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.

Extravillous trophoblast invasion in placenta accreta is associated with differential local expression of angiogenic and growth factors: a cross-sectional study.

OBJECTIVE: Placenta accreta is clinically associated with maternal uterine scar. Our objective was to investigate the biochemical contribution of maternal scarring to hyperinvasive trophoblast. We hypothesised that trophoblast over-invasion in placenta accreta is associated with aberrant invasion-site signalling of growth and angiogenic factors known to be involved in wound healing and promotion of cell invasion through the epithelial to mesenchymal cellular programme. DESIGN: Cross-sectional series. SETTING: Yale-New Haven Hospital. POPULATION: Women with histologically confirmed normal and abnormal placentation. METHODS: Placental invasion site tissue sections were immunostained for endoglin and other angiogenic regulators, and transforming growth factor ß (TGFß) proteins. Maternal serum endoglin, and the vascular endothelial growth factor (VEGF) mediators hypoxia-inducible factor-1α (HIF1α) and endostatin, were assessed using immunoassay. MAIN OUTCOME MEASURES: Differences in median H-score by immunostaining and in mean serum level by immunoassay. RESULTS: By immunostaining, placenta accreta samples demonstrated intervillous endoglin shedding and increased trophoblast expression of its cleavage protein matrix metalloproteinase-14. Absent decidual HIF1α and endostatin were observed in areas of VEGF upregulation. TGFß1 was present in myocytes but not in collagen bundles into which accreta trophoblast invaded. Maternal serum endoglin decreased in praevia and accreta when corrected for gestational age. CONCLUSION: Angiogenic and growth factors at the placental invasion site are altered in accreta, both by decidual absence and within myometrial scar. We postulate this promotes the invasive phenotype of placenta accreta by activating hyperinvasive trophoblast and by dysregulating placental vascular remodelling. FUNDING: Yale Department of Obstetrics, Gynecology and Reproductive Sciences funds. TWEETABLE ABSTRACT: Placenta accreta histology shows dysregulation of angiogenic and growth factors.

The invasive phenotype of placenta accreta extravillous trophoblasts associates with loss of E-cadherin.

INTRODUCTION: Epithelial-to-mesenchymal transition (EMT) is a process of molecular and phenotypic epithelial cell alteration promoting invasiveness. Loss of E-cadherin (E-CAD), a transmembrane protein involved in cell adhesion, is a marker of EMT. Proteolysis into N- and C-terminus fragments by ADAM10 and presenilin-1 (PSEN-1) generates soluble (sE-CAD) and transcriptionally active forms. We studied the protein expression patterns of E-CAD in the serum and placenta of women with histologically-confirmed over-invasive placentation. METHODS: The patterns of expression and levels of sE-CAD were analyzed by Western blot, immunoassay, and immunoprecipitation. Tissue immunostaining for E-CAD, cytokeratin-7 (epithelial marker), vimentin (mesenchymal marker), ADAM10, PSEN-1 and ß-catenin expression were investigated in parallel. RESULTS: N-terminus cleaved 80 kDa sE-CAD fragments were present in serum of pregnant women with gestational age regulation of the circulatory levels. Women with advanced trophoblast invasion did not display circulatory levels of sE-CAD different from those of women with normal placentation. Histologically, extravillous trophoblasts (EVT) closer to the placental-myometrial interface demonstrated less E-CAD staining than those found deeper in the myometrium. These cells expressed both vimentin and cytokeratin, an additional feature of EMT. EVT of placentas with advanced invasion displayed intracellular E-CAD C-terminus immunoreactivity predominating over that of the extracellular N-terminus, a pattern consistent with preferential PSEN-1 processing. DISCUSSION: Local processing of E-CAD may be an important molecular mechanism controlling the invasive phenotype of accreta EVT.

Maternal circulating PlGF concentrations and placenta-related pregnancy complications: First results from the CoLab AngF Study.

