General Information on Preterm Births and Miscarriages

Monika Schreiber, Erich Saling and Jürgen Lüthje
Preterm Births
Alcohol and drug abuse
Contractions and Rupture of the Membranes
Preeclampsia, HELLP
Physical and mental Stress


For many years our non-profit institute has been playing an important role in improving the care of pregnant patients, particularly in the prevention of preterm births and spontaneous late abortions. Among other measures, we have developed the Self-Care-Program for pregnant women. In the meantime we have become a nationwide advice center and are sometimes also receiving inquiries about early abortions, so we have drawn up information about the differences between early abortions, late abortions and preterm births and about their causes.

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Different medical terms are used according to the duration of the pregnancy and the birth weight (see Table 1); a miscarriage (abortion) is the loss of the embryo, the fetus or the baby born dead weighing less than 500 g at birth. A difference is also made as to whether the abortion occurred during the first 12 weeks of the pregnancy (early abortion) or later on (late abortion). A preterm infant is defined as an infant that was born more than 3 weeks prior to the calculated birth date, weighing at least 500 g or less than 500 g that gave a so-called “sign of life” at birth, e. g. that it was able to breath or its heart was beating.

Table 1: Definitions

Description Definition
Miscarriage = abortion
Early abortion less than 12+0 gestational weeks (gw)
Late abortion 12+0 gw */** or more, and less than 500 g birth weight
Stillborn 500 g or more birth weight – infant showing no sign of life
Preterm infant less than 37+0 gw* showing signs of life, or a stillborn with a birth weight of 500 g or more
Mature infant 37+0 gw* or older, independent of weight or condition
* The gestational weeks (gw) are always reckoned from the 1st day of the last menstruation (in latin p.m. = post menstruationem).
For example 17+3 gw = 17 weeks and 3 days after the start of the last menstruation

** Sometimes in the literature the borderline is drawn not before 16+0 gw. Due to clinical aspects Saling recommends the earlier borderline at 12+0 gw (see also Table 2).

The exactly given difference in time noted in Table 1 is important, because the causes of an abortion during the first weeks of pregnancy are to a certain extent very different from those occurring later in the pregnancy (or preterm births). Just a few examples are given in Table 2.

Table 2: Causes of abortions and preterm births dependent on the gestational age

< 12 gw*
Rather 12 gw
to 26 gw
Rather last trimester
(from about 26 gw)
Disturbance of the infantile chromosomes
pid syndrome
Ascending vaginal infection
Severe Preeclampsia
and HELLP-syndrome
*gw = gestational weeks
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Causes of abortions

Regarding miscarriages (abortions) we have to differentiate between “an early abortion”, that is an abortion during the first 12 gestational weeks, and a “late abortion” (see Table 1).

A miscarriage in the first few weeks of pregnancy occurs relatively often. About 11–15 % of all diagnosed pregnancies ends with an abortion. Earlier – before modern pregnancy diagnostics were available – a considerable number of women didn’t actually know that they were pregnant: their menstruation was just “a little bit late” or “the bleeding was heavier than normal”. Even more often the fertilized egg is lost before the next menstruation is expected. This happens in about half of all pregnancies. The most common cause is that the embryo itself wasn’t viable. The early abortion is therefore a so-called “protective mechanism” of nature.

Only a small group of women suffer a recurrent abortion. Therefore, after the first abortion, thorough diagnostics are mostly not necessary. But even after one abortion, particularly when it is a late abortion, some “essential examinations” should be performed. Immediately after the abortion investigations should be made to find out whether there was an infection (vaginal smear, inflammation parameters in the blood, urine check). Before a new pregnancy, it is recommended to perform a vaginal ultrasonic scan, which today can be done in almost all gynecological practices. Table 3 demonstrates the main differences between sporadic abortions (which only occur occasionally) and abortions that happen repeatedly.

