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Biomedical subjects

Byron C Calhoun

Publications and source records attributed to Byron C Calhoun.

12 recordsLinked to original sources
PubMed2006

Fetal growth curves for an ethnically diverse military population: the American Institute of Ultrasound in Medicine-accredited platform experience.

OBJECTIVE: To determine which fetal growth curve provided the best estimates of fetal weight for a cohort of ethnically diverse patients at sea level. METHODS: The study consisted of a population of 1,729 fetuses examined at sea level between January 1, 1997, and June 30, 2000, at 18 weeks, 28 weeks, and term. Gestational age (GA) based on menstrual dates was confirmed or adjusted by crown-rump length or early second-trimester biometry. Fetal weight was estimated by using biparietal diameter, head circumference, abdominal circumference, and femur length. Our fetal growth curves were analyzed with fourth-order polynomial regression analysis, applying four previously defined formulae for fetal growth. RESULTS: Fetal growth curves for estimated fetal weight demonstrated the expected parabolic shape, which varied according to the formulae used. Our curve best fit the following equation: estimated fetal weight = 4.522 - 0.22 x GA age + 0.25 x GA(2) - 0.001 x GA(3) + 5.248 x 10(-6) x GA(4) (R2 = 0.976). SD increased in concordance with GA. CONCLUSION: Madigan Army Medical Center serves a racially mixed, culturally diverse, military community with unrestricted access to prenatal care. Determination of the optimal population-appropriate growth curve at the correct GA assists clinicians in identifying fetuses at risk for growth restriction or macrosomia and therefore at risk for increased perinatal morbidity and death.

Cultural Diversity↗
PubMed2003

The effects of a cyclo-oxygenase II inhibitor on placental artery production of thromboxane and prostacyclin.

OBJECTIVE: The study was undertaken to determine the effects of a cyclo-oxygenase II inhibitor on fetoplacental artery production of prostacyclin and thromboxane A(2). STUDY DESIGN: Eight placentas were obtained from normal parturients at delivery and four chorionic plate arteries were dissected from each placenta. Arteries were incubated in media alone, media plus angiotensin II (1x10(-10) mol), media plus rofecoxib (300 ng/mL), or media plus angiotensin II and rofecoxib. Serial samples were assayed for metabolites of thromboxane B(2) and prostacyclin by enzyme-linked immunosorbent assay. Results were compared by analysis of variance, and P<.05 was considered significant. RESULTS: At 24 hours, 6-keto-prostaglandin F(1alpha) levels in the rofecoxib group (1.74+/-1.39 ng/mg tissue, P<.01) and the rofecoxib plus angiotensin II group (2.15+/-1.85 ng/mg tissue, P<.01) were significantly lower than levels in the control group (4.25+/-2.03 ng/mg tissue). Thromboxane B(2) levels were lower in the angiotensin II group (0.65+/-0.33 ng/mg tissue) than the control group (1.22+/-0.70 ng/mg tissue, P<.05). CONCLUSION: Cyclo-oxygenase II inhibition decreases the production of prostacyclin in fetoplacental arteries and alters the normal ratio of thromboxane A(2) to prostacyclin.

Angiotensin II↗
PubMed2003

Fetoplacental vascular tone is modified by magnesium sulfate in the preeclamptic ex vivo human placental cotyledon.

OBJECTIVE: The purpose of this study was to evaluate fetoplacental vascular tone and response to a vasoconstrictor in placentas of preeclamptic and normotensive pregnancies with and without the presence of magnesium sulfate. STUDY DESIGN: Two cotyledons from each placenta were selected from preeclamptic (n=8) and normotensive (n=7) pregnancies. In one cotyledon from each pair, the maternal circuit was perfused with magnesium sulfate. The fetal arteries were injected sequentially with angiotensin II (10(-10)mol and 10(-11.5) mol). Perfusion pressures and response to angiotensin II were compared, with regard to preeclampsia and exposure to magnesium sulfate. RESULTS: Perfusion pressure was higher in preeclamptic placentas, compared with normotensive placentas (30.4 mm Hg vs 24.4 mm Hg, P=.02). There was a decrease in perfusion pressure with exposure to magnesium sulfate in preeclamptic placentas (22.5 mm Hg, P<.01), but not in normotensive placentas. Fetoplacental vascular response to angiotensin II was not affected by preeclampsia or magnesium sulfate. CONCLUSION: In placentas from preeclamptic pregnancies there is increased fetoplacental perfusion pressure, which decreases with exposure to sulfate.

Angiotensin II↗
PubMed2003

Perinatal hospice. Comprehensive care for the family of the fetus with a lethal condition.

