# Spontaneous Abortion

> NEET-PG OBG notes on spontaneous abortion covering threatened, inevitable, incomplete, complete and missed types with ultrasound and management.

- Canonical URL: https://prepelephant.com/topics/neet-pg/obstetrics-and-gynaecology/spontaneous-abortion
- Exam / course: NEET-PG · Subject: Obstetrics and Gynaecology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Spontaneous Abortion", PrepElephant, https://prepelephant.com/topics/neet-pg/obstetrics-and-gynaecology/spontaneous-abortion

## Direct answer

Spontaneous abortion is the expulsion of a pregnancy before the period of viability — before 20 weeks or 500 g in Indian teaching — occurring in about 10-15 per cent of clinical pregnancies, most in the first trimester. Chromosomal abnormality of the conceptus is the single commonest cause (roughly half or more of early losses). Clinical classification into threatened, inevitable, incomplete, complete and missed abortion rests on the state of the cervical os, the amount of bleeding and ultrasound findings, and treatment ranges from reassurance to medical or surgical evacuation.

## What you must remember

- Threatened abortion: bleeding with a closed os and a live intrauterine pregnancy on ultrasound; the prognosis is mostly good, and management is explanation, avoidance of heavy exertion and review — strict bed rest is not supported by evidence.
- Inevitable abortion: the internal os is open with bleeding and cramping; the pregnancy cannot be salvaged, so evacuation proceeds medically or surgically.
- Incomplete abortion: products of conception are partly retained (open os, bleeding, ultrasound debris); treatment is uterine evacuation — surgical evacuation or misoprostol regimens.
- Complete abortion: everything is expelled, the os closes, bleeding settles and ultrasound shows an empty cavity; expectant follow-up with hCG resolution suffices.
- Missed abortion (early pregnancy loss): the embryo has died but is retained, with brownish discharge, a uterus smaller than dates and ultrasound showing a non-viable gestation without cardiac activity; options are expectant, medical or surgical management.
- Evacuation options: medical — misoprostol (for example 800 micrograms vaginally or 600 micrograms sublingually, repeated per protocol), often preceded by mifepristone; surgical — manual or electric vacuum aspiration or dilatation and curettage; give anti-D to Rh-negative unsensitised women treated beyond the first few weeks.
- Warning features mandating urgent review — heavy bleeding with clots, shoulder-tip pain, faintness or fever — raise ruptured ectopic pregnancy or septic abortion.

## Common confusion

The state of the cervical os is the discriminator students fumble: closed os with bleeding is threatened, open os is inevitable or incomplete, and a re-closed os with an empty scan completes the sequence. Ultrasound refines the labels — cavity debris means incomplete, absent cardiac activity defines missed abortion, and a live intrauterine fetus makes it threatened, the only category in which pregnancy continues. Every woman with early bleeding needs an ectopic excluded before being labelled as having threatened abortion.

## Exam-focused takeaway

Vignettes present bleeding with a described os and ultrasound and ask for the diagnosis and next step; expect anti-D questions for Rh-negative women and mifepristone-misoprostol sequences for medical evacuation. Facts tested include the 20-week or 500 g viability limit, the 10-15 per cent incidence, chromosomal errors as the leading cause, and that bed rest does not prevent miscarriage. Ruptured ectopic red flags hidden inside "threatened abortion" stems are the classic trap.

## Frequently asked questions

### How is threatened abortion diagnosed?

Bleeding with a closed cervical os and ultrasound confirmation of a live intrauterine pregnancy; most such pregnancies continue.

### What distinguishes inevitable from incomplete abortion?

In both the os is open; inevitable abortion means the process has begun with everything still in utero, while incomplete abortion means part of the products has already been expelled.

### What is missed abortion?

Intrauterine fetal or embryonic demise with retention of the conceptus, typically with a uterus smaller than dates and no cardiac activity on ultrasound.

### What is the commonest cause of first-trimester abortion?

Chromosomal abnormality of the conceptus, accounting for roughly half or more of early losses.

### Is anti-D needed after abortion?

Yes, Rh-negative unsensitised women receiving medical or surgical management require anti-D immunoglobulin per protocol.