目的：

探讨孕前超重肥胖与非超重孕妇妊娠期体成分和相位角的变化趋势，并分析妊娠期体成分增长与体重增长、孕中、晚期体重增速之间的关系，探讨孕晚期相位角的影响因素以及孕晚期相位角与体重增长的关系。

方法：

本研究为回顾性队列研究。研究对象为2018-2019年间在北京协和医院和顺义妇幼营养科建档的孕妇。孕前信息包括身高、年龄、孕前体重和体重指数（Body Mass Index, BMI）孕产次等，来自首诊时患者报告。使用Inbody 770（基于BIA技术）测量其在孕早期末（8-14周）、孕中期末（20-28周）及孕晚期末（>35周）的体重、体成分和相位角。计算得出妊娠期体重增长、各时期体重增速、妊娠期体成分增量。采用重复测量方差分析研究超重肥胖组与非超重组妊娠期体成分、妊娠期相位角的变化趋势以及孕前BMI与时期的交互作用。采用方差分析比较妊娠期体重增长超重、适宜和不足三组体成分的变化差异。采用多重线性回归研究妊娠期体重增长及各时期体重增速与体成分增量、孕晚期相位角的关系，并控制混杂因素。

结果：

研究共纳入141名年龄从23-44岁的孕产妇，中位数为31（6）岁，孕前BMI中位数为22.5（5.38），其中超重肥胖（BMI>24）的有53人，占比37.6%。妊娠期平均体重增长13.92±5.15 kg，其中，增重不足15人（10.6 %），增重适宜53人（37.6 %），增重超标73人（51.8 %）。孕中期体重增速超标55人（39 %），孕晚期体重增速超标88人（62.4 %）。

时期和孕前BMI均是妊娠期体成分变化的影响因素。孕14周后各项体成分，包括体质量/率、去脂体重、总水分、细胞内水分、细胞外水分、蛋白质、骨骼肌和矿物质均随妊娠期增加而增长。其中，超重肥胖组和非超重组孕早、中、晚期体脂量分别为27.59±5.22 kg / 16.97±4.17 kg、29.61±5.24 kg / 19.91±4.09 kg和32.18±5.66 kg / 23.4±4.48 kg，各时点之间差异显著；去脂体重分别为44.44±3.92 kg / 38.63±3.62 kg、47.07±4.19kg / 41.31±4.04 kg和50.75±4.25kg / 45.99±4.31kg。各时点间的体成分差异具有统计学意义（P<0.001）.超重肥胖组在各时期各项体成分显著高于非超重组（P<0.001）。非超重组妊娠期体成分增长显著高于超重肥胖组，其中超重肥胖组和非超重组妊娠期体脂量增长分别为4.59±3.53 kg和6.43±2.99 kg，差异具有统计学意义（P=0.001）；去脂体重增长分别为6.31±2.21 kg 和7.36±2.32 kg，差异有统计学意义（P=0.009）。孕中期体成分增长低于孕晚期，孕中期和孕晚期体脂量增长分别为2.59±2.09 kg和3.15±2.22 kg，去脂体重增长分别为2.66±1.71 kg和4.3±2.31 kg，差异均有统计学意义（P<0.05）。时期和孕前BMI存在显著的交互效应。

体重增长超标、适宜和不足组体脂量增长分别为1.15±1.88 kg、4.77±2.58 kg和7.39±2.83 kg；去脂体重增长分别为4.55±1.45 kg、6.54±1.98 kg和7.77±2.3 kg，组间差异均统计学显著（P<0.001）。调整年龄、孕前BMI、产次和孕早期体成分初始值后，妊娠期体重增长与体脂肪和去脂体重增长均具有显著的正相关关系（B_体脂量=0.505，P<0.001；B_去脂体重=0.214，P<0.001）。调整年龄、孕前BMI、产次、体成分基线值后。孕中期体重增速与孕晚期体重增速与体脂肪、去脂体重增长均显著正相关。

超重肥胖组各时期相位角显著高于非超重组。妊娠期相位角呈现孕中期下降、孕晚期上升趋势，孕早、中、晚期相位角分别为4.95±0.51°、4.88±0.49°和5.07±0.5°。仅超重肥胖组孕中期下降与孕早期相比有显著差异。孕前BMI和时期对相位角有显著的交互效应。

孕晚期相位角与细胞内水分、蛋白质、骨骼肌呈显著正相关关系，与细胞外水/总水分有显著负相关关系。调整孕前BMI、年龄和孕早期相位角初始值后，孕中期体重增速显著影响孕晚期相位角。

结论：

孕前超重肥胖和妊娠期体重增长超标的现象较为普遍。孕前超重肥胖人群体成分显著高于非超重人群，妊娠期体脂肪和去脂体重呈增长趋势，且孕晚期增长高于孕中期。孕前非超重的孕妇妊娠期体成分较超重肥胖孕妇增长更多。妊娠期体重增长、孕中、晚期体重增速均与体成分增长有显著的正相关关系。因此孕前适宜的BMI以及妊娠期控制体重增长至关重要。