Table 3: Differences between sporadic and recurrent abortions:

Sporadic Abortion
Recurrent Abortion
2 or less
3 or more
Gestational age
mostly 1st-3rd months
1st & 2nd trimester
Infantile chromosome implement
abnormal in 50 % (aneuploid)
mostly normal
Causes of parental origin
no (seldom)
Yes (often)

Recurrent abortions

In 1–2 % of the women, recurrent abortions occur: In these cases an exact investigation of the cause is necessary (recurrent abortions are also called “habitual abortions”. The conventional definition of a “habitual abortion” is “a spontaneous abortion that occurred for the third time at least”). But today a detailed investigation of the cause should be performed already after the second abortion, particularly when the patient is already advanced in age or emotionally heavily stressed due to the losses.

Possible causes of recurrent abortions:

  • Uterus anomalies, for example deformities, larger or extensive myoma (benign uterine tumors)
  • Infectious causes
  • Hormonal causes
  • Metabolic disorders
  • Genetic causes
  • Immunological causes
  • Abuse of luxury food, stimulants (e. g. coffee), alcohol, tobacco and drugs
  • Psychosocial or social causes
  • Disturbance of blood coagulation (seldom)
  • Not well adjusted severe diabetes (seldom today)
  • Pollutants (seldom)
  • Other risk factors, which result from the past history
  • Often no cause can be detected


A full-length presentation of the diagnostics in recurrent abortions would be too extensive for this article, therefore only a few comments:

  • Detailed obstetrical/gynecological exploration of past history, also taking into account any genetic abnormalities in the family, other illnesses as well as use of alcohol, smoking, stimulants, drugs and danger due to pollution (for example at work)
  • Examination for infections of the vagina, cervix and remaining genital tract (bacterial vaginosis, chlamydia, mycoplasma)
  • Ultrasound examination, in particular vaginal sonography, maybe hysteroscopy
  • Karyotype examination (chromosome analysis) of both partners
  • Hormone analysis (TSH, LH, prolactine, androgene, progesterone)
  • Examination of antiphospholipidant antibodies (for example Anti-Phospherin, Anti-Cardiolipin).
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Causes of preterm birth (and late abortion)

When considering the causes of preterm birth we have to differentiate between:

  1. Preterm birth due to early contractions and/or rupture of the membranes
  2. Preterm birth, because the pregnancy had to be terminated, mostly when the fetus is at high risk (for example severe malnutrition) or when the mother is dangerously ill (for example HELLP syndrome)

Sometimes several causes overlap, for example infections can lead to preterm contractions, to early rupture of the membranes but can also endanger the mother and her baby.

Table 4: Frequent causes and risk factors for preterm birth

Illnesses, resp. criteria from the mother's side

  • Preterm births and miscarriages in the past
  • Infections (most frequently ascending vaginal infections and infections of the urinary tract, but some other infections can also increase the risk, e. g. parodontitis)
  • Physical and emotional stress, psychosomatic disturbances, poor social and domestic situation
  • Severe maternal illness, which would endanger the mother’s life if the pregnancy continued, for example HELLP syndrome
  • Smoking, alcohol, stimulants and drug abuse
  • Hormonal disturbances
  • Situation after receiving fertility medication and/or treatment

Factors concerning the uterus

  • Anatomical incompetence of the cervix, for example after an extensive conisation
  • Anatomical abnormalities of the uterus (for example larger or numerous myoma)
  • Uterine bleeding (for example with placenta praevia)
  • Excessive amount of amniotic fluid (polyhydramnion)
  • If the patient has had two or more induced abortions

Factors concerning the fetus

  • Severe malnutrition of the fetus in case of placental insufficiency and when external care would provide better chances than in utero
  • Malformation of the fetus or severe illness
  • Fetal “stress” (for example chronical lack of oxygen)
  • Multiples


Preterm contractions and premature rupture of the membranes

If labor has not been induced, preterm birth starts mostly by preterm contractions and/or premature rupture of the membranes accompanied by changes at the lower part of the uterus and the cervix, whereby various factors can play an important role (see also Fig. 1).

