Study design
This study was a longitudinal and cross-sectional survey. All pregnant women were recruited at the second half of pregnancy period and were followed until delivery.
Participants and recruitment
This study was conducted in Ahvaz, a city in South of Iran. Subjects were recruited from healthy pregnant women referred to Kurosh and Saa’di health centers, respectively representative of health centers in east and west of Ahvaz. The inclusion criteria were 18–45 years of age at the expected date of delivery, and subjects being at the 20th- 22nd gestational weeks. Since many pregnant woman experience morning sickness during the first months of pregnancy which may continue up to 3rd or 4th months, we decided to use the second half of pregnancy for the study protocol with the other reason being that most of the maternal weight gain occurs in the second half of pregnancy. Exclusion criteria were as follows: those having chronic infectious diseases, metabolic disorders, gestational diabetes, gestational hypertension, pre-eclampsia, eclampsia, twin pregnancy, preterm delivery, eating disorders (anorexia, bulimia), and emotional disorders (depression, stress and anxiety). In the first half of the pregnancy (the first 20 weeks), psychiatric evaluation is performed routinely using the Kessler Psychological Distress Scale (K10), for determination of depression and anxiety.
The sample size was calculated based on the relationship between personality traits of adults and BMI [28]. The following formula was used to calculate sample size. The correlation coefficient (r), α, and β were 0.17, 0.05 and 0.1 respectively. \( n={\left[\frac{z_{1-\frac{\alpha }{2}}+{z}_{1-\beta }}{C}\right]}^2 \), C = 0.5[ln(1 + r)/(1 − r)].
Considering the inclusion criteria and the calculated sample size, 360 pregnant women participated in the study.
Instruments
Three valid and reliable questionnaires, (NEO Five-Factor Inventory, Dutch eating behavior questionnaire and a semi-quantitative food frequency questionnaire) were used to evaluate personality traits, eating behavior and food intake of participants respectively. All questionnaires were completed by trained interviewers at the first visit (after recruitment to the study). The interviewers explained about the questionnaires to the participants, before asking them to complete the questionnaires, also checked and resolved any vague recalls.
Personality traits questionnaire
NEO Five-Factor Inventory (NEO-FFI) by McCrae and Costa [15] was used to measure FFM personality domains. NEO-FFI is one of the most widely-used instruments to describe individual differences in five domains of personality traits (Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness). Neuroticism is the tendency to experience negative emotions (anxiety, anger, and depression). Extravert people are active, sociable, and they search for stimulation. People with the Openness trait are unconventional, imaginative, creative, and artistically sensitive. Agreeableness is the tendency to be altruistic, trusting, modest, and cooperative. Conscientiousness individuals are strong-willed, reliable, persistent, and complying with rules and ethical principles [29].
Eating behavior questionnaire
Eating behaviors (restrained, emotional and external) were assessed using the Dutch eating behavior questionnaire (DEBQ) which has 33-items [30]. Ten items are included in the restraint scale which measures intentional restriction of eating in order to reduce or maintain weight. The DEBQ includes 13 items to evaluate the emotional scale and assesses eating due to emotional disorders such as anger, fear or anxiety, and not the physiological hunger. The DEBQ external scale (10 items) measures eating in response to external food-related stimuli, regardless of the internal state of hunger or satiety.
Food intake questionnaire
The whole diet was assessed using a validated and reliable semi-quantitative food frequency questionnaire (FFQ) that has been designed according to Iranian food guide pyramid [31]. The questionnaire included common foods typically consumed by Iranians. The standard serving sizes were defined in the questionnaire. Participants reported their average frequency of food intake over the past year. The frequency of intake was marked as times per day (e.g. bread), week (e.g. cheese), or month (e.g. fish). In addition, participants reported the serving size. The food frequency recall bias was limited by showing the participants the photographs of various portions and household or standard units. After completing the FFQ, the serving size was converted to grams and the reported amount of each food was converted to a daily intake value [32]. This questionnaire consisted of 45 food items. Some common foods in this questionnaire are as follows: milk, yoghurt, doogh (traditional yoghurt drink), ice cream and cheese consumption were considered in milk and dairy products group; red meat, poultry, fish, egg and legumes as proteins group; bread, rice and pasta as grains group; jam, confection, sugar, and soft drinks as sweets group; and fast foods, butter and oils as fats group.
Anthropometric assessment
Anthropometric indices, including weight gain during the second half of pregnancy as well as the infant’s weight, were measured by trained research staff and recorded in individual health cases. These data were collected from the health cases in health centers. The required amount of weight gain during pregnancy was determined according to the BMI before pregnancy (the weight before pregnancy was collected from the health case of mothers by self-report. The pre-pregnancy weight had been written in the first weeks of pregnancy, so mothers could recall their weight before pregnancy). The final subjects’ weight were taken at 38th week of gestation. Gestational weight gain was considered adequate in the second and third trimesters if the woman was within the range recommended by IOM based on pre-pregnancy BMI. According to IOM recommendation, the rate of weight gain during second and third trimesters for low and normal pre-pregnancy BMI was 0.5 kg and 0.4 kg per week, respectively. If pre-pregnancy BMI was between > 26.0–29.0 kg/m2, the recommended weight gain was 0.3 kg/week. For pre-pregnancy BMI more than 29, the rate of weight gain during second and third trimesters were not specified but the recommendation was that total weight gain must be less than 7.5 kg [24].
Data analysis
Statistical analysis was performed with SPSS version 17.0 software. Data were expressed as means ±standard deviation (SD) for continuous variables or number (percentage) for categorical variables. The normality of data was analyzed using kolmongrov-smirnov test. Pearson correlation test was used to analyze the relationships between the personality traits, and eating behavior, food intake and anthropometric measurements. The One–way analysis of variances (ANOVA) was used to compare the mean of eating behaviors’ score, gestational weight gain, and birth weight of infants among different tertiles of personality traits’ score. Tukey test was used to compare which means differ from the rest. If distribution was not normal, related non-parametric test was used. Analysis of covariance was used to control the potential effect of some covariates such as length of gestation, pre-pregnancy BMI and maternal age. Predicting gestational weight gain and birth weight of infants by personality traits, eating behaviors and food intakes were analyzed using multinomial logistic regression. Reference group was considered adequate for both gestational weight gain and infant birth weight. For gestational weight gain, subjects’ weight gain were considered adequate if they were in line with IOM recommendation (mentioned in the previous section). Also birth weight between 2500 and 4000 g was considered adequate.
