The association between second trimester ultrasound fetal biometrics and gestational diabetes.

OBJECTIVE: Gestational diabetes mellitus (GDM) is the most common metabolic complication of pregnancy. The incidence of GDM is increasing worldwide and 5-25% of pregnancies are diagnosed with GDM depending on screening strategies and diagnostic criteria. GDM may lead to obstetric complications and increases the risk of adult metabolic disease in the offspring. Timely identification of GDM allows for regulation of maternal glucose levels which may reduce the obstetric complications considerably. The aim of this study is to investigate the association between second trimester ultrasound biometrics and GDM. STUDY DESIGN: This is a retrospective cohort study including 2697 singleton pregnancies attending second trimester ultrasound scan at 20 + 0 to 20 + 6 weeks' gestation and giving birth at Aalborg University Hospital in the year 2020. Ultrasound measurements included head circumference (HC), abdominal circumference (AC), femur length (FL) and estimated fetal weight (EFW) by Hadlock's formula. Women with pregestational diabetes were excluded. GDM screening was performed on indication using oral-glucose-tolerance-test (OGTT) including 75 g glucose and a 2-hour serum glucose value ≥ 9 mmol/L was considered diagnostic. The association between fetal biometrics and GDM was investigated by logistic regression. RESULTS: A total of 174 (6.5 %) were diagnosed with GDM. The incidence of GDM in pregnancies with biometrics above the 90th centile was; FL: 10.5 %, HC: 8.8 %, AC: 7.6 %, EFW: 9.3 %. Fetal biometrics above the 90th centile was significantly associated with GDM; ORFL = 2.07, p = 0.001; ORHC = 1.89, p = 0.001; ORAC = 1.63, p = 0.033; OREFW = 1.64, p = 0.036. This association remained significant for HC and FL when adjusted for maternal obesity (Body Mass Index ≥ 27): ORHC(adj)=1.56, p = 0.019; ORFL(adj) = 1.57, p = 0.049. CONCLUSION: At the second trimester scan, fetal biometrics above the 90th centile increase the risk of GDM. In pregnancies that are later diagnosed with GDM fetal growth is increased already at the second trimester scan. Such knowledge underlines the importance of early identification of GDM.

Placental MRI: Longitudinal relaxation time (T1) in appropriate and small for gestational age pregnancies.

OBJECTIVE: The antenatal detection of small for gestational age (SGA) pregnancies is a challenge, which may be improved by placental MRI. The longitudinal relaxation time (T1) is a tissue constant related to tissue morphology and tissue oxygenation, thereby placental T1 may be related to placental function. The aim of this study is to investigate placental T1 in appropriate for gestational age (AGA) and SGA pregnancies. METHODS: A total of 132 singleton pregnancies were retrieved from our MRI research database. MRI and ultrasound estimated fetal weight (EFW) was performed at gestational week 20.6-41.7 in a 1.5 T system. SGA was defined as BW ≤ -15% of the expected for gestational age (≤10th centile). A subgroup of SGA pregnancies underwent postnatal placental histological examination (PHE) and abnormal PHE was defined as vascular malperfusion. The placental T1 values were converted into Z-scores adjusted for gestational age at MRI. The predictive performance of placental T1 and EFW was compared by receiver operating curves (ROC). RESULTS: In AGA pregnancies, placental T1 showed a negative linear correlation with gestational age (r = -0.36, p = 0.004) Placental T1 was significantly reduced in SGA pregnancies (mean Z-score = -0.34) when compared to AGA pregnancies, p = 0.03. Among SGA pregnancies placental T1 was not reduced in cases with abnormal PHE, p = 0.84. The predictive performance of EFW (AUC = 0.84, 95% CI, 0.77-0.91) was significantly stronger than placental T1 (AUC = 0.62, 95% CI, 0.52-0.72) (p = 0.002). DISCUSSION: A low placental T1 relaxation time is associated with SGA at birth. However, the predictive performance of placental T1 is not as strong as EFW.

Placental transverse relaxation time (T2) estimated by MRI: Normal values and the correlation with birthweight.

INTRODUCTION: Placental transverse relaxation time (T2) assessed by MRI may have the potential to improve the antenatal identification of small for gestational age. The aims of this study were to provide normal values of placental T2 in relation to gestational age at the time of MRI and to explore the correlation between placental T2 and birthweight. MATERIAL AND METHODS: A mixed cohort of 112 singleton pregnancies was retrieved from our placental MRI research database. MRI was performed at 23.6-41.3 weeks of gestation in a 1.5T system (TE (8): 50-440 ms, TR: 4000 ms). Normal pregnancies were defined by uncomplicated pregnancies with normal obstetric outcome and birthweight deviation within ±1 SD of the expected for gestational age. The correlation between placental T2 and birthweight was investigated using the following outcomes; small for gestational age (birthweight ≤-2 SD of the expected for gestational age) and birthweight deviation (birthweight Z-scores). RESULTS: In normal pregnancies (n = 27), placenta T2 showed a significant negative linear correlation with gestational age (r = -.91, P = .0001) being 184 ms ± 15.94 ms (mean ± SD) at 20 weeks of gestation and 89 ms ± 15.94 ms at 40 weeks of gestation. Placental T2 was significantly reduced among small-for-gestational-age pregnancies (mean Z-score -1.95, P < .001). Moreover, we found a significant positive correlation between placenta T2 deviation (Z-score) and birthweight deviation (Z-score) (R2  = .26, P = .0001). CONCLUSIONS: This study provides normal values of placental T2 to be used in future studies on placental MRI. Placental T2 is closely related to birthweight and may improve the antenatal identification of small-for-gestational-age pregnancies.