Perinatal Outcomes of Diet Therapy in Gestational Diabetes Mellitus Diagnosed before 24 Gestational Weeks.

To evaluate perinatal outcomes and risk factors for large for gestational age (LGA; birth weight over 90 percentile) in gestational diabetes diagnosed before 24 gestational weeks and treated with diet therapy alone until delivery (Diet Early gestational diabetes mellitus (Diet Early GDM)), we assessed the maternal characteristics and perinatal outcomes of patients with early GDM (n = 309) and normal glucose tolerance (NGT; n = 309) at Keio University Hospital. The gestational weight gain (GWG) expected at 40 weeks was significantly lower in the Diet Early GDM group than in the NGT group. The Diet Early GDM group exhibited a significantly lower incidence of low birth weight (<2500 g) and higher Apgar score at 5 min than the NGT group. Multiple logistic regression analysis revealed that the pre-pregnancy body mass index and GWG expected at 40 weeks were significantly associated with LGA for Diet Early GDM. No differences were observed in random plasma glucose levels in the first trimester, 75 g oral glucose tolerance test values, and initial increase or subsequent decrease between the two groups. Dietary early GDM did not exhibit a worse prognosis than NGT. To prevent LGA, it might be important to control maternal body weight not only during pregnancy but also before conception.

Use of the Japanese gestational diabetes mellitus diagnostic strategy during the COVID-19 pandemic in Japan: A questionnaire survey.

AIM: Some concerns exist that diagnosis of gestational diabetes mellitus (GDM) may be missed when the simplified diagnostic criteria of the Japanese Society of Diabetes and Pregnancy (JSDP) for GDM (published during the COVID-19 pandemic) are used. Moreover, limited data is available regarding how widespread these diagnostic criteria are used when managing GDM during the COVID-19 pandemic. Therefore, this study aimed to determine how GDM diagnosis has changed during the COVID-19 pandemic in Japan. METHODS: The changes in GDM diagnosis during the COVID-19 pandemic were investigated using an online questionnaire to 2159 obstetric facilities in Japan. The questionnaire collected data on facility type, awareness of Japanese GDM diagnostic strategies, modifications to diagnostic methods for early and late GDM, and opinions on GDM management, with the pandemic divided into seven periods. RESULTS: We received responses from 593 facilities (27%). Approximately 90% of the facilities did not change their diagnostic process for early GDM or late GDM (occurring after 24 weeks gestation). However, during the COVID-19 pandemic, 19 facilities discontinued the use of 75-g oral glucose tolerance tests before 24 weeks of gestation, and 17 facilities discontinued it after 24 weeks of gestation, instead using the aforementioned Japanese GDM diagnostic strategy. CONCLUSIONS: Although a limited number of facilities modified their diagnostic method in response to the COVID-19 pandemic, this study demonstrated that those that adjusted their diagnostic method primarily used the Japanese COVID-19 GDM strategy by the JSDP.

Association of maternal obesity with growth of fetal fractional limb volume.

BACKGROUND: Maternal obesity influences birth weight and newborn adiposity. Fetal fractional limb volume has recently been introduced as a useful parameter for the proxy of fetal adiposity. However, the association between maternal adiposity and the growth of fetal fractional limb volume has not been examined. AIMS: To investigate the association of maternal pre-pregnancy BMI with the growth of fetal fractional limb volume. STUDY DESIGN: Prospective cohort study. SUBJECTS: Women with singleton uncomplicated pregnancies enrolled between July 2017 and June 2020. OUTCOME MEASURES: Fetal fractional limb volume was assessed between 20 and 40 weeks' gestation, measured as cylindrical limb volume based on 50 % of the total diaphysis length. The measured fractional limb volume at each gestational week were converted to z-scores based on a previous report. The association between pre-pregnancy BMI and fetal fractional limb volume was examined. Maternal age, parity, gestational weight gain and fetal sex were considered as potential confounding variables. RESULTS: Ultrasound scans of 455 fractional arm volume and thigh volume were obtained. Fractional limb volume increased linearly until the second trimester of gestation, then increased exponentially in the third trimester. Maternal pre-pregnancy BMI was significantly correlated with z-scores of fractional arm volume and thigh volume across gestation. The post-hoc analysis showed the association between pre-pregnancy BMI and fractional arm volume was significant especially between 34 and 40 weeks. CONCLUSIONS: Maternal obesity influences the growth pattern of fetal fractional limb volume. Fractional arm volume may potentially provide a useful surrogate marker of fetal nutritional status in late gestation.

