Bleeding after the first trimester of pregnancy

Essentials

1
Up to 5% of pregnant women will have significant bleeding after 20 weeks’ gestation.
2
Resuscitation of the mother followed by ultrasound localization of the placenta are the priorities of management for patients with heavy vaginal bleeding after 20 weeks’ gestation.
3
Secondary postpartum haemorrhage is commonly caused by endometritis or retained products of conception.

Introduction

Pregnancy is measured in trimesters from the first day of the last menstrual period, totalling 40 weeks. The first trimester of pregnancy is week 1 through week 12, or about 3 months. Vaginal bleeding after the first trimester may be due to a number of causes. The most common is classified as ‘incidental’, where the bleeding is not directly related to pregnancy.

Antepartum haemorrhage

Bleeding from the genital tract that occurs after 20 weeks’ gestation and before the onset of labour is classified as an antepartum haemorrhage (APH). APH complicates 2% to 5% of all pregnancies. It is associated with increased perinatal morbidity and mortality and contributes significantly to health care utilization.

Postpartum haemorrhage

Primary post-partum haemorrhage (PPH) is defined as heavy (>500 mL) vaginal bleeding within 24 hours of delivery and is discussed in Chapter 19.7 .

Secondary postpartum haemorrhage

Secondary PPH is defined as bleeding >24 hours, or up to 6 weeks after delivery, most commonly as a result of infection or retained products of conception.

Antepartum Haemorrhage

Differential diagnosis

Incidental causes

These include bleeding from the lower genital tract, most commonly from physiological cervical erosion or ectropion, where the bleeding may be either spontaneous or post-traumatic, such as post-coital. Other causes that need to be excluded include bleeding from cervical polyps, cervical malignancy and cervical or vaginal infection.

Bleeding from haemorrhoids or vulval varices may also be mistakenly reported as vaginal bleeding.

Placenta praevia

Placenta praevia occurs when the placenta is situated in the lower uterine segment in the third trimester of pregnancy. It occurs in 0.5% of term pregnancies. Bleeding in this situation is usually bright red and painless, unless associated with labour contractions and often presents with several small ‘warning’ bleeds.

Placental abruption complicates around 1% of pregnancies. Bleeding occurs from a normally situated placenta. This may be a marginal bleed (from the placental edge) or in association with significant placental separation.

Bleeding may be revealed when blood escapes through the vagina, or it may be concealed behind the placenta, with no evidence of bleeding from the vagina. A placental abruption may follow relatively minor blunt trauma, such as a fall onto the abdomen, or a shearing force, such as that applied in a motor vehicle deceleration crash. Placental abruption may also occur spontaneously associated with hypertension, pre-eclampsia, thrombophilia or with cocaine use.

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