Habitual Abortion

Habitual abortion is a condition where a woman experiences multiple consecutive pregnancy losses, typically defined as three or more spontaneous miscarriages. While this reproductive problem is relatively uncommon, affecting about 1% of couples, it can cause significant emotional distress and frustration for those trying to build a family.

Table of contents

• What is Habitual Abortion?
• Medical Classification
• How Common Is It?
• Causes of Habitual Abortion
• Psychological Impact and Support
• Outlook and Future Pregnancies

What is Habitual Abortion?

Habitual abortion should be defined as the spontaneous sequential loss of three or more pregnancies that occur before the baby can survive outside the womb^[1]. This is also known as recurrent miscarriage or recurrent pregnancy loss^[3]. The term “spontaneous” means that the pregnancy losses happen naturally and are not intentionally caused.

recurrent miscarriage, recurrent pregnancy loss, recurrent abortion

Abortion, Habitual; Abortion, Spontaneous

Some medical organizations define this condition differently. The American Society for Reproductive Medicine and the European Society for Human Reproduction and Embryology define recurrent pregnancy loss as the spontaneous loss of two or more pregnancies^[4]. The Royal College of Obstetricians and Gynaecologists defines it as three or more first trimester miscarriages^[4]. However, most doctors agree that ectopic pregnancies (when a fertilized egg implants outside the uterus) and molar pregnancies (abnormal tissue growth) should not be counted when making this diagnosis^[4].

The term applies specifically to pregnancy losses that occur before 20 weeks of gestation or when the baby weighs less than 500 grams^[4].

Medical Classification

Not specified in sources

Women experiencing habitual abortion are sometimes referred to as “habitual aborters” in medical literature^[1]. The condition is classified as a form of infertility because it prevents couples from successfully having a baby, even though pregnancy can be achieved^[5].

How Common Is It?

Habitual abortion is not a frequent reproductive problem^[2]. Approximately 5% of couples trying to conceive have two consecutive miscarriages, and about 1% of couples have three or more consecutive losses^[4].

To understand this in context, it’s important to know that single pregnancy loss is much more common. About 15-20% of all recognized pregnancies end in miscarriage^[10]. Most studies show that the spontaneous miscarriage rate is between 10-15%^[4]. However, the true rate of early pregnancy loss may be close to 50% when including very early losses that happen before a woman even knows she is pregnant^[4].

The likelihood of having another spontaneous abortion increases with each successive miscarriage. After one spontaneous abortion, the risk of having another is approximately 15%. However, if two spontaneous abortions occur, the subsequent risk increases to approximately 30%^[4]. After three successive miscarriages, the risk of pregnancy loss is estimated at 30-45%^[4].

Causes of Habitual Abortion

The causes of habitual abortion are varied and often controversial. More than one factor may be present at the same time^[4]. Understanding these causes requires investigation of both genetic and medical factors.

Genetic Causes

According to medical research, about 60% of all recurrent miscarriages result from a genetic abnormality^[10]. Chromosomal abnormalities (problems with the number or structure of chromosomes) in the developing baby may cause 50% of miscarriages^[6]. Pregnancy losses due to chromosomal abnormalities are more common during early pregnancy. Aneuploidy (having an abnormal number of chromosomes) is involved in up to 80% of all spontaneous abortions occurring before 10 weeks of pregnancy but in less than 15% of those occurring after 20 weeks^[6].

Sometimes the parents themselves carry chromosomal abnormalities, such as balanced translocations (when parts of chromosomes are rearranged but no genetic material is missing). These parental chromosomal abnormalities can be passed to the baby and lead to pregnancy loss^[2].

Immunologic Causes

Problems with the immune system can contribute to habitual abortion. Antiphospholipid syndrome is an acquired thrombotic disorder associated with three or more recurrent losses after 10 weeks of pregnancy, after other maternal and genetic causes have been excluded^[6]. This condition involves abnormal antibodies in the blood that can affect pregnancy.

Anatomic Causes

Abnormalities in the structure of the uterus or cervix can cause repeated pregnancy losses. These include polyps (small growths), myomas (also called fibroids, which are benign tumors), adhesions (scar tissue), and cervical insufficiency (when the cervix opens too early during pregnancy)^[6]. Congenital uterine abnormalities (structural problems present from birth) have been identified in some women with habitual abortion^[9].

Endocrine Causes

Poorly controlled chronic disorders related to hormones can contribute to habitual abortion. These include hypothyroidism (underactive thyroid), hyperthyroidism (overactive thyroid), diabetes mellitus, and hypertension (high blood pressure)^[6][2].

Infectious Causes

Various infections have been studied as possible causes of habitual abortion^[2], though their exact role continues to be researched.

Environmental Causes

Environmental factors may play a role in some cases^[4], though specific causes vary.

Unknown Causes

Despite thorough investigation, the cause cannot be determined in up to 50% of women with habitual abortion^[6][8].

Psychological Impact and Support

Habitual abortion is associated with a high degree of anxiety and frustration^[2]. Women who have experienced multiple pregnancy losses often struggle with deep-rooted feelings of loss and sorrow. Some may worry that something they did caused the pregnancy losses^[2].

The importance of psychological support cannot be overstated^[2]. The first step in supporting any woman who has had three or more recurrent abortions is reassurance that the likelihood of successfully carrying the next pregnancy is still higher than the odds of having another miscarriage^[8].

The most important need for couples experiencing unexplained habitual abortion is to explain their chances of having a live baby and offer emotional support^[8]. Healthcare providers should allocate specific time for discussion where couples can express their fears and receive realistic assessments of their chances of having a baby in the future^[8].

Some small studies have found that tender loving care, or psychological support and sympathetic counseling, was associated with successful next pregnancies in up to 80% of cases^[8]. This support may help break the cycle where miscarriage-related stress produces a higher risk of another miscarriage.

Outlook and Future Pregnancies

Despite the challenges, there is reason for hope. Even without any treatment, in the absence of any identifiable cause, research shows that 60-80% of next pregnancies are likely to be carried to term and result in a live birth^[8]. Nearly two-thirds of women who have recurrent miscarriages will eventually carry a full-term, healthy pregnancy, often without treatment^[10].

Various treatment approaches exist depending on the identified cause. Preconceptual therapy (treatment before trying to conceive again) for both the wife and husband is recommended for the successful birth of a viable infant following previous sequential abortion^[1]. When specific causes are identified, such as uterine abnormalities or hormonal imbalances, targeted treatments may improve outcomes^[9].

A plan of investigation and management should be developed for each couple, taking into account their specific circumstances^[2]. Medical evaluation typically includes genetic testing, screening for immune disorders, thyroid testing, diabetes testing, and examination of the uterine structure^[6].