The Influence Of Physical Activity During Pregnancy On Pregnant Outcomes And Infant Growth

BackgroundTo explore an effective, convenient, economic way to improve health status andenhance quality of life is always a concern of health professionals. Lack of physicalactivity and sedentary lifestyle ranked within the top 10 reasons for death anddisability in the world. In recent years, it has been recommended to improve healthstatus through promotion of physical activity. Pregnancy is a special period forwoman, during which the health status is related to both mother and offspring. Due tothe difficulty of measuring physical activity and lack of large sample data, there hasbeen little information of physical activity during pregnancy among Chinese women.The research of maternal physical activity in China is lagging behind and need to beinitiated and developed right now. Meanwhile, in many international researches, therestill remains the inconsistency on the influences of physical activity during pregnancyon pregnant outcomes. The purpose of this study is to explore the suitable maternalphysical activity monitoring tools among Chinese pregnant women, to analyse theinfluence of physical activity during pregnancy on pregnant outcomes and infantgrowth, as well as to understand if there is an interaction between physical activityduring pregnancy and insulin gene polymorph on fetal and infant growth. Furthermore,we will try to put forward some recommendations for clinical monitoring andguidance on physical activity during pregnancy.GoalTo study the influence of the physical activity during pregnancy on pregnantoutcomes and infant growth, to study the association of fetal insulin genepolymorphism with fetal growth and infant growth, as well as the interaction betweenmaternal physical activity and fetal insulin gene polymorphism with the aid of themultidisciplinary approaches involved in field epidemiology and molecular biology.Contents 1,To assess the reliability and validity of the physical activity scale revisedaccording to a Demark scale among Chinese pregnant women.2,To describe the physical activity pattern among Chinese pregnant women: timeand energy expenditure on each physical activity intensity, and total energyexpenditure.3,To observe the influence of physical activity during pregnancy on pregnantoutcomes, such as maternal weight gain, fetal growth, birth size of newborns, deliverymode et al, and to understand the influence of physical activity on infant growth.4,To explore the appropriate technique for clinical monitoring and guidance serviceon physical activity during pregnancy.5,To know the genotypes distribution of INS VNTR Polymorphism among Chinesemainland population. To understand the association of INS VNTR with birth size andinfant growth, as well as its interaction with maternal physical activity on fetal andinfant growth.MethodsWe conducted an observational prospective cohort study combining with the largesample epidemiological investigation and bio-molecule detection. Pregnant womenwere recruited at the 2^nd gestational trimester and their physical activities status wererecorded. The pregnant women needed to fill in the physical activity scale andwearing pedometer simultaneously for 4 days in the 2^nd and 3^rd trimester respectively.For the reliability and validity research, the women being randomly selected from thecohort needed to fill in the physical activity scale for 4 days, and fill in the physicalactivity diary, wearing pedometer for 4 days at the same time. Within 2 weeks, theyneeded to fill in the physical activity scale again.According to step counts by pedometers, the pregnant women were divided into fourdifferent physical activity groups before delivery. Then the cohort was followed up todelivery. The pregnant outcomes were recorded and biological samples were collectedimmediately after delivery. The newborns were followed up until 12 months and thephysical examination data were collected at 42 days, 6 months and 12 months. Therelationships between physical activity and pregnant outcomes, infant growth wereobserved. The influence of fetal insulin gene polymorph on fetal and infant growthwas observed as well. The structured questionnaires scale, monitoring instruments, laboratory detectionwere applied to obtain the quantitative data. Semi-structured interviews were appliedas the qualitative method. The major statistical method included Multiple LinearRegression, Binary Logistic Regression and Mixed Linear Model et al.Main findingsFrom Nov 2005 to Nov 2007, the cohort of pregnant women was established. 