No matter how careful, healthy, or lucky a newly pregnant woman may be, there's no guarantee that she will actually have a baby. According to the U.S. National Institutes of Health, up to half of all pregnancies fail, usually before a woman realizes shes pregnant. In many ways, women who never know about the lost pregnancy are the lucky ones. After a woman gets a positive result on a pregnancy test and starts picturing a new baby in her life, a miscarriage can be heartbreaking.
When a pregnancy ends in miscarriage, one question stands above all others: Why? In most cases, there's no clear answer. Doctors can rarely pinpoint the cause of a miscarriage. (Physicians generally use the term miscarriage to refer to pregnancies that are lost before the 20th week. After that, they're called stillbirths.")
What we do know is that most miscarriages aren't preventable. When a sperm fertilizes an egg, chromosomes fall together in unpredictable ways. Through no fault of the mother or father, a new embryo may have abnormal chromosomes, missing chromosomes, or extra copies of chromosomes. Women have a built-in quality control system that usually rejects such embryos before they can develop.
According to a report in Human Reproduction, if an embryo has a serious genetic problem such as an extra chromosome, there's a 9-in-10 chance that the pregnancy will end in miscarriage during the first trimester. On the positive side, over 90 percent of all embryos with their chromosomes in the right place will make it to the second or third trimester.
According to the March of Dimes, most women who suffer a miscarriage later go on to have healthy pregnancies.
Improving your odds of a successful pregnancy
Many women can lower their risk of a miscarriage with a few simple lifestyle changes and good prenatal care.
For starters, think about what you're putting in your body. Cigarettes, alcohol, and many illegal drugs can raise the risk of miscarriage and other complications. If you use any of these substances, quit before you get pregnant. If you're already pregnant, quit as soon as possible. Federal experts say there is no safe level of alcohol during pregnancy, and smoking has been linked to miscarriage and preterm labor. Staying away from secondhand smoke is a good idea as well.
Other threats may come from unexpected sources. A study published in the New England Journal of Medicine found that five or more cups of coffee a day doubled the risk of miscarriage early in a pregnancy. The link between caffeine and miscarriages is still controversial, however, and many women enjoy a cup of coffee now and then without any apparent problems. For now, the March of Dimes urges all pregnant women to stop drinking large amounts of caffeine, but not necessarily to give up coffee and tea entirely.
You might also need to think twice before popping a pill for that headache. A study published in the British Medical Journal suggested that taking aspirin, ibuprofen, or similar over-the-counter painkillers during pregnancy can raise the risk of a miscarriage by 80 percent. The study found no such risk with acetaminophen (commonly marketed as Tylenol), the drug that most doctors already recommend for treating minor aches and pains during pregnancy. If you're pregnant or trying to get pregnant, it's always a good idea to check with your doctor before taking any medications.
Your doctor can be a valuable ally in your quest for a healthy baby. If you're pregnant or trying to get pregnant, a thorough checkup can determine if you have an illness that could potentially lead to miscarriage. Common examples include lupus, congenital heart disease, kidney disease, uncontrolled diabetes, thyroid disease, and infections of the uterus. In many cases, prompt treatment of these conditions can greatly increase your chance for a healthy pregnancy, especially if treatment starts before you conceive.
If you've had more than one miscarriage, your doctor may run extra tests to get to the bottom of the problem. You may not be producing enough progesterone, a crucial hormone that keeps a pregnancy going. Your doctor may be able to correct this deficiency by prescribing supplements. You may also have fibroids, or an unusually shaped uterus. These obstructions can often be corrected with surgery.
Because there are no guarantees, all pregnant women should watch out for signs of miscarriage or preterm delivery. Call your doctor immediately if you notice vaginal spotting or bleeding at any point during your pregnancy. (If that bleeding comes along with any clots or tissue, try to collect these so your doctor can take a closer look.) Minor bleeding may not signal and emergency, but you'll need to see a doctor to be sure.
March of Dimes. Miscarriage. October 2008. http://www.marchofdimes.com/professionals/14332_1192.asp
National Institutes of Health. Embryos That Implant in Uterus Late Prove More Likely to Die in First Weeks of Pregnancy. http://www.nih.gov/news/pr/jun99/niehs-09.htm
March of Dimes. Stillbirth. http://www.marchofdimes.com/pnhec/188_1121.aspp
Quenby S et al. Recurrent miscarriage: a defect in natures quality control? Human Reproduction. 17(8):1959-1963.
U.S. Pharmacist. Teratogenicity of Drugs.
National Cancer Institute. Secondhand Smoke: Whats the Problem? http://www.nci.nih.gov/newscenter/tip-sheet-secondhand-smokee
Cnattingius S., et al. Caffeine intake and the risk of first-trimester spontaneous abortion. New England Journal of Medicine (Abstract). Volume 343:1839-1845.
Center for the Evaluation of Risks for Human Reproduction. Caffeine. http://cerhr.niehs.nih.gov/genpub/topics/caffeine-ccae.html#Caffeine%20and%20Pregnancyy
March of Dimes. Caffeine in Pregnancy. http://www.marchofdimes.com/professionals/681_1148.aspp
Nemours Foundation. Taking Ibuprophen, Naproxen, and Aspirin During Pregnancy Increases the Risk of Miscarriage. http://kidshealth.org/research/pain_relievers_miscarriage.htmll
American Medical Association. Study suggests link between NSAIDs, aspirin, miscarriage. http://www.ama-assn.org/amednews/2003/10/00