INTRODUCTION: Circulating angiogenic factors are potential markers for preeclampsia, but heterogeneous studies have failed to identify precise predictive/diagnostic properties. The Global CoLaboratory is investigating how to merge published data of angiogenic factors for meta-analysis on an individual sample basis. OBJECTIVE: To amalgamate pregnancy angiogenic factor studies, investigate diagnostic and predictive properties of these markers in preeclampsia and placenta-related pregnancy complications, and to test if measures from disparate platforms can be standardised. This is the first report using PlGF measures to diagnose preeclampsia. METHODS: Data were derived from 15 cohorts, within and outside the CoLaboratory network. Women were classified as either case (confirmed diagnosis of preeclampsia at sampling) or non-case (no preeclampsia at sampling). Individual PlGF measurements from four different analytical platforms were used, along with transformations of the data (e.g. log-transformations, transformations to a baseline platform). Transformed measurements were standardised both for specific platforms and globally, stratifying on gestational age. Different statistical techniques were compared. RESULTS: The database currently contains 1442 cases and 11,512 non-cases, which were used to define an algorithm to merge PlGF measurements from different platforms. Non-case distributions were used to standardise case results. Diagnostic PlGF measurements in relation to preeclampsia will be presented and confirm feasibility. CONCLUSIONS: Future studies can extend this approach to other angiogenic factors, prediction as well as diagnosis and to other placenta-related disorders.

Universal cervical-length screening to prevent preterm birth: a cost-effectiveness analysis.

OBJECTIVE: To determine whether routine measurement of second-trimester transvaginal cervical length by ultrasound in low-risk singleton pregnancies is a cost-effective strategy. METHODS: We developed a decision analysis model to compare the cost-effectiveness of two strategies for identifying pregnancies at risk for preterm birth: (1) no routine cervical length screening and (2) a single routine transvaginal cervical length measurement at 18-24 weeks' gestation. In our model, women identified as being at increased risk (cervical length < 1.5 cm) for preterm birth would be offered daily vaginal progesterone supplementation. We assumed that vaginal progesterone reduces preterm birth at < 34 weeks' gestation by 45%. We also assumed that a decreased cervical length could result in additional costs (ultrasound scans, inpatient admission) without significantly improved neonatal outcomes. The main outcome measure was incremental cost-effectiveness ratio. RESULTS: Our model predicts that routine cervical-length screening is a dominant strategy when compared to routine care. For every 100,000 women screened, $12,119,947 can be potentially saved (in 2010 US dollars) and 423.9 quality-adjusted life-years could be gained. Additionally, we estimate that 22 cases of neonatal death or long-term neurologic deficits could be prevented per 100,000 women screened. Screening remained cost-effective but was no longer the dominant strategy when cervical-length ultrasound measurement costs exceeded $187 or when vaginal progesterone reduced delivery risk at < 34 weeks by less than 20%. CONCLUSION: In low-risk pregnancies, universal transvaginal cervical length ultrasound screening appears to be a cost-effective strategy under a wide range of clinical circumstances (varied preterm birth rates, predictive values of a shortened cervix and costs).

Assessment of the fetal thymus by two- and three-dimensional ultrasound during normal human gestation and in fetuses with congenital heart defects.

OBJECTIVES: Our objectives were to compare the size and volume of the developing fetal thymus obtained by two-dimensional ultrasound (2D-US) and three-dimensional ultrasound (3D-US), develop normative data for thymus volume (TV), and investigate TV in fetuses with congenital heart disease (CHD) and normal twin gestations. METHODS: We studied 321 fetuses (gestational age (GA): 17-39 weeks) including 238 normal singletons, 64 normal twins and 19 singleton fetuses with CHD. We used 2D-US to assess fetal thymus maximum transverse diameter (MTD), maximum transverse area (MTA), anteroposterior diameter (APD) and superoinferior diameter (SID). TV was obtained by 3D-US using virtual organ computer-aided analysis. Measurements were adjusted for estimated fetal weight where appropriate. Linear regression analysis, general linear models and Fisher's Z-transformation were used where appropriate. A nomogram of fetal TV based on singleton gestations was produced according to previously published methods. RESULTS: Ultrasound assessment of the fetal thymus was possible in 95.3% (306/321) of cases. Both 3D-US and 2D-US measurements were significantly correlated with GA (TV r = 0.989; MTA r = 0.918; MTD r = 0.884; APD r = 0.849; and SID r = 0.816; all P < 0.05). After Fisher's Z-transformation, the correlation between the TV and GA was significantly stronger than that between any individual 2D-US measurement and GA (P < 0.05). Normal twin fetuses had TVs similar to those of singletons adjusted for estimated fetal weight and GA (P = 0.85). TV adjusted for estimated fetal weight and GA was significantly lower in fetuses with CHD than in normal singletons (P < 0.05). CONCLUSION: 2D-US and 3D-US are useful tools for evaluation of the size and volume of the human fetal thymus through gestation. Fetal TV by 3D-US seems to reflect normal development of the thymus in utero better than do 2D-US measurements. Lower TV should be expected in association with CHDs.