866 ofphysical activity data and pregnant outcomes were collected. 695 of newborns werefollowed up until 1 year.Ⅰ. The reliability and validity research106 pregnant women participated in the reliability and validity research of physicalactivity scale. The Intra-class correlation coefficient of test-retest reliability of scalefor the total physical activity energy expenditure is 0.87. The result for test-retestreliability on total energy expenditure and each intensity activity all showed good toexcellent agreement. The Spearman correlation coefficient for total physical activitybetween physical activity scale and diary was 0.75. The correlation coefficients fortotal physical activity between physical activity scale and pedometer was 0.45. Bothof them had statistical significance.Ⅱ. The physical activity pattern during pregnancyAccording to the data from physical activity scale, the mean physical activity energyexpenditure was 32.30 Met^*hours. More than 90 percent of time and above 80 percentof energy expenditure was cost on sedentary(the A, B intensity in the scale) and lightintensity(the C, D intensity in the scale) physical activity. The time and energyexpenditure cost on the sedentary physical activity in the 3^rd trimester was more thanthat in the 2^nd trimester and those spent on the light and moderate intensity decreasedfrom 2^nd to 3^rd trimester. No one took part in any vigorous intensity physical activityduring pregnancy. There were 4 pregnant women who had never joined in anymoderate physical activity during pregnancy. According to the pedometer, the meanstep counts for all the pregnant women during pregnancy were 7117.From the qualitative research, the physical activity status was less active than prepregnancy.Both pregnant women and perinatal health care provider supported andencouraged the physical activity during pregnancy. Ⅲ. The influence of physical activity during pregnancy on pregnant outcomes1. The influence of daily physical activity during pregnancy on pregnantoutcomes866 of the pregnant women were categorized into the sedentary, low active, somewhatactive and active groups according to their mean daily step counts during pregnancy.It showed no statistical correlation between daily physical activity and preterm birth.Compared with the sedentary group, women in the active physical activity group hadless pregnant weight gain.The women in the active group of the 2^nd trimester delivered baby with lower birthweight, fetal growth ratio and gestational birth weight Z score than the sedentarygroup. For the daily physical activity in the the3^rd trimester and the mean dailyphysical activity of 2^nd and 3^rd trimester, the women in the somewhat active and activegroup had baby with lower birth weight, fetal growth ratio and gestational birthweight Z score than the sedentary group. For the daily physical activity in the 2^ndtrimester and the mean daily physical activity of 2^nd and 3^rd trimester, women in theactive group had baby with lower ponderal index compared with the sedentary group.Women in the active and somewhat active group of the 3^rd trimester had babies withlower ponderal index compared with sedentary group.We didn't find any relationship between daily physical activity and the incidence ofsmall infant size for gestational age(SGA). There was no influence of daily physicalactivity in 2^nd trimester on the incidence of large size for gestational age(LGA). In the3^rd trimester, compared with the sedentary group, the women in the active andsomewhat active physical activity group had less chance to have large infant size forgestational age. For the mean daily physical activity of 2^nd and 3^rd trimester, comparedwith the sedentary group, the women in the active group had less chance to have largeinfant size for gestational age, with the odds ratio(OR) of 0.31(95% confidenceinterval(CI): 0.15～0.62).We didn't find any relationship between physical activity and low birth weightincidence. There was no influence of physical activity in 2^nd trimester on macrosomiaincidence. In the 3^rd trimester, compared with the sedentary group, the women in thesomewhat active and active groups had less chance to have macrosomia. For the meandaily physical activity status of 2^nd and 3^rd trimester, the women in the somewhat active and active groups had ORs of 0.38(95%CI: 0.18～0.80) and 0.19(95%CI:0.06～0.59) respectively for macrosomia than the sedentary group.In the 2^nd trimester, the women in the somewhat active and active group had lowerrate of