Journal of Womens Health, Issues and Care ISSN: 2325-9795

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Research Article, J Womens Health Issues Care Vol: 4 Issue: 4

Optimal Weight Gain Recommendations For Non- Obese Japanese Pregnant Women

Hidemi Takimoto1*, Reiko Tajirika2, Nobuko Sarukura1, Honami Yoshida3, Noriko Kato3, Toshiro Kubota2 and Tetsuji Yokoyama3
1National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition, 1-23-1 Toyama, Shinjuku-ku, Tokyo 1628636, Japan
2Department of Comprehensive Reproductive Medicine, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 1130034, Japan
3National Institute of Public Health, 2-3-6 Minami, Wako-shi, Saitama 3510197, Japan
Corresponding author : Hidemi Takimoto
National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition, 1-23-1 Toyama, Shinjuku-ku, Tokyo 1628636 Japan
Tel: +81-3-3203-5721; Fax: +81-3-3202-3278
E-mail: [email protected]
Received: February 06, 2015 Accepted: August 05, 2015 Published: August 08, 2015
Citation: Takimoto H, Tajirika R, Sarukura N, Yoshida H, Kato N, et al. (2015) Optimal Weight Gain Recommendations For Non-Obese Japanese Pregnant Women. J Womens Health, Issues Care 4:4. doi:10.4172/2325-9795.1000192

Abstract

Optimal Weight Gain Recommendations For Non- Obese Japanese Pregnant Women

To determine optimal weight gain recommendations for reducing unfavorable pregnancy outcomes in non-obese women, by comparing four different cutoffs for weight gains. Out of 4774 cases in the hospital-based survey of the 2010National Growth Survey of Preschool Children, data on 3547 singleton term deliveries with maternal pre-pregnancy BMI<25.0 were selected. Two cutoffs for adequate weight gains, the Ministry of Health, Labour, and Welfare (MHLW), and the Japan Society for the Study of Hypertension in Pregnancy (JSSHP) weight gain guidelines were applied to identify “insufficient”, “adequate”, and “excess” weight gain groups. Logistic regression analyses were applied to estimate the risks for “insufficient” and “excess” weight gains to selected pregnancy outcomes.

Keywords:

Keywords

Health survey; Infant; Pregnancy outcomes; Weight gain; BMI

Introduction

Weight gain in pregnancy has gained attention in recent years, especially in developed countries, mainly due to the rise in obesity among reproductive age women. In 2009, the United States Institute of Medicine revised its pregnancy weight gain guideline [1], and stressed the importance of women to avoid excess weight gains, in order to reduce their risks for pregnancy-associated hypertension (including preeclampsia and eclampsia), risk of complications in labor and delivery, postpartum weight retention, and other long-term maternal health consequences such as increased risk for type 2 diabetes and cardiovascular disease. In Japan, weight gain in pregnancy has long been used to monitor maternal health status during pregnancy. Since 1965, obstetricians and midwives were required to measure the body weight of the pregnant women on each prenatal visit after 15 weeks, and record it in the Maternal and Child Health Handbook [2]. It has been the usual practice during prenatal care, for pregnant women to be advised to avoid excess weight gain in order to prevent development of preeclampsia, gestational diabetes, fetal macrosomia, or obstructive deliveries. However, official weight gain recommendations had not been issued until 1997, when The Perinatal Committee of the Japan Society of Obstetrics and Gynecology proposed a guideline for the prevention of preeclampsia [3] (Table 1). This recommendation is still actively used in the 2009 guideline of the Japan Society for the Study of Hypertension in Pregnancy (JSSHP) [4].
Table 1: Weight gain recommendations shown in the two co-existing guidelines.
Contrary to other developed countries, obesity among reproductive age women is not endemic in Japan. The latest national data show that obesity (BMI ≥ 25) rates are quite low, which are 7.5% and 13.8 % for women aged 20-29 years and 30-39 years, respectively [5]. Moreover, the proportion of adult women with BMI ≥ 30 is only 3.2%, which is extremely low compared to the OECD average of 23.0% [6]. Although maternal obesity is a risk factor for hypertensive disorders, cesarean deliveries, or maternal mortality [7], rising maternal underweight combined with insufficient pregnancy weight gain may be a larger problem affecting fetal growth, as observed in the recent increase in low birthweight infants [8]. The proportion of underweight (BMI<18.5) in adult women is more than twice (10%) than that of the OECD average of 4% [6], and is especially high in women aged 20-29 years (29.0%) [5]. In order to address the problem of increasing low birthweight, the Japanese Ministry of Health, Labour, and Welfare (MHLW) issued another weight gain recommendation in 2006, in order to promote women to produce a term singleton infant weighing 2500 to 4000g (Table 1) [9].
However, there have been no recent studies on non-obese women using the latest nationwide data. To determine optimal weight gain recommendations for reducing unfavorable pregnancy outcomes in non-obese women, we applied the data from the national survey conducted in 2010.