The role of urinary soluble endoglin in the diagnosis of pre-eclampsia: comparison with soluble fms-like tyrosine kinase 1 to placental growth factor ratio.

OBJECTIVE: Endoglin, an anti-angiogenic glycoprotein expressed on endothelial cells, has been proposed recently as a biomarker of pre-eclampsia (PE). Given that PE is characterised by an imbalance of angiogenic factors, we sought to determine the clinical utility of urinary soluble endoglin, relative to the soluble fms-like tyrosine kinase 1 to placental growth factor (PlGF) ratio, in the diagnosis of PE during gestation. DESIGN: Prospective observational cohort. SETTING: Tertiary referral university hospital. POPULATION: Two hundred and thirty-four pregnant women were enrolled prospectively in the following groups: healthy controls, n = 63; gestational age (GA), median (interquartile range), 33 weeks (27-39 weeks); chronic hypertension, n = 27; GA, 33 weeks (30-36 weeks); mild PE, n = 38; GA, 37 weeks (34-40 weeks); severe PE, n = 106; GA, 32 weeks (29-37 weeks). METHODS: Free urinary levels of soluble endoglin, soluble fms-like tyrosine kinase 1 and PlGF were measured by sensitive and specific immunoassay. Levels for all urinary analytes were normalised to creatinine. MAIN OUTCOME MEASURES: Urinary soluble endoglin, and the soluble fms-like tyrosine kinase 1 to PlGF ratio. RESULTS: In healthy controls, urinary soluble endoglin levels were increased significantly at term relative to those earlier in gestation. Severe PE was characterised by an increased urinary level of soluble endoglin, soluble fms-like tyrosine kinase 1, protein to creatinine ratio and soluble fms-like tyrosine kinase 1 to PlGF ratio compared with all other groups. There was a direct correlation between urinary soluble endoglin and proteinuria that remained after GA correction (R = 0.382, P < 0.001). Urinary soluble endoglin could not differentiate mild PE from severe preterm PE. Overall, soluble endoglin had the ability to discriminate PE from chronic hypertension and healthy controls only in women who were evaluated at <37 weeks of GA. The sensitivity, specificity and accuracy of urinary soluble endoglin alone in the diagnosis of PE or in the identification of women with PE requiring a mandated delivery before 37 weeks of gestation were 70%, 86% and 76%, respectively. These values were inferior to those of the soluble fms-like tyrosine kinase 1 to PlGF ratio (P < 0.001). The addition of urinary soluble endoglin did not improve the diagnostic accuracy of the soluble fms-like tyrosine kinase 1 to PlGF ratio alone. CONCLUSIONS: We have provided evidence that soluble endoglin is present and elevated in the urine of women who develop preterm PE. Urinary soluble endoglin has only limited ability to determine the severity of PE and to distinguish between PE and chronic hypertension both preterm and at term. Compared with urinary soluble endoglin, the soluble fms-like tyrosine kinase 1 to PlGF ratio remains a better marker of disease presence, severity and outcome.

Fetal inflammatory response in women with proteomic biomarkers characteristic of intra-amniotic inflammation and preterm birth.

