeks gestation) and preterm birth (PTB, <37 weeks gestation) in participants who adhered to a randomly assigned docosahexaenoic acid (DHA) dose of 1000 mg/day. STUDY DESIGN: Eleven hundred women with a singleton pregnancy were enrolled before 20-weeks' gestation, provided a capsule with 200 mg/day DHA and randomly assigned to two additional capsules containing a placebo or 800 mg of DHA. In the Bayesian Adaptive Design, new randomization schedules were determined at prespecified intervals. In each randomization, the group with the most EPTB was assigned fewer participants than the other group. Adherence was defined a priori as a postpartum red blood cell phospholipid DHA (RBC-PL-DHA) ≥5.5%.and post hoc as ≥8.0% RBC-PL-DHA, the latter after examination of postpartum RBC-PL-DHA. Bayesian mixture models were fitted for gestational age and dichotomized for EPTB and PTB as a function of baseline RBC-PL-DHA and dose-adherence. Bayesian hierarchical models were also fitted for EPTB by dose adherence and quartiles of baseline RBC-PL-DHA. RESULTS: Adherence to the high dose using both RBC-PL-DHA cut points resulted in less EPTB compared to 200 mg [Bayesian posterior probability (pp) = 0.93 and 0.92, respectively]. For participants in the two lowest quartiles of baseline DHA status, adherence to the higher dose resulted in lower EPTB (≥5.5% RBC-PL-DHA, quartiles 1 and 2, pp = 0.95 and 0.96; ≥8% RBC-PL-DHA, quartiles 1 and 2, pp = 0.94 and 0.95). Using the Bayesian model, EPTB was reduced by 65%, from 3.45% to 1.2%, using both cut points. Adherence also reduced PTB before 35, 36 and 37 weeks using both cut points (pp ≥ 0.95). In general, performance of the nonadherent subgroup mirrored that of participants assigned to 200 mg. CONCLUSION: Adherence to high dose DHA reduced EPTB and PTB. The largest effect of adherence on reducing EPTB was observed in women with low baseline DHA levels. CLINICALTRIALS: gov (NCT02626299).

Early pregnancy prediction of spontaneous preterm birth before 32 completed weeks of pregnancy using plasma RNA: transcriptome discovery and initial validation of an RNA panel of markers.

OBJECTIVE: To compare the second-trimester plasma cell-free (PCF) transcriptome of women who delivered at term with that of women with spontaneous preterm birth (sPTB) at or before 32 weeks of gestation and identify/validate PCF RNA markers present by 16 weeks of gestation. DESIGN: Prospective case-control study. SETTING: Academic tertiary care centre. POPULATION: Pregnant women with known outcomes prospectively sampled. METHODS: PCF RNAs extracted from women at 22-24 weeks of gestation (five sPTB up to 32 weeks and five at term) were hybridised to gene expression arrays. Differentially regulated RNAs for sPTB up to 32 weeks were initially selected based on P value compared with control (P < 0.01) and fold change (≥1.5×). Potential markers were then reordered by narrowness of distribution. Final marker selection was made by searching the Metacore™ database to determine whether the PCF RNAs interacted with a reported set of myometrial Preterm Initiator genes. RNAs were confirmed by quantitative reverse transcription polymerase chain reaction and tested in a second group of 40 women: 20 with sPTB up to 32 weeks (mean gestation 26.5 weeks, standard deviation ±2.6 weeks), 20 with spontaneous term delivery (40.1 ± 0.9 weeks) sampled at 16-19+5  weeks of gestation. MAIN OUTCOME MEASURE: Identification of PCF RNAs predictive of sPTB up to 32 weeks. RESULTS: Two hundred and ninety-seven PCR RNAs were differentially expressed in sPTB up to 32 weeks of gestation. Further selection retained 99 RNAs (86 mRNAs and 13 microRNAs) and five of these interacted in silica with seven Preterm Initiator genes. Four of five RNAs were confirmed and tested on the validation group. The expression of each confirmed PCF RNA was significantly higher in sPTB up to 32 weeks of gestation. In vitro study of the four mRNAs revealed higher expression in placentas of women with sPTB up to 32 weeks and the potential to interfere with myometrial quiescence. CONCLUSIONS: The PCF RNA markers are highly associated with sPTB up to 32 weeks by 16 weeks of gestation. TWEETABLE ABSTRACT: Women destined for spontaneous preterm birth can be identified by 16 weeks of gestation with a panel of maternal plasma RNAs.

