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PubMedDate not supplied

Maternal age, gravidity, and pregnancy spacing effects on spontaneous fetal mortality.

Differentials in the probability of pregnancy loss are examined using pregnancy history data from eight WFS surveys in developing countries. Multiple logistic regression equations are estimated. The probability of loss varies substantially over the reproductive career. Both higher-order pregnancies and those conceived at older ages are more likely to terminate in loss. maternal age differentials are more pronounced for lower-order pregnancies. First and second pregnancies conceived over age thirty suffer especially high levels of loss. Pregnancies conceived relatively soon after the termination of the previous pregnancy are more likely to be lost, as are pregnancies conceived after long intervals. Risk of loss is higher for women previously experiencing loss, and the effect persists beyond the pregnancy following the loss.

Adolescent↗
PubMed1977

Response of arterial segments from gravid human uterus to multiple concentrations of lignocaine.

Nine uterine artery segments were obtained during Caesarean hysterotomy. The amount of isometric tension developed by each segment when exposed to 3, 6, 10, 20, 50, 100, 1000 and 2000 microng/ml of lignocaine hydrochloride (Xylocaine) was measured. All nine segments contracted in response to the 1000- and 2000-microng/ml concentrations. Eight of nine, six of nine, and three of nine responded to the 100-, 50- and 20-microng/ml concentrations, respectively; one segment contracted in response to all concentrations. A dose-response curve indicated that maximum responses were obtained at the 1000-microng/ml concentration (0.1%). Although local anaesthetics are usually considered vasodilators, this study indicates that lignocaine causes the uterine artery to constrict in concentrations in excess of 20 microng/ml. Such concentrations might occur after paracervical block or accidental intravascular injection, but would not be expected in association with extradural analgesia.

Arteries↗
PubMed1996

Gravid health status, medication use, and risk of neuroblastoma.

The epidemiology of neuroblastoma suggests that prenatal exposures may be important etiologic factors in this disease. The authors describe the role of maternal health status and prenatal medication usage and risk of neuroblastoma. This retrospective study was based on completed interviews with 183 histologically confirmed neuroblastoma cases aged 0-14 years diagnosed among residents of New York State (excluding New York City) between 1976 and 1987. Controls were matched to cases on year of birth and race and were drawn from the New York State live birth certificate registry. Interviews were satisfactorily completed with 85% of the cases and 87% of controls. Significantly elevated odds ratios were noted for vaginal infections during pregnancy (odds ratio (OR) = 2.2, 95% confidence interval (CI) 1.2-4.0), medical treatments for vaginal infection during pregnancy (OR = 2.4, 95% CI 1.2-4.9), and any reported use of sex hormones during pregnancy (OR = 3.0, 95% CI 1.3-6.9). Point estimates for any hormone use suggested elevated risk among male offspring (OR = 4.4, 95% CI 1.5-13.3). Among the individual exposures comprising any hormone use, only hormone use related to infertility was observed to be significant (OR = 10.4, 95% CI 1.2-89.9). A protective effect was noted for self-reported vitamin use (OR = 0.28, 95% CI 0.03-0.69). Although it is not possible to presume a specific role for prenatal hormone exposure as initiator or promoter, these findings lend support to an association between prenatal hormone exposure and risk of neuroblastoma.

Adolescent↗
PubMed2003

Effects of endotoxin and macrophage-related cytokines on the contractile activity of the gravid murine uterus.

Immune cell trafficking and activity are implicated in the parturition process, but little is known about the role of macrophages in control of uterine contractility at term. In the present study, we tested the hypothesis that endotoxin (lipopolysaccharide [LPS]) enhances uterine contractile activity through a mechanism that involves activation of resident macrophages. Various uterotonins and anti-inflammatory mediators were added to a standard muscle bath preparation that contained strips of uterus from Day 15 pregnant C3H/HeN mice. Spontaneous and agonist-induced contractile activity was enhanced following LPS treatment. LPS increased amplitude but not frequency of contractions. Addition of anti-inflammatory cytokines, interleukin 10 or transforming growth factor beta, to suppress macrophage activation did not block LPS-induced increases in contractility. By contrast, indomethacin given to block prostaglandin production suppressed the LPS-induced increase in amplitude of contractions. These findings suggest that an inflammatory response, possibly mediated by activation of macrophages and prostaglandins, participates in the regulation of amplitude but not frequency of contractile activity by the murine uterus before onset of parturition.

Animals↗
PubMed2004

Differential expression of the vascular endothelial growth factor-receptor system in the gravid uterus of yorkshire and Meishan pigs.

Litter size in the pig is limited by uterine capacity, which is dependent on uterine size, placental size, and vascularity. Placentae of U.S. pig breeds, such as the Yorkshire, exhibit marked growth from mid to late gestation, increasing their surface area of endometrial attachment. In contrast, placentae of the prolific Chinese Meishan pig exhibit little growth from mid to late gestation; instead, they exhibit a marked and progressive increase in the density of placental blood vessels. Vascular endothelial growth factor (VEGF) is a potent angiogenic and permeability-enhancing factor that is produced and secreted by placentae of several species, including the pig. The activity of VEGF is mediated through two specific receptors (VEGF-R1 and VEGF-R2), both of which are expressed by placental and endometrial tissues in pigs and are thought to play a role in mediating increased vascularization and/or permeability at the fetal-maternal interface. The objectives of the present study were to determine concentrations of VEGF in fetal blood and placental fluids as well as placental and adjacent endometrial mRNA expression of VEGF, VEGF-R1, and VEGF-R2 on Days 30, 50, 70, 90, and 110 of gestation in Yorkshire and Meishan pigs. Day 90 Meishan conceptuses exhibited marked increases (P < 0.05) in placental VEGF mRNA expression as well as fetal blood and allantoic fluid concentrations of VEGF, which remained elevated through Day 110. In contrast, Yorkshire conceptuses failed to exhibit increases in placental VEGF mRNA expression or concentrations of VEGF in fetal blood or allantoic fluid until Day 110. Receptor mRNA expression patterns differed between Meishan and Yorkshire conceptuses, but no difference was found in their expression levels. Placental efficiency (fetal weight/placental weight) was higher (P < 0.05) on Days 90 and 110 in Meishan than in Yorkshire conceptuses. The earlier increase in VEGF protein and mRNA expression in the Meishan versus the Yorkshire conceptus may explain the previously reported increased vascularity and increased placental efficiency of this breed compared the Yorkshire breed.

