Impact of dietary counseling on the perception of diet in patients with gestational diabetes mellitus

Abstract

Aims/introduction

Medical nutrition therapy is the cornerstone of gestational diabetes mellitus (GDM) treatment. Patients with GDM should receive dietary counseling regarding diet and exercise.

Materials and methods

To study patients’ perception level of diet and their level of understanding after dietary counseling, we analyzed 225 reports of dietary counseling of patients with GDM prepared by dieticians. We also assessed the patients’ level of understanding after dietary counseling by asking questions regarding the counseling content. The answers to the questions were aggregated, and substantially similar answers were grouped and categorized.

Results

The dieticians’ suggestions were well understood by the patients. Moreover, the patients also identified their previous incorrect eating habits, such as excessive carbohydrate restriction or inappropriate fruit intake. Although distributed frequent meals were recommended by the dieticians, few patients actually practiced this for various reasons. Some patients were apparently influenced by dietary information from the mass media.

Conclusion

Dietary counseling was regarded as helpful and acceptable to most patients with GDM in our hospital, and many suggestions were recognized as informative for modification of previous dietary habits. By providing the results of the questionnaire survey to the dieticians, they can improve the quality of their counseling, which is expected to result in better individual care of the patients.

Introduction

Gestational diabetes mellitus (GDM), characterized by glucose intolerance, is a common perinatal complication that develops during pregnancy [1–3]. The American Diabetes Association (ADA) defines GDM as “diabetes diagnosed in the second or third trimester of pregnancy that was not clearly overt diabetes prior to gestation” [4]. The evidence provided by the HAPO study [5] formed the basis of the recent International Association of Diabetes and Pregnancy Study Groups criteria for the screening and diagnosis of GDM [6, 7]. However, not all experts accept these criteria to diagnose GDM, and the estimated incidence of GDM may vary depending on the diagnostic criteria used, the population, and the source of the data [1, 2, 4]. Therefore, the exact prevalence of GDM is unknown [1, 8]. However, in the past few decades, its prevalence has shown an apparent increase across different ethnic groups and is expected to grow together with the increase in the prevalence of obesity as well as that in the mean maternal age [9–12].

GDM has a considerable negative impact on the health outcomes of mother and fetus during pregnancy. Women with GDM are at an increased risk of spontaneous abortion, preeclampsia, and cesarean section, whereas babies are also at risk of fetal anomalies, macrosomia, fetal demise, neonatal hyperbilirubinemia, and neonatal hypoglycemia; GDM may also increase the risk of obesity and type 2 diabetes in the fetuses later in their lives [5, 13–16]. Women with GDM are at a higher risk for the development of impaired glucose tolerance (IGT) and cardiovascular diseases than women without GDM; moreover, they have a seven-fold higher risk of developing type 2 diabetes within 5 to 10 years [17–20].

First-line treatment for most women diagnosed with GDM is a change in lifestyle including dietary advice (medical nutrition therapy: MNT), physical activity, education, and self-monitoring of blood glucose (SMBG) [1, 13, 21]. If glycemic targets cannot be achieved with diet and lifestyle changes, pharmacologic therapy may be started. Although evidence of the ideal nutritional prescriptions for women with GDM is still lacking [1, 22, 23], the importance of dietary therapy in GDM is well established [9]. Therefore, an individualized nutrition plan developed by a discussion between the woman and a registered dietitian familiar with the management of GDM is particularly important [13, 24, 25]. Adequate MNT should promote the intake of high-quality ingredients, appropriate gestational weight gain, normoglycemia, the absence of ketosis, and adequate fetal growth [13, 26, 27]. Despite the importance of MNT, the degree of intellectually-acquired dietary knowledge and level of adherence vary in patients with GDM. Furthermore, with the development of advanced communication methods and mass media, patients with GDM can acquire more information than ever and be easily influenced by this information. However, the available information differs substantially in quality and is sometimes misleading or even harmful to the health of women with GDM. Therefore, understanding the real-world perception of patients with GDM regarding diet is important and may contribute to better MNT in this population.