Materials and Methods

The study population consisted of 4774 infants who participated in the National Growth Survey of Preschool Children in 2010. This survey is conducted by the Ministry of Health, Labour, and Welfare (MHLW) every ten years, and consists of two major datasets. We applied the hospital-based survey data, which was conducted in 146 hospitals, out of 150 which were randomly selected from each prefecture by the Ministry, from the 1294 obstetric facilities registered in the 2009 version of the Survey of Medical Facilities [10]. Information regarding maternal health status during pregnancy, such as pregnancy induced hypertension (PIH), diabetes, and anemia were collected through the hospitals’ birth records. Both elective and emergency cesarean deliveries were recorded as “cesarean delivery”.
According to the latest JSSHP criteria [4], PIH was defined as the first onset of hypertension (systolic blood pressure ≥ 140 mmHg and/or a diastolic blood pressure ≥ 90 mmHg), or hypertension accompanied by proteinuria between 20weeks gestation to 12weeks postpartum. PIH was recorded as either moderate or severe. Moderate PIH was defined as a hypertensive state (systolic blood pressure: 140 -160mmHg and/or a diastolic blood pressure: 90 -110mmHg) with or without proteinuria (urinary protein excretion of 0.3 -2g in a 24- hour urine collection). Severe PIH was defined as a hypertensive state (systolic blood pressure: 160 mmHg or higher and/or a diastolic blood pressure: 110 mmHg or higher) with or without heavy proteinuria (urinary protein excretion of 2g or more in a 24-hour urine collection). Both pre-gestational and gestational diabetes were recorded as “diabetes”. Anemia was defined as presenting hemoglobin values less than 110 g/L, according to the definition by WHO [11]. For fetal outcomes, mean birthweight, proportion of low birthweight (< 2500 g), macrosomia (≥ 4000 g), light-for-dates (LFD), heavy-fordates (HFD), and mean gestational length in weeks were selected. To identify light-for-dates or heavy-for-dates infants, the latest gestational age specific standard birthweights issued by the Japan Society of Pediatrics [12] were applied. The infant were identified as LFD if his/ her birthweight was less than the 10th percentile value, and HFD if his/ her birthweight was larger than the 90th percentile value.
The anonymous dataset used for the current study was provided through the permission of the authority; the Ministry of Health, Labour and Welfare. Subjects’ consent to participate was obtained by the Ministry. The data for the final analyses was selected through the process as shown in Figure 1. Because the MHLW and JSSHP recommendations apply different pre-pregnancy BMI cutoff values for obesity (Table 1), we excluded 407 cases with BMI 25.0 or over so that the two recommendations could be compared using the same subjects. The study subjects were categorized into “insufficient”, “adequate” or “excess” weight gain groups, using the two separate cutoffs.
Figure 1: Data selection process.
Comparisons between groups for continuous variables were done by one-way ANOVA. Categorical variables were compared using chi-square tests. For the estimation of the odds ratios of the weight gain group to pregnancy outcomes, single-variable logistic regression analyses were applied after adjusting for confounding factors. The population attributable fraction (PAF) of selected factors to each outcome was calculated using the following equation, where ni is the number of the outcome in the ith risk category, RRi is the relative risk (odds ratio [OR]) in the ith risk category (RR=1 in the referent category). PAF serves as an estimated reduction proportion of the outcome if all women had “adequate” weight gains [13].
All statistical analyses were conducted using the SPSS 17.0 statistics software. The P value of less than 0.05 (two tailed) was considered as statistically significant.

