PV bleeding in the neonate

Last edited 05/2019

Neonatal uterine bleeding (NUB) occurs in approximately 4% of newborns and represents, similarly as menstrual bleeding

  • evident NUB is relatively rare - however biochemical proofs of vaginal bleeding can be found in 25-61% of neonates, depending on different methods used to detect it (1)

  • pathophysiology:
    • some authors consider withdrawal of maternal oestrogen as the aetiological factor (3)
      • in utero, maternal oestrogen diffuses across the placenta into the fetal circulation
      • after birth, oestrogen levels in the infant fall, resulting in a physiologic vaginal discharge that can be blood tinged or frankly bloody
        • the discharge usually disappears within 10 days (3)
    • others suggest that vaginal bleeding occurs because of a progesterone (PG) withdrawal bleeding (1)
      • concentration of progesterone in the fetal circulation increases dramatically to levels much higher than those found in the maternal circulation (4)
      • visible menstrual bleeding occurs as a consequence of a physiological progesterone (PG) withdrawal

  • NUB appears always in the first week, with its highest frequency on the 5th day of life and must be regarded as a physiologic event (2)
    • if any genital bleeding lasts longer than one week or appears for the first time after that period then expert advice should be sought



  • anatomy of neonatal uterus (large cervix to corpus ratio) and the presence of thick mucus inside the cervical canal are considered predisposing factors for the possibility that a great number of neonatal bleedings are not clinically evident (1)
    • the concept of retrograde menstruation with shedding of endometrial cells through fallopian tubes into the peritoneum is of paramount importance in the pathogenesis of endometriosis
    • study evidence has previously demonstrated that NUB, present in a 3.87% of newborns, was almost absent in preterm babies (0,8%), and more frequent in post-term (9.1%) than in at term babies (4.4%) (1)
      • seems, therefore, that a condition of PG resistance has to be considered physiologic in newborns and that an altered endometrial response to hormonal stimulation could be linked to conditions of fetal distress. Moreover, this PG resistance is likely to persist till the onset of menarche and even beyond, increasing the risk of obstetrical syndromes when pregnancy occurs in early teenage (1)
      • considering that the hormonal environment is the same for all neonates, a particular hormonal sensibility (or insensibility) has to be involved in the pathogenesis of NUB (1)
  • clinical studies have linked the risk of bleeding to a series of events indicating fetal distress (1)
  • early-onset endometriosis may be caused by menstruation-like bleeding in the neonate, leading to tubal reflux and ectopic implantation of endometrial stem/ progenitor cells (1)
  • persistence of partial progesterone resistance in adolescent girls may compromise deep placentation and account for the increased risk of major obstetrical syndromes, including preeclampsia, fetal growth retardation and preterm birth (1)