Multi-professional training for obstetric emergencies in a U.S. hospital over a 7-year interval: an observational study.

OBJECTIVE: Birth is less safe than it can be. We adapted the UK-developed PROMPT (PRactical Obstetric Multi-Professional Training) course to local practices and initiated annual training. STUDY DESIGN: This observational study used quality assurance data from University of Kansas Hospital 2 years before and 7 years after intervention encompassing 14,309 consecutive deliveries from January 2006 through December 2014. An events/trials approach was applied to changes in proportions over time. RESULT: PROMPT was associated with progressive decreases in rates (P<0.05) of brachial plexus injury and umbilical artery pH <7.00 exclusive of catastrophic events. Reduced rates (P<0.05) of cesarean section, episiotomy and higher perception of nurse/physician communication were documented. Hypoxic ischemic encephalopathy (HIE) rates declined progressively by >50% (P=NS). These improvements occurred despite younger faculty and higher rates of complicated pregnancies (P<0.05). Estimated health-care costs avoided exceeded annual training costs. CONCLUSION: Local annual multi-professional training as provided by PROMPT was temporally associated with improved obstetric outcomes.

The active components of effective training in obstetric emergencies.

Confidential enquiries into poor perinatal outcomes have identified deficiencies in team working as a common factor and have recommended team training in the management of obstetric emergencies. Isolated aviation-based team training programmes have not been associated with improved perinatal outcomes when applied to labour ward settings, whereas obstetric-specific training interventions with integrated teamwork have been associated with clinical improvements. This commentary reviews obstetric emergency training programmes from hospitals that have demonstrated improved outcomes to determine the active components of effective training. The common features identified were: institution-level incentives to train; multi-professional training of all staff in their units; teamwork training integrated with clinical teaching and use of high fidelity simulation models. Local training also appeared to facilitate self-directed infrastructural change.

Prevalence of viral DNA in amniotic fluid of low-risk pregnancies in the second trimester.

AIM: The association between fetal viral infection and adverse pregnancy outcome is well documented. However, the prevalence of common viral pathogens in the amniotic fluid of normal pregnancies is not established. The purpose of this study was to determine this prevalence in asymptomatic patients. METHODS: This was a prospective observational study of patients at low risk for viral infection who were referred for second-trimester genetic amniocentesis. In patients with normal fetal anatomy on ultrasound and a normal fetal karyotype, a 2-ml aliquot of amniotic fluid obtained at amniocentesis was analyzed by multiplex polymerase chain reaction for cytomegalovirus (CMV), parvovirus B19, adenovirus, enterovirus, herpes simplex virus (HSV), respiratory syncytial virus (RSV) and Epstein-Barr virus (EBV). RESULTS: Among 686 patients, advanced maternal age was the most common indication for genetic testing (n = 469, 68.4%), followed by elevated aneuploidy risk on triple screen (n = 164, 23.9%), elevated maternal serum alpha-fetoprotein (n = 20, 2.9%), previous aneuploidy (n = 16, 2.3%) and family history of inheritable disease (n = 14, 2.1%). Forty-four (6.4%) amniotic fluid samples were positive for viral genome. A single genome was amplified in 41 samples (93%). In three samples, two viral genomes were identified. Adenovirus was most frequently identified (37/44), followed by CMV (5/44), EBV (2/44), enterovirus (2/44) and RSV (1/44). Parvovirus and HSV were not identified. There was a bimodal seasonal variation in prevalence, with the highest prevalence during the summer and late winter. CONCLUSION: Viral genome is commonly found in amniotic fluid with a sonographically normal fetus, and the prevalence follows a seasonal pattern. The mechanism, significance and effects of this asymptomatic viral presence require further study.

Qualitative venous Doppler waveform analysis improves prediction of critical perinatal outcomes in premature growth-restricted fetuses.