Pregnancy outcomes following radical trachelectomy for early-stage cervical cancer: A retrospective observational study in the Kanto area, Japan.

OBJECTIVE: The authors aimed to investigate the prevalence of pregnancy and obstetric outcomes in patients who underwent radical trachelectomy (RT) for early-stage cervical cancer in the Kanto area, Japan. METHOD: A survey among 113 perinatal centers affiliated with the Kanto Society of Obstetrics and Gynecology was conducted to investigate their experience in managing pregnancies following RT, between 2010 and 2020. The association between preterm delivery (before 34 gestational weeks) and a midtrimester short cervix (<13 mm) was evaluated. RESULTS: The authors retrospectively collected maternal and perinatal data from 13 hospitals. There were 135 pregnancies among 115 women following RT. Of the 135 pregnancies, 32 were miscarriages (<12 gestational weeks: n = 22; >12 gestational weeks: n = 10), and 103 were delivered after 22 gestational weeks. The incidences of preterm delivery before 28 and 34 gestational weeks were 8.7% and 30.1%, respectively. A midtrimester short residual cervix was associated with preterm delivery (P = 0.046). CONCLUSION: Since more than 100 pregnancies were recorded after RT in the Kanto area, many physicians had more opportunities to manage pregnancy after RT. Pregnancy following RT is associated with increased risk of preterm delivery, and midtrimester short residual cervix is a good predictor of preterm delivery.

Efficacy and safety of a telemedicine system in subjects with gestational diabetes mellitus (TELEGLAM): Study protocol for a randomized controlled trial.

Background: Strict glycemic control is important to prevent perinatal complications in patients with gestational diabetes mellitus (GDM). Patients often require insulin injection, and frequent hospital visits are necessary to adjust the dose of insulin, which is considered burdensome for pregnant patients. Telemedicine may reduce the burden of hospital visits, and previous studies have reported its safety in GDM patients. This study aimed to evaluate the efficacy of telemedicine in GDM patients, focusing on patient satisfaction and health economic indicators. Methods: This is a single-center, two-arm, randomized, open-label parallel-group study. Subjects will be selected from the patient population attending the Department of Endocrinology, Metabolism, and Nephrology, Keio University School of Medicine, Japan. Patients diagnosed with GDM by an oral glucose tolerance test (OGTT) by 29 weeks and 6 days of gestation who have undergone self-monitoring of blood glucose (SMBG) and insulin injection are eligible for inclusion. In the intervention group, telemedicine will be administered using the MeDaCa telemedicine system developed by the Medical Data Card, Inc., Tokyo, Japan. Subjects in the control group will be examined face-to-face every 2-3 weeks, as usual. We set health economic indicators and patient satisfaction as the primary endpoints, and will perform a cost-consequence analysis. Glycemic control indicators and perinatal outcomes will be evaluated as secondary endpoints. Conclusions: Eligible patients are currently being recruited. Recruitment will be completed when the expected number of patients are enrolled.

Factors associated with low birthweight among late preterm singletons in Japan using pregnancy birth registry data.

Late preterm (LP, born between 34 0/7 and 36 6/7 weeks of gestation) infants may experience several adverse outcomes, similar to those experienced by low birthweight (LBW, birthweight <2500 g) infants. However, while LP infants are often born with LBW, the association between LP and LBW remains unknown. This study aimed to investigate LBW rate and independent risk factors for LBW in LP singleton neonates. We retrospectively analyzed data of LP singleton neonates, born between 2013 and 2017, from the Japan Society of Obstetrics and Gynecology Successive Pregnancy Birth Registry System. The exclusion criteria included stillbirths and infants with missing data. Logistic regression analyses were performed to investigate maternal and perinatal factors associated with LBW in LP singletons. LBW was observed in 62.5% (n = 35,113) of 56,160 LP singleton births. In the multiple logistic regression analysis, LBW in LP neonates was independently associated with modifiable maternal factors, including pre-pregnancy underweight, inadequate gestational weight gain, and smoking during pregnancy, as well as non-modifiable factors, including younger maternal age, nulliparity, hypertensive disorder of pregnancy, preeclampsia, cesarean section delivery, and female offspring. According to the Japanese pregnancy birth registry data, more than half of LP neonates were LBW. We previously discussed the issue of LBW regarding infants with different backgrounds, as there are many different causes of LBW. Several risk factors should be subdivided and considered for the risk of LP and LBW.