Mechanisms that can lead to preterm birth

Fig. 1: Conditions and mechanisms that can lead to preterm birth

Please click on the miniature picture.

Regarding a number of the causes listed in Table 4, prevention is impossible or limited. Where some chances are existent, they are discussed below

Regular prenatal checks made by the physician or midwife are an important method of prevention. In this way a considerable number of abnormalities can be detected in good time and appropriate consequences can be started if necessary.

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Smoking is the main cause of nutritional deficiency of the fetus (hypotrophy or uterine growth retardation, also known as malnutrition). It has been proven that smoking constricts the blood vessels – including those of the placenta – so that less blood reaches the fetus. Smoking does not only constrict the blood vessels momentarily, but can also impair the placenta permanently, in a similar way as arteriosclerosis. This can lead to a situation whereby the fetal supply of blood, oxygen and nutrition is insufficient (this is known as placental insufficiency). In cases of serious placental insufficiency labor frequently has to be induced.

In order to protect her infant, every pregnant woman who had previously been a smoker, should definitely try to give up smoking (in the transitional period e. g. nicotine plasters can help). If she is unsuccessful in her attempt: every single cigarette less counts!

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Alcohol, stimulants and drug abuse

Alcohol does not cause preterm labor, but rather leads to impairments of the baby (in particular growth retardation, malformations and also mental retardation). A certain amount of alcohol or a period of time during pregnancy during which alcohol consumption is certainly harmless for the unborn child is not known. Therefore, the unanimous recommendation of all experts is to completely abstain from alcohol during the entire pregnancy.

A number of studies have shown that consumption of too much coffee or liquorice increases the risk of preterm birth, and so coffee and liquorice should only be consumed in small quantities.

Also illegal drugs (especially marihuana, cocaine and ecstasy) can lead to preterm birth and should therefore be avoided. In the case of heroin there is an additional risk of infections (use of non-sterile syringes). This is one of the reasons, why heroin-addicted mothers in Germany are given the replacement substance Methadon.

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Premature rupture of the membranes and preterm contractions

There are various reasons (see Fig. 1 and Table 4 above) that can lead to premature rupture of the membranes and to preterm contractions, but one of the most frequent causes, which in fact can be prevented particularly easy, is the ascending infection of the genital tract.

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A greater part of preterm birth is caused by ascending infections starting in the vagina. These infections can spread into the uterus and can cause changes in the area of the lower part of the uterus – the isthmus uteri – and can lead to preterm labor, to premature rupture of the membranes and then to preterm birth, maybe even to an infection of the unborn infant as well as the mother. Infections also often cause late abortions (abortions after 12+0 weeks of gestation).

Therefore during the regular prenatal care examinations special attention should be given to any signs of a disturbance of the vaginal flora or of an already existing infection. It is even more successful, when additionally each pregnant woman herself makes some observations and performs self-care checks at home, in order to obtain early information as to whether she is at risk of experiencing a miscarriage or a late abortion. (You can read more about this under “Self-Care-Program for Pregnant Women”.)

Infections of the urinary tract occur quite often during pregnancy and are mostly noticed by clear discomfort, particularly by a burning sensation when urinating or by the urge to urinate). But also infections without discomfort (so-called “asymptomatic infections”) increase the risk of preterm labor. This is why urine samples should be regularly checked within the framework of the prenatal care examinations. When there is discomfort, that points to an infection of the urinary tract, it is recommendable to have an examination made at once.

