Failure to progress; Vaccine exposure during pregnancy; This is an observational study case initially received from other health professional on 04-Nov-2019, concerning a 19-year-old female, pregnant subject of body weight 188 lbs, height 61 inches and body mass index (BMI) 35.5, enrolled in a prospective observational safety study.  The subject's medical history included body mass index high (BMI 35.5), anaemia and herpes simplex virus type 1 (HSV 1).   The subject's concomitant medications included ferrous sulfate for anaemia and Valtrex (valaciclovir hydrochloride) for HSV 1.  The subject's obstetrical history noted that the subject had no previous pregnancies. 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's last menstrual period (LMP) date was 17-Feb-2019. The subject's estimated date of delivery (EDD) was reported as 24-Nov-2019 and corrected estimated date of delivery (CEDD) was not reported. The type of pregnancy was singleton. The subject did not use tobacco, alcohol or illicit drugs during pregnancy.   On 16-May-2019, the subject underwent sequential first and nuchal translucency. No MCMs were noted.  On 11-Jul-2019, the subject underwent targeted ultrasound and no MCM was noted.  On 01-Oct-2019, polyhydramnios was noted as pregnancy complication.  On 09-Oct-2019, at approximately 33 weeks of gestation (calculated per LMP), the subject was administered Afluria QIV [influenza vaccine; batch number: P100112488, dose, route of administration, anatomical location and expiration date: not reported] (explicitly coded as 'Vaccine exposure during pregnancy') for an influenza immunisation.  On 19-Nov-2019, polyhydramnios was considered resolved.  At 40.0 weeks of gestation (as reported), the subject gave a live birth to a female neonate, delivered via caesarean low transverse method of delivery. Delivery was complicated with failure to progress. The neonate's birth weight was 2785 grams, head circumference and length were not reported. The appearance, pulse, grimace, activity and respiration (APGAR) scores were 8 at one minute and 9 at five minutes. APGAR score was not reported for 10 minutes. There was no major congenital malformation identified at birth.  The outcome of event arrested labor' was not reported.   The event of arrested labor' was assessed as serious due to criterion of medical significance.   The reporter did not provide causality assessment to Afluria QIV.   Follow ups received from other health professional on 12-Dec-2019: Indication, start date, stop date, dose, route and frequency provided for concomitant. Information regarding pregnancy complications updated. Anaemia added in the subject's medical history. Confirmed that HSV 1 started prior to conception and therefore it removed as an event and added in the subject's medical history. Linked case removed. Company comment updated. Narrative was amended accordingly.  Follow up information received from other health professional on 10-Feb-2020: Pregnancy outcome received. New event arrested labor' added. Stop date added and outcome changed from not reported' to resolved' for the event vaccine exposure during pregnancy. Narrative was amended accordingly.   Company comment: The subject experienced arrested labour 1 month 15 days after receiving Afluria QIV. Vaccine was administered at 33 weeks of gestation. Chronology is plausible. The subject's medical history included body mass index high (BMI 35.5), anaemia and herpes simplex virus type 1 (HSV 1). Causal role of the suspect vaccine cannot be totally excluded and is assessed as unlikely related (defaults to related for reporting purposes). Vaccine exposure during pregnancy is assessed as unrelated per company's conventions.; Sender's Comments: The subject experienced arrested labour 1 month 15 days after receiving Afluria QIV. Vaccine was administered at 33 weeks of gestation. Chronology is plausible. The subject's medical history included body mass index high (BMI 35.5), anaemia and herpes simplex virus type 1 (HSV 1). Causal role of the suspect vaccine cannot be totally excluded and is assessed as unlikely related (defaults to related for reporting purposes). Vaccine exposure during pregnancy is assessed as unrelated per company's conventions.