Chorioamnionitis; Failure to progress; Vaccine exposure during pregnancy; This is an observational study case, reported by other health professional and initially received on 15-Apr-2020, concerning a 30-year-old pregnant, female subject of body weight 148.6 lbs, height 67 inches and body mass index (BMI) 23.3, enrolled in a prospective observational safety study.  The subject's current medical condition was not reported.  The subject's concomitant medications included Prenatal vitamins (unspecified vitamins and minerals) for pregnancy.  The subject's obstetrical history noted that the subject had no previous. The subject had no history of offspring with major congenital malformation (MCM). Also, the subject had no maternal or paternal history with MCM. The subject did not use tobacco, alcohol or illicit drugs during pregnancy.   The subject's last menstrual period (LMP) date was 31-May-2019. The subject's estimated date of delivery (EDD) was reported as 06-Mar-2020 and corrected estimated date of delivery (CEDD) was not reported. The type of pregnancy was singleton.   On 27-Jul-2019, the subject underwent dating ultrasound and results were normal, per reporter. There were no MCMs noted  On 07-Aug-2019, the subject underwent haemoglobin electrophoresis and results were negative, per reporter. The subject also underwent prenatal bloodwork and results were normal, per reporter. There were no MCMs noted.  On 28-Aug-2019, the subject underwent first trimester screen and results were negative, per reporter. There were no MCMs noted.  On 09-Sep-2019, the subject underwent GC chlamydia cultures and results were negative, per reporter. There were no MCMs noted.  On 12-Sep-2019, the subject underwent maternal alpha fetoprotein (AFP) and results were negative, per reporter. There were no MCMs noted.  On 10-Oct-2019, at approximately 18 weeks of gestation (calculated per LMP), the subject was administered Afluria QIV (Flu Vaccine Egg Split QIV CSL) [influenza vaccine, subunit influenza virus vaccine polyvalent, batch number: P100123038, dose, route of administration, anatomical location and expiration date: not reported] (explicitly coded as 'Vaccine exposure during pregnancy') for an influenza immunisation.   On the same day, the subject underwent anatomic scan and results were normal, per reporter. There were no MCMs noted.  On an unspecified date, unknown amount of time after vaccination, the pregnancy was complicated with chorioamnionitis.  At gestation age of 39.3 weeks (as reported), the subject delivered a live birth, male neonate via low transverse caesarean section. The delivery was complicated with failure to progress. The characteristics of the neonate included birth weight: 3728 grams, head circumference: 34 cm, length: 50.8 cm and appearance, pulse, grimace, activity, and respiration (APGAR) scores were 9 (one minute) and 9 (five minutes). There was no APGAR score data for 10 minutes reported. No MCM was identified at birth.   At the time of this report, the outcome of the event of 'chorioamnionitis' was not reported.  The events of 'arrested labour' and 'chorioamnionitis' were considered serious due to the criterion of medical significance, per company.  The reporter did not provide causality assessment.  This case is linked to the case 202002955 (corresponding baby case).  Company comment: A pregnant subject was administered Afluria QIV at 18 weeks of gestation. The subject experienced amniotic cavity infection unknown amount of time after vaccination and arrested labour 4 months and 20 days after vaccination. Chronology needs more clarification for chorioamnionitis. Causal role of the suspect vaccine is unassessable for amniotic cavity infection. More information regarding medical history is needed. For the event of arrested labour, causality is assessed as not related due to unsuggestive temporal relationship. Vaccine exposure during pregnancy assessed as not related per company's conventions.; Sender's Comments: A pregnant subject was administered Afluria QIV at 18 weeks of gestation. The subject experienced amniotic cavity infection unknown amount of time after vaccination and arrested labour 4 months and 20 days after vaccination. Chronology needs more clarification for chorioamnionitis. Causal role of the suspect vaccine is unassessable for amniotic cavity infection. More information regarding medical history is needed. For the event of arrested labour, causality is assessed as not related due to unsuggestive temporal relationship. Vaccine exposure during pregnancy assessed as not related per company's conventions.