Other infections do not lead to abortions so often, but occasionally. It is possible to have an infection of the membranes, the placenta and/or of the amniotic fluid leading to an infection of the baby. In most cases it is caused by a so-called ascending infection (see above). But sometimes an infection can be caused for example by an amniotic fluid withdrawal (amniocentesis). A direct infection of the blood paths via the placenta is also possible. Due to the inflammation there is a bodily defense reaction (in both mother and baby), whereby various substances are released (among others prostaglandines) which can cause contractions. Some maternal infectious diseases, for example German Measles, Measles and Toxoplasmosis can be transferred to the fetus. Depending on the stage of the pregnancy, such infections can lead to an impairment of the infant (particularly German Measles) or to a miscarriage or early abortion (for example Measles). In the case of virus infections like Measles or German Measles the best way to prevent them is to have a vaccination before the start of the pregnancy (provided you didn’t have these illnesses when you were a child). Toxoplasmosis can lead to abortions or to an impairment of the baby. If the mother has never had a toxoplasmosis infection and therefore does not have protection through antibodies, she should avoid eating raw meat (for example mince, tartar) and be particularly careful of any contact with cats (cats can transfer toxoplasmosis).

But other feverish events or diarrhea and even parodontitis can sometimes also cause an abortion. Fever can among other things lead to labor by releasing prostaglandines. Due to extreme movement of the intestines, (peristalsis), diarrhea can lead to contractions. Also, one shouldn’t underestimate a Parodontitis. It is not ’just’ a small local infection. Actually, it is like a big, infected wound and the substances caused by the bodily defense reaction (see above) can lead to preterm labor. Therefore it is recommendable to treat parodontitis – best before pregnancy – and in case of other illnesses to contact the physician even in the case of slight illness, (for example flu) and if necessary take a remedy suitable for pregnant patients to combat fever, such as acetylsalicylic acid (e. g. Aspirin®).

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Miscarriages and preterm births in the past

Women who have already had one or more late abortions (after 12 gestational weeks) or preterm births, are at higher risk of suffering a recurrent miscarriage or preterm birth in the next pregnancy. The risk increases with the number of losses already suffered. In cases of recurrent early abortions before 12 gestational weeks, please read “Causes of abortions” on this page.

During the 12th to 32nd weeks of gestation ascending genital infections are the main causes of miscarriages and abortions and for example lead to preterm contractions and/or to premature rupture of the membranes.

Taking all pregnancies into consideration, ascending genital infections fortunately do not occur that often. The majority of women possess an undisturbed vaginal milieu, and this generally prevents an ascension of infections. However in some women the vaginal milieu becomes disturbed. In most of these cases, it is sufficient, if these disturbances are detected early enough and then are treated accordingly. This is in fact the goal of our “Self-Care-Program for pregnant women”.

But particularly for women who have had recurrent late abortions or very preterm births, this seems not to be sufficient. In such cases we recommend performing the operative Early Total Cervix Occlusion as a preventive measure. It is indicated in women who have suffered 2 or more miscarriages or preterm births between the 12th and 32nd weeks of gestation and in whom an infection could be identified as being the cause, or when no other specific cause could be found. You can read more about this in our information: “Early Total Cervix Occlusion”.

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Preecalmpsia (EPH gestosis) and HELLP-Syndrome

Severe forms of the preeclampsia (previously known as pregnancy toxaemia) and the HELLP syndrome are often reasons why a pregnancy has to be terminated early.

In the case of preeclampsia, also called EPH gestosis, fluid collects in the legs and arms (edema), protein is present in the urine (proteinuria) and high blood pressure (hypertension) appears. In severe cases an eclampsia can develop, whereby phases of cramp can occur, which put the life of both mother and her infant at high risk. The first symptoms for this (in addition to the gestosis-symptoms) can be: severe headache, flickering before the eye, feeling not well at all.

A HELLP-syndrom can develop on the basis of a preclampsia, but sometimes it can occur without any previous warning. The symptoms are mostly: severe pains in the stomach and back, the diagnosis will then be made using blood tests: (H = haemolysis, that is the disintegration of the red blood cells, EL = elevated liver laboratory levels, LP = low platelet count (not enough platelets for the blood coagulation).