OBJECTIVE: To describe our experience in providing a program of structured interdisciplinary care for the families of fetuses prenatally diagnosed with a lethal congenital anomaly. STUDY DESIGN: We developed a comprehensive "perinatal hospice" program for the supportive care of families with fetuses known to have a lethal condition. Upon prenatal diagnosis of a lethal fetal condition, parents were presented with the option of elective pregnancy termination versus a multi-disciplinary program of ongoing supportive care until the time of spontaneous labor or until delivery was required for obstetric indications. We evaluated patient use of this new service and the natural history of pregnancies managed in this fashion. RESULTS: The population consisted of 33 patients carrying a fetus with a clearly delineated lethal anomaly. Twenty-eight (85%) chose to participate in the perinatal hospice program. Of these, 11/28 (39%) had an intrauterine fetal death and 17/28 (61%) delivered a live-born infant. Among the live-born infants were 12 vaginal deliveries, 4 preterm and 8 at term. Obstetric indications or maternal request resulted in cesarean delivery for 5/28 (18%), 4 preterm and 1 at term, all live born. All live-born infants died within 20 minutes to 2 months. There were no maternal complications. CONCLUSION: The availability of a structured program providing ongoing, comprehensive, multidisciplinary, supportive perinatal care offers a tangible and safe alternative to early elective pregnancy termination for patients carrying a fetus with a lethal congenital condition.

Adult↗
PubMed2002

Connexin 43 expression in normal versus dysfunctional labor.

OBJECTIVE: We sought to determine whether connexin 43 (Cx43), the major myometrial gap junction protein, is differentially expressed in normal versus dysfunctional labor. STUDY DESIGN: Myometrial biopsies were obtained from 28 patients undergoing cesarean section and grouped into the following categories: (1) no labor, (2) dysfunctional labor, and (3) normal labor. Northern and Western analyses were performed to determine Cx43 messenger RNA (mRNA) and protein expression, respectively. Localization of Cx43 protein was determined by immunohistochemistry. RESULTS: Labor was associated with increased Cx43 mRNA expression (P <.05). This association was not true for protein. There was no difference in mRNA or protein expression between patients with normal labor versus those with dysfunctional labor. The extent of Cx43 immunohistochemical staining was not significantly different among the groups (P >.05). CONCLUSION: Dysfunctional labor is not associated with aberrant Cx43 mRNA or protein expression or with a reduction in immunodetectable Cx43 gap junctions.

Adult↗
PubMed2002

The effect of fetal acidemia on fetal-placental vascular tone and production of the inflammatory cytokines interleukin-6 and tumor necrosis factor-alpha.

OBJECTIVE: Our purpose was to determine the effects of fetal acidemia on placental vascular tone and production of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha). STUDY DESIGN: With use of an ex vivo placental perfusion model, the maternal and fetal circulation of two cotyledons from five human placentas were perfused for 4 hours. The fetal circulation of one cotyledon was perfused with acidemic (pH 6.90) Hanks' balanced salt solution (HBSS), whereas the fetal circulation of the other cotyledon was perfused with physiologic (pH 7.35) HBSS. Fetal venous effluents were collected hourly, and IL-6 and TNF-alpha concentrations were determined by enzyme-linked immunosorbent assay. Cotyledon perfusion pressures were recorded every 10 minutes. Paired t tests were used to compare differences in cytokine production and perfusion pressure between the cotyledons. RESULTS: Fetal-placental vascular perfusion pressure was consistently reduced from baseline under acidemic, but not physiologic, conditions with statistical significance achieved from 20 minutes onward (P <.05). IL-6 and TNF-alpha increased exponentially over time for both conditions (P <.05). There was no difference in cytokine production when acidemic conditions were compared with physiologic conditions (P <.05). CONCLUSION: Fetal-placental vasodilation may be a compensatory mechanism to improve acidemic conditions. Unlike fetal hypoperfusion or fetal hyperoxia, fetal acidemia does not result in elevated placental cytokine levels.

Acids↗
PubMed2002

Informed consent and birth: protecting the pelvic floor and ourselves.

The controversy over elective cesarean versus vaginal birth with regard to pelvic floor trauma has left many caregivers and patients confused. With the growing evidence to support the development of fecal incontinence as a result of childbirth, we believe that it is imperative to reevaluate modern obstetric practices both for the patient's benefit and for our medical-legal protection. Our attention and energy need to be focused on good informed consent regarding these risks along with improved postpartum surveillance for injury.

Fecal Incontinence↗
PubMed2002

Maternal ethnicity and variation of fetal femur length calculations when screening for Down syndrome.

