[Association between gestational diabetes mellitus and preterm birth subtypes].

Objective: To investigate the association between gestational diabetes mellitus (GDM) and preterm birth subtypes. Methods: Based on the cohort of pregnant women in Anqing Prefectural Hospital, the pregnant women who received prenatal screening in the first or second trimesters were recruited into baseline cohorts; and followed up for them was conducted until delivery, and the information about their pregnancy status and outcomes were obtained through electronic medical record system and questionnaire surveys. The log-binomial regression model was used to explore the association between GDM and preterm birth [iatrogenic preterm birth, spontaneous preterm birth (preterm premature rupture of membranes and preterm labor)]. For multiple confounding factors, the propensity score correction model was used to compute the adjusted association. Results: Among the 2 031 pregnant women with a singleton delivery, the incidence of GDM and preterm birth were 10.0% (204 cases) and 4.4% (90 cases) respectively. The proportions of iatrogenic preterm birth and spontaneous preterm birth in the GDM group (n=204) were 1.5% and 5.9% respectively, while the proportions in non-GDM group (n=1 827) were 0.9% and 3.2% respectively, and the difference in the proportion of spontaneous preterm birth between the two groups was significant (P=0.048). Subtypes of spontaneous preterm were further analyzed, and the results showed that the proportions of preterm premature rupture of membranes and preterm labor in the GDM group were 4.9% and 1.0% respectively, while the proportions in the non-GDM group were 2.1% and 1.1% respectively. It showed that the risk of preterm premature rupture of membranes in GDM pregnant women was 2.34 times (aRR=2.34, 95%CI: 1.16-4.69) higher than that in non-GDM pregnant women. Conclusions: Our results showed that GDM might increase the risk of preterm premature rupture of membranes. No significant increase in the proportion of preterm labor in pregnant women with GDM was found.

[Observation and experiment: a causal perspective].

Observation and experiment and their related connotations and concepts remain vague, which affects the correct understanding of research design and the judgment of the validity of causal inference. This article borrows the concept of phase transition in physics, combines causal thinking and causal diagrams, firstly establishes the relationships among the attribute, state, event, and phenomenon, and then identifies two ways with the opposite causal structures to acquire phenomena-human observations and human manipulated experiments. In causal inference, the ways mentioned above, intervention and assignment of exposure are affected by their own causal mechanisms. Finally, intervention is a causal concept, a core link among known phenomena, unknown phenomena available for measurement, and natural causality. Based on this, the two strategies in classifying research design are analyzed, and intervention method and non-intervention method are proposed, as is comprehensive and concise. Observations and experiments provide the basis for all scientific knowledge and should be viewed as concepts with a unified connotation. The accurate classification of research designs based on the law of causality and measurement process may be one of the best options worthy of in-depth study.

[Association and interaction of pre-pregnant body mass index and gestational weight gain of women on neonatal birthweight].

Objective: To investigate the association between maternal pre-pregnant body mass index and gestational weight gain, as well as their interaction on neonatal birthweight. Methods: We built a cohort in Anqing Municipal Hospital from January 2014 to March 2015, enrolling pregnant women who decided to give birth in this hospital. All women were asked to fill a questionnaire for basic information collection. Medical information of both pregnant women and their newborns were obtained through electronic medical record. Chi-square analysis, multinomial logistic regression, multiplicative and additive interaction methods were used to analyze the association between pre-pregnant body mass index and gestational weight gain as well as their interactions on birth weight of the neonates. Results: A total of 2 881 pregnant women were included in this study. Of the 2 881 newborns, 359 (12.46%) were small for gestational age (SGA) and 273 (9.48%) were large for gestational age (LGA). After adjusting the possible confounding factors, results from the multinomial logistic regression showed that pre-pregnancy underweight women were more possible to deliver SGA (aRR=1.33, 95%CI: 1.02-1.73). If the gestational weight gain was below the recommended criteria, the risk of SGA (aRR=1.64, 95%CI: 1.23-2.19) might increase. Pre-pregnancy overweight/obese could increase the risk of being LGA (aRR=1.86, 95%CI: 1.33-2.60). Maternal gestational weight gain above the recommendation level was associated with higher rates of LGA (aRR=2.03, 95%CI: 1.49-2.78). Results from the interaction analysis showed that there appeared no significant interaction between pre-pregnancy BMI and gestational weight on birthweight. Conclusion: Pre-pregnancy body mass index and gestational weight gain were independently associated with neonatal birthweight while pre-pregnancy BMI and gestational weight gain did not present interaction on birthweight.

[Comparison of results of two immunoassays for detection of hepatitis B surface antigen in pregnant women].

