Bone metabolism biochemical indicators can reflect the state of bone transformation timely, which not only play an essential physiological role in individuals' normal growth and development but also are related to the development of many diseases. This paper reviews the progress on the correlation of serum bone metabolism biochemical indicators during pregnancy and the neonatal period to provide a reference for achieving adequate intrauterine nutritional reserves in the fetus and individualized nutritional guidance in the neonatal period.

Objective:To study the correlation of bone metabolism biomarkers between newborn twins and their mothers during pregnancy.Methods:From January 1, 2018 to June 30, 2022, newborn twins with mild symptoms admitted to the neonatal department of our hospital were retrospectively reviewed. The clinical data of the twins and their mothers were collected, including bone metabolism biomarkers of the twins within 3 d after birth and their mothers within last month during pregnancy. The twins were assigned into different groups according to gestational age(GA), birth weight(BW), the relationship between BW and GA(appropriate for GA(AGA),small for GA(SGA) and large for GA(LGA), birth season, gender, and the mothers' age, ethnicity, pre-delivery body mass index (BMI), gestational BMI increase, number of births and chorionic properties. The correlations of bone metabolism biomarkers between the twins and their mothers were analyzed.Results:A total of 302 pairs of twins were included. The incidence of insufficient or deficient serum 25-(OH)D 3 was 97.4% among the mothers, and 87.7% among the twins. The levels of blood phosphorus ( r=0.262, P<0.001) and 25-(OH)D 3 ( r=0.239, P=0.002) in mothers were positively correlated with the twin with larger BW. No significant differences existed in 25-(OH)D 3 between genders, AGA,SGA and LGA, birth season, and mothers' age, ethnicity, pre-delivery BMI, gestational BMI increase and chorionic properties( P>0.05). 25-(OH)D 3 in the twins were positively correlated with BW and 25-(OH)D 3 of mothers before delivery ( P<0.05) and negatively correlated with number of births ( P<0.05). Conclusions:In most mothers and their newborn twins, 25-(OH)D 3 are insufficient or deficient. The levels of blood phosphorus and 25-(OH) D 3 are correlated between the newborns and their mothers. The lower the BW of the newborn, the more times the mother give birth and the lower the mother's pre-delivery 25-(OH)D 3 level, the lower the newborn's 25-(OH)D 3 level.

Objective:To investigate the reference ranges for thyroid function and its influencing factors in preterm infants at 14 d after birth.Methods:This retrospective study involved 514 preterm infants who met the inclusion criteria in Affiliated Hospital of Inner Mongolia Medical University from January 1, 2019 to December 31, 2021. They were divided into three group according to their gestational age [early premature group (26-31 +6 weeks, n=153), middle premature group (32-33 +6 weeks, n=129) and late premature group (34-36 +6 weeks, n=232)] or birth weight (BW) [<1 500 g group ( n=129), 1 500-2 000 g group ( n=120) and ≥2 000 g group ( n=265)]. Venous blood samples were collected from the infants at 14 d after birth and their thyroid function was determined by chemiluminescence immunoassay. The reference values of free triiodothyronine (FT 3), free thyroxine (FT 4) and thyroid stimulating hormone (TSH) were calculated based on the values of 95% confidence intervals ( CI) and expressed as percentiles in the range from P2.5 to P97.5. Mann-Whitney U test or Kruskal-Wallis H test was used to compare those thyroid hormone levels between groups. Spearman correlation analysis was used to study the correlation of gestational age or birth weight with FT 3, FT 4 and TSH levels. The factors influencing the levels of thyroid hormones were analyzed by multiple linear regression. Results:The reference ranges for FT 3, FT 4 and TSH were 1.53-3.72 pg/ml, 0.81-1.91 ng/dl and 1.32-7.80 μIU/ml in the early premature infants, 1.74-4.16 pg/ml, 0.90-2.82 ng/dl and 0.63-7.64 μIU/ml in middle prematures and 2.07-4.88 pg/ml, 1.09-2.27 ng/dl and 1.14-7.06 μIU/ml in late prematures. The reference ranges for the above three indexes were 1.53-4.06 pg/ml, 0.81-1.83 ng/dl and 1.14-7.84 μIU/ml in premature infants with BW<1 500 g, 1.67-3.98 pg/ml, 0.88-2.97 ng/dl and 0.94-7.64 μIU/ml in those whose BW between 1 500 g and 2 000 g and 1.91-4.75 pg/ml, 1.09-2.31 ng/dl and 1.14-6.32 μIU/ml in those whose BW≥2 000 g. Multiple linear regression showed that the level of FT 3 was positively correlated with gestational age ( β=0.119, P<0.05) and birth weight ( β=1.950×10 －4, P<0.05); that of FT 4 was positively correlated with gestational age only ( β=0.031, P<0.05); and TSH level was negatively correlated with birth weight ( β=－4.250×10 －4, P<0.05). Conclusions:Gestational age and birth weight are the factors influencing thyroid function in preterm infants at 14 d after birth. Evaluation of thyroid function with FT 4 and TSH should based on the references ranges of different gestational age and birth weight .