Our hospital, Sanno Hospital, is a private hospital with multiple medical departments and specializes in infertility treatment and pregnancy care. Including those in Sanno birth center, the facility specialized in delivery, the hospital annually treats an average of 1218 pregnant women. Therefore, we encounter patients with GDM on a daily basis. In this study, patients diagnosed with GDM were recommended to receive dietary counseling and initiate SMBG. To promote effective and feasible MNT, medical staff should be able to provide appropriate knowledge concerning diet to patients and ensure that the patients correctly understand the suggestions of the dietician. Therefore, we investigated the knowledge and understanding of patients with GDM regarding diet before and after dietary counseling in clinical settings.

Materials and methods

Screening for GDM

We screened pregnant women for GDM and “overt diabetes in pregnancy” by a two-step approach. The screening test was considered positive if a random blood glucose level at an early stage of pregnancy (12–15 gestational weeks) was high (cutoff value ≥ 100 mg/dL); urine had glucose at any stage of pregnancy; and a 50-g glucose challenge test performed between gestational weeks 24 and 28 was positive (cutoff value ≥ 140 mg/dL). Moreover, subjects with high-risk factors for GDM such as the family history of type 2 diabetes, history of GDM, and obesity were considered positive. Then, we performed a 75-g oral glucose tolerance test (OGTT) in subjects with positive screening test results, except those diagnosed with “overt diabetes in pregnancy.” According to the criteria of International Association of Diabetes and Pregnancy Study Groups [7], if one or more values of glucose reach or exceed the following thresholds in a 75-g OGTT, subjects are diagnosed with GDM: 92 mg/dL (5.1 mmol/L) for fasting plasma glucose (FPG); 180 mg/dL (10.0 mmol/L) for 1-h plasma glucose (1-h PG); and 153 mg/dL (8.5 mmol/L) for 2-h PG. Moreover, if any of the following criteria are fulfilled, a pregnant woman is diagnosed with “overt diabetes in pregnancy” [28]: (1) FPG ≥ 126 mg/dL, (2) HbA1c ≥ 6.5%, (3) definite diabetic retinopathy, (4) random blood glucose ≥ 200 mg/dL beside having any of (1)–(3), or 2-h PG ≥ 200 mg/dL with any of (1)–(3).

Subjects

Attending doctors (diabetologists) explained the results of 75-g OGTT to all pregnant women who took the test. Those who were diagnosed with GDM were advised to receive dietary counseling from registered dieticians and were recommended to initiate SMBG. The individual information of women diagnosed with/without GDM such as age, gestational week in which they underwent 75-g OGTT, parity, the results of 50-g glucose challenge test, HbA1c levels, Hb levels, medical family history of diabetes, height, bodyweight before pregnancy, current body weight, and whether they received infertility treatment was acquired from the chart records.

Dietary counseling

Patients diagnosed with GDM were asked to record in as much detail as possible all foods and beverages consumed and to complete 3-day food diaries. Three registered dieticians in our hospital provided 1-h dietary counseling, once or more if necessary, based on the food diaries. Briefly, the dieticians checked and evaluated the contents of the food diaries of individual patients and gave them suggestions about an appropriate diet. They also gave suggestions regarding exercise, provided that the patients were not prohibited to do so by the obstetricians. The reports of individual dietary counseling were kept on an electrical medical chart in our hospital. The contents of these reports were analyzed, and points for which the dieticians counseled the patients with GDM were extracted and categorized into groups. After the dietary counseling, doctors in charge of the patients asked them the following questions during the outpatient clinic: (1) Did you find the dietary counseling helpful? If not, why? (2) What, if anything, did you learn through the dietary counseling? (3) Is there anything that the dietician recommended that you had already done before the counseling? (4) Were there any incorrect dietary habit you might have had before the counseling? And what were they? (5) Have you tried eating more meals of smaller portions (distributed frequent meals)? If not, please explain why. The answers for these questions, kept on an electrical medical chart, were aggregated, and substantially similar answers were grouped and categorized. The protocol for this research project was approved by a suitably constituted Ethics Committee of Sanno Hospital (approval No. 17-S-19, approval date; Feb 17, 2018), and it conforms to the provisions of the Declaration of Helsinki. Informed consent was obtained from all subjects.

