Threatened miscarriage - symptoms, signs, causes and treatment options

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.

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%

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 miscarriages are associated with a blighted ovum. It is likely that abnormal chromosomes are more prevalent.

Pregnancy Tests

Pregnancy tests are designed to determine the presence of the pregnancy hormone HCG. Until twenty years ago, pregnancy tests were biological, relying on the affects of the hormone on animals. There could be a cross-reaction with other hormones, notably LH. Many women reaching the menopause could have a false alarm as LH levels rise at the menopause and when they missed their periods their pregnancy tests could be falsely positive. Modern pregnancy tests are monoclonal they react only with the specific hormone they are designed to detect. In the early weeks of pregnancy, the HCG level doubles every two days. Whereas the old pregnancy tests would become positive with a concentration of 3,000 IU (about two weeks after the missed period) the monoclonal tests show a positive result at between 25 and 50 IU and these levels are reached before a period is missed.

The accuracy of modern pregnancy tests are not only useful in the early detection of pregnancy but also in assisting in the management of early pregnancy problems such as threatened miscarriage or possible ectopic pregnancy.

A lady presented with vaginal bleeding and left sided pelvic pain. Her pregnancy test was positive and ultrasound did not show any sign of a pregnancy either within or outside the uterus (ectopic pregnancy). Her beta HCG level was 365 units suggesting a very early pregnancy at most. Two days later the level had fallen to 180 units which indicated that the pregnancy was not continuing. We could not say for certain whether this had been an intra-uterine pregnancy that miscarried or a possible ectopic pregnancy that was being resolved by nature but no operative intervention was required.

Treatment of Miscarriage

The options for managing miscarriage are outlined in Figure 12.1. If miscarriage is threatened, you will usually be advised to rest for a few days and a repeat scan will confirm whether the pregnancy is continuing. There have been several important developments in the management of miscarriage in recent years. The combination of highly sensitive pregnancy tests and ultrasound will usually assist in providing an accurate diagnosis. Many hospitals now have an early pregnancy assessment unit that specialise in these problems. This should allow you to see an expert in a dedicated area where you can receive sympathetic assistance away from busy, and often fraught, accident and emergency departments.

At one time, we believed that if you miscarried between seven and thirteen weeks, there were likely to be retained products of pregnancy and an ERPC (evacuation of retained products of conception) was indicated to reduced the risk of infection and bleeding.

In the days before legal termination of pregnancy (Chapter 19) infection with induced abortion was relatively common. These septic abortions could be life threatening. Current opinion is that the risk of infection and bleeding has been overstated and a conservative approach now seems safe.

From your point of view, this means that you may not need an operation which, as always, carries an element of risk (surgery risks) and furthermore delays waiting for an operation slot are avoided. A repeat scan about ten days after the diagnosis of incomplete abortion will usually confirm that nature has solved the problem for you and the womb has completely emptied itself. If a miscarriage is incomplete, oral misoprostol 600 micrograms may be as safe as surgical evacuation.

If you are Rhesus negative you should be offered an injection of Anti-D to reduce the chance of rhesus problems in a future pregnancy. Guidelines for the administration of Anti-D are currently under review.

The emotional aspects of miscarriage can be difficult to deal with particularly if you have had difficulty conceiving or if this is not your first miscarriage. There is inevitably a time of grieving. A trained counsellor with a special interest in miscarriage can provide support and help you come to terms with your loss.

Pregnancy after Miscarriage.

If you are pregnant after a previous miscarriage, the chances are that the pregnancy will be successful. Even after three miscarriages, your chance of a successful pregnancy is 55%.

Usually nature has detected some problem such as a chromosome abnormality (genes - chromosomes) and decides that it is in your interests to discontinue this pregnancy and give you an early chance to start a successful one. A blighted ovum (Q12.4), or an embryo with an abnormality would be reasons for spontaneous miscarriage. Occasionally there may be a different and perhaps remedial cause which would need consideration if you have three miscarriages.

How can we ensure that I will not miscarry again?

It is an understandable cry from the heart from couples who experience the devastation of recurrent pregnancy loss that there must be one explanation and one perfect treatment. Even if a cause is identified we are unlikely to achieve success rates better than 75% within the foreseeable future. Half of the fifteen percent of pregnancies that miscarry can be attributed to a genetic problem of the embryo and we do not have a remedy for this. It is only in the last ten years that we have begun to find some treatable explanations for recurrent miscarriages.

For those with identified antiphospholipid antibody problems aspirin alone or in combination with heparin has been shown to be beneficial. Twenty percent of women have PCOS (Q7.2) and this syndrome may perhaps account for a greater proportion of recurrent miscarriages. Metformin looks promising on theoretical grounds but we still lack the scientific proof that is required. The role of bacterial infection and the possible benefit of antibiotics is an example of a new area that is being investigated. There is a suggestion that 'tender loving care', with frequent assessment during pregnancy, may help. There is no evidence that hormone support in pregnancy or low-dose aspirin for those without evidence of antiphospholipid antibody problems improves the outcome.

There is some evidence that metformin treatment for PCOS may be beneficial but more robust research is required before it can be implemented in routine clinical care.

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