BACKGROUND: Our aim was to test the hypothesis that qualitative ductus venosus and umbilical venous Doppler analysis improves prediction of critical perinatal outcomes in preterm growth-restricted fetuses with abnormal placental function. METHODS: Patients with suspected intrauterine growth restriction (IUGR) underwent uniform fetal assessment including umbilical artery (UA), ductus venosus (DV) and umbilical vein (UV) Doppler. Absent or reversed UA end-diastolic velocity (UA-AREDV), absence or reversal of atrial systolic blood flow velocity in the DV (DV-RAV) and pulsatile flow in the umbilical vein (P-UV) were examined for their efficacy to predict critical outcomes (stillbirth, neonatal death, perinatal death, acidemia and birth asphyxia) before 37 weeks' gestation. RESULTS: Seventeen (7.6%) stillbirths and 16 (7.1%) neonatal deaths were observed among 224 IUGR fetuses. Forty-one neonates were acidemic (19.8%) and seven (3.1%) had birth asphyxia. Logistic regression showed that UA-AREDV had the strongest association with perinatal mortality (R(2) = 0.49, P < 0.001), stillbirth (R(2) = 0.48, P < 0.001) and acidemia (R(2) = 0.22, P = 0.002) while neonatal death was most strongly related to DV-RAV and P-UV (R(2) = 0.33, P = 0.007). UA waveform analysis offered the highest sensitivity and negative predictive value and DV-RAV and P-UV had the best specificity and positive predictive values for outcome prediction. Overall, DV-RAV or P-UV offered the best prediction of acidemia and neonatal and perinatal death irrespective of the UA waveform. In fetuses with UA-AREDV, prediction of asphyxia and stillbirth was significantly enhanced by venous Doppler. CONCLUSION: Prediction of critical perinatal outcomes is improved when venous and umbilical artery qualitative waveform analysis is combined. The incorporation of venous Doppler into fetal surveillance is therefore strongly suggested for all preterm IUGR fetuses.

Pregnancy and estradiol decrease GTPase activity in the guinea pig uterine artery.

The mechanisms by which pregnancy redistributes cardiac output in an organ-specific manner are poorly understood. We propose that it is consequential to estrogen-mediated alterations in G protein-mediated signal transduction. Aortas and uterine (UAs) and mesenteric arteries (MAs) were obtained from late-pregnant, nonpregnant, or ovariectomized guinea pigs chronically treated with 17beta-estradiol. High-affinity GTPase activity was assayed enzymatically. The cGMP generated in response to the endothelium-dependent agonist ACh was measured in UAs incubated with or without cholera toxin (CTX, which inhibits G(s)alpha). Pregnancy significantly decreased UA but not aorta or MA GTPase activity. 17beta-Estradiol decreased UA GTPase activity compared with untreated ovariectomized animals. ACh increased cGMP in pregnant but not nonpregnant UAs. Pretreatment of nonpregnant UAs with CTX increased ACh-induced cGMP levels similar to pregnancy. Thus pregnancy and estradiol decrease the GTPase activity of a CTX-sensitive G protein in UAs, increasing receptor-dependent cGMP release. This alteration in receptor-mediated G protein coupling in UAs may contribute to the characteristic cardiovascular adaptation to pregnancy.

Leveraging healthcare for the greater good: lessons learned from the National Centers of Excellence in Women's Health.

The creation of the National Centers of Excellence in Women's Health (CoE) program in 1996 by the Office on Women's Health, Department of Health and Human Services, included the stipulation that each institution awarded a CoE contribute at least a 25% match for the federal funds. Even the combination of these two sources of monies was insufficient for each CoE to accomplish its goals, however, so leveraging funds became necessary for each CoE to function effectively. The forms of leveraging varied from CoE to CoE, in part as a result of the institutional environment and the unique possibilities each permitted and in part as a result of the creativity of the leaders of the CoEs. This paper describes the concepts and some applications of leveraging in the setting of the CoEs, which might be applicable to other settings as well.

Use of McRoberts' position during delivery and increase in pushing efficiency.

McRoberts' position is used during the second stage of labour to facilitate delivery of the fetal shoulders. Few clinical studies have been done to measure its efficacy. We measured intrauterine pressure in 22 women in term labour, after the vertex reached 3+ station, in the dorsal lithotomy position. Patients pushed with legs either in stirrups or hyperflexed by 1358 (McRoberts' position). Maternal valsalva transiently increased the expulsive force by 32% over naturally occurring contractions. Use of McRoberts' position almost doubled the intrauterine pressure developed by contractions alone (from 1653 mm Hg s to 3262 mm Hg s [97%]).

