Enumerate the causes of, and describe, placenta praevia and abruptio placentae and outline management of antepartum Haemorrhage.

Definition

Antepartum haemorrhage (APH) is bleeding from or into the genital tract after the 28th week of pregnancy (period of viability) and before the birth of the baby. It complicates 3–5% of pregnancies and remains an important cause of maternal and perinatal morbidity and mortality.

Causes of Antepartum Haemorrhage

Causes

• Placental bleeding (the major group) — placenta praevia and abruptio placentae (accidental haemorrhage).
• Unexplained / indeterminate haemorrhage — including marginal sinus bleeding.
• Extra-placental (local) causes — cervical ectropion, polyp or carcinoma, vaginal/cervical trauma or infection, and vasa praevia (fetal vessels crossing the os, with fetal blood loss).

A. Placenta Praevia

Definition

Placenta praevia is implantation of the placenta, wholly or partially, over the lower uterine segment (over or close to the internal os).

Types/degrees (Dutta) — Type I (low-lying):

• lower margin in the lower segment but not reaching the os
• Type II (marginal): reaches the margin of the internal os but does not cover it
• Type III (incomplete/partial central): covers the os partially
• Type IV (complete/central): covers the internal os completely even when dilated.
• Type II posterior is termed the dangerous placenta praevia. Risk factors include multiparity, advanced maternal age, previous caesarean/uterine scar, multiple pregnancy, and prior curettage.

Clinical features — painless, causeless, recurrent, apparently external bleeding (bright red); a soft, relaxed, non-tender uterus; a high or floating presenting part with frequent malpresentations; and a fetal condition usually proportionate to visible blood loss.

Diagnosis — by transabdominal/transvaginal ultrasound for placental localisation. A vaginal examination is contraindicated outside a fully-equipped theatre ("double set-up").

Management — depends on bleeding, maturity and fetal state.

• Expectant (McAfee–Johnson) when bleeding is slight, mother and fetus are stable and the fetus is preterm: admission and bed rest, correction of anaemia, anti-D if Rh-negative, corticosteroids for lung maturity if < 34 weeks, and close surveillance until ≥ 37 weeks or until bleeding forces delivery.
• Active management for heavy/continued bleeding, term pregnancy or fetal distress: resuscitation and delivery — caesarean section for major degrees (Types III–IV, and Type II posterior), with vaginal delivery considered only in minor degrees with a cephalic presentation and minimal bleeding.

B. Abruptio Placentae (accidental Haemorrhage)

Definition

Abruptio placentae is premature separation of a normally situated placenta after 28 weeks and before delivery.

Types — revealed (blood escapes through the cervix), concealed (blood collects behind the placenta, no external loss) and mixed. Grades (Sher) — Grade 0 (diagnosed retrospectively), Grade 1 (mild, < ¼ separated), Grade 2 (moderate, ¼–⅔, fetus alive), Grade 3 (severe, > ⅔, fetal death ± coagulopathy). Predisposing factors include pre-eclampsia/hypertension, trauma, sudden uterine decompression, short cord, folate deficiency, smoking and a previous abruption.

Clinical features — painful vaginal bleeding (often dark), a tense, tender, "woody-hard" uterus with poorly-felt fetal parts, signs of shock out of proportion to visible loss (in concealed type), and frequently fetal distress or death.

Complications — haemorrhagic shock, Couvelaire uterus (uteroplacental apoplexy), DIC, acute renal failure (acute tubular/cortical necrosis), postpartum haemorrhage and fetal death.

Management — this is an emergency.

• Resuscitate — large-bore IV access, restore blood volume with crystalloids and blood/blood products, monitor vitals, urine output and central venous pressure; correct coagulopathy (fresh frozen plasma, cryoprecipitate, platelets) guided by clotting studies.
• Deliver — if the fetus is alive and delivery is not imminent, caesarean section; if the cervix is favourable and labour is rapid, amniotomy with oxytocin and vaginal delivery. If the fetus is dead, vaginal delivery is preferred after stabilisation provided maternal condition allows.
• Watch for postpartum haemorrhage (active third-stage management) and renal failure in the puerperium.

Differentiating Placenta Praevia from Abruptio Placentae

In placenta praevia the placenta is implanted in the lower uterine segment, over or near the internal os, causing painless, causeless, recurrent bleeding with a soft, relaxed uterus. In abruptio placentae a normally-sited placenta separates prematurely, forming a retroplacental clot: bleeding is painful and may be concealed, the uterus is tense, tender and 'woody', and the fetus is often distressed or dead, with a serious risk of DIC.

WHY a Vaginal Examination Is Forbidden in APH

The first rule of antepartum haemorrhage is why a digital vaginal examination must never be performed until placenta praevia has been excluded by ultrasound. If the placenta lies over or near the internal os, an examining finger passing through the cervix can separate it from the lower segment and tear the large dilated sinuses there, converting a modest 'warning' bleed into torrential, uncontrollable haemorrhage that can exsanguinate the mother within minutes — and it may do so far from an operating theatre or blood bank. The lower segment is poorly contractile, so it cannot arrest such bleeding by retraction as the upper segment does. The safe sequence is therefore: resuscitate, confirm the placental site by ultrasound (quick, safe and definitive), and only then — if the placenta is normally sited — examine. If examination is unavoidable in a bleeding woman of unknown placental site, it is performed as a 'double set-up' examination in theatre, fully prepared to proceed immediately to caesarean section. Understanding that the lower segment cannot control bleeding explains why this single prohibition is the first thing taught about APH.

WHY Abruption Causes Shock Out of Proportion and DIC

A crucial concept is why abruptio placentae endangers the mother far more than the visible blood loss suggests. Two mechanisms explain it. First, the bleeding may be concealed: blood collects behind the placenta and within the myometrium rather than escaping through the cervix, so a woman may be in profound hypovolaemic shock with little or no external bleeding — the tense, tender, 'woody' uterus and the degree of shock, not the visible loss, are the guide. Second, the retroplacental clot and damaged decidua release large amounts of thromboplastin into the maternal circulation, triggering disseminated intravascular coagulation — the clotting cascade is consumed, fibrinogen falls, and the blood ceases to clot, so that the woman then bleeds from the uterus, from venepuncture sites and from any incision. This is compounded by Couvelaire uterus (blood extravasating into the myometrium, impairing contraction and predisposing to atonic PPH) and by acute renal failure. Recognising that abruption threatens through concealed loss, DIC and postpartum atony — not merely through what is seen — explains why management is aggressive resuscitation with blood and clotting products, and prompt delivery.

• APH = bleeding from the genital tract after 28 weeks; the two major causes are placenta praevia and abruptio placentae.
• Praevia: painless, causeless, recurrent bleeding with a soft, relaxed uterus and a usually live fetus.
• Abruption: painful, continuous bleeding (often concealed), a tense, tender uterus, fetal distress, and shock out of proportion to visible loss.
• Never perform a digital vaginal examination until ultrasound has excluded placenta praevia.
• Abruption risks DIC, Couvelaire uterus, PPH and renal failure — resuscitate and deliver.