Homoclinic-doubling and homoclinic-gluing bifurcations in the Takens-Bogdanov normal form with D 4 symmetry.

In this paper, we investigate the dynamics of a fourth-order normal form near a double Takens-Bogdanov bifurcation. The reduced system of this normal form possesses eight pairs of homoclinic orbits for certain parameter values. The nonlinear time transformation method is applied to obtain an analytical approximation of the homoclinic orbit in the perturbed system and to construct the homoclinic bifurcation curve as well. Using numerical continuation, period-doubling and homoclinic-doubling cascades emanating from a codimension-2 bifurcation point are found. A codimension-2 homoclinic-gluing bifurcation point at which several homoclinic orbits concerning the origin glue together to form a new homoclinic orbit is also obtained. It is shown that in the vicinity of these bifurcation points, the system may exhibit chaos and chaotic attractors.

[Relationship between reproductive history and preterm births in the last pregnancy, in Shaanxi province].

Objective: To analyze the incidence of preterm delivery among single live neonates and the association between maternal reproductive history and preterm birth. Methods: A questionnaire survey was conducted on reproductive history among women at childbearing age who were selected through multi-stage stratified random sampling method in Shaanxi, during 2010-2013. Samples would include women at childbearing age and in pregnancy or having had definite pregnancy outcomes. Results: A total of 29 608 women at childbearing age with their infants, were studied. The overall incidence of premature delivery among the single live birth neonates under this study, was 2.7% during 2010-2013. Results from the logistic regression model showed that factors as: having had history with preterm delivery (OR=7.99, 95%CI: 5.59-11.43), age of the mothers, older than 35 (OR= 2.03, 95% CI: 1.59-2.59) and with history of birth defects (OR=1.54, 95% CI: 1.01-2.34) were at higher risks for premature delivery in neonates. Intervals on pregnancies between 3-4 years (compared with ≤2 years, OR=0.74, 95% CI: 0.58-0.93), between 5-6 years (compared with ≤2 years, OR=0.66, 95%CI: 0.52-0.82), or> 6 years (compared with ≤2 years, OR=0.48, 95%CI:0.37-0.61) together with numbers of parity as 1 (compared with primiparas, OR=0.80, 95%CI: 0.67-0.95), as ≥2 (compared with primiparas, OR=0.62, 95% CI: 0.39-0.97) etc. were protective factors to preterm delivery. Factors as: history of preterm delivery, mothers age (older than 35 years) and intervals of pregnancy, appeared influential to the age of gestation, under the ordinal polytomous logistic regression analysis. Conclusion: The incidence of preterm births among single live birth neonates in Shaanxi was lower than the average national level. Programs related to health care services prior to conception and during pregnancy, together with increasing the self-care consciousness of childbearing aged women etc, should all be strengthened in order to reduce the occurrence of preterm birth, in Shaanxi province.

[Factors related to the influence on congenital malformation of body surface in Shaanxi province].

Objective: To investigate the influencing factors on congenital malformation of body surface. Methods: Multi-stage stratified random sampling method was adopted. A questionnaire survey was conducted among the childbearing aged women who experienced more than 28 weeks pregnancy or having definite pregnancy outcomes in Shaanxi, during 2010-2013. Results: Results from the logistic regression model showed that factors as: intrahepatic cholestasis of pregnancy (OR=21.76, 95%CI: 4.46-106.25), histories with abnormal pregnancy or reproduction (OR=11.88, 95%CI: 9.14-15.45), having birth defects in the family (OR=6.15, 95%CI: 2.66-14.23), being twins (OR=5.74, 95% CI: 3.34-9.86), being worker (compared with others, OR=2.47, 95% CI: 1.30-4.68) or farmer (compared with others, OR=1.91, 95%CI: 1.14-3.20), less than 4 times of antenatal care (compared with >7, OR=1.84, 95% CI: 1.28-2.64), occupational exposure to related risks during pregnancy (OR=1.74, 95% CI: 1.26-2.42), mother's hometown was from mid-part of Shaanxi (compared with northern Shaanxi, OR=1.65, 95%CI: 1.20-2.28), mother's native residence was from the rural areas (OR=1.75, 95% CI: 1.13-2.71), drug use (OR=1.64, 95% CI: 1.26-2.13) etc. were risk factors for congenital malformation of body surface. Iron supplement during pregnancy (OR=0.46, 95%CI: 0.21-0.99) appeared as protective factor for congenital malformation of body surface. Conclusion: The following factors seemed to be of risk for congenital malformation of body surface, including: mother's native area was from the middle part of Shaanxi and living in rural area, being worker or farmer, histories of abnormal pregnancy and reproduction, history of birth defects in the family, being twins, with antenatal care less than 4 times, occupational exposure to dangerous materials, drug use, intrahepatic cholestasis during pregnancy etc.

[Effect of folic acid supplementation in childbearing aged women during pregnancy on neonate birth weight in Shaanxi province].

OBJECTIVE: To investigate the effect of folic acid supplementation in childbearing aged women during pregnancy on the birth weight of newborns in Shaanxi province. METHODS: A questionnaire survey was conducted among the childbearing aged women selected through multistage stratified random sampling in Shaanxi during 2010-2013, all of these childbearing aged women were in pregnancy or had definite pregnancy outcomes. The birth weight of newborns and folic acid supplementation during pregnancy were used as the dependent variables and independent variables respectively in multiple linear regression model and quantile regression model and confounding factors were controlled. RESULTS: Multiple linear regression analysis showed that the birth weight of newborns whose mothers had folic acid supplementation during pregnancy were significantly higher than those whose mothers had no folic acid supplementation during pregnancy, an average increase of 29.56 g(B=29.56, t=4.69 and P<0.01). Quantile regression analysis showed from very low to higher percentiles(q=0-0.55, q=0.65, q=0.75-0.80), the birth weights of newborns whose mothers supplemented folic acid were higher than those whose mother did not supplement folic acid, the difference was significant, but the increase varied. As the increase of the percentiles of birth weight, the body weight increase declined gradually in those whose mothers had folic acid supplementation compared with those whose mothers had no folic acid supplementation. CONCLUSION: Folic acid supplementation during pregnancy can increase the birth weight of newborns, the influence was greater in newborns with lower body weight than in newborns with higher body weight.