Endotoxemia causing fetal bradycardia during urosepsis.

BACKGROUND: Fetal bradycardia is a recognized response to maternal hypothermia associated with hypoglycemia, tocolysis with magnesium sulfate, or urosepsis, and it is thought to be a direct response to the decrease in the maternal core temperature. CASE: A 25-year-old white woman, gravida 1, para 0, at 31 1/7 weeks' gestation was admitted with a diagnosis of pyelonephritis. The baseline fetal heart rate was 120 beats per minute with accelerations. Within 3 hours of admission, the patient became hypothermic (35.1C) and, concomitantly, the fetal heart rate baseline declined to 90 beats per minute with marked variability. Despite sustained maternal hypothermia, the fetal heart rate baseline rose to 120 beats per minute. It was another 6 hours before the patient's temperature rose above 38.5C. Her urine and blood cultures were positive for Serratia rubidacea infection. The patient delivered a healthy infant at 39 weeks' gestation. CONCLUSION: Fetal bradycardia in the presence of urosepsis might be due to the release of endotoxin from gram-negative bacteria, triggering production of cardiotoxic cytokines, rather than to maternal hypothermia alone.

Pregnancy enhances G protein activation and nitric oxide release from uterine arteries.

We hypothesized that pregnancy modulates receptor-mediated responses of the uterine artery (UA) by altering G protein activation or coupling. Relaxation and contraction to NaF (0.5-11.5 mM), acetylcholine (10(-9)-10(-5) M), and bradykinin (10(-12)-3 x 10(-5) M) were measured in isolated UA of pregnant and nonpregnant guinea pigs. Responses were measured in the presence and absence of either cholera toxin (2 microg/ml) or pertussis toxin (Galpha(s) and Galpha(i) inhibitors, respectively). NaF relaxation was endothelium dependent and nitro-L-arginine sensitive (a nitric oxide synthase inhibitor). Relaxation to NaF, acetylcholine, and bradykinin were potentiated by pregnancy. Cholera but not pertussis toxin increased relaxation to acetylcholine and bradykinin in UA from nonpregnant animals, had no effect in UA from pregnant animals, and abolished the pregnancy-induced differences in acetylcholine relaxation. Cholera toxin potentiated the bradykinin-induced contraction of UA of both pregnant and nonpregnant animals, whereas pertussis toxin inhibited contraction of UA from pregnant animals only. Therefore, pregnancy may enhance agonist-stimulated endothelium-dependent relaxation and bradykinin-induced contraction of UA by inhibiting GTPase activity or enhancing Galpha(s) but not Galpha(i) activation in pregnant animals. Thus the diverse effects of pregnancy on UA responsiveness may result from hormonal modulation of G proteins coupled to their specific receptors.

Natriuretic peptide-induced relaxation of myometrium from the pregnant guinea pig is not mediated by guanylate cyclase activation.

We tested both relaxation and cGMP generation by atrial (ANP), brain (BNP), and C-type natriuretic peptide (CNP) in oxytocin-stimulated myometrium from near-term pregnant guinea pigs to investigate the ability and mechanism of natriuretic peptides to inhibit myometrial contractility. Myometrial strips were contracted by 10(-8) M oxytocin, and relaxation to the cumulative addition (10(-9)-10(-6) M) of the natriuretic peptides measured. Maximal relaxation to BNP was significantly greater than to ANP (52 versus 32% respectively; p < 0.05), whereas CNP failed to produce relaxation. However, the increase in cGMP produced by BNP (10(-7) M) was significantly less than that produced by ANP (10(-7) M) (4.5 versus 7.0 times basal; p < 0.05); CNP did not increase myometrial cGMP. Anantin, a competitive blocker of the guanylate cyclase A receptor, significantly reduced the increase in cGMP produced by ANP and BNP, but had no effect on relaxation induced by either peptide. Rp-8-Br-cGMP, an inhibitor of the cGMP-dependent protein kinase, did not alter BNP-induced relaxation. The atrial natriuretic peptide-fragment 4-23 amide, a natriuretic peptide clearance receptor agonist, failed to inhibit oxytocin-stimulated myometrial contraction. We conclude that natriuretic peptide induced relaxation of oxytocin-stimulated myometrium from the pregnant guinea pig is not mediated by either guanylate cyclase A or B activation, is independent of the cGMP pathway, and does not involve clearance receptor activation. Our results suggest that natriuretic peptide-induced relaxation of pregnant myometrium is mediated via a novel mechanism.