Results

During April 2016 to February 2020, the Department of Obstetrics and Gynecology and Birth Center at Sanno hospital handled 4770 deliveries and 1299 pregnant women were suspected of having GDM. Of these, 1164 showed positive for the 50-g glucose challenge test, 74 showed high glucose levels at an early stage of pregnancy (12–15 gestational weeks), 43 had glucose in urine, and 18 women exhibited high-risk factors for GDM. Six women did not take 75-g OGTT owing to the following reasons: rejection to participate, transfer to a different hospital. The remaining 1293 women took 75-g OGTT, of which 423 were diagnosed with GDM (characteristics of these patients are shown in Table 1). Among them, 77 women received dietary counseling from their doctors in charge (diabetologists); 18 did not receive dietary counseling either from the dieticians or doctors because they had received it before (in their previous pregnancies with a history of GDM) or they thought that they already had enough knowledge about diet; 7 were exempted from dietary counseling because they or their family members were dieticians or diabetologists; and 1 patient was transferred to another hospital before dietary counseling. The remaining 320 women with GDM received dietary counseling from the dieticians, and we could ask 225 of these patients the questions and analyze the answers.

Table 1.

Basic characteristics of patients with GDM

Variables	Mean ± SD or N (%)
Maternal age (years)	36.33 ± 4.41
Gestational age at diagnosis (weeks)	27.09 ± 3.84
Height (cm)	159.29 ± 5.49
Pre-gestational body weight (kg)	52.68 ± 8.30
Body weight at diagnosis (kg)	58.86 ± 9.12
Family history of diabetes
Positive	124 (29.3)
Negative	140 (33.1)
Not sure	159 (37.6)
Parity	0.50 ± 0.67
Positive medical history of infertility treatment	163 (38.5)
50-g OGTT (mg/dl)
1 h	162.44 ± 18.27
75-g OGTT (mg/dl)
Fasting	85.16 ± 8.31
1 h	174.50 ± 25.66
2 h	151.88 ± 26.05
Number of abnormal points of 75-g OGTT
1 point	284 (67.1)
2 points	121 (28.6)
3 points	18 (4.3)

Measurements for every variable could not be obtained for all patients

N sample size, OGTT oral glucose tolerance test

Table 2 shows the issues that the dieticians explained to the patients. Besides diet, the dieticians also emphasized the importance of exercise, liquid intake, and salt restriction. For question 1, the results showed that 211 patients (93.8%) said that dietary counseling was helpful (answered “yes”), whereas 14 patients (6.2%) were not satisfied (they answered “not so helpful”). The representative reasons for answering “not so helpful” were “I already know much about proper diet,” “This was nothing new to me,” or “I am myself a dietician.” Similar answers to question 2 were grouped and are shown in Table 3. The grouped answer “(I learned) what are carbohydrates and how much can be ingested” indicated that the patients realized that the foods they thought were vegetables (e.g., lotus root, pumpkin, edible root, potato, yam, or corn) are actually classified as carbohydrates. Answers “I used to eat too much fruits” (40 patients), “I used to eat too much dry fruits” (6 patients), and “I should have eaten more fruits” (4 patients) were grouped as “Appropriate fruit intake.” The answers “I used to eat too much fish and meat,” “I used to eat too much dairy products because I thought they are healthy,” and “I didn’t think soybean products are classified as protein” were grouped as “Appropriate protein ingestion.” The representative answers to question 3 are summarized in Table 4. Sufficient intake of liquids and of vegetables were the most common items that patients kept in mind and already practiced. Table 5 shows the representative answers to question 4. Answers such as “I thought rice is better than bread or pasta,” “Edible roots or gelatin noodles look healthy so I thought I should eat a lot,” “I believed that I can eat anything during pregnancy,” “My mother-in-law persuaded me to eat a lot for my baby, and I also believed it,” or “I tried to eat a lot, although I didn’t feel like eating so much” were grouped as “My knowledge about actual nutrition was incorrect.” For question 5, 36 patients (16.0%) said that they tried divided meals (answered “yes”), 178 patients (79.1%) said that they did not try taking divided meals (answered “no”), and 11 patients (4.9%) said that they did not try taking divided frequent meals all the time, but only “sometimes.” The reasons for not trying to eat distributed frequent meals were grouped and are shown in Table 6. The most frequent reason for the difficulty in trying distributed frequent meals was that the patients were working outside.

