Delivery at 36,9 weeks of gestation; Vaccine exposure during preganancy; This observational study case, initially received on 30-Oct-2019 from other health professional and concerned a 22-year-old, pregnant, female subject of body weight: 160 lbs, height: 63 inches and body mass index (BMI): 28.3, enrolled in, a prospective observational safety study.  The subject's current condition included sickle cell trait, high body mass index and nausea. The subject's concomitant medications included Prenatal vitamins (minerals nos; vitamins nos) for pregnancy and vitamin B6, ondansetron and Unisom (doxylamine succinate) for nausea.   The subject's obstetrical history included two previous pregnancies with one preterm live birth and one spontaneous abortion. The subject had no history of offspring with major congenital malformation (MCM) and no relevant maternal and paternal medical history. The subject did not use tobacco, alcohol or illicit drugs during pregnancy.  The subject's last menstrual period (LMP) date was 08-Jul-2019. The subject's estimated date of delivery (EDD) was reported as 13-Apr-2020 and corrected estimated date of delivery (CEDD) was reported as 21-Apr-2020. The type of pregnancy was singleton. The pregnancy was complicated by subject's increased BMI and sickle cell trait gene.  On 04-Oct-2019, at approximately 12 weeks of gestation (calculated per LMP),  the subject was administered Afluria QIV (Flu Vaccine Egg Split QIV CSL)(influenza vaccine, dose reported as 0.5 mg; route of administration: intramuscular; anatomical location: right deltoid) (explicitly coded as 'vaccine exposure during pregnancy') for influenza immunisation. The batch number reported was P100112488.  On the same day, first sequential, nuchal translucency screening test and prenatal panel revealed no MCM. Also, on this day the subject underwent hemoglobinopathy test, which showed maternal sickle cell trait.  At gestational age of 36.9 weeks (as reported), the subject delivered via caesarean method, live birth male neonate. The characteristics of the neonate included birth weight of 2381 grams, head circumference and length were not reported. Appearance, pulse, grimace, activity, and respiration (APGAR) scores at one, five and ten minutes were not reported. No MCM was identified at birth. No pregnancy complications were noted.   The outcome of 'premature delivery' was not reported.  The event of 'premature delivery' was considered to be medically significant by a Physician within Seqirus's Pharmacovigilance and Risk Management Department.  The reporter did not provide a causality assessment.  This case is linked with 202101464 (the corresponding baby case).  Additional information received from other health professional on 14-Nov-2019: Report type amended from spontaneous to report from study [study ID, patient ID, center ID added and study drug coded]. Vitamin B6 and Unisom amended from concomitant medication to treatment and doses, frequencies and indications were added. Dose, route of administration, indication and frequency added for Prenatal Vitamins. Narrative amended accordingly.  Additional information received from other health professional on 23-Dec-2019, with additional information (being processed together) on the same day: Subjects medical history updated; route of administration and anatomical location for vaccine added and dose recorded in narrative; vitamin B6, ondansetron and Unisom (doxylamine succinate) changed from treatment to concomitants.  Narrative amended accordingly.   Additional information received on 18-Feb-2021 from other health professional: Classification special case with no AE removed. Pregnancy outcome received and pregnancy information updated. Stop date added and outcome changed from not reported to resolved for the event of 'vaccine exposure during pregnancy'. Premature delivery added as a new event and therefore, the case was updated from non-serious to serious. Narrative was amended accordingly.  Company comment:The pregnant subject experienced premature delivery approximately six months after vaccination with the suspect product, Afluria QIV. The patient was administered vaccine at approximately 12 weeks of gestation. Chronology is unsuggestive. The subject's medical history of high body mass index, two previous pregnancies with one preterm live birth and one spontaneous abortion confounds causality for the event. Considering all above mentioned, causal relationship for premature delivery is assessed as not related due to due to biological implausibility, unsuggestive chronology and presented confounders. Vaccine exposure during pregnancy is assessed as not related per company's conventions.; Sender's Comments: The pregnant subject experienced premature delivery approximately six months after vaccination with the suspect product, Afluria QIV. The patient was administered vaccine at approximately 12 weeks of gestation. Chronology is unsuggestive. The subject's medical history of high body mass index, two previous pregnancies with one preterm live birth and one spontaneous abortion confounds causality for the event. Considering all above mentioned, causal relationship for premature delivery is assessed as not related due to due to biological implausibility, unsuggestive chronology and presented confounders. Vaccine exposure during pregnancy is assessed as not related per company's conventions.