OBJECTIVE: To determine whether current methods for detecting Down syndrome based on fetal femur length calculations are influenced by ethnicity. METHODS: The study population consisted of all fetuses scanned between 14 and 20 completed weeks' gestation from April 1, 1997, to January 1, 2000. The expected femur length was calculated from the biparietal diameter. The variance from the expected femur length, compared with the biparietal diameter, was calculated, and the mean variations were compared by maternal race. Ethnic-specific formulas for expected femur length were derived by simple regression. RESULTS: There was a statistically significant difference in femur length in the Asian group compared with all other groups, as well as the white group compared with the black and Asian groups (P < .05). However, there was no significant difference between the black and Hispanic groups or the white and Hispanic groups. The Asian group had the largest variation, with the measured femur length being less than the expected femur length. All groups studied had a mean expected femur length less than the mean measured femur length. On the basis of the ethnic-specific formulas for femur length, there was a significant decrease in patients that would undergo further evaluation for Down syndrome. CONCLUSIONS: There is a significant difference in the mean expected femur length by biparietal diameter among fetuses in the second trimester with regard to ethnicity. Using ethnic-specific formulas for expected femur length can have a considerable impact on the use of sonographic risk factors for Down syndrome screening. Further data are required for use of femur length as a screening tool in the genetic sonogram.

Adult↗
PubMedDate not supplied

Relationship between the extent of histologic villous mineralization and stillbirth in aneuploid and euploid fetuses.

OBJECTIVE: To describe the relationship between the degree of placental histologic villous mineralization (VM) and stillbirth in aneuploid and euploid fetuses. METHODS: The extent of VM for aneuploid and gestational age-matched euploid placentas was graded semiquantitatively on a 0 to 3 scale based on the number of terminal or stem villi containing mineralizations in forty x10 fields of view. The extent of VM was analyzed in relation to fetal status at delivery (liveborn or stillborn) for both aneuploid and euploid fetuses. RESULTS: For 14 available aneuploid placentas, grade 0 or 1 VM was recorded for seven aneuploid specimens, of which two were stillborn. Grade 2 or 3 VM was recorded for seven aneuploid specimens, of which six were stillborn. Fourteen gestational age-matched euploid placentas served as controls. Grade 0 or 1 VM was observed in nine euploid specimens, of which four were stillborn. Grade 2 or 3 VM was observed in five euploid specimens, of which four were stillborn. For aneuploid fetuses, stillbirth was significantly more frequent with grade 2 or 3 VM compared with grade 0 or 1 VM (chi(2) = 4.667, P <.05). This relationship did not exist for euploid fetuses (chi(2) = 1.659, P >.05). CONCLUSION: Histologic VM is not a universal finding in, or exclusive to, stillbirths. Aneuploid but not euploid stillbirths show increased histologic VM compared with livebirths. This may implicate impaired placental or circulatory function as a mechanism for death in aneuploid fetuses.

Aneuploidy↗
PubMedDate not supplied

Natural history of twin gestation complicated by in utero fetal demise: associations of chorionicity, prematurity, and maternal morbidity.

OBJECTIVES: To evaluate the pathophysiology by which the in utero death of 1 twin might increase morbidity to its co-twin survivor and its mother. To assess previously reported risks for maternal disseminated intravascular coagulopathy, peripartal hemorrhage, retained placenta and infection, as well as the fetal risk of prematurity. MATERIAL AND METHODS: A retrospective analysis of the natural history of twin pregnancies from three institutions was performed. A total of 1,989 cases of twin pregnancy were identified, Wayne State University included 1,266 cases from 1984 to 1993; Madigan Army Medical Center 136 cases, 1995-2000, and Rockford Regional Perinatal Center, 587 cases, 1990-2000. The findings were classified by the presence or absence of fetal death in utero (IUFD) as follows: both IUFD (0/0); 1 IUFD (0/+), and both live born (+/+). A case-control study was performed on the subgroup of patients for whom complete records as to chorionicity, etc., were available. RESULTS: Of the 1,989 cases reviewed there were 49 both IUFD (0/0), 61 complicated by 1 IUFD (0/+), and 1,879 with both live born (+/+). The overall fetal death rate for this twin cohort was 55/1,000. IUFD of 1 or both twins was related to an increased risk of previable delivery 55% in 0/0, and 28% in 0/+ versus 4% for +/+ with p<0.001. IUFD also was associated with early preterm delivery (mean gestational age at delivery of 23 (0/0) and 30 (0/+) versus 35 (+/+) weeks). Chorionicity as well as maternal risks were examined in the case-control study (24 (0/0), 43 (0/+), 134 (+/+)) with the following results: monochorionic placentation was more likely in pregnancies complicated by IUFD (54% (0/0), 51% (0/+) versus 14% (+/+); p<0.001). Retained placenta, requiring dilation and curettage, occurred more frequently when both twins died in utero, but may be related to the earlier gestational age at delivery. DISCUSSION: Independent of retained placenta, there is no difference in the maternal risks for hemorrhage, abruption, coagulopathy or infection between groups. Immaturity at delivery and monochorionicity are more common in pregnancies complicated by fetal demise. Neonatal morbidity and developmental outcome will be the focus of a longitudinal study comparing cotwin survivors to twins matched for chorionicity and gestational age at delivery.

Case-Control Studies↗