Table 2.

Top 15 issues that the dieticians explained to patients with GDM

Topics	N (%)
Importance of exercise, ideally after the meal	211 (93.8)
Necessity of sufficient fluid intake	177 (78.7)
Necessity of sufficient vegetable ingestion	161 (71.6)
Salt restriction, if it’s necessary	112 (49.8)
Snacks can be consumed but content and timing should be considered	107 (47.6)
How to eat a well-balanced diet. Combination of food materials is important	59 (26.2)
Explain about frequent distributed meals	57 (25.3)
What are carbohydrates and how much can be ingested	53 (23.6)
Appropriate fruit intake	47 (20.9)
Chew well while eating	43 (19.1)
Extreme restriction of carbohydrate should be avoided	31 (13.8)
There is no serious problem so far. Keep your present diet habit	28 (12.4)
Appropriate protein ingestion. Be careful about content and amount of protein intake	18 (8.0)
Be careful about the timing of meals. Dinner time should not be too late	13 (5.8)
Avoid sweet beverages such as juice	6 (2.7)

The numbers in the right column indicate the numbers and percentages of the individual points described in the reports of dietary counseling by the dieticians. Multiple answers were allowed

Table 3.

Top 15 answers of patients with GDM to question 2 “What, if anything, did you learn through the dietary counseling?”

Answers	N (%)
Importance of exercise, ideally after a meal	200 (88.9)
Necessity of sufficient fluid intake	174 (77.3)
Necessity of sufficient vegetable ingestion	158 (70.2)
What are carbohydrates and how much can be ingested	108 (48.0)
How to eat a well-balanced diet. Combination of food materials is important	84 (37.3)
Salt restriction, if it’s necessary	62 (27.6)
Be conscious of the order of meal consumption	59 (26.2)
Appropriate fruit intake	50 (22.2)
Snacks can be consumed but content and timing should be considered	37 (16.4)
Extreme restriction of carbohydrates should be avoided	34 (15.1)
Appropriate protein ingestion	19 (8.4)
What are oily foods. Not to ingest too much fat	15 (6.7)
Be careful about timing of meals. Dinner time should not be too late	11 (4.9)
I already know much about proper diet but after dietary counseling, I could rearrange my knowledge	7 (3.1)
I used to eat only twice a day. I have to eat at least three times a day	7 (3.1)

The numbers in the right column indicate the numbers and percentages of the individual answers of patients. Multiple answers were allowed

Table 4.

Top 5 answers of patients with GDM to question 3 “Is there anything that the dietician recommended that you had already done before the counseling?”

Answers	N (%)
Sufficient liquid intake	48 (21.3)
Eat sufficient amount of vegetable	38 (16.9)
Proper exercise	12 (5.3)
I’ve been already doing everything that I was recommended at the counseling	5 (2.2)
Reduce salt intake	2 (0.9)

The numbers in the right column indicate the numbers and percentages of the individual answers of patients. Multiple answers were allowed

Table 5.

Top 15 answers of patients with GDM to question 4 “Were there any incorrect dietary habit you might have had before the counseling? And what were they?”

Answers	N (%)
Excessive fruits and dry fruits intake. I like them and I used to believe that they are good for health	80 (35.6)
Lack of exercise	50 (22.2)
After I got pregnant, I started craving sweets and used to eat too much	36 (16.0)
I didn’t have enough knowledge about carbohydrates and often ate too much of them	32 (14.2)
I extremely restricted my carbohydrate intake. I should have taken carbohydrates properly	29 (12.9)
I often dine out and eat meals sold at a convenience store	25 (11.1)
Lack of liquid intake	24 (10.7)
I should have been careful about snacks. I used to eat too much and too often	22 (9.8)
Lack of vegetable ingestion	21 (9.3)
My knowledge about actual nutrition was incorrect	16 (7.1)
I should have been careful about sweet beverages. I used to drink too much and too often	15 (6.7)
Excessive protein intake. Because I believed soybean products are good for health, I used to eat too much	15 (6.7)
I sometimes eat only 1 or 2 meals per day	15 (6.7)
I always eat quickly	14 (6.2)
My meal time is irregular. Dinner time tends to be late	13 (5.8)

The numbers in the right column indicate the numbers and percentages of the individual answers of patients. Multiple answers were allowed

Table 6.

