Effect of maternal smoking on birth weight of twins: a study from the Dutch Twin Register

Since twins weigh about 20 % less than singletons at birth, maternal smoking may be a more severe risk for them than for singletons. Therefore, the effect of.maternal smoking during pregnancy on birth weight was investigated in a group of 5376 twins. All necessary information was collected by a questionnaire filled out by the mother of the twins. Gestational age explains more than 75 % of the variance in birth weight. Other effects were tested with gestational age as a covariate. Apart from zygosity (DZ twins weigh more than MZ twins), birth order (first born twins weigh more than second born twins) and sex (boys weigh more than girls), there was a very significant birth weight reducing effect (more than 8%) maternal smoking as well as a significant influence of maternal age (young mothers give birth to smaller children). There were no interactions with maternal smoking. Keywords

Womens' preference in Down syndrome screening

Objective To determine the knowledge of pregnant women about prenatal tests. and what tests they would choose if offered. Also, the preference of pregnant women for second-trimester or first-trimester screening was assessed. Patients and methods Pregnant women receiving antenatal care in a decentralized primary care system (n = 80). and pregnant women that were offered a prenatal diagnosis Lit the Academic Medical Centre (n = 195), were asked to complete a questionnaire. Results The response rate was over 80%. Most women in both groups preferred a screening test for Down syndrome to be performed in the first trimester of pregnancy. A combination of nuchal translucency measurement and first-trimester serum screening was the option of choice. The screening possibilities For Down syndrome were less well known to the women in the low-risk group compared with the women in the high-risk group. The offer of a prenatal screening test would have been declined by more than 30% of women at low risk For carrying a fetus with Down syndrome. Conclusions Our results Show that women prefer screening for Down syndrome to be performed in the first trimester of pregnancy Using both serum and ultrasound tests. In women at low risk for Down syndrome the knowledge of prenatal screening methods was less. as well as the acceptance of prenatal screening being, lower. Copyright (C) 2002 John Wiley Sons, Ltd

Left-handedness in twins: Genes or environment?

Twin family data can cast light on the longstanding problem about the influences of genes and environment on the etiology of left-handedness. Therefore, hand preference was assessed in 1700 adolescent twin pairs and their parents. Left-handedness (LH) appeared not significantly enhanced among twins compared to the general population. In addition the following observations were made: (1) Significant more LH in first born twins than in second born twins. (2) Significant higher left-handedness association in MZmm pairs compared to DZmm pairs and not or may be marginally so in MZff versus DZff pairs. These results, combined with the observations that (a) left-handed fathers increase the probability of LH in sons but not in daughters; (b) LH in mothers increases LH prevalence in both sons and daughters to the same degree; and (c) very low birth weight, corrected for the effect of gestational age, increases LH prevalence in first born twins only, make an environmental explanation more likely. The possibility that exposure to prenatal male hormones - to which low birth weight and high birth stress children are more vulnerable - might be a crucial condition for the etiology of LH, is discusse