In Italy, the screening and diagnosis of GDM follows the guidelines published in 2011 by the Istituto Superiore di Sanità (ISS) [3]. At the first visit during pregnancy, it is important to exclude the presence of “Overt diabetes” in all women. The criteria for the diagnosis of overt diabetes are either FPG ≥ 126 mg/dL, or random plasma glucose ≥ 200 mg/dL, or glycated hemoglobin (HbA1c) ≥ 6.5%. After that, according to the risk of GDM, an OGTT is prescribed at different gestational ages. In case of high risk (previous GDM, pre-pregnancy BMI ≥ 30 kg/m2, glucose value at first visit between 100–125 mg/dl) an OGTT is prescribed at 16–18 weeks; in case of medium risk (pre-pregnancy BMI ≥ 25 and < 30 kg/m2, age ≥ 35 years, previous macrosomia, positive family history of diabetes), an OGTT is prescribed at 24–28 weeks. Screening is not recommended for women at low risk of GDM (cases that do not fulfill any medium- or high- risk criteria). High risk women with a normal OGTT at 16–18 gestational weeks must repeat the OGTT at 24–28 gestational weeks. In response to the COVID-19 pandemic, there was need for substantial changes in the procedures for accessing healthcare. So, after a diagnosis of overt diabetes was excluded, when the OGTT could not be safely performed, the diagnosis of GDM was considered acceptable if FPG was ≥ 92 mg/dL. In order to consider the impaired FPG as an acceptable surrogate for the diagnosis of GDM, the FPG measurement should have been performed within the recommended time window for the risk level (high or medium risk) [3]. Although with limited numbers, our experience carried out in a single-centre trial demonstrated that performing GDM diagnosis with a single value of FPG might loose one third of cases of GDM. Also in The United Kingdom, the Royal College of Obstetricians and Gynaecologists (RCOG) published guidance relating GDM screening and diagnosis during the COVID 19 pandemic in March 2020 [9]. The guidance was similar to that proposed by the Italian Diabetologist Associations with the two-step testing approach, but different with the test used in UK recommended by The National Insitute for Health and Clinical Excellence (NICE). In particular, according to NICE, a 75 g oral glucose tolerance test (OGTT) should be offered at booking for women with previous GDM, whereas women with risk factors for GDM (body mass index above 30 kg/m2, previous macrosomic baby weighing 4.5 kg or more, previous gestational diabetes, first-degree relative with diabetes, an ethnicity with a high prevalence of diabetes) should be tested with a 75 g OGTT at 24–28 weeks and diagnosis is made when fasting glucose is ≥ 5.6 mmol/L (≥ 100 mg/dl) or 2-h post glucose ≥ 7.8 mmol/L (≥ 140 mg/dl) [10]. On the other hand, the RCOG recommended stopping the 2- hour OGTT during the Covid 19 pandemic and suggested a two-step approach. Indeed, patients with NICE risk factors for GDM were tested with HbA1c and random plasma glucose (RPG) at the first visit. In case RPG is ≥ 11.1 mmol/l (≥ 200 mg/dl) a diagnosis of type 2 diabetes is made. On the other hand, if a value of 41–47 mmol/l (5.9–6.5%) of HbA1c is present, a diagnosis of ‘pre-diabetes’ is made. Women with the previous cited values of RPG or Hb1Ac and a prior history of GDM should be managed as GDM. As a second step, the RCOG recommended testing at 28 weeks, and a diagnosis of GDM is made if any of the following criteria is satisfied: FPG ≥ 5.3 mmol/l (≥ 96 mg/dl) or HbA1c ≥ 39 mmol/mol (5.7%) or RPG ≥ 9 mmol/l (≥ 160 mg/dl) [9]. A retrospective study [11] performed in a single-centre evidenced that screening GDM with RCOG COVID 19 criteria failed to detect more than half cases who might be diagnosed with NICE recommendations, with a result worse than ours. According to these results, it is evident that something more should have been done during the pandemic period in order to diagnose GDM still taking into consideration the restrictions related to the pandemic. In particular, as also stated by RCOG it is evident that the OGTT cannot be safely replaced by any single test [9]. For this reason, all services should return to the previous strategies as soon as it is allowed by the local risks associated to the pandemic. Concerning the comparison between those women with GDM diagnosed with only IADPSG criteria and those diagnosed with only WHO’99 criteria, some considerations can be made. Indeed, the Atlantis Diabetes in Pregnancy Program conducted in Ireland revealed that the prevalence of GDM in a European population increased to 12.4% when using the IADPSG criteria as compared to 9.4% when using the WHO criteria. There were statistically significant adverse pregnancy outcomes in the IADPSG group as compared to the WHO group [11]. Also an Indian study demonstrated that the prevalence of GDM in the population studied was 26.7% higher by the IADPSG criteria compared to the WHO 1999 criteria and this was comparable with many other studies carried out all over the world [12,13,14]. Furthermore, a systematic review by Wendland et al. [15] showed that both the WHO and the IADPSG criteria had similar increase in adverse pregnancy outcomes in terms of large for gestational age babies, cesarean delivery, and pre-eclampsia. The weakness of this study is the limited number of women enrolled; however it’s of interest comparison of risk factors and clinical outcomes between the 2 groups. In particular, the number of overweight and obese women diagnosed with IADPSG criteria was significantly higher than the WHO’99 criteria, which seems to identify two different phenotypes in relation to anthropometric measures. This condition has probably a consequence on clininical outcomes; in particular, pre-term birth and hypertensive syndromes did not t reach a significant difference only for the limited number of women enrolled. It seems that WHO ‘99 group experienced the lowest rate of all clinical outcomes considered, even if it was nether monitored nor treated. Even if the limited sensitivity of WHO’99 criteria has been reported in a recent meta-analysis on screening and diagnosis of GDM in India,this country still uses these criteria [16]. In conclusion, it is not easy to establish advantages and disadvantages of the different diagnostic methods available for GDM, and this might be explained by the fact that despite almost 50 years of research, there is still no agreement on the optimal gestational diabetes screening. More research is needed in order to find the best diagnostic approach because also the OGTT is not always so accurate for GDM diagnosis due to its difficult reproducibility and correct execution (17). Moreover, a more accurate diagnostic approach based also on a complete evaluation of the risk factors associated with neonatal adverse outcomes may be useful.