Top 10 answers of patients with GDM to the question “Please explain why you have not tried distributed meals?”

Answers	N (%)
I am still working and it is difficult to do so during the working hours	56 (31.5)
Because, so far, my glycemic control is good. I will try distributed meals if my glycemic control gets worse	53 (29.8)
No special reason for not trying it. Simply because I didn’t think about it	33 (18.5)
Nobody explained to me about distributed meals	12 (6.7)
I tend to skip breakfast. I have to eat three meals regularly before I try distributed meals	10 (5.6)
I have to take care of other children and don’t have time to eat frequently	6 (3.4)
Basically, I am a small eater. I can’t divide my meal more than what I eat now	6 (3.4)
I don’t feel hungry. Once I eat something, I feel full and don’t feel like eating something anymore	3 (1.7)
It’s too much trouble to prepare frequent distributed meals	2 (1.1)
I eat snacks frequently. I have to quit eating snacks before I try distributed meals	2 (1.1)

The numbers in the right column indicate the numbers and percentages of the individual answers of patients who had not tried distributed meals. Multiple answers were allowed

Discussion

To achieve appropriate glycemic control and reduce the risk of the perinatal complications in patients with GDM, dietary counseling is especially important. Glycemic control can be confirmed by SMBG and, among 225 subjects, 181 patients (80.4%) continued SMBG during pregnancy. At each patient visit, we checked SMBG results and discussed the relationship between the actual glucose levels and dietary pattern. In addition, when SMBG results were unsatisfactory, the patients recalled the dietician’s advice and attempted to correct their dietary habits voluntarily.

In this study, patients well understood and remembered the information communicated and emphasized by the dieticians. The top three points for which counseling was provided by the dieticians, as indicated in their counseling report (Table 2), aligned with the top three answers of the patients, in response to questions concerning their learning during the counseling (Table 3). The only point that patients did not remember well was “Salt restriction, if necessary.” Although the dieticians indicated in 49.8% of the counseling reports that they actually explained it, only 27.6% patients responded that they had heard about it. Excessive salt consumption is a well-known factor in hypertension. To prevent pregnancy-induced hypertension, the Japan Society for the Study of Hypertension in Pregnancy recommends a salt intake of less than 10 g per day [29]. Despite the importance of adequate salt intake during pregnancy, the reason why few patients remembered the recommendation is unclear. We speculate that because salt is not directly related to glycemic control and has no risk of exacerbating GDM, the patients may have given the recommendation less weight.

