Delivery at 32.7 weeks of gestation; Vaccine exposure during pregnancy; This is an observational study case, initially received from other health professional on 30-Jan-2020, concerning a 18-year-old, pregnant, female subject of body weight 146 lbs, height 65 inches and body mass index (BMI) 24.3, enrolled in, a prospective observational safety study on pregnancy outcome in women immunized with Afluria QIV, a seasonal quadrivalent vaccine, during pregnancy.   The subject's medical history included chlamydia.   The subject's concomitant medication included Prenatal vitamin (unspecified vitamins and minerals) for pregnancy.  The subject's obstetrical history noted that the subject had no previous pregnancies. The subject had no maternal or paternal history with major congenital malformations (MCMs). Also, the subject had no history of offspring with MCMs. The subject did not use tobacco, alcohol or illicit drugs during pregnancy.  The subject's last menstrual period (LMP) date was 30-Jul-2019. Estimated delivery date (EDD) was reported as 05-May-2020, while corrected delivery date (CEDD) was reported as 26-Mar-2020. The pregnancy was singleton.  On 04-Oct-2019, the subject underwent non-invasive prenatal test and ultrasound. No MCMs were noted.  On 10-Oct-2019, the subject underwent maternal serum alpha-fetoprotein (MSAFP) / serum markers and no MCMs were noted.  On 11-Nov-2019, at gestational age of 14 weeks (calculated per LMP), the subject was administered Afluria QIV (Flu Vaccine Egg Split QIV CSL) [influenza vaccine; batch number: P100112488, dose, anatomical location, route of administration and expiration date: not reported] (explicitly coded as Vaccine exposure during pregnancy') for influenza immunisation.   On the same day, the subject underwent 20-week anatomy scan and echogenic intracardiac focus right ventricle (EIFRV) was noted, while no MCMs were noted.  On 15-Mar-2020, at 32.7 weeks of gestation (as reported), the subject delivered a live birth male neonate via vaginal method of delivery. The neonate's birth weight was 3374 grams, while head circumference and body length were not reported. The appearance, pulse, grimace, activity and respiration (APGAR) scores were 9 at one minute and 9 at five minutes. APGAR score was not reported for 10 minutes. There was no MCM identified at birth.   At the time of this report, the outcome of event premature delivery' was not reported.   The event of premature delivery' was considered as serious due to the criterion of medical significance.   The case is linked to case 202001584 (the corresponding child case).  Follow up information received from other health professional on 01-Jun-2020: Pregnancy outcome was received. New event 'premature delivery' was added and the case was upgraded from non-serious to serious. Stop date added and outcome changed from 'not reported' to 'resolved' for  the event of 'vaccine exposure during pregnancy'. Narrative was amended accordingly.   Company comment: A pregnant subject experienced premature delivery, four months after receiving Afluria QIV. Vaccine was administered at gestational age of 14 weeks. Chronology is unsuggestive. Causality was confounded by subject's medical history of chlamydia. However, causal role of the suspect vaccine cannot be excluded and is assessed as unlikely related (defaults to "related" in the safety database for reporting purposes). Vaccine exposure during pregnancy assessed as not related per company's conventions.; Sender's Comments: A pregnant subject experienced premature delivery, four months after receiving Afluria QIV. Vaccine was administered at gestational age of 14 weeks. Chronology is unsuggestive. Causality was confounded by subject's medical history of chlamydia. However, causal role of the suspect vaccine cannot be excluded and is assessed as unlikely related (defaults to "related" in the safety database for reporting purposes). Vaccine exposure during pregnancy assessed as not related per company's conventions.