Objective: To evaluate and compare the detection consistency of hepatitis B surface antigen (HBsAg) by two immunoassays: enzyme-linked immunosorbent assay (ELISA) and electrochemiluminescent immunoassay (ECLIA). Methods: A prospective study was conducted among 2 296 pregnant women recruited consecutively from January 1, 2014 to January 31, 2015 in a hospital. Blood samples were collected from them for the detection of HBsAg by using ELISA and ECLIA, Kappa test was performed on the results. Nested polymerase chain reaction and sequencing of HBV S gene were also performed in all samples. Phylogenetic analysis was performed using Mega 6.0 software. Results: The two methods had high detection consistence of HBsAg (Kappa=0.71). There were significant differences in detection result of B genotype and adw2 serotype HBV strains between two methods. Among 123 identified HBV strains, 113 belonged to genotype B and available for further analysis. The difference in detection of substitution rates between two methods or different positive groups were not significant. Compared with ELISA single positive group, the ECLIA single positive group had completely different substitution sites. Conclusion: The two methods had high detection consistence of HBsAg, but there were still 32.4% HBV DNA positive cases in ELISA/ECLIA single positive group, and complete complementary substitution sites between ELISA single positive group and ECLIA single positive group. Our results suggested that more effective detection procedure should be considered for the possible impact of the HBV silent transmission and infection.

[Influence of intrahepatic cholestasis during pregnancy on the incidence of preterm birth].

Objective: Intrahepatic cholestasis during pregnancy (ICP) and its relation to incidence of preterm birth (PTB) were under study. Methods: A prospective cohort study was carried out that including all the hospitalized pregnant women with live singleton births, from January 2014 to March 2015 in Anqing Municipal Hospitals. Informed consent was followed in every pregnant woman with related demographic information collected through questionnaire and hospital electronic medical record system. Both univariate and multi-variate statistical methods were used to analyze the relations between ICP and incidence of PTB. Results: A total of 2 758 pregnant women were included in this study. The incidence proportions of ICP and PTB appeared as 7.25% and 16.28% respectively. Results from the logistic regression analysis showed that ICP increased the risk of both overall PTB (RR=2.33, 95%CI: 1.67-3.25) and medically indicated PTB (RR=8.46, 95%CI: 5.45-13.12), but not the spontaneous PTB (RR=0.94, 95%CI: 0.57-1.54). Conclusion: ICP seemed to have increased the risk on medically indicated PTB but not the spontaneous PTB.

Duration of viraemia in Chinese acute sporadic hepatitis E.

Acute sporadic hepatitis E (ASHE) cases induced by hepatitis E virus genotype 4 (HEV-4) are increasing in China. Our study aimed to estimate the duration of HEV-4 viraemia in Chinese ASHE. A total of 619 serum specimens from 499 ASHE patients were examined for the presence of HEV RNA. The association between viraemia detection and serum sampling time was compared between subtypes. The cumulative probability of HEV viraemia detection was determined using Kaplan-Meier survival analysis, and the viraemia duration was estimated. A total of 42.7 % of serum specimens were positive for HEV RNA and all the isolated strains were identified as genotype 4 and subsequently assigned to five subtypes. Among the patients infected with subtypes 4d and 4i, the time interval from the initiation of clinical symptoms to serum specimen sampling was shorter than that among the patients with subtypes 4a, 4b and 4h. Kaplan-Meier analysis was conducted with 101 sequential specimens as well as with both 101 sequential specimens and 236 single negative specimens. The cumulative probability of HEV-4 viraemia detection was estimated to decline quickly to approximately 10 % within 32 days after the initiation of clinical symptoms and then to decline very slowly to 5 % by the 41st day and to zero by the 131st day. The majority of ASHE cases maintain detectable HEV-4 viraemia within one month after onset, whereas a small portion of cases maintain long-term viraemia and may act as a reservoir for further transmission.

Seasonal pattern of hepatitis E virus prevalence in swine in two different geographical areas of China.

We studied seasonal patterns of swine hepatitis E virus (HEV) infection in China. From 2008 to 2011, 4200 swine bile specimens were collected for the detection of HEV RNA. A total of 92/2400 (3·83%) specimens in eastern China and 47/1800 (2·61%) specimens in southwestern China were positive for HEV. Seasonal patterns differing by geographical area were suggested. In eastern China, the major peak of HEV RNA prevalence was during March-April, with a minor peak during September-October, and a dip during July-August. In southwestern China, the peak was during September-October and the dip during March-April. The majority of subtype 4a cases (63/82, 76·83%) were detected in the first half of the year, while the majority of subtype 4b cases (26/29, 89·66%) were concentrated in the second half of the year, suggesting that different subtypes contribute to different peaks. Our results indicate that the distribution of HEV subtypes is associated with seasonal patterns.