Carbohydrates (CHOs) are the most important nutrient that affects glucose levels after meals. In this study, before the dietary counseling, 14.2% patients were uncertain about the foods classified as CHO and ate too much CHO, whereas 12.9% patients said that their CHO intakes were extremely limited (Table 5). CHO-restricted diets or low-CHO diets (LCDs), defined as CHO intake providing < 35–45% of the total daily energy intake or < 130 g CHO per day for a non-pregnant woman [26, 30, 31], remain popular for weight loss [32, 33] and the improvement of glycemic control [26]. However, the long-term safety and efficacy of these diets is still a matter of debate and concern [32–34]. Moreover, the association between adherence to LCDs and type 2 diabetes [32, 35, 36] or cardiovascular disease [32, 37, 38] remains controversial. Complete avoidance of CHO is discouraged because CHO are an important dietary source of energy, vitamins, minerals, and fiber content [39]. Complex CHOs, such as whole grains [40], contain high amounts of dietary fiber. A higher intake of total dietary fiber or whole grains are associated with a reduced risk of some non-communicable diseases (NCDs) [41]. For adults, the daily intake of total dietary fiber should be no less than 25–29 g; daily amounts greater than 30 g may provide additional benefits [41]. However, LCDs are typically low in fiber [42], which may contribute to various NCDs [41]. Also insufficient fiber intake may exacerbate constipation in pregnancy [26]. Despite these concerns, 12.9% of the patients tried LCDs to lower postprandial glycemic levels in the present study. Although there is no concrete evidence, the recommended optimal proportion of CHO in the diet of women with overt diabetes or GDM ranges from 40–45% of energy intake to 60% [27]. Compared with a high-CHO diet (55% CHO), a diet with a CHO content of 40% did not reduce the need for insulin treatment in women with GDM in a previous study [43]. In addition, over-restriction of CHO was reported to increase the risk of fetal macrosomia [44]. Therefore, moderate CHO intake, as opposed to complete avoidance or heavy restriction of CHO, is usually recommended to achieve postprandial euglycemia [44]. To fulfill energy requirements, LCDs tend to have a higher content of saturated fats and proteins from animal sources [32, 42, 45]. Pre-pregnancy consumption of LCDs with high protein and fat from animal food sources has a positive association with GDM risk; however, LCDs with vegetable food sources did not show an association with GDM risk [32, 46]. Similarly, among women with a history of GDM, the intake of LCDs containing plant-based protein and fat content showed no significant association with the risk of developing type 2 diabetes, whereas the intake of LCDs containing protein and fat content from animal sources was associated with a higher risk of developing type 2 diabetes. We suggest that patients with GDM should avoid extreme restriction of CHO. Instead, they should consider consuming proteins and fats from vegetables rather than animal sources [32].

As shown in Table 5, 35.6% patients acknowledged excessive fruit consumption. After dietary counseling, 22.2% patients could understand the appropriate amount of fruit intake (Table 3). Most of the patients who acknowledged excessive fruit intake consumed fruits because of their palatability, especially during the period of morning sickness, or because they believed that fruits were health promoting and had cosmetic effects. Fruits have relatively low energy density and low glycemic load, besides having high antioxidant and fiber content [47–49]. In addition, fruits are rich in numerous bioactive components, including minerals, vitamins, carotenoids, floats, flavonoids, and polyphenol, which have been suggested to alleviate oxidative stress and improve insulin sensitivity and/or pancreatic β-cell function [50, 51]. However, some types of fruits contain relatively high amounts of sugars, such as fructose, which may impair pancreatic β-cell function in humans [50–52]. Regarding the relationship between fruit consumption and type 2 diabetes risk, epidemiological studies have reported mixed results [47, 53–56]. The overall health effect of fruits is likely the result of many bioactive compounds and probably dependent on the individual’s baseline consumption level [50]. The glycemic index and polyphenol content substantially differ between types of fruits [47, 57]. A previous study suggested that the excessive consumption of fruits during the second trimester of pregnancy, especially moderate- and high-glycemic index fruits, such as citrus fruit and tropical fruit, increases the occurrence of GDM [47].

Pregnant women often experience abdominal distension and difficulty in eating. Distributed meals, i.e., frequent food intake with small portions, may alleviate abdominal discomfort and still provide sufficient total calories. Therefore, distributed meals can provide benefit to pregnant women with/without GDM. To the best of our knowledge, there have been no trials investigating this intervention in GDM [22, 39]. However, the majority of the guidelines recommend the distribution of CHO into three small-to-moderate-sized meals and 2–4 snacks (one in the evening after dinner) [22, 27, 58–60] to reduce postprandial hyperglycemia [1]. Previous studies have reported the efficacy of distributed frequent meals using continuous glucose monitoring [61, 62]. A CHO-controlled diet, evenly distributed meals throughout the day with adequate nutrition, good glycemic control, and avoiding ketonuria are thought to be beneficial to reduce complications associated with GDM [21, 63]. Despite these favorable effects, only 16.0% patients took distributed meals owing to various reasons as shown in Table 6. The most common reason for not taking distributed meals was that the patients were working. According to the Japanese Environment and Children’s Study [64], 52.8% of pregnant women worked during their second trimester. Our results reflect the impact of this social working condition.