A capture methyl-seq protocol with improved efficiency and cost-effectiveness using pre-pooling and enzymatic conversion.

OBJECTIVE: The opportunities for sequencing-based methylome analysis of clinical samples are increasing. To reduce its cost and the amount of genomic DNA required for library preparation, we aimed to establish a capture methyl-seq protocol, which adopts pre-pooling of multiple libraries before hybridization capture and TET2/APOBEC-mediated conversion of unmethylated cytosine to thymine. RESULTS: We compared a publicly available dataset generated by the standard Agilent protocol of SureSelect XT Human Methyl-Seq Kit and our dataset obtained by our modified protocol, EMCap, that adopted sample pre-pooling and enzymatic conversion. We confirmed that the quality of DNA methylation data was comparable between the two datasets. As our protocol, EMCap, is more cost-effective and reduces the amount of input genomic DNA, it would serve as a better choice for clinical methylome sequencing.

Genome-wide association study of preterm birth and gestational age in a Japanese population.

Preterm birth (PTB), defined as the birth of a baby at <37 weeks of gestation, is known to be the main cause of neonatal morbidity and mortality. Here, we report genetic associations between preterm birth and gestational age in a Japanese population. We conducted a genome-wide association study (GWAS) of 384 cases who delivered prematurely and 644 controls and considered gestational age as a quantitative trait in 1028 Japanese women. Unfortunately, we were unable to identify any significant variants associated with PTB or gestational age using the current sample. We also examined genetic associations previously reported in European populations and identified no associations, even with the genome-wide subthreshold (p value < 10-6). This data report aims to provide summary statistics of current GWASs on PTB in a Japanese population for future meta-analyses of genetics and PTB with larger sample sizes.

Ultrasonographic Prediction of Placental Invasion in Placenta Previa by Placenta Accreta Index.

This study aimed to investigate the diagnostic accuracy of the placenta accreta index (PAI) for predicting placenta accreta spectrum (PAS) in women with placenta previa. We analyzed 33 pregnancies with placenta previa at Keio University Hospital. The PAI was assessed in the early third trimester, and PAS was diagnosed histologically or clinically defined as retained placenta after manual removal attempts. The PAI and incidence of PAS were analyzed. Ten women (30%) were diagnosed with PAS and had higher volumes of perioperative bleeding (p = 0.016), higher rate of requiring uterine artery embolization (p = 0.005), and peripartum hysterectomy (p = 0.0002) than women without PAS. A PAI > 2 was the most useful cut-off point for predicting PAS and was more sensitive than prediction values using traditional evaluation (history of cesarean section and placental location). Post-hoc analysis revealed a higher rate of previous history of cesarean delivery (30% vs. 4.4%, p = 0.038), severe placental lacunae (≥grade2) (70% vs. 8.7%, p = 0.0003), thin myometrial thickness (90% vs. 22%, p = 0.0003), anterior placenta (100% vs. 30%, p = 0.0002), and presence of bridging vessels (30% vs. 0%, p = 0.0059) in PAS women. PAI could help predict the outcomes of women with placenta previa with and without a history of cesarean delivery to reduce PAS-induced perinatal complications.

Risk factors of neonatal hypoglycemia in neonates born to mothers with gestational diabetes.

Hypoglycemia is one of the most significant problems in neonates born to mothers with gestational diabetes (GDM). This study aimed to identify novel predictors of hypoglycemia in neonates born to mothers with GDM. A total of 443 term singleton infants from mothers diagnosed with GDM and cared for at Keio University Hospital between January 2013 and December 2019 were included in this study. Neonatal hypoglycemia was defined as hypoglycemia of less than 47 mg/dL at 1 or 2 or 4 h after birth, according to previous studies. Among 443 full-term singleton neonates born to mothers with GDM, 200 developed hypoglycemia (45%). Gestational weight gain (GWG), HbA1c at 1st trimester, HbA1c at GDM diagnosis, and the incidence of insulin therapy in the neonatal hypoglycemia group were significantly higher than those in the non-neonatal hypoglycemia group (p = 0.016, p = 0.032, p = 0.011, and p = 0.017, respectively). Regarding the multiple regression analysis adjusted for nulliparity, GWG, and gestational weeks at delivery, the odds ratio for maternal HbA1c ≥5.2% at 1st trimester was 1.63 (p = 0.034), and maternal insulin therapy during pregnancy was 1.72 (p = 0.015). In conclusion, HbA1c in the 1st trimester and insulin therapy during pregnancy were good predictors of hypoglycemia in neonates born to GDM mothers, especially when their HbA1c was 5.2% or more. Further research will be necessary to improve the perinatal management of hypoglycemia.