The exact reasons are still not known, but some risk factors have come to light, such as hereditary aspects, or kidney disease and/or high blood pressure before the start of the pregnancy. In some women immunologic reasons or abnormalities in blood coagulation (thrombophilia) could stimulate the disease.

Previously women were advised to eat food without salt and to eat only fruit and rice on one day a week in order to dehydrate. But nowadays this isn’t considered a suitable solution. On the contrary food with a lot of protein seems to have a good effect

Also in this case the most important preventative measure is to have regular prenatal care examinations, when the blood pressure is measured and the urine is checked. In this way risk factors and abnormalities can be dealt with quickly.

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Physical and mental stress

Pregnancy is a natural event. The ever growing little person takes a lot of physical and emotional energy from the mother. Therefore any work which involves hard physical stress or excessive mental or emotional stress should be avoided.

Too intensive emotional or physical stress can increase the risk of preterm labor; probably via the detour of an impaired immune system, which then can increase the susceptibility of a vaginal or other infection. But hormones due to stress can also lead to early abortions.

According to the examinations performed in our institute we have concrete proof that in women who have symptoms of prematurity, 65 % of them said that they were in a stress situation, there are impairments of the immune system and due to this, ascending infections may possibly be fostered.

Much more research should be made regarding the exact connections between stress, impaired immunity, ascending infections and prematurity. We think that the following suggestions are the most suitable to achieve prevention of preterm births on a wide scale:

  • all pregnant women should be informed very early on in the pregnancy about all the medical preventative measures which are listed in our Prematurity-Prevention-Program, in particular participation in our Self-Care Program for pregnant women and
  • if indicated: Intensified care by physician or midwife and possibly psychological or a psychosocial support is recommended.

Now some advice as to how the pregnant woman can protect herself from overexertion.

Women who work on a regular basis are protected in many countries by maternity guiding rules that stipulate what she is allowed to do. For example in Germany the employer must have a couch ready, so that the expectant mother can have a little rest if necessary. The attending physician or the local health insurance company can give more information.

Within the private sphere physical hard work should be avoided (for example, hanging wallpaper, carrying boxes for moving house). Often just before the arrival of the expected baby there is “an awful lot to do”: the nursery has to be ready, perhaps even a move into another flat. There is a special rule – expectant mothers are allowed to pack the boxes, but someone else has TO CARRY THEM. There’s no reason why a pregnant woman shouldn’t do what she feels like doing, as long as she doesn’t overload herself. Quite different is the situation when her physician has ordered her to rest and avoid any physical stress. In this case she really “has to take it easy”. If nobody is available to help her to do the housework and look after the family, she should see if she can get an external service. In Germany such a service is supported by the health insurance company, in other countries the regulations might be different.

Normal physical activity, like going for a walk, swimming, doing gymnastics or light training (see Table 5) are very good during the pregnancy and are a good preparation for labor – they are also suitable for reducing stress after an “awful day”. Any kind of sport that is too strenuous or is dangerous should be avoided (see Table 5). In particular pregnant women who are not trained in a certain kind of sport shouldn’t start it, but should rather choose one of the sports recommended in Table 5. In doubt, it is always best to talk to your physician about it.

In a lot of cases it isn’t easy to avoid emotional conflicts. Perhaps the parents hadn’t planned to have a child at that particular time, perhaps there are problems in the relationship or maybe financial difficulties. Sometimes it is already a great help when the expectant mother doesn’t feel she’s on her own. We recommend:

Let yourself be helped by members of the family or by friends, or in an advice center and of course by your physician or midwife. If you feel “it’s all too much”, your doctor or the midwife can give you a sick note for a longer period. Take care of yourself. Just then, when you have children already, it is difficult to find the time to gain “time for oneself” for relaxation and recovery. Perhaps a babysitter, a relative or friends could look after your children for a few hours.

