Miscarriage risk by week: what the studies show

Worrying about this is very common, and looking up numbers can make it feel worse. If you have bleeding or pain, please don’t rely on a chart. Contact your midwife, doctor or early pregnancy unit.

Call your emergency number if you have severe tummy pain, shoulder pain, heavy bleeding, or you feel faint.

One study followed 696 women who had no symptoms and came for a routine first antenatal visit. It shows how quickly the chance of miscarriage fell with each later week.

Tong et al., Obstetrics & Gynecology, 2008. Only 11 women in this study miscarried, so the exact figures are uncertain, and the small rise at 10 weeks is likely to be chance. These figures apply to women with no symptoms, not to anyone with bleeding or pain.

A systematic review found the highest weekly rates before week 13. By week 14 the rate had fallen below 10 in every 1,000 women per week, and it kept falling up to week 20. Across weeks 5 to 20, the total risk ranged from 11 to 22 in 100 between the studies it included.

A major review in The Lancet put the overall risk at about 15 in 100 recognised pregnancies. March of Dimes says about 8 in 10 miscarriages happen before week 12.

Studies count differently. Some include very early losses and some don’t, and some start counting from a later week. The age and health of the people in each study also matter, so treat every figure here as a rough guide.

A Norwegian study of 421,201 pregnancies found the risk was lowest at age 25 to 29, at about 10%. It rose quickly after 30 and reached 53% at 45 and over.

The same study found that the risk was higher after previous miscarriages, and highest after three in a row. Most people who have had a miscarriage still go on to have a successful pregnancy.

Not necessarily. ACOG says bleeding happens in 15 to 25 in 100 pregnancies in the first trimester. In one US study, about 12% of women with bleeding miscarried, compared with 13% of those without. Most of that bleeding was spotting or light, and that figure doesn’t apply to heavy bleeding.

Always tell your midwife or doctor about any bleeding, because only an assessment can tell you the cause. Heavy bleeding, or bleeding with severe pain, needs urgent help.

ACOG says miscarriage is usually a random event. About half of early miscarriages happen because the embryo doesn’t develop properly, often because of an abnormal number of chromosomes. It says working, exercising, arguments, having sex and morning sickness don’t cause miscarriage.

Some things are linked with a higher risk, including smoking, alcohol, a lot of caffeine, some health conditions, and being over 35. The Lancet review also lists Black ethnicity and stress among linked factors, while ACOG says stress doesn’t cause miscarriage. A link in a study doesn’t show that something caused any one person’s loss.

We’re so sorry. You don’t have to go through this alone, and it’s normal to need support, whenever it happened. Your GP or pregnancy unit can arrange counselling, and these organisations can help:

• UK: Miscarriage UK, 0303 003 6464
• UK: Tommy’s midwives, 0800 014 7800
• US: March of Dimes and Share Pregnancy & Infant Loss Support