OBJECTIVE: To determine the relationship between presence of amniotic fluid (AF) biomarkers characteristic of inflammation (defensins 2 and 1 and calgranulins C and A) and fetal inflammatory status at birth. DESIGN: Prospective observational cohort. SETTING: Tertiary referral University hospital. POPULATION: One hundred and thirty-two consecutive mothers (gestational age, median [interquartile range]: 29.6 [24.1-33.1] weeks) who had a clinically indicated amniocentesis to rule out infection and their newborns. METHODS: Intra-amniotic inflammation was diagnosed by mass spectrometry surface-enhanced-laser-desorption-ionization time of flight (SELDI-TOF). The AF proteomic fingerprint (mass-restricted [MR] score) ranges from 0-4 (none to all biomarkers present). The intensity of intra-amniotic inflammation was graded based on the number of proteomic biomarkers: MR score 0: 'no' inflammation, MR score 1-2: 'minimal' inflammation and MR score 3-4: 'severe' inflammation. At birth, cord blood was obtained for all women. Severity of histological chorioamnionitis and early-onset neonatal sepsis (EONS) was based on established histological and haematological criteria. Interleukin-6 (IL-6) levels were measured by sensitive immunoassays. The cord blood-to-AF IL-6 ratio was used as an indicator of the differential inflammatory response in the fetal versus the AF compartment. MAIN OUTCOME MEASURES: To relate proteomic biomarkers of intra-amniotic infection to cord blood IL-6 and to use the latter as the primary marker of fetal inflammatory response. RESULTS: Women with intra-amniotic inflammation delivered at an earlier gestational age (analysis of variance, P<0.001) and had higher AF IL-6 levels (P<0.001). At birth, neonates of women with severe intra-amniotic inflammation had higher cord blood IL-6 levels (P=0.002) and a higher frequency of EONS (P=0.002). EONS was characterised by significantly elevated cord blood IL-6 levels (P<0.001). Of the 39 neonates delivered by mothers with minimal intra-amniotic inflammation, 15 (39%) neonates had umbilical cord blood IL-6 levels above the mean for the group and 2 neonates had confirmed sepsis. The severity of the neutrophilic infiltrate in the chorionic plate (P<0.001), choriodecidua (P=0.002), umbilical cord (P<0.001) but not in the amnion (P>0.05) was an independent predictor of the cord blood-to-AF IL-6 ratio. Relationships were maintained following correction for gestational age, birthweight, amniocentesis-to-delivery interval, caesarean delivery, status of the membranes, race, MR score and antibiotics and steroid exposure. CONCLUSIONS: We provide evidence that presence of proteomic biomarkers characteristic of inflammation in the AF is associated with an increased inflammatory status of the fetus at birth. Neonates mount an increased inflammatory status and have positive blood cultures even in the context of minimal intra-amniotic inflammation.

Proteomics of the amniotic fluid in assessment of the placenta. Relevance for preterm birth.

Proteomics is the study of expressed proteins and has emerged as a complement to genomic research. The major advantage of proteomics over DNA-RNA based technologies is that it more closely relates to phenotypes and not the source code. Proteomics thus holds the promise of providing a direct insight into the true mechanisms of human diseases. Historically, examination of the placenta has been the first modality to subclassify pathogenetic entities responsible for preterm birth. Because placenta is a key pathophysiological participant in several major obstetrical syndromes (preterm birth, pre-eclampsia, intrauterine growth restriction) identification of relevant biomarkers of placental function can profoundly impact on the prediction of fetal outcome and treatment efficacy. Since proteomics is a young science and studies that associate proteomic patterns with long-term outcome require follow-up of children up to school age, using placental pathological footprints of cellular injury as intermediate outcomes can be useful in the interim. Furthermore, knowledge on the identity of the dysregulated proteins may provide the needed breakthrough insight into novel pathophysiological pathways and unravel possible targets for therapeutical intervention that could not have been envisioned through hypothesis-driven approaches.

Placental growth factor in the cerebrospinal fluid of women with preeclampsia.

OBJECTIVE: Recent data suggest that excess circulating soluble fms-like tyrosine kinase-1 (sFlt-1) may causally relate to preeclampsia. This study investigates the levels of sFlt-1, VEGF, and PlGF in cerebrospinal fluid (CSF) of patients with preeclampsia and normotensive controls. METHODS: CSF was collected from preeclamptic patients (n=15) and controls (n=7) at the time of spinal anesthesia and assayed for PlGF, sFlt-1, and VEGF (total and free) by specific immunoassays. RESULTS: All sought angiogenic factors were measurable. Levels of free PlGF but not sFlt-1 or VEGF (total or free) were increased in CSF of preeclamptic women. There was no significant difference in the ratios of angiogenic factors in the CSF of women with preeclampsia. There was no correlation between levels of angiogenic factors and CSF cell counts or severity of symptoms. CONCLUSION: Elevated levels of PlGF in CSF preeclamptic women may promote vascular permeability and contribute to the hypertensive encephalopathy seen in such patients.

