Risk of premature birth in multifetal pregnancy

Surprising lack of sex differences in normal cognitive aging in twins

Sex differences in the etiology of normal cognitive functioning in aging remain largely unexplored. We conducted an investigation of genetic and environmental contributions to sex differences in level of cognitive performance and rate of decline in the Swedish Adoption/Twin Study of Aging (SATSA) (Finkel & Pedersen, 2004) data set. Behavioral genetic parameterizations of a latent growth curve model were fit to longitudinal data on 11 cognitive measures. Seven hundred and ninety-eight non-demented individuals had cognitive data across four waves of measurement covering 13 years. Participants ranged in age from 44 to 88 at first testing wave; 60% were female. Results indicated sex differences in mean performance for five cognitive measures and in rates of decline for Information and Card Rotations. Only Synonyms demonstrated sex differences in genetic and environmental contributions to mean performance: heritability was higher in men than women. Despite differential longevity and susceptibility to disease, there are no consistent indications that men and women show different patterns of cognitive aging.

Increase in low-birth-weight infants in Japan and associated risk factors, 1980-2000

AIM

To investigate possible factors related to the recent rise in prevalence of low-birth-weight (LBW) infants in Japan.

METHODS

A data set comprising 11,746 infants from the Children and Infant Growth Surveys (1980, 1990, and 2000) was analyzed.

RESULTS

The proportion of LBW infants was 4.2% in 1980, 6.1% in 1990, and 8.3% in 2000. The maternal smoking prevalence increased from 6.5% in 1990 to 10.9% in 2000. When multivariate logistic regression analysis was applied to estimate the risk for LBW from 1990 to 2000, the following were selected as independent factors: preterm delivery, early term delivery, female sex of the infant, maternal primiparity, multiple gestation, maternal short stature, older maternal age (>24 years), and maternal smoking. The population attributable fraction (PAF) of preterm plus early term delivery and multiple gestations to LBW was 85.1% in 1990, and 89.3% in 2000. The PAF of maternal smoking was 6.4% in 1990, and 7.4% in 2000.

CONCLUSIONS

The increase in preterm deliveries and multiple gestations were found to be the important factors with regard to the increase in LBW infants in Japan. The increased prevalence of maternal smoking was not substantially associated with the increase in LBW infants.

Antithrombin III activity and platelet count are more likely to decrease in twin pregnancies than in singleton pregnancies

BACKGROUND

It is not known whether antithrombin III activity and platelet count are more likely to decrease in women with twin pregnancies than singleton pregnancies.

METHODS

We enrolled 56 consecutive women with twin pregnancies and 692 consecutive women with singleton pregnancies. Antithrombin III activity and platelet count were determined at 26-31 weeks and again at 32-40 weeks of gestation. Thrombin-antithrombin complex, and plasmin-alpha2 plasmin inhibitor complex were measured simultaneously in some women.

RESULTS

In twin pregnancies, both antithrombin III activity (111 +/- 8.2%) and platelet count (244 +/- 60 x 109/l) at 28.6 +/- 1.0 weeks decreased over time to 91 +/- 12% and 205 +/- 59 x 109/l, respectively, at 35.2 +/- 1.2 weeks; these decreases were significantly greater than in singleton pregnancies. However, a small number of women with singleton pregnancies had a significant decrease in antithrombin III activity in the absence of preeclampsia. The serum thrombin-antithrombin complex was significantly higher in twin pregnancies than in singleton pregnancies (9.7 +/- 4.2 ng/ml vs. 6.7 +/- 4.4 ng/ml, respectively, p < 0.01), and this increase correlated significantly with the decrease in antithrombin III activity in twin pregnancies (r = -0.459, p < 0.001).

CONCLUSIONS

Antithrombin III activity and platelet count show a greater decrease in twin than in singleton pregnancies, perhaps due to a greater increase in thrombin generation.