Risk of miscarriage: how long should you be concerned?

The risk of miscarriage is not a single figure: it drops very rapidly as the weeks go by, and it depends heavily on the mother’s age. The overall figure of 15 to 20 per cent that is quoted everywhere does not apply to either the sixth week or the twelfth.

Week by week

These figures relate to pregnancies in which a heartbeat has been detected, which makes all the difference: it is from this point onwards that the prognosis improves significantly.

• Before 6 weeks, before a heartbeat is visible: the risk remains high, at around 20 to 25 per cent.
• 6 to 7 weeks, with a heartbeat: approximately 9 to 10 per cent.
• 8 weeks: around 5 per cent.
• 10 weeks: around 2 per cent.
• 12 weeks and beyond: less than 1–2 per cent.

In other words, an ultrasound scan showing a heartbeat at seven weeks reduces the risk to below 10 per cent, and by the end of the first trimester it drops to a very low level.

The effect of age

This is the most significant factor, as it affects the rate of chromosomal abnormalities in eggs. The risk of miscarriage in a confirmed pregnancy is around 10–12 per cent before the age of 30, 15 per cent at age 33, 20 to 25 per cent at age 38, 40 per cent at age 42, and exceeds 50 per cent for women aged 44 and over. It is this trend, rather than any personal vulnerability, that accounts for most early pregnancy losses after the age of 40.

The father’s age also plays a role, albeit to a lesser extent, from around the age of 45, particularly through the fragmentation of sperm DNA. The corresponding article can be found here.

What really increases the risk

Smoking, regular alcohol consumption, a very high or very low body mass index, poorly controlled diabetes, untreated hypothyroidism, antiphospholipid syndrome, certain uterine abnormalities, and a severe infection accompanied by a high fever. These factors can be addressed, at least in part, and this is where the bulk of what depends on you comes into play.

What does not increase the risk

This needs to be made clear, because women often blame themselves: neither sexual intercourse, nor moderate exercise, nor everyday stress, nor carrying shopping, nor air travel, nor a minor annoyance, nor a meal that doesn’t agree with you. Strict bed rest has never been shown to be beneficial, even in cases of first-trimester bleeding, and it carries its own risks.

Caffeine is a matter of debate: French and European guidelines set a cautious limit of around 200 mg per day – equivalent to two cups of coffee – although no causal link has been demonstrated at moderate doses.

After IVF

The risk is not higher because of the procedure itself: it reflects the age and clinical indications of the patients concerned. At the same age, a frozen embryo transfer and natural conception yield comparable success rates. With egg donation, the risk depends on the donor’s age and therefore falls to the level seen in a young woman, around 10–15 per cent, regardless of the recipient’s age.

Chromosomal testing of embryos reduces the risk of miscarriage by excluding aneuploid embryos. It does not eliminate the risk: around 5–8 per cent of pregnancies resulting from a tested euploid embryo still end in miscarriage. Details of PGT-A can be found here.

Key points

Waiting until the twelfth week to announce a pregnancy is a common practice, not a rule. Some women prefer to share the news early so as not to bear the burden of a potential loss alone; others do not. Both choices are valid, and knowing the actual figures helps you make an informed decision rather than one based on social superstition.

Frequently asked questions

Source: https://fertilitegrece.com/en/blog/miscarriage-risk-by-week/ — Triada Baloukoudis, IVF patient coordination in Greece. General information, not medical or legal advice. Printed on

Triada Baloukoudis
Independent IVF patient coordinator in Thessaloniki, with 24 years of experience supporting patients travelling from abroad. More · Contact · Facebook