Preterm premature rupture of the membranes; Gestational age at outcome 31.9 weeks/Premature delivery; Vaccine exposure during pregnancy; This is a serious observational study case initially received from other health professional on 20-Jun-2019, concerning a 20-year-old, adult female pregnant subject of body weight: 265 lbs, height: 64 inches and body mass index (BMI): 45.5 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 4 previous pregnancies which included 2 full term live births, one preterm live birth and one spontaneous abortion. The subject did not have any history of previous birth defect. The subject's family history showed no maternal/paternal history with major congenital malformations. The subject's historical condition included bacterial vaginosis and chlamydia (from 18-Sep-2018 to 28-Sep-2018) and urinary tract infection (from 10-Sep-2018 to 20-Sep-2018). The subject's historical drugs included Zithromax (azithromycin, 4 tablets once orally) for chlamydia, Metrogel (metronidazole, 0.75 percent twice daily vaginally) for bacterial vaginosis. The subject's current condition included herpes simplex type 1 (HSV 1, since 03-Apr-2018). The subject's concomitant medications included Prenatal vitamins (minerals NOS, vitamins NOS) for pregnancy.  The subject's last menstrual period (LMP) date was 23-Jul-2018. The type of pregnancy was singleton. The subject did not consume alcohol and tobacco during pregnancy. The subject had consumed illicit-drug marijuana (but not ongoing at the time of report) during pregnancy and the urine drug screen was positive.  On 10-Sep-2018, the subject underwent spinal muscular atrophy screen and fibrosis mutation analysis and no congenital malformation was reported. On 19-Sep-2018, the subject underwent ultrasound scan and no congenital malformation was reported.  On 17-Oct-2018, approximately at gestational age of 12 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 07-Nov-2018, the subject underwent ultrasound scan and on 17-Nov-2018, the subject underwent quad screen test and no congenital malformation was reported.  At 4 months and 14 days after vaccination, the subject a delivered female infant at gestational age of 31.9 weeks (coded as premature delivery) through caesarean method. The pregnancy complication was reported as preterm premature rupture of membranes. The infant's characteristics included birth weight of 2183 g, head circumference was 29.8 cm and length was 45.1 cm. Appearance, pulse, grimace, activity and respiration (APGAR) score at one minute was 7 and at five minutes was 8. No major congenital malformation was identified at birth.   The subject's estimated delivery date (EDD) was 29-Apr-2019 and corrected estimated delivery date (CEDD) was 29-Apr-2019.  This case is linked to case ID 201904026 (parent child link).; Reporter's Comments: A 20-year-old female pregnant subject experienced preterm premature rupture of membranes and premature delivery, more than 4 months after receipt of Flu Vaccine Cell Subunit QIV at approximately 12 weeks of gestation (considered as vaccine exposure during pregnancy). Considering the implausible temporal relationship between vaccination and reported events preterm premature rupture of membranes and premature delivery, causality assessed as not related. Multigravida (4 previous pregnancies which includes 2 full term live birth, 1 spontaneous abortion and 1 preterm live birth) state of pregnancy, gestational history of bacterial vaginosis, chlamydia and concurrent condition HSV 1 infection are considered as known risk factors. The event vaccine exposure during pregnancy assessed as not related considering the intended use of vaccine. The company assessed the case as serious (medically significant).