Animals↗
PubMed1992

Different patterns of myometrial activity and 24-h rhythms in myometrial contractility in the gravid baboon during the second half of pregnancy.

Two clearly distinct epochs of myometrial contractility were observed in 13 pregnant baboons when recorded either as intraamniotic pressure (IAP) or myometrial electromyogram (EMG). Contractures, epochs lasting longer than 3 min, were the characteristic form of myometrial activity throughout pregnancy. Contractures generated only small increases in IAP. Short-lived contractions, generating larger increases in IAP, were characteristic of labor and delivery. Power spectral analysis of IAP and myometrial EMG activity proved to be an effective means whereby periods when the myometrium was in the contractures or contractions mode could be easily distinguished. Concomitantly recorded maternal intraabdominal temperature showed significant 24-h variations. When myometrial activity switched from low-amplitude, long-lasting regular contractures of pregnancy to contractions, the switch always occurred around the onset of darkness. Five baboons went into spontaneous labor, 3 prematurely and 2 at term. In these animals the switch from contractures to contractions occurred for several nights before delivery. The recurrence and timing of the switch from contractures to contractions for several nights before delivery were similar to the pattern we and others have observed in the pregnant rhesus monkey. The presence of 24-h periodicity in the patterns of specific types of myometrial activity in another nonhuman primate lends support to the view that similar 24-h patterns of myometrial activity may occur in pregnant women.

Animals↗
PubMed1998

The tocolytic effect of catecholamines in the gravid rat uterus.

UNLABELLED: Maternal catecholamines increase dramatically in labor because of pain and emotional stress. Because the uterus is richly endowed with both alpha- and beta-adrenergic receptors, catecholamines could alter uterine activity. We assessed the effect of clinically encountered concentrations of these catecholamines on uterine activity and modeled the effect of the abrupt reduction in circulating epinephrine that occurs during effective labor analgesia. Term pregnant rat uteri were excised, and cross-sectional rings were mounted for isometric force recording. Log concentration-response curves for epinephrine, norepinephrine, and their combination on uterine activity were constructed from 10(-12) to 10(-6) M. Catecholamine responses were repeated in the presence of phentolamine, an alpha-adrenergic blocker or propranolol, a beta-adrenergic blocker. The abilities of oxytocin and of washout of catecholamines to reverse catecholamine-induced changes in uterine activity were also assessed. Epinephrine caused dose-dependent reductions in uterine activity, blocked by propranolol. Epinephrine concentrations in the clinical range(10(-9) to 10(-8) M; 100-1000 pg/mL) decreased uterine activity to 49.6% +/- 6.6% (mean +/- SE) of control. Norepinephrine caused a dose-dependent increase in uterine activity, which was blocked by phentolamine. In the clinical range (10(-8) M), uterine activity was 139.2% +/- 13.40% of control. The combination of both catecholamines, however, was nearly as tocolytic as epinephrine alone. Oxytocin antagonized catecholamine-induced tocolysis, and washout of epinephrine or both catecholamines increased uterine activity. We conclude that mixed catecholamines are significantly tocolytic at concentrations encountered in laboring women. In this in vitro model, reduction in epinephrine concentration, comparable to that which occurs during effective analgesia, significantly increases uterine activity. IMPLICATIONS: Maternal catecholamines increase in labor, but epinephrine decreases dramatically after regional analgesia. In this study, we found that norepinephrine and epinephrine together decrease uterine contractile activity and that decreased epinephrine causes significantly increased uterine activity.

Adrenergic alpha-Antagonists↗
PubMed2000

The effect of nitroglycerin on the gravid uterus in sheep and rabbits.

UNLABELLED: Clinical reports suggest that nitroglycerin (TNG) has an effect on the uterus that is detected by the obstetrician on palpation, but not obvious by measurement of uterine pressure. This study was designed to compare the effects of TNG on uterine compliance and tension. We used three sets of experiments to evaluate the effect of TNG on the uterus. In vivo experiments were conducted on laboring ewes and rabbits 2 h postpartum to measure the effect of TNG on active uterine tension. An in vitro experiment was also conducted by using isolated uterine strips from term pregnant rabbits to evaluate the effect of TNG on uterine compliance. TNG had no discernible effect on uterine intracavitary pressure or frequency of contraction in either laboring ewes or postpartum rabbits at doses that were sufficient to reduce the mean arterial pressure. TNG did, however, increase the compliance of uterine tissue from rabbits at term, whereas S-nitroso-N-acetylpenicillamine failed to produce a similar effect. Thus, the perceived relaxant effects of TNG may be caused by an increase in uterine compliance, which may facilitate efforts by the obstetrician to manipulate the uterus. While the mechanism of action remains unclear, it appears to be independent of nitric oxide. IMPLICATIONS: The administration of nitroglycerin may have a relaxant effect on the uterus. These experiments were conducted to elucidate the effect of nitroglycerin on the peripartum uterus by measuring active tension and compliance.

Adrenergic beta-Agonists↗