At the time of dietary counseling, the dieticians also explained the potential benefits of physical activity and recommended patients with GDM to do post-prandial exercise if it was not forbidden by their obstetrician owing to certain medical complications or contraindications [65, 66]. The dieticians recommended exercise to 93.8% patients (Table 2); 88.9% patients understood and remembered the recommendation (Table 3). Physical activities improve insulin resistance and limit gestational weight gain by increasing energy expenditure [20, 65] and may prevent, reduce or delay the need for insulin in GDM [6, 67–70]. Most guidelines regarding exercise during pregnancy support moderate-intensity exercise three or more times per week [65, 66, 68].

Some answers of the patients (as shown in Table 5) showed that they used and believed information from the mass media, social networking sites or friends. According to a study that surveyed the association between people’s health literacy and sources of health information, healthcare professionals were the most consulted and trusted source of health information; however, people with lower health literacy tended to use and trust health information from social media and blogs or celebrity web pages, which may contain misleading and less accurate information [71]. Some other studies also reported that low health literacy was associated with a lower rate of consultation with doctors/healthcare providers, books, newspapers, and magazines for obtaining health information than with television and radio [72–76]. Thus, we recommend that the sources from which patients acquire health information be identified and the knowledge of patients corrected, if necessary.

For women with pre-existing type 1 or type 2 diabetes, multidisciplinary team care, both prior to conception and during pregnancy, has been shown to minimize maternal and fetal risks, and the multidisciplinary team should be involved in the GDM management as well [59]. After the questionnaire survey, the doctors provided some feedback to the dieticians regarding the patients who required special attention, and the doctors and dieticians shared the dietary information in a timely manner by direct discussion, when necessary. With this strategy, we believe that the dietician can verify the effects and issues to be considered with counseling. We hope that this process will lead to an improvement in the quality of counseling and eventually contribute to the better individual care of patients with GDM.

Our study had some limitations. First, self-reported dietary intake is known to be subject to measurement error [9], and dietary under-reporting is a common problem, especially in women [77–79]. Therefore, it is possible that the patients did not correctly complete their food diaries, which could have affected the accuracy of the study. Food frequency questionnaire (FFQ) is considered to be a better method to capture dietary patterns than 24-h recalls [80]; therefore, we should have considered the use of FFQs instead of asking the patient to keep 3-day diaries. Second, because this survey was carried out at a single medical institute, the sample size was small and the results of the survey may not be generalized. The subjects were limited to the patients of our hospital who may have special characteristics such as living or working in urban cities close to our hospital, in a developed area of Tokyo. Moreover, the average delivery age of the subjects was higher than the national average because of deliveries after long-term infertility treatments, which 38.5% of the patients with GDM in our hospital had received (shown in Table 1). Therefore, the results of the present study may not be applicable to the general population. Finally, although the content and guiding principles of dietary counseling were standardized among the dieticians in our hospital, the counseling methods and content were not exactly the same, and this may affect the quality and uniformity of the counseling.

In conclusion, dietary counseling was regarded as helpful and acceptable by most patients with GDM in our hospital. Some suggestions given by the dieticians were already practiced by some patients before counseling, but many suggestions were recognized as newly provided and informative which helped patients modify their previous dietary habits. Frequent distributed meals were not taken sufficiently owing to various reasons. As dietary information from the mass media seemed to influence some of our patients with GDM, we should identify the content and sources of information so as to provide them with appropriate information regarding diet, if necessary. By providing the results of the questionnaire survey to the dieticians, they can improve the quality of their counseling, which in turn is expected to increase the contribution to the patients. Further research with a larger number of subjects from multiple medical facilities is required to confirm our findings.

Author contributions

All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by Miyako Kishimoto. The first draft of the manuscript was written by Miyako Kishimoto, and all authors commented on previous versions of the manuscript. All authors have read and approved the final manuscript.

Compliance with ethical standards

Disclosure

The authors MK, RK, and YO declare that they have no conflict of interest in this work.

Ethical approval

All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and/or with the Helsinki Declaration of 1964 and later versions.

Informed consent

Informed consent or substitute for it was obtained from all patients for being included in the study.