Obstetric outcomes after medroxyprogesterone acetate treatment for early stage endometrial cancer or atypical endometrial hyperplasia: a single hospital-based study.

BACKGROUND: To investigate perinatal outcomes in pregnancy after high-dose medroxyprogesterone acetate (MPA) therapy for early stage endometrial cancer (EC) and atypical endometrial hyperplasia (AEH) and to determine whether pregnancy after MPA therapy is at a higher risk of placenta accreta. METHODS: Data of 51 pregnancies in 46 women who received MPA therapy for EC or AEH and delivered after 22 weeks of gestation at Keio University Hospital were reviewed. A retrospective matched case-control study was performed to determine the risk of placenta accreta in pregnancy after MPA therapy compared with singleton pregnancies without any history of maternal malignancy treatments. RESULTS: The incidence of placenta accreta was higher in the MPA group than in the control group (15.7 vs. 0%, p = 0.0058). However, no differences in other perinatal outcomes were observed between groups. While gestational weeks at delivery in the MPA group were later than those in the control group (p = 0.0058), no difference in the incidence of preterm delivery was recorded between groups. In the MPA therapy group, the number of patients who underwent ≥ 6 dilation and curettage (D&C) was higher in the placenta accreta group than in the non-placenta accreta group (50.0 vs. 14.0%, p = 0.018). Patients with ≥ 6 D&Cs demonstrated a 6.0-fold increased risk of placenta accreta (p = 0.043, 95% CI 1.05-34.1) than those receiving ≤ 3 D&Cs. CONCLUSION: Pregnancy after MPA therapy is associated with a high risk of placenta accreta. In cases in which the frequency of D&C is high, placenta accreta should be considered.

The Associated Factors of Low Birthweight Among Term Singletons in Japan: A Pregnancy Birth Registry Analysis.

BACKGROUND: Progress in reducing the global low birthweight (LBW) has been insufficient. Although the focus has been on preventing preterm birth, evidence regarding LBW in term births is limited. Despite its low preterm birth prevalence, Japan has a higher LBW proportion than other developed countries. This study aimed to examine the prevalence of LBW in term singleton births and its associated factors using a national database. METHODS: We retrospectively analyzed the data of neonates registered in the Japan Society of Obstetrics and Gynecology Successive Pregnancy Birth Registry System who were born 2013-2017. Exclusion criteria included stillbirths, delivery after 42 gestational weeks, and missing data. Logistic regression analyses were performed to investigate the maternal and perinatal factors associated with LBW in term singletons using the data of 715,414 singleton neonates. RESULTS: The overall prevalence of LBW was 18.3%, and 35.7% of LBWs originated from singleton term pregnancies. Multiple logistic regression analyses indicated that both modifiable and non-modifiable factors were independently associated with LBW in term neonates. The modifiable maternal factors included pre-pregnancy underweight, inadequate gestational weight gain, and smoking during pregnancy, while the non-modifiable factors included younger maternal age, nulliparity, hypertensive disorders of pregnancy, cesarean section delivery, female offspring, and congenital anomalies. CONCLUSION: Using the Japanese pregnancy birth registry data, more than one-third of LBWs were found to originate from singleton term pregnancies. Both modifiable and non-modifiable factors were independently associated with LBW in term neonates. Prevention strategies on modifiable risk factor control will be effective in reducing LBW worldwide.

Prophylactic administration of human amniotic fluid stem cells suppresses inflammation-induced preterm birth via macrophage polarization.