Chorion releases a factor that inhibits oxytocin-stimulated myometrial contractility in the pregnant guinea pig.

It was postulated that chorion releases a substance necessary for the maintenance of uterine quiescence during pregnancy. A decrease in the release of this substance at the end of the pregnancy would be necessary for normal myometrial activation. This hypothesis was tested by demonstrating the ability of chorion to inhibit oxytocin-stimulated myometrial contractility in vitro. Tissues were obtained from timed pregnant Duncan-Hartley guinea pigs either at pre-term or near-term gestation. Myometrial strips were placed in organ baths for isometric tension measurement and contractions stimulated by oxytocin (10(-8) mol/l). Fetal membranes or conditioned medium from chorion were added directly to the organ bath. Near-term chorion and chorion conditioned-medium decreased oxytocin-stimulated contractile activity to 39% and 49% respectively. Neither pre-term nor near-term amnion reduced oxytocin-stimulated myometrial contractile activity. Relaxation induced by pre-term chorion was greater than near-term chorion (23% and 41% of the oxytocin-induced basal level respectively; P < 0.05). Further, chorion-induced relaxation was independent of the gestational age of the myometrium. Human chorion from a term, not-in-labour woman also inhibited oxytocin-stimulated guinea pig myometrial contractility. It was concluded that the chorion releases a substance or substances that reduce oxytocin-stimulated myometrial contractility and may be involved in the maintenance of uterine quiescence during pregnancy.

Application of a functional genomics approach to identify differentially expressed genes in human myometrium during pregnancy and labour.

The molecular mechanisms regulating uterine relaxation and contraction during pregnancy are poorly understood. In the present study, we used for the first time a functional genomics approach applying gene array technology to identify novel candidate genes involved in the regulation of uterine quiescence and contractility during pregnancy. The purpose of this approach was to obtain a molecular snapshot of the expression profile of gene transcripts as a function of the time dependent process regulating myometrial quiescence. Using this approach, we found several genes whose expression in human myometrium was altered with the onset of labour. For example, the expression of insulin-like growth factor (IGF)-II, calgranulin A and B, and G-protein coupled receptor were decreased while the expression of IGF-binding proteins, Ca(2+)/CaM binding protein kinase C substrate, and angiotensin converting enzyme were increased in the labouring, compared with non-labouring, pregnant myometrium. The differentially-expressed genes include several genes whose roles in myometrial quiescence are yet to be understood, although they have been reported to regulate vascular smooth muscle tone. Our findings illustrate the advantage of a functional genomics approach over a single gene analysis in identifying a large number of novel and potentially important genes mediating uterine smooth muscle contractile activity.

Differential alterations in responsiveness in particulate and soluble guanylate cyclases in pregnant guinea pig myometrium.