妊娠期相位角呈先下降后上升的趋势。孕晚期相位角能够反映身体蛋白质和细胞外水分占比情况，并且与孕中期体重增长相关性显著。通过研究相位角可以一定程度了解孕妇的营养情况。

Objective：

To investigate the trend of body composition and PhA during pregnancy among overweight/obese and non-overweight pregnant women; and to analyze the association of the increase of body composition with GWG and the rate of GWG in each trimester,  and to analyze the factors of phase angle at late pregnancy and the relationship between phase angle at late pregnancy and weight gain.

Methods：

This study was a retrospective cohort study with objects registered in nutritional department of Peking Union Medical College Hospital and Shunyi maternal and child health care hospital from 2018 to 2019. Pre-pregnancy information including height, age, pre-pregnancy weight and BMI and parity et, al were obtained from patient reports at first visit. Body composition and PhA at the end of first trimester（8-14 weeks）, second trimester (20-28 weeks) and third trimester(>35 weeks) were measured using an Inbody 770 instrument based on BIA technology. The GWG and tri-rGWG were calculated. Repeated measures ANOVA was used to analyze the trend of body composition and PhA during pregnancy in overweight and non-overweight pregnant women and the interaction effect of pre-pregnancy BMI and period. Multivariate line regression analysis was used to study the association of the increment of body composition, PhA in late pregnancy with GWG and the rate of GWG in each trimester, and to control confounders.

Results：

A total of 141 pregnant women aged from 23 to 44 years with a median pre-pregnancy BMI of 22.5 (5.38) kg / m² were recruited in the study, of whom 53 exceeded 24kg /m², representing 37.6 %. Average GWG was 13.92 ± 5.15 kg, of which, 15 (10.6 %) were underweight, 53 (37.6 %) had appropriate weight gain, and 73 (51.8 %) had excessive weight gain. There were 55 (39 %) women who had excessive rGWG in the second trimester and the number in the third trimester was 88 (62.4 %).

Both period and pre-pregnancy BMI were independent effect factors for changes in body composition during pregnancy. All body components, including BFM/PFM, FFM, TBW, ICW, ECW, protein, skeletal muscle, and minerals increase with trimester of gestation after 14 weeks of gestation. Among which, the body fat mass of the overweight/obese group and the non-overweight group in the first, second and third period of pregnancy were 27.59 ± 5.22 kg/16.97 ± 4.17 kg, 29.61 ± 5.24 kg/19.91 ± 4.09 kg, and 32.18±5.66 kg/23.4 ± 4.48 kg, respectively, with significant differences between different period; The fat free mass were 44.44 ± 3.92 kg/38.63 ± 3.62 kg, 47.07 ± 4.19 kg/41.31 ± 4.04 kg, and 50.75 ± 4.25 kg/45.99 ± 4.31 kg, respectively. The differences in body composition between different time points were statistically significant (P<0.001). The body components were significantly higher in the overweight/obese group than the non-overweight group. The growth of body composition in non-overweight group were significantly higher than the overweight/obese group. The growth during the third trimester was higher than in second trimester. There was a significant interaction effect of period and pre-pregnancy BMI.

GWG significantly affected BFM and FFM gain, adjusting age, pre-pregnancy BMI, parity and initial values of body composition. The rGWG during the second and third trimester significantly affected the growth of BFM and FFM, after adjustment for age, pre-pregnancy BMI, the initial value of body composition in the first trimester.

The PhA decreased during the second trimester and increased in the third trimester, and the difference between first and second trimester was significant only observed in the overweight group. PhA were significantly higher at all times in overweight group than non-overweight group. There was a significant interaction effect of pre-pregnancy BMI and period on PhA.

There was a significant positive correlation between PhA and ICW, protein, and skeletal muscle in the third trimester, and a significant negative correlation between phase angle and ECW/TBW. After adjustment for the initial values of pre-pregnancy BMI, age, and PhA in first trimester, the rGWG in second trimester significantly affected PhA in the third trimester.

Conclusion：

Pre-pregnancy overweight and excessive GWG are relatively common. The body composition in overweight group was significantly higher. The maternal BFM and FFM increase significantly during pregnancy, and the increase was higher in the third trimester than in the second trimester. Women who were not overweight had a greater increase in body composition than overweight women. GWG and rGWG during the second and third trimester can significantly affect body composition growth. Therefore, an appropriate BMI before pregnancy, as well as a proper GWG during pregnancy, are crucial.

The PhA showed a decrease and then an increase during pregnancy. The PhA in third trimester is a proxy of the value of body protein and the proportion of ECW. PhA was affected by weight gain during the second trimester. The nutrition of pregnant women can be known to some extent by studying the phase angle.