Prevention of low birth weight by early risk detection : Relationship between maternal parameters and neonatal birth weight

学位の種類: 博士（保健学）. 報告番号: 甲第4487号. 学位記番号: 新大院博（保）甲第25号. 学位授与年月日: 平成30年3月23日Low birth weight (LBW) is defined as weighing less than 2500 g at birth, irrespective of gestational age. It is an important risk factor for neonatal morbidity and mortality, as well as a risk for health, growth, and developmental problems in later life. The global rates of LBW are estimated to be 15% to 20% of all births, representing more than 20 million annual births. Although, the majority of LBW deliveries occur in developing countries, the incidence of LBW is a global issue. Sri Lanka is a developing country which was recently upgraded to a lower-to-middle-income country. The rate of LBW in Sri Lanka has fluctuated around 17% for many years, with the most recent national statistics indicating 16% of all live births are LBW. The negative health consequences of a high incidence of LBW deliveries are also an extra burden on the country‘s health care resources, facilities and future plans. This study aimed to find an effective method for early risk detection of LBW in order to implement preventive strategies. A prospective longitudinal study was launched in a tertiary care hospital in Sri Lanka from October 2015 to June 2016. In total, 150 pregnant women who were between 18 and 24 weeks of gestation were included and followed up until delivery. In the overall procedure of data collection, there were 9 exclusions (spontaneous abortions n = 2, multiple fetuses identified at the 20-week ultrasound scan n = 2, maternal desire to deliver at another hospital n = 3 and withdrawal for personal reasons n = 2) between recruitment and baby delivery, resulting in 141 women in the maternal data set. Maternal weight at the time of delivery was collected for 119 women. Researchers failed to collect neonatal data for 14 women and one mother–baby pair was excluded due to low apgar score at 5th minute of birth, resulting in 126 neonatal data set. The study consisted of three parts with the objectives of assessing the effects of maternal nutrition, passive smoking or exposure to wood fuel smoke and pregnancy physical activity on neonatal birth weight. Maternal nutrition was assessed by two parameters as maternal dietary intake and maternal anemia. Socio-demographic data were collected using an interviewer-administered questionnaire. Measurements of maternal height and body weight were taken using standard scales. Maternal dietary intake was assessed using a validated food frequency questionnaire around 22 and 34 weeks of gestation. A structured interviewer-administered questionnaire was used to assess passive smoking and exposure to wood fuel smoke at 30 weeks of gestation. At the same time, exposure was assessed using a breath carbon monoxide monitor. Pregnancy physical activity was assessed using a validated pregnancy physical activity questionnaire which was administered at the same time of dietary assessment, around 22 and 34 weeks gestation.Second trimester (around 22 weeks gestation) maternal dietary data was used to assess the association between maternal dietary intake and neonatal birth weight (n = 141). All women who fulfilled the criteria of having undergone anemia screening at both first antenatal clinic visit and at 28–30 weeks gestation and of having delivered a term singleton neonate were selected for assessment of the association between maternal anemia and birth weight (n = 52). Data on maternal exposure to tobacco smoke and wood fuel smoke was available only for 87 women. By excluding women with missing birth weight data this particular analysis was limited to 76 maternal–neonatal units. Data on pregnancy physical activity was available for 139 women around 22 weeks gestation and for 62 women around 34 weeks gestation. There was a moderate positive correlation between total gestational weight gain and birth weight (p = 0.02), holding pre-pregnancy body mass index and gestational age fixed. The total gestational weight gain of women with low carbohydrate intake during the second trimester (229–429 g/day) was 2.2 kg lower than that of women with moderate carbohydrate intake (430–629 g/day) (95% CI 0.428–4.083 kg; p = 0.016). Similarly, babies of women with low carbohydrate intake during the second trimester were 312 g lighter than those with a moderate carbohydrate intake (95% CI 91–534 g; p = 0.006). Analysis of hemoglobin data showed that the babies whose mothers were anemic during the third trimester had lower mean birth weight than those born to women who were not anemic during the third trimester (p = 0.017). No differences in dietary intake were found between third trimester anemic and non-anemic women (p > 0.05). Women who were exposed to tobacco smoke every day delivered neonates with significantly lower mean birth weight (2,703 ± 539 g) than did women who were only exposed once a week (3,125 ± 464 g) (p < 0.05). A 1-minute increase in cooking time in a kitchen without a chimney increased women‘s expired air carbon monoxide concentration by 0.038 ppm (p = 0.006). Significant reduction in time spent in physical activity and total energy expenditure were observed as pregnancy progressed. No significant association was found between pregnancy physical activity and birth weight. A number of important conclusions can be drawn from the results of this study. First, it can be concluded that maintaining a moderate level of carbohydrate intake during the second trimester may promote favorable total gestational weight gain and neonatal birth weight in Sri Lankan context. Second, maternal anemia in the third trimester is associated with a low mean birth weight. However, the high prevalence of maternal anemia in the third trimester among Sri Lankan women cannot be explained solely by macro and micronutrient deficiencies. Moreover, maternal exposure to tobacco smoke during pregnancy is followed by low mean birth weight of their babies. Finally, there is no significant impact of moderate physical activity on neonatal birth weight. Careful management of these modifiable factors in Sri Lanka is essential components of strategies seeking to prevent LBW.博士（保健学）新潟大