A 20 year old woman, 32 weeks gestation, presents to the emergency department with a history of painless vaginal bleeding after intercourse

A 20 year old woman, 32 weeks gestation, presents to the emergency department with a history of painless vaginal bleeding after intercourse. On examination, a soft and relaxed uterus is noted with a fundal height of 32 cm. CTG is reactive. She has not attended any antenatal clinics previously and has not had any previous ultrasound scans. She has a pulse of 122 beats/minute, a blood pressure of 84/60 mmHg and a respiratory rate of 28 breaths/minute. What is the the SINGLE most likely diagnosis?

A. Abruption of placenta secondary to pre-eclampsia
B. Placenta accreta
C. Placenta praevia
D. Preterm labor
E. Vasa praevia

Placenta praevia Placenta praevia describes a placenta lying wholly or partly in the lower uterine segment. This is common early in the pregnancy, but is most often not associated with bleeding.

The key clinical feature is painless bleeding after 24 weeks of gestation.

Risk factors • previous placenta praevia • multiple pregnancies

Note: 5% will have low-lying placenta when scanned at 16-20 weeks gestation incidence at delivery is only 0.5%, therefore most placentas rise away from cervix

Clinical features • Painless vaginal bleed • uterus not tender • lie and presentation may be abnormal • fetal heart usually normal

Note: the painless late-pregnancy bleeding may occur during rest or activity, suddenly and without warning. It may be preceded by trauma, coitus, or pelvic examination.

Diagnosis This is based on the presence of painless late-trimester vaginal bleeding with an obstetric ultrasound showing placental implantation over the lower uterine segment.