retained placenta; Maternal exposure during pregnancy; This spontaneous retrospective pregnancy case was reported by a physician and describes the occurrence of MATERNAL EXPOSURE DURING PREGNANCY (Maternal exposure during pregnancy) and RETAINED PLACENTA OR MEMBRANES (retained placenta) in a 37-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 013L20A and 039K20A) for COVID-19 vaccination.     The patient's past medical history included In vitro fertilization (IVF transfer (5 day FET)) on 19-Jun-2020. Previously administered products included for Product used for unknown indication: Tetanus shot on 12-Jan-2021. Concomitant products included MINERALS NOS, VITAMINS NOS (PRENATAL VITAMINS [MINERALS NOS;VITAMINS NOS]) for Vitamin D deficiency, VITAMIN D3 for an unknown indication.   On 27-Dec-2020, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 27-Jan-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. The patient's last menstrual period was on 02-Jun-2020 and the estimated date of delivery was 05-Mar-2021. On 27-Dec-2020, the patient experienced MATERNAL EXPOSURE DURING PREGNANCY (Maternal exposure during pregnancy). On an unknown date, the patient experienced RETAINED PLACENTA OR MEMBRANES (retained placenta). The patient received mRNA-1273 (Moderna COVID-19 Vaccine) beginning around the  thirty-fourth week of the pregnancy. The vaginal delivery occurred on 12-Mar-2021, which was reported as Full-term. For neonate 1, the birth weight was 4235 grams (9lbs 5oz) with an APGAR score of 9 and 9 at (1, 5 minutes). The outcome was reported as Term Birth w Complications. Patient delivered baby boy on 12-Mar-2021 at 40.5 weeks gestation,emergency D&C for mother with 3U PRBCs for retained placenta. Baby weight at birth was 9lbs 5.4 oz with length of 22 inches. Patient is breastfeeding. There were no perinatal complications for the infant, no identified fetal/infant abnormalities on delivery and no identified infant abnormalities at 1-month post-partum. On 27-Jan-2021, MATERNAL EXPOSURE DURING PREGNANCY (Maternal exposure during pregnancy) had resolved. At the time of the report, RETAINED PLACENTA OR MEMBRANES (retained placenta) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 29-Jul-2020, Ultrasound antenatal screen: large subchorionic hemorrhage (Inconclusive) large subchorionic hemor. On 28-Sep-2020, Ultrasound antenatal screen: marginal cord insertion (Inconclusive) marginal cord insertion. On 08-Dec-2020, Blood glucose: 161 (High) Elevated. On 12-Dec-2020, Blood glucose: normal (normal) normal. On 21-Feb-2021, Group B streptococcus neonatal sepsis: positive (Inconclusive) postive.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   Treatment information was not provided.   Most recent FOLLOW-UP information incorporated above includes: On 05-Feb-2021: Followup Received on 5 Feb 2021 contains patient demographic details,first and second dose details,relevant history and concomittant medication. On 11-Jun-2021: Pregnancy Outcome Form added and contains information regarding delivery procedure, historical condition, concomitant medication, laboratory investigations and infant details.