Cognitive demands of executing postural reactions: does aging impede attention switching?

A new dual-task paradigm was used to investigate age-related differences in attentional dynamics during rapid balancing reactions evoked by small, unpredictable antero-posterior platform movements. The perturbations were delivered while subjects performed a continuous visuo-motor pursuit-tracking task. Onset of significant deviation in tracking was inferred to indicate switching of attentional resources between tracking and balancing tasks. Although tracking deviation was equally likely to occur subsequent to postural perturbation in healthy young and older adults, deviation onset was delayed, on average, by 67% (123 ms) in the older subjects. Delay in onset of tracking deviation correlated with subsequent delay in generating the peak stabilizing postural response at the ankle. These results suggest that impaired attentional dynamics may exacerbate postural instability in older adults.

Non-linear development of postural control and strategy use in young children: a longitudinal study.

This longitudinal analysis confirmed a non-monotonic pattern of postural control development in children from age 5 to 8 years suggested by previous cross-sectional studies. Postural control was considered in terms of control strategy and its variability operationalized by mean and standard deviation of center of pressure (COP) velocity; and of effectiveness and its variability operationalized by mean and standard deviation of COP anteroposterior (a-p) excursion. Periods of significant variability were used to indicate behavioral transitions. Seventeen healthy children (nine males, eight females) aged 5-6 years (61.5-75 months) were tested at 3- to 4-month intervals up to age 8 years (83-97 months) in eyes-open quiet stance on a force platform for 30 s in each of ten trials. Data were reorganized into six developmental categories based on adjacent test dates prior to (-1) and after (+1, +2, +3, +4) a subject's trial with the lowest COP velocity (0). Developmental category is proposed to represent level of sensorimotor integrative skill. Within-subject ANCOVAs revealed a significant effect (P<0.0001) for developmental category with covariance due to height, weight and actual age removed. Post hoc tests showed a significant effect (P<0.0001) on measures of strategy. However, differences in COP velocity (type of strategy used) and differences in its variability (denoting a transition between strategies) were not always coincident. Performance outcome (COP a-p excursion) changed near linearly across categories. It was concluded that a non-monotonic change in control strategy as indicated by COP velocity describes the development of quiet stance equilibrium. A transition occurs from a primarily open-loop to incorporation of open- and closed-loop components of control. Honing of strategy used precedes and follows transitions. Constriction of velocity and excursion may typify the early stages of bimodal strategy. Developmental categories describe affiliation with the strategy employed and may represent differentiable levels of sensorimotor integrative skill. They may be more useful in assessing progression of equilibrium control than consecutive age in years.

Perinatal outcome of triplet gestation: does prophylactic cerclage make a difference?

OBJECTIVE: To compare the perinatal outcome of triplet gestations with and without prophylactic cerclage. METHODS: A retrospective chart review of all triplet gestations delivered between January 1988 and June 1997 was performed. Only women initiating prenatal care before 15 weeks gestation were included. The cerclage group was compared to the no-cerclage group for maternal and perinatal outcome variables. Student t-test, Chi-square, and Fisher's exact test were used for analysis. RESULTS: Twenty of the 59 (33.8%) sets of triplet gestations had prophylactic cerclage. There were no differences between groups when compared for maternal age, parity, preterm labor rate, gestational diabetes, anemia, antenatal steroid use, histologic chorioamnionitis, and postoperative endometritis. In addition, there were no differences in mean birth weight, Apgar scores, respiratory distress syndrome (RDS), intraventricular hemorrhage/periventricular leucomalacia (IVH/PVL), and neonatal mortality. Although the mean gestational age at delivery for the cerclage group (32.8+/-2.4 weeks) was not different from the no-cerclage group (31.5+/-3.6 weeks), the proportion of pregnancies delivered at 31 weeks or more, and at 32 weeks or more, was significantly higher in the cerclage group (90 vs. 62%, P = .02; 80 vs. 54%, P = .05), respectively. In addition, the incidence of extremely low birth weight (LBW) was significantly decreased in the cerclage compared with the no-cerclage group (1.7 vs. 15.4%, P = .005). CONCLUSIONS: Prophylactic cerclage decreased significantly the incidence of extremely LBW neonates in triplet pregnancies. The proportion of neonates delivered at 31 weeks or more, and at 32 weeks or more was higher in the cerclage group.

Perinatal outcome of triplet gestation: does prophylactic cerclage make a difference?