Ascending inflammation from the vagina is a major cause of preterm birth. Currently, this condition-especially when uncontrolled-has no effective treatment. Human amniotic fluid stem cells (hAFSCs) are mesenchymal stem cells known to exert potent anti-inflammatory effects in animal models of perinatal diseases, such as periventricular leukomalacia, myelomeningocele, and neonatal sepsis. However, hAFSC therapy for inflammation-induced preterm birth has not been tested. In order to determine the therapeutic effect of hAFSC transplantation, we employed a preterm mouse model of ascending infection; this model was constructed by administering lipopolysaccharide to pregnant mice. We investigated the preterm birth rate and evaluated the inflammation of tissues, which is related to progressive infections, such as those involving the cervix, placenta, and lavage cells, using real-time qPCR. Further, we tracked the fluorescence of fluorescently labeled hAFSCs using an in vivo imaging system, and hAFSC aggregation was evaluated using immunohistochemistry analysis. We also investigated the presence of multiple types of peritoneal macrophages via flow cytometry analysis. Finally, we performed sphere culturing and co-culturing to determine the therapeutic effects of hAFSCs, such as their anti-inflammatory effects and their potential to alter macrophage polarization. We found that hAFSC administration to the peritoneal cavity significantly reduced inflammation-induced preterm birth in the mouse model. The treatment also significantly suppressed inflammation of the placenta and cervix. Transplanted hAFSCs may have aggregated with peritoneal macrophages, switching them from an inflammatory to an anti-inflammatory type. This property has been reported in vivo previously, but here, we examined the effect in vitro. Our findings support the hypothesis that hAFSCs suppress inflammation and reduce preterm birth by switching macrophage polarity. This study is the first to demonstrate that hAFSCs are effective in the treatment and prevention of inflammation-induced preterm birth.

Fetal growth restriction and a single umbilical artery are independent predictors of hypospadias during pregnancy.

INTRODUCTION: Little is known about the association between hypospadias and small fetuses, as well as the pathological implications of fetal growth restriction (FGR). Thus, we aimed to investigate the association between hypospadias and small fetuses using a database of fetal ultrasound and obstetric events. METHODS: A cohort of male singleton infants delivered after 22 weeks of gestation at Keio University Hospital between 2013 and 2019 was retrospectively reviewed. FGR was defined according to the Delphi criteria. Logistic regression analysis was performed to identify the significant predictors of hypospadias. Placental pathology was reviewed in cases with hypospadias. RESULTS: Of the 2,040 male infants included in the present study, 23 had hypospadias. The prevalences of a single umbilical artery (SUA), small for gestational age, maternal hypertensive disorders of pregnancy, and a small placenta, were significantly higher in infants with hypospadias. Multiple logistic regression analysis revealed that FGR (odds ratio [OR] = 9.39; 95% confidence interval [CI], 2.50-35.3) and the presence of a SUA (OR = 33.4; 95% CI, 8.00-139.5) were independently and significantly associated with hypospadias. When FGR was stratified by the time of onset, its association with hypospadias was significant regardless of the time of onset. Moreover, placental histological findings suggested that fetal vascular malperfusion might play a role in hypospadias. DISCUSSION: FGR and SUAs are independent prenatal predictors of the development of hypospadias, and fetal vascular malperfusion of the placenta may be involved in the etiology of hypospadias.

Human Amniotic Fluid Stem Cells Ameliorate Thioglycollate-Induced Peritonitis by Increasing Tregs in Mice.

Mesenchymal stem cells (MSCs) affect immune cells and exert anti-inflammatory effects. Human amniotic fluid stem cells (hAFSCs), a type of MSCs, have a high therapeutic effect in animal models of inflammation-related diseases. hAFSCs can be easily isolated and cultured from amniotic fluid, which is considered a medical waste. Hence, amniotic fluid can be a source of cells for MSC therapy of inflammatory diseases. However, the effect of hAFSCs on acquired immunity in vivo, especially on regulatory T cells, has not yet been fully elucidated. Therefore, in this study, we aimed to understand the effects of hAFSCs on acquired immunity, particularly on regulatory T cells. We showed that hAFSCs ameliorated the thioglycollate-induced inflammation by forming aggregates with host immune cells, such as macrophages, T cells, and B cells in the peritoneal cavity. Further, the regulatory T cells increased in the peritoneal cavity. These results indicated that, in addition to helping the innate immunity, hAFSCs could also aid the acquired immune system in vivo against inflammation-related diseases by increasing regulatory T cells.

Adenocarcinoma in situ or early-stage cervical cancer is a risk factor for preterm delivery after cervical conization: a multicenter observational study.

