Gestational diabetes; Vaccine exposure during pregnancy; Elevated early 1 hour glucose test; This is a serious observational study case, initially received other health professional on 31-Oct-2018, concerning a 38-year-old, adult, pregnant female subject enrolled in a prospective observational safety study on pregnancy outcomes in women immunized with Afluria QIV, a seasonal quadrivalent vaccine, during pregnancy.  The subject did not have any history of offspring with major congenital malformation. Also, the subject had no maternal or paternal history with major congenital malformations. The subject did not have prior history of use of tobacco, alcohol or illicit drugs during pregnancy. The subject's risk factor included advanced maternal age.  The subject's last menstrual period (LMP) date was 08-Apr-2018. The subject had singleton type of pregnancy.    On 01-Jun-2018 and 25-Jun-2018, ultrasound examinations were performed, and no congenital malformation was noted. On 16-Jul-2018, Materni-T 21 genetic test and nuchal translucency test were performed, and no congenital malformation was noted.  On 09-Oct-2018, at approximately 26 weeks of gestational age, the pregnant subject was administered Flu Vaccine Egg Split QIV CSL (influenza vaccine, batch number: YF40208, dose, route of administration, expiry date and anatomical location: not reported) (explicitly coded as vaccine exposure during pregnancy) for an unknown indication.  On an unspecified date in 2018, early 1-hour glucose test was performed which revealed elevated values. It was reported that no known risk factors were identified pertaining to elevated 1-hour glucose test. On 29-Oct-2018, at gestational age of 27 weeks, the subject failed 3-hour glucose test and was diagnosed with gestational diabetes that was controlled with diet.   The outcome of the event gestational diabetes was not reported.  On 15-Jan-2019, at 39 weeks gestation, the subject delivered a normal live birth to a male neonate by caesarean method. The characteristics of the neonate included birth weight: 3670 grams and APGAR (appearance, pulse, grimace, activity, and respiration) scores were 8 at one minute and 9 at five minutes. No major congenital malformations (MCMs) were identified at birth. The subject's pregnancy complication included large for gestational age.   The subject's estimated date of delivery was reported as 22-Jan-2018.  This case is linked to the case 201903005 (baby case).   Follow up received from the investigator on 10-Apr-2019: The pregnancy outcome details (gestational age at pregnancy outcome: 39 weeks, delivery type: caesarean, birth type: live birth, foetal outcome: normal, and neonatal characteristics included gender: male and birth weight: 3670 grams, APGAR scores were 8 at one minute and 9 at five minutes). No major congenital malformations (MCMs) were identified at birth.  The subject's pregnancy complication included large for gestational age. The linking sentence was added in the narrative. The narrative was amended accordingly.  Follow up received from investigator on 02-May-2019: Added reporter's details in the general tab. Added Gestational diabetes' as a risk factor in patient tab. The narrative was amended accordingly.  Non-significant follow up received from investigator on 02-May-2019: The Gestational diabetes' was changed from risk factor' to current condition'. The narrative was amended accordingly.  Follow up received from other health professional on 30-May-2019: The event 'gestational diabetes' was added in the event tab. Hence, the case was upgraded from non-serious to serious. It was reported that no known risk factors were identified pertaining to elevated 1-hour glucose test. The subject failed to 3-hour glucose test at 27 weeks gestation and was diagnosed with gestational diabetes that was controlled with diet. The narrative and case comment were amended accordingly.; Reporter's Comments: A 38-year-old pregnant subject experienced blood glucose increased, unspecified day after receipt of Flu vaccine Egg split QIV (considered as vaccine exposure during pregnancy) and was eventually diagnosed with gestational diabetes, 20 days post vaccination. Considering the pregnant state of the subject, advanced maternal age (risk factors), which provide more plausible explanation rather than study vaccine. Hence, the events gestational diabetes and blood glucose increased assessed as not related to study vaccine. The event vaccine exposure during pregnancy assessed as not related considering the intended use of the vaccine. The company assessed the event 'gestational diabetes' as serious (medically significant).