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.

Effect of stimulatory and inhibitory drugs on uterine electrical activity measured noninvasively from the abdominal surface of pregnant rats.

OBJECTIVE: Our purposes were (1) to identify and analyze parameters of uterine electrical activity that change during active term and preterm labor in response to stimulatory (oxytocin) or inhibitory (terbutaline) agents and (2) to correlate the information obtained from abdominal surface measurement of electrical activity with intrauterine pressure and with the electrical activity measured directly from the uterine surface in vivo. STUDY DESIGN: Electromyographic activity was acquired simultaneously from the uterine wall and the abdominal surface by means of unipolar electrodes. Electromyographic activity was recorded in the 0.3 to 50-Hz range and digitized at 200 samples per second. Intrauterine pressure was measured via an intrauterine catheter. The effect of cumulative doses of oxytocin and terbutaline on power density spectrum, amplitude, number and duration of electromyographic bursts, and intrauterine pressure was recorded in anesthetized rats during spontaneous active term labor (n = 7) and induced preterm labor (n = 6). RESULTS: Bursts of electromyographic activity recorded from the abdominal surface mirrored those from the uterine wall, albeit at a lower amplitude. During active term labor, lower concentrations of oxytocin did not significantly affect power-density-spectrum energy, amplitude, or number of bursts per unit time. The duration of electromyographic bursts increased dose dependently. Myometrial contractions were phasic, with return to the baseline between phases. As the concentration of oxytocin increased, the energy, amplitude, and number of bursts per unit time declined while the intrauterine pressure continued to rise until the contraction became tetanic, without return to the baseline. In rats with induced preterm labor, terbutaline inhibited uterine contractility by decreasing the intrauterine pressure. This was accompanied by a progressive decrease in the power density spectrum, amplitude, number, and duration of the uterine wall and abdominal surface electrical bursts. CONCLUSIONS: First, uterine electromyographic activity measured noninvasively from the abdominal surface reflects changes in uterine electrical activity and intrauterine pressure measured directly and invasively in term and preterm labor, as well as during treatments to stimulate or inhibit labor. Second, this noninvasive method may be useful in monitoring uterine activity in vivo. Third, clinical studies to evaluate this technology in human subjects are warranted.

Distinct regulation of nitric oxide and cyclic guanosine monophosphate production by steroid hormones in the rat uterus.

It has previously been reported that uterine nitric oxide (NO) production is enhanced during rat pregnancy compared to non-pregnant, labouring or postpartum states. The present hypothesis is that these changes in uterine NO production during pregnancy are caused by the interplay of oestrogen and progesterone. It is further postulated that changes in cyclic guanosine monophosphate (cGMP) production closely follow the changes in uterine NO synthesis. To test these hypotheses a variety of hormonal regimens (17beta-oestradiol, progesterone and combinations) were applied to different rat models (prepubertal, non-pregnant intact and ovariectomized as well as pregnant rats). The production of nitric oxide (NO) as well as basal and in-vitro NO-stimulated cGMP tissue content were measured in parallel. NO production was measured by the accumulation of nitrites and nitrates in a 24 h incubation medium as analysed by Greiss reaction. cGMP content was measured by radioimmunoassay. Diethylenetriamine/NO (DETA/NO) was used as NO donor. NO production in the rat uterus was markedly increased by pregnancy compared to other physiological (prepubertal, or cycling dioestrus) and experimentally induced (OVX) states. In contrast, uterine cGMP was significantly decreased in pregnancy. Pregnancy also inhibited the elevation in uterine cGMP after in-vitro NO challenge. Chronic 17beta-oestradiol treatment in prepubertal and/or OVX models increased NO production and also mimicked the effect of pregnancy on cGMP. Administration of progesterone in prepubertal rats induced a parallel decrease in both uterine NO and cGMP. In conclusion, sex steroid hormones distinctly regulate uterine NO and cGMP production depending upon the dose and regimen used, as well as the animal's reproductive state.