What Are the Risks for Miscarriage or Pregnancy Loss?
Pregnancy loss is more common than most people think, with approximately one out of every five pregnancies ending in miscarriage.
Approximately one out of every five pregnancies ends in miscarriage.
Most pregnancy losses occur in the first 12 weeks. Sometimes it may be missed as a miscarriage.
Genetic Abnormalities and Pregnancy Loss
Because women are born with all the eggs they will ever have, over time their eggs accumulate genetic abnormalities, which can lead to the formation of genetically abnormal embryos.
Even in their 20s and early 30s, up to one third of a woman’s eggs may be genetically abnormal and can give rise to embryos that are prone to implantation failure and miscarriage.
Therefore, the majority of pregnancy losses are caused by chromosomal abnormalities in the embryo.
In addition, there are a number of other risk factors that may also increase a woman’s likelihood of experiencing pregnancy loss. There is a large body of research which has provided convincing evidence that there are very few ways, if any, that factors such as diet, physical activity, stress-levels, etc. can influence whether a woman experiences pregnancy loss. For this reason, it is important that women diagnosed with a miscarriage refrain from self-blame and speak to their doctor to gain a better understanding of the most likely causes of pregnancy loss.
As the likelihood of chromosomal abnormalities in a woman’s eggs, and the embryos they give rise to, increases with age, so does the risk of pregnancy loss.
Women under the age of 35 have about a 15 percent chance of losing a pregnancy.
Women between the ages of 35 and 45 have a 20 to 35 percent chance of losing a pregnancy.
Women over the age of 45 have around a 50 percent chance of experiencing a miscarriage.
There are certain lifestyle factors and behaviors that may increase a woman’s risk of pregnancy loss.
Alcohol: Several studies have suggested that consuming four or more alcoholic drinks per week in early pregnancy is associated with an increased risk of miscarriage.
A 2008 study published in Obstetrics and Gynecology found that binge drinking three or more times during pregnancy increased risk of stillbirth. Alcohol also increases the risk of a child developing Fetal Alcohol Syndrome.
Cigarettes: Smoking cigarettes is associated with both infertility and loss of pregnancies.
According to the American Society for Reproductive Medicine (ASRM), female smokers who are using IVF have higher rates of pregnancy loss. The effects of smoking are also more pronounced in older patients.
Caffeine: Consuming large amounts of caffeine during pregnancy is also related to pregnancy loss, especially in early trimester pregnancies.
A 2008 study by the Kaiser Permanente Division of Research found that women who consumed 200 mg or more caffeine each day (two or more cups of regular coffee) were twice as likely to experience a loss as women who consumed no caffeine. According to The American College of Obstetricians and Gynecologists (ACOG), moderate caffeine consumption (less than 200mg per day) does not appear to be a major contributing factor in miscarriage or pregnancy complications such as preterm birth.
Previous Pregnancy Loss
Having two or more pregnancy losses confers a slightly increased risk of having a subsequent pregnancy loss. Studies from large samples of pregnant women show that if a woman has had two pregnancy losses, her chance of having a third is 20 percent. For women who have had four previous pregnancy losses, her chance of having a fifth is 40 percent.
Thrombophilia and Pregnancy Loss
Thrombophilia is a genetic predisposition to abnormal blood clotting, which can increase a woman’s risk of stroke and/or heart attack.
In pregnancy, thrombophilia can cause blood vessels in the placenta to clot. This can impair the blood supply that provides oxygen and nutrients to a developing pregnancy, which can result in a pregnancy loss.
Depending on the type of thrombophilia, a doctor may prescribe blood-thinning medication to reduce the risk of blood clots in pregnancy. Women with identified thrombophilias should speak to their doctor regarding what additional steps, if any, should be taken to protect their health and to prevent miscarriage.
Uterine abnormalities can cause pregnancy loss by limiting the growth of the fetus or restricting blood flow to the placenta.
These uterine abnormalities may include:
- having a uterus with an abnormally shaped cavity
- a uterus with a cavity divided by a wall (also known as a septum)
- uterine fibroids
- uterine scars
Women with fibroids that may be affecting their fertility can undergo a surgical treatment called a myomectomy, which removes the fibroids but preserves the uterus.
Women with an identified uterine abnormality should speak with their doctor about possible risks in pregnancy and whether there is an option to undergo surgical correction of the abnormality.
Abnormalities of the uterus cause about 10 to 15 percent of recurrent pregnancy loss.
Other Risk Factors
Other risk factors that may be related to pregnancy loss include exposure to toxins (radiation, lead, mercury, cleaning solvents, and pesticides), poorly controlled diabetes, obesity, hormonal problems, and certain infections.
Women with known toxic exposures or underlying medical issues should consult their doctor as soon as they become pregnant or decide that they want to try to conceive.
Dr. Lucky Sekhon is a reproductive endocrinologist and infertility specialist and board–certified obstetrician and gynecologist. She specializes in diagnosing and treating reproductive issues and has particular expertise in fertility preservation (egg freezing), LGBTQ family building, and in vitro fertilization with preimplantation genetic testing of embryos. She also uses minimally invasive techniques such as laparoscopy and hysteroscopy to treat a variety of surgical conditions including endometriosis and uterine factor infertility. Dr. Sekhon is an assistant clinical professor at the Icahn School of Medicine at Mount Sinai, a fellow in the American College of Obstetrics and Gynecology and an active member of the American Society for Reproductive Medicine.