The Associations Of Pregestational BMI And Gestational Weight Gain With BP Levels During Pregnancy

Background and ObjectiveIn the last half century,the prevalence of overweight and obesity has been substantially rising among reproductive age women.At the same time,hypertension disorder has become a serious global public health issue and in the 2015 Health Statistic Annals of China,the hypertension disorder of pregnancy(HDP)toped 2nd in the overall causes of maternal death.In addition,though the diagnosis of HDP is based on an arbitrary cut-off point of SBP ?120mmHg and(or)DBP ?80 mm Hg,studies reported that the normal blood pressure levels is not only associated with intrauterine growth retardation,pregnancy complications,but also results in cardiovascular disease of mother in their future life.Though it has been universally acknowledged that pregestational overweight and obesity is a strongest risk factor of HDP,the Institute of Medicine(IOM)emphasized that more researches were urged to elucidate the association of gestational weight gain with HDP.Furthermore,there is inconsistence between the results from the limited studies which focused on the association of gestational weight gain(GWG)with BP levels.Therefore,based on the data derived from women who took prenatal care in a tertiary hospital in Zhejiang province,this study aimed to elucidate the relationship of pregestational BMI and GWG with BP levels,and further to investigate the impact of period-specific GWG on the above outcomes.We hope to identify the "window period"of GWG,in which GWG exerted maximal impact on BP levels and thus help health care provider to guide pregnancy women acquire optimal GWG to prevent the adverse outcome related to BP.Material and MethodThe perinatal care information of women who were registered during 2001?2015 were extracted from Electronic Medical Recorder System(EMRS)of the hospital.If the pregnant women had no complete data about perinatal examination,suffered from GHD related disease such as chronic diabetes and hypertension,they were excluded from this study.A database was created,which included the information about social demographic information,life behavior information and perinatal physical examination.Firstly,Multivariable linear regression model was conducted to investigate the association of period-specific GWG with BP levels.Multilevel model(MLM)was applied to investigate the longitudinal association of pregestational BMI and GWG with BP levels.Finally,Cox proportional hazard model was used to explore the association of pregestational BMI and GWG with HDP.ResultsTotally,40 366 eligible women were included in this study.Among them,609(1.50%)were diagonised with gestational hypertension(GH).Multivariable linear regression analysis revealed that pregestational BMI((3 of SBP:0.70?0.79;of DBP 0.45?0.56;Unit:mmHg/kg/m2)and GWG(? of SBP:0.36?0.45;of DBP 0.19?0.27;Unit:mmHg/kg)were statistically associated with BP levels during pregnancy.Besides,as pregnancy progressed,the association of pregestational BMI with SBP marginally attenuated,but its association with DBP show minor increase.Besides,the GWG during different period produced different effect on BP levels:In most situations,the SBP was most strongly associated with the GWG of the nearest period;In contrast,the DBP was most closely associated with the GWG of the earliest period in most of situation.MLM revealed that compared with women of normal pregestational weight,those with pregestational underweight had lower SBP(2.22 mmHg,P<0.0001)and DBP(1.15 mmHg,P<0.0001);those with pregestational overweight or obesity had higher SBP(4.51 mmHg,P<0.0001)and DBP(3.68 mmHg,P<0.0001).GWG was positively associated with BP levels during pregnancy(SBP:?=0.39 mmHg/kg,P<0.0001;DBP:0.25 mmHg/kg�<0.0001).In addition,a negative interaction of pregestational BMI and GWG on SBP was also observed in MLM.Cox proportional hazard model showed that pregestational overweight or obesity was a risk factor of GH(RR = 3.23,P<0.0001),and pregestational underweight was a protective factor of GH(RR = 0.65,P = 0.0010).Besides,GWG rate below IOM recommendation was a protective factor of GH(RR = 0.62,P = 0.0108).Further analysis showed that GWG rate below IOM at both first and late trimester were protective factors of GH(first:RR = 0.75,P = 0.0426,late:0.54,0.0001);but only GWG rate above the IOM recommendation during the first trimester was statistically associated with higher risk of GH(RR =1.34,P = 0.0048).When stratified by pregestational BMI status,for women of pregestational underweight,it was only GWG rate during the late trimester that was statistically associated with GH(RR = 0.40,P ?0.0121);In contrast,it was only GWG rate during the first trimester that was statistically associated with GH for normal or overweight/obese women.ConclusionBoth pregestational BMI and gestational weight gain were statistically and positively associated with BP levels and the occurrence of GH during pregnancy.Besides,there was also a negative interaction between them on SBP among normaltensive women.The relationships of BP levels and pregestational BMI varied across the pregnancy,so did the relationship of BP levels and period-specific GWG.In addition,for women with different pregestational BMI status,GWG rate in first or late trimester showed different associations with GH.