OBJECTIVE: Pregnancy after conization is associated with a high risk of preterm delivery. However, because risk factors for preterm delivery after conization remain unknown, we conducted a multicenter observational study to investigate risk factors associated with preterm delivery. METHODS: We selected patients who had previously undergone conization and reviewed medical records from 18 hospitals in cooperation with Keio University School of Medicine between January 2013 and December 2019. Women were classified as nulliparous and primiparous, and a multiple logistic regression analysis was performed to evaluate the relative contributions of the various maternal risk factors for preterm delivery (i.e. delivery before 37 gestational weeks). RESULTS: Among 409 pregnant women after conization, 68 women delivered preterm (17%). The incidence of nulliparity (p = .014) was higher and a history of preterm delivery (p = .0010) was more common in the preterm delivery group than in the term delivery group. Furthermore, the proportion of women diagnosed with adenocarcinoma in situ (AIS) and cervical cancer in the preterm delivery group was higher than that in the term delivery group (p = .0099 and .0004, respectively). In multiple regression models in nulliparous women, cervical cancer or AIS (Odds ratio [OR]: 4.16, 95% CI: 1.26-13.68, p = .019) and a short cervix in the second trimester (OR: 13.41, 95% CI: 3.88-46.42, p < .0001) increased the risk of preterm delivery. Furthermore, a history of preterm delivery (OR: 7.35, 95% CI: 1.55-34.86, p = .012), cervical cancer or AIS (OR: 5.07, 95% CI: 1.24-20.73, p = .024), and a short cervix in the second trimester (OR: 4.29, 95% CI: 1.11-16.62, p = .035) increased the risk of preterm delivery in the multiple regression models in primiparous women. CONCLUSION: Pregnant women who previously underwent conization are at risk for preterm delivery. The histological type of AIS and cervical cancer was evaluated as a risk factor for preterm delivery. KEY MESSAGESPrior preterm delivery, presence of a short cervix, and cervical cancer or AIS were predictors of preterm delivery after conization.The depth of conization in cervical cancer or AIS group was significantly larger than that in the CIN group.

DNA methylation analysis of cord blood samples in neonates born to gestational diabetes mothers diagnosed before 24 gestational weeks.

INTRODUCTION: Genome-wide methylation analyses of gestational diabetes mellitus (GDM) diagnosed after 24 gestational weeks (late GDM (L-GDM)) using cord blood have been reported. However, epigenetic changes in neonates born to mothers with GDM diagnosed before 24 gestational weeks (early GDM (E-GDM)) have not been reported. We investigated DNA methylation in neonates born to mothers with E-GDM using cord blood samples. RESEARCH DESIGN AND METHODS: Genome-wide DNA methylation analysis was performed using an Illumina EPIC array to compare methylation rates of 754 255 autosomal sites in cord blood samples from term neonates born to 162 mothers with GDM (E-GDM: n=84, L-GDM: n=78) and 60 normal glucose tolerance (normal OGTT) pregnancies. GDM was diagnosed based on Japan Society of Obstetrics and Gynecology criteria modified with International Association of Diabetes in Pregnancy Study Group criteria. In this study, all GDM mothers underwent dietary management, while self-monitoring of blood glucose and insulin administration was initiated when dietary modification did not achieve glycemic control. RESULTS: There were no significant differences in genome-wide DNA methylation of cord blood samples between the GDM (E-GDM and L-GDM) groups and normal OGTT group or between the E-GDM and normal OGTT groups, L-GDM and normal OGTT groups, and E-GDM and L-GDM groups. CONCLUSIONS: This is the first report to determine the DNA methylation patterns in neonates born to mothers with E-GDM. Neonates born to mothers with GDM, who were diagnosed based on Japan Society of Obstetrics and Gynecology criteria, may not differ in DNA methylation compared with those born to normal OGTT mothers.

Impaired early phase insulin secretion associated with gestational diabetes mellitus in underweight women.

BACKGROUND: No reports have focused on the clinical and metabolic characteristics of gestational diabetes (GDM) in underweight women. The aim of this study is to investigate the clinical and metabolic features of underweight GDM (pregravid BMI, <18.5 kg/m2: U-GDM). MATERIALS AND METHODS: Women diagnosed with GDM were categorized based on their pre-pregnancy BMI as either underweight (n = 49) or normal weight (pregravid BMI, 18.5-25.0 kg/m2: n = 271: N-GDM). During the study period, GDM was diagnosed using the International Association of Diabetes in Pregnancy Study Group criteria. Women with multi-fetal pregnancies, fetal congenital anomalies, overt diabetes in pregnancy, and pre-gestational diabetes mellitus were excluded. RESULTS: There were no notable differences in maternal age at delivery and the rate of nulliparous between the U-GDM and N-GDM groups. Regarding antepartum oral glucose tolerance test profiles, women with U-GDM exhibited significantly lower fasting plasma glucose (FPG) levels than those with N-GDM (p < .01). The Insulinogenic Index of women with U-GDM was significantly lower than that of women with N-GDM (p < .05). CONCLUSION: Impaired early phase insulin secretion was associated with GDM onset in underweight women.