Newborn vaginal bleed (Estrogen Withdrawal Bleed)

• Estrogen withdrawal is the most common cause of uterine bleeding in the newborn.
• fetus is exposed to maternal estrogens in utero
• Postnatally, infant estrogen levels decrease to prepubertal amounts, prompting uterine withdrawal bleeding.
• bleeding may be preceded by a physiologic clear or whitish vaginal discharge (similar to leukorrhea) that later becomes pink or blood-tinged.
• usually occurs during the second or third week of life and does not last for more than a few days.
• amount of blood loss is negligible.
• Maternal estrogen exposure also can cause breast tissue enlargement in both male and female neonates.

DDX

• Diaper dermatitis, a common entity in infants, usually is not associated with bleeding. Minimal skin bleeding can be seen with severely macerated rashes
• Vitamin K  deficiency can cause bleeding, but the intramuscular administration of vitamin K immediately after birth is a universal practice. In addition, other signs of bleeding, such as petechiae, probably would accompany the uterine bleeding.
• A urinary tract infection in the neonate generally manifests as poor feeding, irritability, fever, or lethargy. In addition, the infant may have poor weight gain. Vaginal bleeding does not occur with urinary tract infections, and rarely is the urine grossly bloody.
• Vaginitis is unusual in the neonate unless there is a congenital anomaly (eg, ectopic urethra).
   

References:
American Academy of Pediatrics Vitamin K Ad Hoc Task Force.
Controversies concerning vitamin K and the newborn. Pediatrics.
1993;91:1001-1003
Sanfilippo JS. Gynecologic problems of childhood: history and physical
examination. In: Behrman RE, Kliegman RM, Jenson HB, eds. Nelson
Textbook of Pediatrics. 16th ed. Philadelphia, Pa: WB Saunders Co;
2000:1659