Threatened Miscarriage - Introduction

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

A miscarriage may be early  - during the first 14 weeks of pregnancy, or late. The vast majority are early - only about 1% of miscarriages are late.

The definition of a miscarriage 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 miscarriage - the medical term for an early pregnancy loss is abortion - tends to start with bleeding, and pain may then develop.

A threatened miscarriage is characterized by bleeding early in the pregnancy but the pregnancy continues.

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 miscarriage

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

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

Miscarriage symptoms

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

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

The second miscarriage symptom is pelvic pain.

The third miscarriage 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 miscarriage and pregnancy symptoms continue, and the miscarriage is only discovered in a routine scan. This is a missed miscarriage.

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

Cause of Miscarriage

Often the cause of a miscarriage remains unknown. The most common cause for miscarriage 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 miscarriage but do not cause miscarriage by themselves.

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

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

Prevalence Of Miscarriage

It is thought that between 10 and 20% of pregnancies miscarry. Most miscarriages 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%