This is an observational study case initially received from other health professional on 18-Feb-2019, concerning a 37-year-old, adult female pregnant subject of body weight: 224 lbs, height:  66 inches and body mass index (BMI): 36.2 enrolled in a prospective observational safety study on pregnancy outcomes in women immunized with seasonal cell culture influenza trivalent (TIVc) or quadrivalent (QIVc) vaccine during pregnancy. The subject had 5 previous pregnancy reported as full-term live birth, out of which one infant had anencephaly. The subject's family history included offspring with major congenital anomaly, reported as anencephaly. The subject was a tobacco user. The subject use to consume 20 cigarettes/tobacco products per day. The subject's current conditions included headache and allergy. The subject's concomitant medications included hydroxyzine for allergies. The subject's last menstrual period (LMP) date was 25-May-2018. The type of pregnancy was singleton. On 15-Nov-2018, the subject underwent ultrasound and no major congenital malformation was noted. On 19-Nov-2018, at gestational age of 25 weeks, the subject was administered Flu Vaccine Cell Subunit QIV NVD (influenza vaccine, subunit influenza virus vaccine polyvalent, batch number: 252664, dose, route of administration, anatomical location and expiry date: not reported) (explicitly coded as vaccine exposure during pregnancy) for an unknown indication. On 19-Nov-2018, Q Natal test was performed, and no major congenital malformation was noted. On 26-Nov-2018, 7 days after vaccination, the patient developed vaginitis. The subject was treated with Metrogel (metronidazole gel, bid: from 26-Nov-2018 to 27-Nov-2018). On 26-Nov-2018, ultrasound, cystic fibrosis mutation analysis, spinal muscular atrophy (prenatal test) and haemoglobin electrophoresis were performed, and no major congenital malformation was noted. On 27-Nov-2018, the patient recovered from vaginitis. On 24-Jan-2019, ultrasound was performed, and no major congenital malformation was noted. On 31-Jan-2019, another ultrasound scan was performed, and no major congenital malformation was noted. At 35.9 weeks of gestational age the subject gave birth to a live male infant, vaginally. No pregnancy complication and congenital malformation were noted. The infant's birth weight was 2715 g, head circumference was 31.8 cm and length was 51.4 cm. The appearance, pulse, grimace, activity, and respiration (APGAR) score at 1 minute was 8 and at 5 minutes was 9. The subject's estimated delivery date (EDD) was 10-Mar-2019.; Reporter's Comments: A 37-year-old pregnant subject experienced vaginitis, 7 days after receipt of Flu Vaccine Cell Subunit QIV NVD (considered as vaccine exposure during pregnancy) and preterm labour, 2 months 21 days post vaccination. Considering the infective aetiology of the event vaginitis, causal role of suspect vaccine is ruled out. The other factors such as subject's age, tobacco use and multigravida(gravida 5 with history of 1 anencephaly in previous pregnancy) are considered as more plausible cause rather than the suspect vaccine. Hence, the event pre-term labour assessed as not related. The decision to administer a vaccine during pregnancy is related to medical decision made by the mother and her physician and is not related to any property of the medication. Hence, the event vaccine exposure during pregnancy assessed as not related considering the intended use of the vaccine. The company assessed the event 'pre-term labour' as serious (medically significant).