When a couple have already suffered an abortion or a miscarriage, the next pregnancy is always worrying or uneasy. For some couples it is helpful to have not only “purely medical” advice but also psychological advice during the pregnancy. Talking with other couples who have been in a similar situation can also be of help. You can find addresses of self-help groups for example in the internet. Our German site provides some links to self-help groups in German speaking countries.

Table 5: recommended or less recommended sport activities during pregnancy
(after Friese, Dudenhausen and others (2003). BabyCare and also Passloer)

Recommended sport activities

  • Swimming
  • Hiking, long walks (but avoid extreme differences in altitude in the mountains)
  • Cycling (avoid uneven roads)
  • Easy jogging (special jogging shoes to combat vibration), (Nordic) walking
  • Light gymnastic exercise, breathing exercise
  • Muscle training (light), stretching
  • Exercises for relaxation
  • Tai-Chi, Chi-gong, Yoga (you should speak to the teacher, as some exercises should not be performed during pregnancy)
  • Cross-country skiing
  • Dancing

Sport activities that are suitable in a limited way

  • Strenuous jogging or running (not suitable when not “in form”)
  • Snorkelling
  • Sauna (only for a short time and not during the first gestational weeks)
  • Aerobics (where possible not a lot of jumping or turns, better to go to a special aerobic course for pregnant women)
  • Sport at a high altitude (above 2000 meters is not recommendable)
  • Rowing
  • Floor exercises (Avoid any exercises with high jumps and risk of stretching)
  • Sailing
  • Table tennis
  • Inline-skating (people who haven’t practised can fall down easily)

Sport activities not recommended at all

  • Sport involving hard knocks or quick acceleration
  • Sport with the risk of falling over, for example surfing, hang-gliding, alpine ski
  • Squash (for people without practice, but also risk of falling over when practiced)
  • Tennis (for people who haven’t practiced, but also risk of falling over)
  • Diving (absolutely forbidden)
  • Riding (for people not used to it)
  • Handball, football and other team sports (risk of getting injured)
  • Fighting-sports
  • Power sport, body building
  • Light athletics
  • Apparatus gymnastics
  • Weight lifting
  • Bungee-jumping, parachuting, etc.
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Diabetes mellitus

Diabetes mellitus that has not been correctly treated can lead to abortions, to preterm births or to an impairment of the infant as well as to complications for the mother and the baby. Therefore women who suffer from diabetes should make sure that their blood sugar level has been regulated before and during the pregnancy and should be treated by a doctor who is an expert in this field and who has experience in treating diabetic pregnant women.

Nowadays when the diabetes has been correctly regulated the risk of an early abortion or miscarriage is hardly increased. Some women who are not normally diabetic develop a so-called “Pregnancy Diabetes”. This kind of disturbance often has no symptoms, but it can – undetected – lead e. g. to a preterm birth, to complications during labor and to metabolic disturbances in later life, for instance obesity. This is why a so-called sugar tolerance test (oral glucose tolerance test, abbreviated oGTT) is recommended for pregnant women.

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A healthy, well-balanced and varied diet protects both the mother and her baby. There are a number of recommendations to be found in books and on the internet.

During pregnancy, the following substances are recommended to be taken additionally:

  • folic acid (a lack of this can lead to miscarriages or to malformations of the back or to a hydrocephalus)
  • iodine

Sometimes even if the patient has taken food containing iron, such as lean meat, pulses and dark vegetables, she may suffer from iron-deficiency, and her physician will prescribe an iron preparation.

In order to have enough intake of essential fatty acids (particularly long chain omega-3 fatty acids), it is recommendable to eat fish twice a week (one of these meals should be fatty sea fish. Alternatively one could consume fish oil or vegetable preparations of alga containing these acids. Generally it is not necessary to take other minerals or vitamins when you have a well-balanced diet, and in any case you should always consult your physician before taking any other substances, as an overdose of some substances could lead to an impairment of the infant.