OBJECTIVE: The mechanism underlying myometrial quiescence during pregnancy is unknown. Our group has previously shown that during pregnancy myometrial cyclic guanosine monophosphate content rises to several hundred times the nonpregnant levels, only to abruptly decline days before the onset of labor. Cyclic guanosine monophosphate plays an integral role in the relaxation of smooth muscle. The aim of this investigation was therefore to determine the effects of pregnancy on both soluble and particulate guanylate cyclase enzymatic activities and messenger ribonucleic acid expressions. STUDY DESIGN: Myometrium was obtained from randomly cycling adult nonpregnant guinea pigs and near-term (50-60 days' gestation) pregnant guinea pigs of similar chronologic age. Subcellular fractions were prepared by differential ultracentrifugation. Guanylate cyclase activity was determined by the conversion of guanosine triphosphate to cyclic guanosine monophosphate under basal or stimulated conditions in either the soluble guanylate cyclase or particulate guanylate cyclase fraction. A nitric oxide donor, S-nitroso- N-penacillamine, was used to activate soluble guanylate cyclase (n = 10 animals in each group). Several natriuretic peptides (atrial natriuretic peptide, brain natriuretic peptide, and C-type natriuretic peptide) and uroguanylin were used to stimulate the different particulate guanylate cyclase isoforms guanylate cyclase A, guanylate cyclase B, and guanylate cyclase C, respectively, in pregnant (n = 8) and nonpregnant (n = 6) animals. Cyclic guanosine monophosphate content was measured by radioimmunoassay, and enzymatic activity was expressed as picomoles of cyclic guanosine monophosphate per milligram of protein per minute. Total guanylate cyclase represented the sum of soluble guanylate cyclase and particulate guanylate cyclase activities for a tissue. To investigate whether the observed changes in guanylate cyclase activity were paralleled by changes in receptor expression, messenger ribonucleic acid levels of the genes for guanylate cyclase A and guanylate cyclase B isoforms were quantified by ribonuclease protection assay (n = 5 animals in each group). RESULTS: Under basal conditions particulate guanylate cyclase represented 78% (nonpregnant state) to 88% (during pregnancy) of the total guanylate cyclase activity in the guinea pig myometrium. Pregnancy further reduced myometrial soluble guanylate cyclase (both basal and stimulated by nitric oxide) relative to the nonpregnant state. Pregnancy selectively increased atrial natriuretic peptide-stimulated particulate guanylate cyclase activity (attributed to guanylate cyclase A), although it did not change basal myometrial particulate guanylate cyclase activity in general. Guanylate cyclase B (particulate guanylate cyclase stimulated by C-type natriuretic peptide) and guanylate cyclase C (particulate guanylate cyclase stimulated by uroguanylin) activities were unaltered by pregnancy. The selective increase in responsiveness of particulate guanylate cyclase to atrial natriuretic peptide during pregnancy was not paralleled by an increased in level of messenger ribonucleic acid for the gene for guanylate cyclase A. CONCLUSION: Pregnancy reduced the in vitro responsiveness of the myometrial soluble guanylate cyclase to nitric oxide while increasing the responsiveness of the particulate isoform to atrial natriuretic peptide and brain natriuretic peptide through a mechanism independent of any change in receptor expression.

Chronic hypoxia increases the NO contribution of acetylcholine vasodilation of the fetal guinea pig heart.

To investigate the effect of chronic hypoxia (HPX) on vasodilation of the fetal heart, we exposed pregnant guinea pigs to room air or 12% O(2) for 4, 7, or 10 days. We excised hearts from anesthetized fetuses (60 +/- 3 days; 65-day gestation = term) and measured changes in both the coronary artery pressure of the isolated constant-flow preparation and endothelial nitric oxide synthase (eNOS) mRNA of fetal ventricles. Dilator responses to cumulative addition (10(-9)-10(-5) M) of acetylcholine and sodium nitroprusside in prostaglandin F(2alpha) (5 x 10(-6) M)-constricted hearts were similar among normoxia (NMX), 4-, 7-, and 10-day HPX (control). Nitro-L-arginine (L-NA, 10(-4)M), a NOS inhibitor, inhibited maximal acetylcholine dilation of hearts exposed to 10-day HPX greater than NMX, 4-, and 7-day HPX. Hypoxia (after 7 and 10 days) increased eNOS mRNA of fetal ventricles compared with NMX and 4-day HPX. 4-Aminopyridine (3 mM), a voltage-dependent K(+)-channel inhibitor, inhibited acetylcholine- but not sodium nitroprusside-induced dilation of NMX and 10-day HPX hearts to a similar magnitude. Glibenclamide (10(-5) M), an ATP-sensitive K(+)-channel inhibitor, had no effect on vasodilation. We conclude that chronic HPX increases the contribution of NO but does not alter K(+)-channel activation in response to acetylcholine-stimulated coronary dilation. Thus increases in NO production via upregulation of eNOS gene expression may be an adaptive response to chronic HPX in the fetal coronary circulation.

Association of fetal and maternal carboxyhemoglobin levels in normal and Rh-alloimmune pregnancies.

