Miscarriage
A miscarriage is the loss of a pregnancy during the first 23 weeks. It is a common complication of early pregnancy and can be an unhappy, frightening and lonely experience. In part 2 of a 3 part focus on miscarriage, we discuss the causes and different types of miscarriage.
What is miscarriage?
A miscarriage is a pregnancy that spontaneously ends before the 24th week. Unfortunately, miscarriage is very common, with around 10 to 15% of recognized pregnancies ending this way (1, 2). Most happen within the first 12 weeks of pregnancy (3, 4) and it is thought that as many as 40% of eggs that are fertilised miscarry, although frequently too early in pregnancy to be noticed (5).
Causes of miscarriage
The causes of miscarriage are not entirely understood. Several factors have been correlated with higher miscarriage rates, but whether they cause miscarriages is debatable. The following factors are thought to contribute:
- Genetic abnormalities - A pregnancy with a genetic problem has a very high probability of ending in miscarriage; more than half of all first-trimester miscarriages are thought to be caused by chromosomal abnormalities in the foetus (5, 6). These abnormalities are usually random and generally do not reflect the genetic makeup of the parents. However in a small percentage of couples, one partner may have a chromosome problem which has not been previously apparent.
- Infection - Minor infections like coughs and colds are harmless. However, high fevers and certain infections such as rubella (German measles), listeria and toxoplasmosis can cause a miscarriage to occur.
- Age - Miscarriage rates increase steadily with age, with more substantial increases after age thirty five (7).
- Physical problems - womb abnormalities (such as a misshapen cervix or fibroids - benign growths of the wall of the womb) can cause a miscarriage. However, such problems can often be corrected with surgery.
- Autoimmune causes - these occur when the body's own immune system acts against itself, causing blood clotting in the placenta and preventing normal pregnancy progression (8).
- Other health problems - undiagnosed or poorly controlled diabetes, kidney disease, thyroid problems, high blood pressure or polycystic ovarian syndrome can all contribute to miscarriage.
- Alcohol - heavy consumption during pregnancy can be a risk factor.
- Cigarette smoking - Tobacco smokers have an increased risk of miscarriage (9). An increase in miscarriage is also associated with the father being a cigarette smoker (10).
In the vast majority of cases, there is no way of preventing a miscarriage and no viable cause can be found. However, there is still a good chance that a sufferer of singular or recurrent miscarriages will eventually deliver a healthy baby.
Symptoms of miscarriage
The most common symptom is bleeding from the vagina (11) (varying from light spotting to heavy bleeding), sometimes accompanied by lower abdominal, pelvic or back pain. Around 50% of women who seek clinical treatment for bleeding during pregnancy will go on to have a miscarriage (12).
If the miscarriage proceeds, the bleeding usually becomes heavier and solid material is occasionally passed with the blood. Usually the womb empties itself completely and the bleeding gradually subsides over the next few days. However, symptoms will vary and some woman will experience no symptoms at all.
Types of miscarriage
There are several different types of miscarriage, as described below:
- Threatened miscarriage - categorised by vaginal bleeding early in pregnancy which is not enough to dislodge the embryo. The pregnancy is likely to continue successfully if an ultrasound scan shows the heartbeat of the developing baby.
- Inevitable miscarriage - a threatened miscarriage may lead to an inevitable miscarriage if the bleeding worsens and the cervix opens. A miscarriage is then unavoidable.
- Incomplete miscarriage - when a miscarriage has started but tissue remains in the womb and bleeding continues. Admission to hospital is usually required to complete the miscarriage.
- Complete miscarriage - when the pregnancy has been lost, the womb is empty, bleeding has stopped and the cervix has closed.
- Delayed or missed miscarriage - when the developing baby has died before 24 weeks but without pain, bleeding or tissue loss. The mother may therefore be unaware that her foetus has died and may only discover during a routine ultrasound scan.
- Septic abortion - occurs when the tissue from a missed or incomplete abortion becomes infected. The infection of the womb carries risk of spreading infection (septicaemia) and is a grave risk to the life of the woman.
- Blighted ovum - where a fertilised egg has not divided as it should, resulting in a pregnancy sac that contains no foetus. A blighted ovum eventually results in miscarriage, though miscarriage may not occur for weeks.
