This is a serious observational study case, initially received from other health professional on 12-Mar-2019, concerning a 32-year-old adult female pregnant subject (Ethnicity: Unknown) of body weight: 150 lbs, height: 45 inches and body mass index (BMI): 52.1, enrolled in study.  The subject had no maternal and paternal history of major congenital malformations. The subject had no history of offspring with major congenital malformations. The subject's obstetrical history included one full term live birth, 1 preterm live birth and 1 spontaneous abortion. The subject's last menstrual period (LMP) date was reported as 18-Feb-2018. The subject's historical conditions included bacterial/ yeast vaginosis (from 13-Apr-2018 to 27-Apr-2018) and historical drug included: METROGEL (from 16-Apr-2018 to an unspecified date). On an unspecified day the subject underwent cervix cerclage procedure (reported as cerclage placed). The subject did not use tobacco, alcohol or illicit drugs during pregnancy. The subject's current conditions included: cervical incompetence, anaemia and mild polyhydramnios. The subject's concomitant medication included Prenatal vitamins for pregnancy, PROCARDIA for cervical incompetence and ferrous sulfate for anaemia. On 05-Apr-2018, the subject underwent cystic fibrosis mutation analysis, hemoglobin electrophoresis and a prenatal test for spinal muscular atrophy, and no congenital malformations were found. On 13-Apr-2018, the ultrasound prenatal test was performed, and the results showed no congenital malformation. On 19-Jun-2018, the ultrasound prenatal test was performed, and the results showed no congenital malformation. On 03-Oct-2018, at 32 weeks of gestational age, the subject was administered Influenza vaccine, 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 09-Oct-2018, the ultrasound prenatal test was performed, and the results showed no congenital malformation. On 16-Oct-2018, 13 days after vaccination, the subject had preterm labour. On 29-Oct-2018, 26 days after vaccination, the subject developed herpes simplex virus infection. The subject received the treatment drug nifedipine (dose: 20 mg, every 8 hours, orally) (from 16-Oct-2018 and still ongoing at the time of report) and MAKENA (dose: 1 syringe as reported, intramuscularly) (from 18-Oct-2018 until 13-Nov-2018) for preterm labor. The subject received VALTREX (dose: 500 mg, qd, orally) (from 29-Oct-2018 and still ongoing at the time of report) for Herpes simplex virus infection. In Nov-2018, the mother delivered a female neonate at 37.1 weeks gestation by vaginal method. The neonate's birth weight was 2194 grams, head circumference was 30.5 cm and body length were 48.3 cm. The Appearance, Pulse, Grimace, Activity, and Respiration (APGAR) scores were 5 (one minute), 9 (five minutes) and 9 (10 minutes). At the time of delivery, no pregnancy complications were reported. On 25-Nov-2018, the subject had recovered from the event preterm labor. At the time of this report, the subject had not recovered from the event herpes infection. The estimated delivery date (EDD) was reported as 03-Dec-2018. Reporter's Comments: A 32-year-old female pregnant subject experienced Preterm labour, 13 days after receipt of Flu Vaccine Cell Subunit QIV at 32 weeks of gestation (considered as vaccine exposure during pregnancy) and Herpes simplex virus infection, 26 days post vaccination. The subject's obstetrical history included one full term live birth, 1 preterm live birth and 1 spontaneous abortion and the current conditions included cervical incompetence. Despite plausible temporal association of the event preterm labour to vaccine administration, other factors such as pregnancy history (multigravida, preterm live birth) and underlying condition cervical incompetence provide a more plausible explanation of the event. Hence, causality assessed as not related to study product. The event Herpes simplex infection assessed as not related to inactivated study vaccine considering the infective aetiology of the event. 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 (preterm labor) as serious (medically significant).