Results

Maternal and infant characteristics according to weight gain status
Maternal and infant characteristics, according to maternal weight gain status using the two different cutoffs, are shown in Table 2. According to the MHLW cutoffs, 19.1% had “insufficient”, 58.5% had “adequate”, 22.3% had “excess” weight gains. According to the JSSHP guideline, 19.2% had “insufficient”, 40.6% had “adequate”, and 40.2% had “excess” weight gains. In spite of applying different cutoffs, maternal age was significantly younger , maternal weight at delivery and weight gain were larger in all “excess” weight gain groups, compared to the “insufficient” group. Similarly, infant birthweight and gestational age were significantly larger, in all “excess” weight gain groups compared to the “insufficient” group. The proportion of low birthweight and LFD infants was significantly lower in all “excess” weight gain groups compared to the “insufficient” group. There were no significant differences in the proportion of diabetes among the different weight gain categories. The proportion of HFD infants was significantly higher in all “excess” weight gain groups compared to the “insufficient” group.
Table 2: Maternal and infant characteristics according to the weight gain categories according to the four separate cutoffs for maternal weight gain.
Relations between maternal PIH, diabetes, anemia and selected pregnancy outcomes are shown in Table 3. Maternal moderate or severe PIH was related to significantly higher proportion of cesarean deliveries, LBW and LFD infants (P<0.05). Maternal diabetes was related to higher proportion of cesarean deliveries (P=0.05) and HFD infants. Maternal anemia was significantly related with lower proportion of LBW infants (P=0.03).
Table 3: Relations between maternal PIH, diabetes, anemia and selected pregnancy outcomes.
Risk estimates of weight gain status to pregnancy outcomes
In order to examine the effect of “insufficient” and “excess” weight gains to pregnancy outcomes (cesarean delivery, PIH, diabetes, anemia, LBW and macrosomia), logistic regression analyses were applied to estimate the odds ratios as presented in Table 4. The PAFs for each outcome are also presented. For all analyses, the results were adjusted for maternal age, height, pre-pregnancy BMI, parity, infant gender, gestational age, and birthweight. For cesarean delivery, the results were further adjusted for total PIH and diabetes. For LBW, macrosomia, LFD and HFD, the results were further adjusted for total PIH, diabetes, and anemia.
Table 4: Results of the logistic regression analyses on the effect of insufficient or excess weight gains to selected pregnancy outcomes, according to the four cutoffs.
Regarding cesarean delivery, significantly higher odds ratios were observed in the “excess” weight gain groups, according to the JSSPH cutoff. Significantly higher odds ratios were observed for total PIH in the “excess” weight gain group (>12 kg) according to the MHLW cutoffs. Diabetes risks were not related to weight gain categories. The odds ratios for LBW were significantly higher in both “insufficient” weight gain groups. The odds ratios for LBW were significantly lower in both “excess” weight gain groups. Significantly higher odds ratio was observed for macrosomia in the “excess” weight gain group according to the MHLW cutoff. Compared to the “adequate” weight gain group, the odds ratios for LFD were significantly higher in both “insufficient” weight gain groups, and they were significantly lower in all “excess” weight gain groups. Significantly lower odds ratios were observed for HFD in both “insufficient” weight gain groups, and were significantly higher both “excess” weight gain groups.
When the MHLW cutoff was adhered, 14.1% reduction in total PIH, 9.0% reduction in LBW, 55.9% reduction in macrosomia, 5.3% reduction in LFD, 4.8% reduction in HFD, and 4.6% increase in anemia were estimated. When the JSSPH cutoff was adhered, 6.9% reduction in cesarean deliveries, 8.0% reduction in HFD, 2.5% increase in LBW and 9.1% increase in LFD were estimated.