- Ectopic pregnancy - when the fertilised egg attaches itself outside the cavity of the uterus. An ectopic pregnancy is not usually capable of surviving and in most instances an embryo is not developed and a woman will spontaneously miscarry.
- Molar pregnancy - a rare problem that can occur when an abnormal fertilised egg starts to grow in the uterus. The cells that should become the placenta grow too quickly and leave no room for a baby to develop.
When to see a Health Professional
It is important to watch out for the following warning signs during pregnancy:
- Sudden decrease in pregnancy signs
- Bleeding from the vagina with or without cramps
- Mild to severe back or stomach pain
- Contractions (painful and happening regularly)
- Feeling weak or faint
- Passing tissue and/or clots
All these symptoms are potentially serious and must be treated immediately.
Diagnosis of miscarriage
A miscarriage can be confirmed via ultrasound, blood and urine tests or by the examination of the passed tissue. Genetic tests may also be performed to look for abnormal chromosome arrangements. Follow up appointments may be offered to discuss any questions or worries. Some areas also offer pre-pregnancy counselling for people who want to talk about future pregnancies.
In part 3 we will focus on how to cope with feelings following a miscarriage and the process of trying again.
About the author
Miscarriage affects many people and can have a devastating impact. However, you don’t have to struggle alone. The Miscarriage Association can offer support as and when you need it; we hope you will find the information and encouragement that you need to help you through.
Contact:
Miscarriage Association, registered UK Charity
Ruth Bender Atik, National Director
Telephone: 01924 200795
Email: ruth@miscarriageassociation.org.uk
Helpline 01924 200 799. Mon-Fri 9am-4pm
www.miscarriageassociation.org.uk
References:
1) American College of Obstetricians and Gynecologists (ACOG) (2008). Management of Recurrent Early Pregnancy Loss. ACOG Practice Bulletin, 24.
2) Reddy, U.M., (2007). Recurrent Pregnancy Loss: Nongenetic Causes. Contemporary Ob/Gyn, 63-71.
3) Rosenthal, S., (1999). The Second Trimester. The Gynecological Sourcebook. WebMD.
4) Francis, O., (1959). An analysis of 1150 cases of abortions from the GovernmentR.S.R.M.Lying-inHospital, Madras. J Obstet Gynaecol India 10 (1) 62–70
5) Michels, T & Tiu, A., (2007). Second Trimester Pregnancy Loss. American Family Physician, 76, 9, 1341-1346.
6) American College of Obstetricians and Gynecologists (ACOG) (2005). Repeated Miscarriage. ACOG Patient Education Pamphlet AP100, Washington, DC.
7) Heffner, L., (2004), Maternal Age – How old is too old? New EnglandJournal of Medicine 351 (19):1927–29.
8) Center For Human Reproduction (2011). Miscarriages. Retrieved from: http://www.centerforhumanreprod.com/miscarriages.html
9) Ness, R., Grisso. J., Hirschinger, N., Markovic, N., Shaw, L., Day, N., Kline, J., (1999). Cocaine and tobacco use and the risk of spontaneous abortion. N Engl J Med 340 (5): 333–9.
10) Venners, S., Wang, X., Chen, C., Wang, L., Chen, D., Guang, W., Huang, A., Ryan, L., O'Connor, J., Lasley, B., Overstreet, J., Wilcox, A., Xu, X., (2004). Paternal smoking and pregnancy loss: a prospective study using a biomarker of pregnancy. Am J Epidemiol 159 (10): 993–1001.
11) Gracia, C., Sammel, M., Chittams, J., Hummel, A., Shaunik, A., Barnhart, K., (2005). "Risk factors for spontaneous abortion in early symptomatic first-trimester pregnancies". Obstet Gynecol 106 (5 Pt 1): 993–9.
12) Everett, C., (1997). Incidence and outcome of bleeding before the 20th week of pregnancy: prospective study from general practice. British Medical Journal 315 (7099)
13) Bupa (2011). Miscarriage. Retrieved from: http://www.bupa.co.uk/individuals/health-information/directory/m/miscarriage
14) Net Doctor (2011). Miscarriage. Retrieved from: http://www.netdoctor.co.uk/diseases/facts/miscarriage.htm
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