Maternal Thyroid Function and Birth Weight in Twins.

CONTEXT: Thyroid hormones are associated with birth weight in singleton pregnancy. Twin pregnancies need more thyroid hormones to maintain the normal growth and development of the fetuses compared with single pregnancy. OBJECTIVE: We aimed to investigate the association of thyroid hormones and birth weight in twins. METHODS: This was a retrospective cohort study in a Chinese population. Pregnant women who received regular antenatal health care and delivered live-born twins from 2014 to 2019 were included (n = 1626). Linear mixed model with restricted cubic splines and logistic regression models were used to estimate the association of thyroid hormones with birth weight and birth weight discordance in twins. RESULTS: We observed that both thyrotropin (TSH) and free thyroxine (FT4) were not associated with birth weight in twins overall, while when stratifying on fetal sex or chorionicity, there were nonlinear association between FT4 levels and birth weight in boys (Pnonlinear < .001) and in dichorionic (DC) twins (Pnonlinear = 0.03). Women with levels of FT4 lower than the 10th percentile had a higher risk of birth weight discordance in their offspring than women with normal FT4 levels (range, 2.5 to 97.5 percentiles) (odds ratio = 1.58; 95% CI, 1.05-2.33). CONCLUSION: Our study suggests there was an association of FT4, but not TSH, with birth weight and birth weight discordance varied by sex and chorionicity. These findings could have implications for obstetricians to be aware of the importance of FT4 levels in preventing birth weight discordance in twin pregnancy.

Prepregnancy Overweight and Obesity Are Associated with an Increased Risk of Preterm Birth in Chinese Women.

INTRODUCTION: The association between obesity before pregnancy and preterm birth varies with age and ethnicity. OBJECTIVE: To study the association between early body mass index (BMI) and risk of preterm birth in Chinese women. METHODS: This was a hospital-based retrospective cohort study including 36,596 Chinese women who gave birth to a live singleton infant from 2015 to 2018. Women were classified as underweight (BMI <18.5), normal weight (BMI 18.5 to <23), overweight (BMI 23 to <27.5), or obese (BMI ≥27.5) according to the most recent criteria for Asian women. Multivariate log-binomial regression models were used to estimate the relative risks (RRs) and 95% confidence intervals (95% CIs) for preterm birth among different groups. RESULTS: Compared to women with normal weight, women with overweight or obesity before pregnancy had an increased risk of preterm birth; the RRs and 95% CIs were 1.22 (95% CI: 1.08-1.37) and 1.30 (95% CI: 1.01-1.69), respectively. The greatest risk of extremely preterm birth was observed in obese women. The estimators were robust when considering the maternal age and rate of gestational weight gain (GWG) during pregnancy. CONCLUSIONS: Women with overweight and obesity had an increased risk of preterm birth regardless of GWG in early pregnancy. Our study suggests that it is beneficial to lose weight before conception for both overweight and obese women who plan to become pregnant.

Maternal TSH level and TPOAb status in early pregnancy and their relationship to the risk of gestational diabetes mellitus.

Subclinical hypothyroidism is common in pregnant women and often related to adverse pregnancy outcomes, but its relationship with gestational diabetes remains controversial. In particular, the impact of thyroperoxidase antibodies status on the relationship between subclinical hypothyroidism and gestational diabetes is not clear. We investigated the association between combined thyroid stimulating hormone (TSH) level and thyroperoxidase antibodies status in early pregnancy (<20 weeks of gestation) and gestational diabetes mellitus. A total of 7084 pregnant women met the inclusion criteria, which included thyroperoxidase antibodies-positive subclinical hypothyroidism [TSH(H)TPOAb(+)] (n = 78), thyroperoxidase antibodies-negative subclinical hypothyroidism [TSH(H)TPOAb(-)] (n = 281), thyroperoxidase antibodies-positive euthyroidism [TSH(N)TPOAb(+)] (n = 648), and thyroperoxidase antibodies-negative euthyroidism [TSH(N)TPOAb(-)] (n = 6077). Of the 7084 cases included in our study, 1141 cases were diagnosed with gestational diabetes mellitus at 24-28 weeks of pregnancy. The prevalence of gestational diabetes mellitus in TSH(N)TPOAb(-), TSH(H)TPOAb(-), TSH(N)TPOAb(+), and TSH(H)TPOAb(+) was 14.65, 19.57, 24.85, and 46.15 %, respectively. Compared with TSH(N)TPOAb(-) women, the risk of gestational diabetes mellitus was increased in all other groups of women in early pregnancy. After dividing early pregnancy into first and second trimesters, we found that TSH(H)TPOAb(-) women in the first trimester do not show this increase. Our study suggests that subclinical hypothyroidism and thyroperoxidase antibodies-positive euthyroidism in early pregnancy are associated with an increased risk of gestational diabetes mellitus.

