Antepartum haemorrhage, commonly abbreviated as APH, refers to any bleeding from or into the genital tract occurring from the 22nd week of pregnancy up until the birth of the baby. In the Nigerian context, many clinical guidelines use 28 weeks as the lower limit based on the threshold of fetal viability in our environment, but international standards trace it back to 22 weeks. This bleeding originates from the maternal vessels or the placental site. It excludes "show," which is the small, blood-tinged mucus discharge seen at the onset of true labour. Bleeding before 22 weeks is classified instead as early pregnancy bleeding, such as miscarriage or ectopic pregnancy.
Bleeding in late pregnancy is grouped into distinct clinical categories based on where the blood comes from and how it behaves. The two major anatomical causes are abnormalities of placental implantation, such as placenta praevia, and premature separation of a normally sited placenta, known as placental abruption. Sometimes, bleeding arises from fetal vessels crossing the internal os, termed vasa praevia. When thorough clinical examination and ultrasound fail to reveal any specific placental lesion, the condition is categorized as unexplained APH. Knowing these categories helps the midwife anticipate maternal and fetal risks.
Placenta praevia occurs when the placenta implants wholly or partially in the lower uterine segment, near or covering the internal cervical os. As the lower uterine segment stretches and the cervix begins to efface in the third trimester, the placental attachment is inevitably disrupted, tearing maternal blood vessels and causing painless, bright red bleeding. Risk factors frequently seen in busy Nigerian clinics include multiparity, previous cesarean section, advanced maternal age, and a history of uterine curettage. Midwives must remember that digital vaginal examination is strictly contraindicated when placenta praevia is suspected, as touching the low-lying placenta can trigger catastrophic, life-threatening haemorrhage.
Placental abruption involves the premature separation of a normally implanted placenta from the uterine wall before the delivery of the baby. Unlike placenta praevia, the bleeding is often dark red and accompanied by continuous abdominal pain, backache, and a tense, tender uterus. Triggers and strong associations include pregnancy-induced hypertension, preeclampsia, abdominal trauma from falls or road traffic accidents, sudden uterine decompression such as rapid amniotic fluid loss, and cord entanglement. In severe cases, blood accumulates behind the placenta, leading to concealed abruption where external bleeding does not match the true extent of maternal blood loss.