caesarean section and selective caesarean section than the sedentary group. Inthe 3^rd trimester, the women in the low active, somewhat active and active group hadlower rate of caesarean section and selective caesarean section than the sedentarygroup. For the mean daily physical activity of 2^nd and 3^rd trimester, compared with thesedentary group, the women in the low active, somewhat active and active group hadORs of 0.60 (95%CI: 0.36～0.99), 0.30(95%CI: 0.18～0.50), 0.23(95%CI: 0.13～0.41)respectively for undergoing caesarean section. The women in the low active,somewhat active and active group had ORs of 0.57(95%CI: 0.34～0.95), 0.32(95%CI:0.19～0.55), 0.20(95%CI: 0.11～0.38), for selective caesarean section than thesedentary group.We didn't find influence of maternal physical activity on length of labor and newbornAPGAR scores.2. The influence of daily moderate physical activity energy expenditure duringpregnancy on pregnant outcomesAccording to the quartiles of mean daily moderate physical activity energyexpenditures, 866 of the pregnant women were categorized intoⅠ,Ⅱ,Ⅲ,Ⅳgroupswith the increasing energy expenditures levels.There was no statistical correlation between daily moderate physical activity energyexpenditure and preterm birth incidence.Compared with theⅠgroup, the women in theⅣgroup had less pregnant weightgain.In the 2^nd and 3^rd trimester, the women of theⅢ,Ⅳgroups delivered baby with lowerbirth weight than theⅠgroup. For the mean daily moderate physical activity energyexpenditure of 2^nd and 3^rd trimester, the women in theⅡ,Ⅲ, andⅣgroups deliveredbaby with lower birth weight than theⅠgroup. For the daily moderate activity energyexpenditure in the 2^nd trimester and the mean daily moderate activity of the 2^nd and 3^rdtrimester, the women in theⅡ,Ⅲ,Ⅳgroups delivered baby with lower fetal growthratio, lower gestational birth weight Z score and lower ponderal index than theⅠgroup. The women in theⅢ,Ⅳgroups of the 3^rd trimester had baby with lower fetalgrowth ratio, lower gestational birth weight Z score and ponderal index than theⅠgroup. We didn't find any relationship between moderate physical activity and incidence ofsmall infant size for gestational age. For moderate activity energy expenditure in the2^nd trimester, the women in theⅣgroup had less chance to delivery large infant sizefor gestational age than theⅠgroup. Compared with theⅠgroup, women in theⅢ,Ⅳgroups in the 3^rd trimester had less chance to have baby with large size forgestational age. For the mean daily moderate activity energy expenditure of 2^nd and3^rd trimester, compared with theⅠgroup, the women in theⅡ,Ⅲ,Ⅳgroups had lesschance to have large infant size for gestational age, with the ORs of 0.55(95%CI:0.35～0.86), 0.50(95%CI: 0.32～0.79) and 0.37(95%CI: 0.23～0.60).We didn't find any relationship between moderate physical activity and low birthweight incidence. The women in theⅣgroup in 2^nd trimester had less chance formacrosomia than theⅠgroup. The women in theⅢandⅣgroups in the 3^rd trimesterhad less chance for macrosomia than theⅠgroup. For the mean daily moderatephysical activity energy expenditure of 2^nd and 3^rd trimester, the women in theⅡ,Ⅲ,Ⅳgroups had ORs of 0.52(95%CI: 0.27～1.00), 0.48(95%CI: 0.25～0.93) and 0.38(95%CI: 0.19～0.77) for macrosomia than theⅠgroup.The women in theⅢandⅣgroups in the 2^nd trimester had lower rate of caesareansection and selective caesarean section than theⅠgroup. The women in theⅡ,Ⅲ,Ⅳgroups of the 3^rd trimester had lower rate of caesarean section and selective caesareansection than theⅠgroup. For the mean daily moderate physical activity energyexpenditure of 2^nd and 3^rd trimester, compared with theⅠgroup, the women in theⅡ,Ⅲ,Ⅳgroups had ORs of 0.53(95%CI: 0.33～0.85), 0.43(95%CI: 0.27～0.68) and 0.28(95%CI: 0.18～0.44) for undergoing caesarean section. The women in theⅡ,Ⅲ,Ⅳgroups had ORs of 0.53(95%CI: 0.32～0.86), 0.43(95%CI: 0.27～0.70) and 0.27(95%CI: 0.17～0.43) for selective caesarean section than theⅠgroup.We didn't find influence of maternal moderate physical activity energy expenditureon length of labor and newborn APGAR scores.3. The influence of daily physical activity energy expenditure during pregnancy oninfant growth695 of newborns were successfully followed up and the infant growth data werecollected. For the women of the active group of the 2^nd trimester, their infants hadlower weight and lower BMI Z scores than the sedentary group. For the women of thesomewhat active and active groups in the 3^rd trimester, their infants had lower weight,smaller head circumference and lower BMI Z scores than the sedentary group. For the women of somewhat active and active groups of the mean daily physical activity of2^nd and 3^rd trimester, their infants had lower weight, smaller length and headcircumference Z score than the sedentary group. Finally, for the women in the activegroup of the daily physical activity of the 2^nd and 3^rd trimester, their infants had lowerBMI Z scores than the sedentary group.