OBJECTIVE: To compare paired antepartum fetal/maternal COHb ratios in whole blood from control and alloimmunized pregnancies and to examine the relationships between fetal and maternal COHb. METHODS: COHb levels were measured in paired fetal and maternal blood samples obtained at cordocentesis in 47 control and 16 Rh-alloimmunized pregnancies. COHb was determined by gas chromatography. Results were analyzed by t-test, regression and analysis of covariance. RESULTS: Although fetal/maternal COHb ratios for control and alloimmunized pregnancies were not statistically significantly different, i.e. 1. 11+/-0.04 and 1.26+/-0.09, respectively (P=0.09), fetal COHb levels were higher in Rh-alloimmunized fetuses (P=0.0002). Fetal COHb levels were also higher than paired maternal levels among the alloimmunized group (P=0.011), but not among the control group (1. 04+/-0.04, P=ns). In univariate regression analysis, fetal and maternal COHb levels were significantly correlated with one another in both control (r=0.52, P=0.0002) and alloimmunized pregnancy groups (r=0.52, P=0.05). Comparison of the slopes of the fetal versus maternal COHb plots for the two groups showed a significant difference (P=0.02), with the alloimmunized group having the steeper slope. CONCLUSION: Differences in the antepartum fetal-maternal COHb relationships in control and alloimmunized groups likely reflect increased endogenous CO production among alloimmunized fetuses as a result of pathologic hemolysis.

Chronic 17beta-estradiol replacement increases nitric oxide-mediated vasodilation of guinea pig coronary microcirculation.

BACKGROUND: Estrogen is cardioprotective of the coronary circulation by mechanisms incompletely understood. This study determined the effect of chronic 17beta-estradiol replacement on dilator responses to acetylcholine and sodium nitroprusside of the isolated coronary microcirculation. METHODS AND RESULTS: Adult female guinea pigs were ovariectomized, and a 21-day-release pellet containing 0.0, 0.1, 0.25, 0.5, or 1.0 mg 17beta-estradiol was implanted subcutaneously. Serum estradiol concentrations ranged from 3.9 to 74.9 pg/mL, increasing with the dose of estradiol. After 19 to 20 days, the animals were euthanized, and their hearts were removed and perfused with buffer at constant flow on an isolated heart apparatus. Both perfusion pressure and contractile force were measured in prostaglandin F(2alpha)-constricted hearts. Vasodilation to the cumulative addition of the endothelium-dependent agonist acetylcholine (10(-9) to 10(-5) mol/L) and the nitric oxide (NO) donor sodium nitroprusside (10(-9) to 10(-5) mol/L) was measured before and after NO synthesis inhibition by nitro-L-arginine (LNA, 10(-4) mol/L). Baseline coronary resistance was unaltered by estradiol, although LNA increased resistance in estradiol-treated hearts more than in ovariectomized controls. Chronic 17beta-estradiol increased sensitivity (measured by -log EC(50) values) but not maximal response to acetylcholine compared with ovariectomized controls. Differences were abolished by LNA at all doses of estradiol. Sodium nitroprusside-induced dilation was unaffected by estradiol replacement. CONCLUSIONS: Chronic 17beta-estradiol replacement, at doses producing hormone levels within the physiological range, enhances dilator sensitivity of the coronary microcirculation through enhanced NO production by the endothelium, independent of changes in NO sensitivity of the vascular smooth muscle. Thus, estradiol enhances NO production as a protective mechanism of the coronary microcirculation.

Molecular mechanism of cGMP-mediated smooth muscle relaxation.

Contraction and relaxation of smooth muscle is a tightly regulated process involving numerous endogenous substances and their intracellular second messengers. We examine the key role of cyclic guanosine monophosphate (cGMP) in mediating smooth muscle relaxation. We briefly review the current art regarding cGMP generation and degradation, while focusing on the recent identification of the molecular mechanisms underlying cGMP-mediated smooth muscle relaxation. cGMP-induced SM relaxation is mediated mainly by cGMP-dependent protein kinase activation. It involves several molecular events culminating in a reduction in intracellular Ca(2+) concentration and a decrease in the sensitivity of the contractile system to Ca(2+). We propose that the cGMP-induced decrease in Ca(2+) sensitivity is a strategic way to achieve "active relaxation" of the smooth muscle. In summary, we present compelling evidence supporting a key role for cGMP as a mediator of smooth muscle relaxation in physiological and pharmacological settings.