Our PA study was a longitudinal study using convenience sampling to recruit pregnant women who received an early pregnancy assessment in a certain month from July 2017 to November 2018 in 14 maternal and child health hospitals and 10 teaching hospitals located in 15 provinces of China. The location of the study recruiting hospital was previously published . All 24 hospitals were public hospitals, and the cost of perinatal health care was largely covered by the government maternity insurance program and partly by individuals. Population characteristics that are biologically plausible or historically associated with PA were considered to be determinants investigated in our study. Detailed interviews were conducted during the initial visit to the recruitment clinic in early pregnancy to collect population characteristics. Participants were invited to attend the PA level assessment twice, the first being done early in pregnancy during the initial clinic visit and the second being done in the middle or end of pregnancy. pregnancy during an antenatal clinic visit after 24 weeks gestation.
The inclusion criteria for the study population were as follows: (1) age 16 years or older, (2) pregnancy (the) 12 weeks, based on estimate based on last menstrual period; (3) permanent resident of the student recruitment district; (4) regular prenatal inspection with the intention of giving birth in the study recruiting hospital; and (5) able to complete the PA assessment online. The exclusion criteria were as follows: (1) serious chronic diseases such as heart failure, pulmonary hypertension, restrictive lung disease, chronic kidney disease, autoimmune disease, epilepsy, malignant tumors or other diseases that would restrict PA during pregnancy; and (2) multiple pregnancy. Written informed consent was obtained from all participants and the study was approved by the Ethics Review Board of Peking Union Medical College (HS-1345).
Of 4,750 women who met the inclusion criteria for our PA study, 102 were excluded due to serious chronic disease and 32 due to multiple pregnancy. A total of 1,994 people refused to participate. Fifty participants could not remember their PA in the previous 7 days during the first PA assessment. A total of 2,572 women completed the first PA assessment in early pregnancy. Seventy-five had a miscarriage or an abortion between the two assessments. Twelve participants could not remember the PA on the second PA assessment. A total of 2485 women with both information on PA in early and mid- or late-pregnancy were ultimately included in the data analysis of the present study (Fig. 1).
Physical activity assessment
PA was assessed in early and mid or late pregnancy using the International Physical Activity Questionnaire (IPAQ-SF) validated for the Chinese population. [32, 33]. IPAQ addresses three types of PA: high intensity PA, medium intensity PA and walking. High-intensity PA refers to activities that require intense physical effort and make breathing much more difficult than normal, such as lifting heavy objects, digging, or doing aerobics. . Moderate-intensity PA refers to activities that require moderate physical exertion and make breathing a little more difficult than normal, such as carrying light loads, biking at a steady pace, or table tennis. . Walking includes all walking for occupation, transportation, housekeeping, exercise, and recreation. The frequency (days) and duration (minutes) of each PA during the previous seven days were studied. Total energy expenditure (TEE) on PA per week was calculated as a total of three types of PA reported in the MET × minutes per week value. Values of 3.3, 4.0, and 8.0 were assigned to represent MET values of walking, mid-intensity PA, and high-intensity PA, respectively .
According to the IPAQ-SF, the TEE on PA ≥ 600 MET min / week is defined as “moderate level” , and WHO recommends a minimum of 600 MET min / week of PA to obtain a health benefit . Therefore, we defined PA with ETO 600 MET min / week as sufficient PA and PA with ETO
Determinants included demographic, pregnancy and health characteristics. Demographic characteristics included age, region of residence, ethnicity, level of education, annual household income and occupation. The characteristics of pregnancy included parity and intention to become pregnant. Health characteristics included pre-pregnancy BMI and history of smoking or alcohol.
Age, ethnicity, and intention to become pregnant were considered biologically plausible determinants of PA. Education level, income, occupation, parity, BMI and smoking were determinants that were historically associated with PA [26,27,28,29, 36].
The residential region, which was ranked in eastern, central and western China according to economic development according to the China Yearbook of Health Statistics, was considered a plausible determinant of PA. East China was the most urbanized and industrialized, while West China was the most rural and agrarian. East China was considered the fastest growing region, followed by Central China and West China. Seven, nine and eight recruiting hospitals were located in eastern, central and western China, respectively.
Pregnancy was defined as an intentional pregnancy if the couple intended to conceive. Pregnancy was defined as an unwanted pregnancy if it had been conceived accidentally. Pre-pregnancy BMI (kg / m2) was calculated based on self-reported pre-pregnancy weight in kilograms and height in centimeters. BMI was classified as underweight, normal weight, overweight and obesity (
The characteristics of the population of all women included in the study are described. Categorical data is expressed as frequencies and percentages. Continuous data are expressed as means, standard deviations (SD), medians, and interquartile ranges (IQR). TEO on PA, energy expenditure on each type of PA and the proportion of energy expenditure on each type of PA compared to TEO on PA were compared between onset and middle or end of pregnancy using Wilcoxon’s signed rank test. The proportions of women with sufficient PA levels were compared between early and mid to late pregnancy using the McNemar test. Multivariate logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI) to address the following: (1) associations between population characteristics and sufficient PA in the middle or at the end of pregnancy in all women included in the study, (2) associations between population characteristics and increased PA among the subset of women with insufficient PA levels in early pregnancy, and (3) associations between population characteristics and decreased PA among the subset of women with sufficient PA levels in early pregnancy. P values