Fetal sex differences in human chorionic gonadotropin fluctuate by maternal race, age, weight and by gestational age.

Circulating levels of the placental glycoprotein hormone human chorionic gonadotropin (hCG) are higher in women carrying female v. male fetuses; yet, the significance of this difference with respect to maternal factors, environmental exposures and neonatal outcomes is unknown. As a first step in evaluating the biologic and clinical significance of sex differences in hCG, we conducted a population-level analysis to assess its stability across subgroups. Subjects were women carrying singleton pregnancies who participated in prenatal and newborn screening programs in CA from 2009 to 2012 (1.1 million serum samples). hCG was measured in the first and second trimesters and fetal sex was determined from the neonatal record. Multivariate linear models were used to estimate hCG means in women carrying female and male fetuses. We report fluctuations in the ratios of female to male hCG by maternal factors and by gestational age. hCG was higher in the case of a female fetus by 11 and 8% in the first and second trimesters, respectively (P<0.0001). There were small (1-5%) fluctuations in the sex difference by maternal race, weight and age. The female-to-male ratio in hCG decreased from 17 to 2% in the first trimester, and then increased from 2 to 19% in the second trimester (P<0.0001). We demonstrate within a well enumerated, diverse US population that the sex difference in hCG overall is stable. Small fluctuations within population subgroups may be relevant to environmental and physiologic effects on the placenta and can be probed further using these types of data.

Coupling an ultrasonic propagation code with a model of the heterogeneity of multipass welds to simulate ultrasonic testing.

The knowledge of the anisotropic and heterogeneous behaviour of the material is the key point for understanding ultrasonic testing. In the case of austenitic stainless steel multipass welds, there was no exact knowledge. The succession of passes and complex solidification processes makes the modelling of the resulting grain orientation difficult. The MINA model allows such a description. Coupling this model with the new propagation code ATHENA permits a very good understanding of the propagation of elastic waves in this kind of complex media. After discussing the existing models of grains orientations for multipass welds, we show how the new MINA model allows to simulate the anisotropic heterogeneous structure in a more realistic manner. We introduce the simulated grains structure and the real one, obtained by macrographs, into the ATHENA propagation code. We obtain a very good correlation between the two simulated propagations. A first experimental application is also successful. We show in a quantitative and qualitative way that the modelling results are close to the experimental measurements on a thick austenitic weld.