Objective: To compare the perinatal outcome of triplet gestations with and without prophylactic cerclage.Methods: A retrospective chart review of all triplet gestations delivered between January 1988 and June 1997 was performed. Only women initiating prenatal care before 15 weeks gestation were included. Management guidelines for triplets were uniform with the exception of use of prophylactic cerclage placed at 14 +/- 1 weeks gestation. Hospitalization was reserved for maternal medical and obstetric conditions, or fetal indications. Tocolytics were initiated only for persistent uterine contractions with intact membranes. All deliveries were effected by cesarean section at 37 weeks or less for maternal or fetal indications. All neonates were cared for at our institution. The cerclage group was compared to the no cerclage group for gestational age at delivery and maternal and neonatal complications. Descriptive statistics, Student t test, and Mann-Whitney U test were used for analysis.Results: Fourteen of the 51 (27.4%) sets of triplets had cerclage. There were no differences between groups when compared for maternal age, length of hospital stay, preterm labor rate, steroid use, histologic or clinical chorioamnionitis, and postoperative complications. In addition, there were no differences in mean birth weight, Apgar scores, respiratory distress syndrome, intraventricular hemorrhage/periventricular leucomalacia, NICU stay, and neonatal mortality. Although the mean gestational age at delivery for the cerclage group (33.1 +/- 2.7 weeks) was not different from the no cerclage group (31.7 +/- 3.7 weeks), the proportion of pregnancies delivered at 31 weeks or more was significantly higher in the cerclage group (13/14 vs 23/37, P =.03).Conclusions: Prophylactic cerclage may influence the proportion of triplet gestations delivered at 31 weeks or more. Lack of differences in the other parameters may be reflective of the small sample size.

Pemphigus vulgaris and pregnancy: risk factors and recommendations.

Pemphigus vulgaris during pregnancy is exceedingly rare; only 15 cases with immunopathologic confirmation have been reported. In the four cases associated with fetal mortality the mother's disease was active and required high doses of corticosteroids and adjuvant therapy with azathioprine or dapsone for control. A pregnant woman with limited disease is described. At the time of delivery her pemphigus vulgaris antibody titer was 1:640. A full-term, healthy male infant was completely free of skin lesions after a spontaneous vaginal delivery.

Comparison of nifedipine and ritodrine for the treatment of preterm labor.

Treatment of preterm labor with beta-sympathomimetics has been questioned because of the many maternal and fetal complications associated with its use. Nifedipine, a calcium antagonist, has been shown to suppress uterine activity in vitro and in vivo. A randomized prospective study was performed to compare the efficacy of nifedipine to ritodrine in the suppression of preterm labor. Data obtained from 42 women, of which 19 were randomized to the ritodrine group and 23 to the nifedipine group, were analyzed. Ritodrine and nifedipine proved to be equally effective in the suppression of preterm labor. However, the nifedipine group had fewer maternal and fetal complications.

Doppler velocimetry and placental disease.

Quantitative placental examinations were performed on 47 women who had Doppler flow velocity studies of the umbilical artery during their pregnancy. The systolic-diastolic ratio of the umbilical artery was used as the measurement parameter to divide the study population into two groups. Group 1 consisted of women with normal systolic-diastolic ratios (systolic-diastolic less than 3), and group 2 consisted of women with an elevated systolic-diastolic ratio (systolic-diastolic greater than or equal to 3). The group with an increase in systolic-diastolic ratio had more perinatal complications as demonstrated by two stillbirths, a higher incidence of cesarean deliveries for fetal distress, and more admissions to the neonatal intensive care unit. Significant differences were found when gestational age at delivery, placental weight, birth weight, and the number of small muscular arteries in the placenta were compared. Since gestational age may have accounted for the difference in placental findings, patients were matched for gestational age. The placental weights were comparable, but there were fewer small muscular arteries in those patients with an increase in systolic-diastolic ratio (p less than 0.001). In addition, when these findings were examined to determine the influence of diminished uterine flow velocity, none was found.

Riboflavin concentration in maternal and cord blood in human pregnancy.

Riboflavin concentration was measured in sera of a control population and in a series of paired maternal and cord sera. The assay technique was carefully validated and appears to be specific and reproducible. The mean riboflavin concentration in 12 apparently healthy adults was 116 +/- 46 nmol/L (SD). In 20 uneventful pregnancies the cord serum concentration was generally higher than the maternal concentration (158 +/- 47 nmol/L versus 113 +/- 35 nmol/L; p = 0.001). The cord-to-maternal ratio in paired sera averaged 1.45 +/- 0.44. There was no detectable difference in binding of riboflavin to cord and maternal serum proteins as measured by equilibrium dialysis (59.0% +/- 17% versus 60.8% +/- 16%). Comparison of protein binding by paired cord and maternal sera yielded a ratio of 0.99 +/- 0.13. The transplacental gradient of riboflavin concentration is unrelated to protein binding and is consistent with active transport by the placenta, as previously demonstrated in vitro.

Biochemical differences related to birth order in triplets.

This is the first report to date on biochemical parameters in triplets. Umbilical artery and venous pH, PO2, PCO2, lactate and base deficit were measured in seven sets of triplets. Other parameters compared were route of delivery, one- and five-minute Apgar score, birth weight, relative birth order and sex. Twenty-one viable infants were born from three induced and four spontaneous pregnancies. Female: male sex ratio was 1.6:1.0. All triplets within a set were delivered by the same route--six sets by cesarean section and one set vaginally. There were no significant differences, according to Student's t-test, in birth weight, Apgar scores and biochemical parameters related to birth order. Comparison of umbilical artery and umbilical venous pH, PO2, PCO2, lactate and base deficit differences did not demonstrate evidence of acidosis or significant base deficit in the third triplet when compared with the first two, suggesting that the duration in utero after deliver of the firstborn is not associated with metabolic acidosis or hypoxia in the absence of any obstetric complication or anesthetic problem.