Ⅳ. The exploration of clinical monitoring and guidance approaches on physicalactivity during pregnancy1. There were great demands for physical activity guidance service by pregnantwomen. The books, magazines, internet, family and friends were the major source formaternal physical activity information and there was limited source for medical staffto expand their physical activity knowledge. Physical activity during pregnancy canenhance the confidence for pregnant women who preferred the natural delivery andmay help to achieve the labor. The physical activity scale and pedometer wereregarded as the appropriate tools to reflect the physical activity status duringpregnancy and they were thought suitable to being applied in daily health care service.2. The area under a receiver operating characteristic(ROC) curve of the predictiveindicator Y for macrosomia was 0.846. The predictive indicator had sensitivity of0.83 and specificity of 0.77. It could be applied as a resource saving approach in theclinical work.3. For the mean steps of the 2^nd and 3^rd trimester, 5000 steps or above could begin toimprove pregnant outcome such as the decreased caesarean section. 7500 steps orabove could lead to more improvement of pregnant outcomes such as decreased birthweight, macrosomia incidence and caesarean section. 1.1 hours or above of Eintensity moderate physical activity in the scale during pregnancy could produce theimprovement for several pregnant outcomes such as decreased birth weight,macrosomia incidence and caesarean section. For higher intensity of moderateactivities, the time could be shortened.4. The maternal physical activity analysis software could help perinatal health carersprovide effective, convenient and economic service for pregnant women on physicalactivity monitoring and guidance.Ⅴ. The influence of INS VNTR on fetal and infant growthThe frequencies of INS VNTR genotypesⅠ/Ⅰ,Ⅰ/Ⅲ,Ⅲ/Ⅲwas 91.13%, 8.70% and0.17% and it was in accordance with Hardy-Weinberg rule. The frequency of INSVNTRⅠ,Ⅲallele was 95% and 5%. The different distribution of the genotypebetween Chinese and Caucasian indicated the race specific gene distribution. We did not find any influence of INS VNTR polymorph on fetal and infant growth. Nointeraction was found between maternal physical activity and INS VNTR polymorphon fetal and infant growth.Conclusion1. The results showed good reliability and acceptable validity for the physical activityscale explored in this study. It was an appropriate tool to monitor physical activityamong Chinese pregnant women with the characters similar to our researchpopulation..2. Pregnant women spent most of their time and energy expenditure on light andsedentary activities. With the increase of gestational age, the physical activities ofpregnant women became less active.3. From the study, we didn't find any negative affection of physical activity onpregnant outcomes. On the contrast, we found some potential benefits of participationin physical activity during pregnancy, such as decreased maternal weight gain, birthweight, fetal growth ratio, gestational birth weight Z score, ponderal index, decreasedincidence of large infant size for gestational age and macrosomia, decreased caesareansection and selective caesarean section rate. Furthermore, it was found the sustainedinfluence of physical activity during pregnancy on infant growth, which indicated theimportant influence of physical activity on both mother and offspring.4. There were great demands for perinatal physical activity guidance service. Theappropriate technique for clinical physical activity guidance needed to be exploredand developed. The explored monitoring and guidance approach in this study such aspredictive indicator for macrosomia, the suggestion for physical activity guidance andanalysis software for physical activity during pregnancy could be applied in theclinical work.5. With the low frequencies ofⅢ/Ⅲgenotype andⅢallele in population of Chinamainland, we didn't find the influence of INS VNTR gene polymorphism on birthsize and infant growth. Further study concerning on this fact is needed.