Paternal age and offspring congenital heart defects: a national cohort study.

Paternal age has been associated with offspring congenital heart defects (CHDs), which might be caused by increased mutations in the germ cell line because of cumulated cell replications. Empirical evidences, however, remain inconclusive. Furthermore, it is unknown whether all subtypes of CHDs are affected by paternal age. We aimed to explore the relationship between paternal age and the risk of offspring CHDs and its five common subtypes using national register data in Denmark. A total of 1,893,899 singletons born in Denmark from 1977 to 2008 were included in this national-based cohort study. Cox's proportion hazards model with robust sandwich estimate option was used to estimate the hazards ratio (95% confidence interval) for the associations between paternal age and all CHDs, as well as subtypes of CHDs (patent ductus arteriosus (PDA), ventricular septal defect (VSD), atrial septal defect (ASD), tetralogy of fallot (TOF) and coarctation of the aorta (CoA)). We did not observe an overall association between paternal age and offspring CHDs. However, compared to the paternal age of 25-29 years, paternal age of older than 45 years was associated with a 69% increased risk of PDA (HR45+ = 1.69, 95%CI:1.17-2.43). We observed similar results when subanalyses were restricted to children born to mothers of 27-30 years old. After taking into consideration of maternal age, our data suggested that advanced paternal age was associated with an increased prevalence of one subtype of offspring congenital heart defects (CHDs), namely patent ductus arteriosus (PDA).

Correlation between exposure to magnetic fields and embryonic development in the first trimester.

OBJECTIVE: To explore the correlation between maternal magnetic field (MF) exposure in daily life and embryonic development. METHODS: A cross-sectional study was conducted among 149 pregnant women who were seeking induced abortion of unwanted pregnancies. Participating women were asked to wear an EMDEX Lite magnetic field meter for a 24-h period to obtain MF exposure level within 4 weeks following the abortion. Embryonic bud and sac lengths were measured through B-mode ultrasound before the surgical abortion. Embryo sections were prepared and examined for histological changes, and the apoptosis status of the deciduas was examined using the TUNEL apoptosis assay. RESULTS: Embryonic bud length was inversely associated with maternal daily MF exposure level; the association was statistically significant at the time-weighted-average and 75th percentile of MF exposure levels, with coefficients of -3.09 (P = 0.0479) and -3.07 (P = 0.0228), respectively. Logistic regression for examining the risk of higher MF exposure indicated that women with her 75th percentile of daily MF measurements ≥0.82 mG had a 3.95-fold risk of having a fetus with a shorter embryonic bud length than those whose daily MF exposure were <0.82 mG. MF exposure was associated with a higher degree of apoptosis, but the association was not statistically significant. We failed to find a statistical correlation between MF exposure and embryonic sac length and histological changes in the first trimester. CONCLUSION: Prenatal MF exposure may have an adverse effect on embryonic development.

Calorimetry study of microwave absorption of some solid materials.

In practice, the dielectric constant of a material varies the applied frequency the material composition, particle size, purity, temperature, physical state (solid or liquid), and moisture content. All of these parameters might change during processing, therefore, it is difficult to predict how well a material will absorb microwave energy in a given process. When the temperature is measured by a digital thermometer, it could not accurately reflect the true temperature of the bulk materials, especially for mixed materials. Thus, in this paper we measured the microwave absorption characteristics of different materials by calorimetry. The microwave power levels, irradiation times, and masses of the materials were varied. It was difficult to predict the microwave energy absorption characteristics of reagent-grade inorganic compounds based on their color, metallic cation, or water stoichiometry. CuO, MnO2, Fe3O4, and MnSO4 x H2O (Taishan) strongly absorbed microwave energy. Most of the remaining inorganic compounds were poor absorbers, with silica hardly absorbing any microwave energy. Carbon-based materials had significantly different microwave absorption characteristics. Activated carbon and coke were especially sensitive to microwaves, but different types of coal were poor absorbers. The jamesonite concentrate absorbed microwave energy strongly, while the zinc concentrate was a poor absorber.