Missed Abortion - Introduction

An abortion is a pregnancy that ends before the baby can survive outside the womb because it has not yet reached viability.

An abortion may be early  - during the first 14 weeks of pregnancy, or late. The vast majority are early - only about 1% of abortions are late.

The definition of a abortion is a spontaneous loss of a pregnancy before 24 weeks: in the UK we calculate the duration of a pregnancy from the first day of the last period (LMP). A abortion - the medical term for an early pregnancy loss is abortion - tends to start with bleeding, and pain may then develop.

A missed abortion is characterised by there being no reasons to have suspected that the pregnancy is not going to continue but the embryo has died.

An inevitable abortion means that the pregnancy cannot be salvaged. It may be incomplete, with pregnancy products still in the cavity of the womb or complete with nothing remaining.

The combination of modern pregnancy tests and ultrasound will usually determine the situation quite quickly. Pregnancy tests these days should become positive within ten days of conception (i.e. even before the first missed period).

Ultrasound begins to show a pregnancy within the uterus by five or six weeks (a week or two after the first missed period). On occasion, it may be too early to diagnose the situation accurately and tests may need to be repeated to see what changes occur.

Types of abortion

Table 12.1 indicates the various terms most frequently associated with abortion.

Type of abortion Description
Spontaneous Abortion This is when the abortion occurs naturally as opposed to being induced.
Induced Abortion The pregnancy is terminated artificially.
Threatened Abortion There is bleeding and sometimes pelvic pain but the cervix is closed and ultrasound indicates an ongoing pregnancy within the uterus.
Inevitable Abortion The pregnancy is not continuing.
Complete Abortion An inevitable abortion and the uterus has completely emptied itself.
Incomplete Abortion An inevitable abortion with products of the pregnancy still present in the uterus.
Missed Abortion There are no reasons to have suspected that the pregnancy is not going to continue but the embryo has died.
Septic Abortion The abortion has been complicated by infection.
Recurrent or habitual Abortion Most authorities recommend that these terms should be used only for three or more consecutive abortions although there is a tendency towards two.
Early Abortion Abortion in the first few weeks of the pregnancy.
Late Abortion Abortion after the first few weeks.
First trimester Abortion Abortion before thirteen weeks of pregnancy.
Second trimester Abortion Abortion after thirteen weeks and before twenty four weeks.

Abortion symptoms

The first abortion symptom is vaginal bleeding, which can range from spotting to being heavier than a period.

A little spotting may be an early sign of abortion although fortunately this may amount to no more than a threatened abortion and the pregnancy continues.

The second abortion symptom is pelvic pain.

The third abortion symptom is cessation of pregnancy symptoms including breast tenderness, morning sickness and having to pass urine more frequently than usual.

Sometimes there may be no sign or symptom to suggest abortion and pregnancy symptoms continue, and the abortion is only discovered in a routine scan. This is a missed abortion.

A threatened abortion occurs when there is vaginal bleeding but ultrasound confirms a viable pregnancy.

Cause of Abortion

Often the cause of a abortion remains unknown. The most common cause for abortion is a blighted ovum - the afterbirth type tissues develop but there is no baby.

Another common cause is a genetic defect and nature decides not to allow the pregnancy to continue.

Smoking and obesity may contribute to abortion but do not cause abortion by themselves.

Similarly,  stress may play a role in pregnancy loss, but it hasn't been shown to cause abortion on its own.

The cause for recurrent abortions is discussed Q12.16 to Q12.21.

Prevalence Of Abortion

It is thought that between 10 and 20% of pregnancies miscarry. Most abortions occur in the early weeks of pregnancy. Ultrasound screening for fetal anomaly has shown the incidence of non-viable pregnancy at 10-13 weeks to be 2.8%

Blighted Ovum

Normally the fertilised egg divides and part becomes the embryo (future baby) and part becomes the afterbirth type tissue (trophoblast) and the membranes that form a fluid filled bag around the baby. When there is a blighted ovum, the afterbirth tissues develop alone without the development of the baby. Blighted ovum hasalso been referred to as an 'anembryonic pregnancy'. Nearly half of early abortions are associated with a blighted ovum. It is likely that abnormal chromosomes are more prevalent.