Discussion

By using the most recent nationwide hospital-based retrospective data on singleton term births, we examined the effect of two major weight gain recommendations, in order to determine the optimal weight gain ranges for achieving improved pregnancy outcomes, in non-obese Japanese women. As shown in Table 2, regardless of the difference, women who gained “insufficient” weight were older, shorter, multiparous, and their infants were born lighter and earlier compared to women who gained “excess” weight. We speculate that younger primiparas had better knowledge about the 2006 MHLW recommendations, so they had a more positive view toward weight gains. Our prior study in 2006, which was conducted on 248 pregnant women [14] with similar pre-pregnancy BMI values (mean value: 20.4 ± 3.7) compared to the current population, support this speculation. These women desired weight gains between 7.0 ± 1.3 kg to 9.6 ± 1.3 kg, which was quite similar to the “adequate” weight gain range for “normal-weight” women shown in the JSSPH guideline.
As shown in Table 3, pregnancy complications were related to pregnancy outcomes. Although the total number of PIH cases were small (N=85), 38.8% of them underwent cesarean delivery, and 18.8% of the case infants were LBW/ LFD. The effect of maternal diabetes on infant macrosomia was not statistically significant, because there was only one macrosomic infant among diabetic mothers. However, when HFD was applied instead of macrosomia, the association to maternal diabetes was significant. Maternal anemia, on the other hand, was related to lower incidence of LBW and may be related to lower incidence of LFD. Third trimester anemia is unlikely to be associated with adverse pregnancy outcomes [15]. But the current results suggest the possibility that iron supplementation administered to anemic women may have resulted in enhanced fetal growth. The higher proportion of anemia in women with “insufficient” weight gain compared to “excess” weight gain women (Table 2) suggest that poor nutrition may be related to anemia.
The logistic regression analyses by applying the two different cutoffs for maternal weight gain (Table 4) produced mixed results for the outcomes examined. Adherence to the MHLW cutoff would be effective in decreasing PIH cases, macrosomia, and HFD but the reduction in LBW would be only 9.0%, and the reduction in LFD only 5.3%. Adherence to the JSSPH cutoff would be most effective in reducing cesarean deliveries and HFD infants, but would result in 2.5% increase in LBW and 9.1% increase in LFD. Judging from the above results, advising women on weight gains according to the MHLW cutoff may be better to achieve optimal pregnancy outcomes among Japanese women. According to the 2010 Vital Statistics Report, the total number of macrosomia was 8,713 (0.8%), while LBW was 103,049 (9.6%) among 1,071,304 live-births [16]. From the public health perspective, decreasing the number of LBW cases is much more a priority than reducing macrosomia. However, there is a future need to investigate whether HFD is related to other unfavorable obstetric outcomes, such as obstructed labor or atonic hemorrhage [17].
The current analyses failed to present associations between maternal diabetes and weight gains. The major problem was that the current survey method did not distinguish pre-existing diabetes and gestational diabetes, and lacked information whether excess weight gains preceded the onset of gestational diabetes. Also, we could not rule out the possibility of weight gain restriction due to suppressed energy intake after the diagnosis of diabetes. Future surveys should collect the information regarding when diabetes was diagnosed, and how.
Although our study sample was from Japanese women who are generally shorter and lighter compared to women in other countries, the effect of “insufficient” or “excess” weight gains to pregnancy outcomes were similar to that of previous reports from other countries [18-20]. Our study provides additional evidence for providing weight gain recommendations for women with shorter stature. For example, the US guideline [1] recommends underweight women (BMI<18.5) to gain weight 12.5-18 kg, and normal weight (BMI: 18.5-24.9) to gain 11.5-16 kg for all women, regardless of their ethnicity or stature. The results of our study suggest that shorter women with Asian ethnicity should set their weight gain target closer to the lower limit of the US guideline.
Future studies should be conducted by prospectively, following weight gain patterns according to each trimester, and identifying when pregnancy complications develop. Until then, advising healthy non-obese women with a single fetus according to the current MHLW cutoffs may be most efficient in reducing PIH, LBW, macrosomia, LFD, and HFD cases. Setting a strict upper limits for weight gain, as in the JSSPH cutoff, may be unnecessary for these Asian non-obese women.

Acknowledgement

All authors contributed equally to this study. This study was supported by the 2012 Ministry of Health, Labour, and Welfare, Health and Labour Research Grant, Research on Children and Families (Grant No. H24-Jisedai-Ippan-004).

Disclosure

The authors declare no conflict of interest or financial relationship (within the past 12 months) with a biotechnology manufacturer, a pharmaceutical company, or other commercial entity that has an interest in the subject matter or materials discussed in the manuscript.

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