The highest risk for pregnancy loss (miscarriage) is in the earliest weeks of pregnancy, particularly before 12 weeks, with the risk being highest in the first 3-5 weeks, often before a person even knows they are pregnant, though specific weekly rates vary by study. For induced abortion, the highest volume occurs very early, within the first six weeks, but the procedure is safest and most common before 12 weeks, with risk increasing as pregnancy progresses, though it remains safe later on.
Risk of Miscarriage by Week
Your risk of miscarriage is greatest between weeks 0 and 10. In the early days of pregnancy, you likely don't yet know you're pregnant. A miscarriage may simply seem like a late period.
In 2022, two out of five (40.2%) of reported abortions occurred within the first six weeks of pregnancy. Another 38.4% happened between seven and nine weeks, and 14.2% within 10 and 13 weeks. Put another way, 92.8% of reported abortions were performed before three and a half months of pregnancy.
A pregnancy is in its earliest stages during the first trimester, which provides a variety of abortion options. Early abortions can be performed with surgery or with medication if the pregnancy is less than 10 weeks (measured from the first day of the last menstrual period, and confirmed with ultrasound in our clinic).
What week do most miscarriages happen? More than 80% of miscarriages happen during the first trimester or by the end of the 14th week.
Most miscarriages happen between 6 and 8 weeks gestation. We know that most of these occur due to a major genetic abnormality in the fetus.
The fetus is most vulnerable during the first 12 weeks.
It is safe, simple and low-risk when done under 12 weeks of pregnancy. If it has been more that 12 weeks since your last period the abortion procedure may be more complicated.
Chromosome conditions
If your baby inherits a chromosome condition, they'll not be able to develop properly. This causes a miscarriage. It's not possible to tell which parent passed on the chromosome condition. Chromosome conditions are thought to be the most common cause of an early miscarriage.
Threatened miscarriages occur in the first half (up to 20 weeks) of pregnancy, but most commonly in the first trimester (13 weeks) of pregnancy.
Depending on where you live and your nurse or doctor, the abortion pill can be offered as early as about 4 weeks after your last period, and you can get an in-clinic abortion as early as about 5 weeks after your last period, depending on your medical situation.
When during pregnancy do most abortions occur? The vast majority of abortions occur during the first trimester of a pregnancy. In 2021, 93% of abortions occurred during the first trimester – that is, at or before 13 weeks of gestation, according to the CDC.
Generally speaking the earlier in the pregnancy you have an abortion, the safer it is. In other words complications are slightly more common between 14 and 18 weeks than before 14 weeks, but less common than they are after 18 weeks.
A pregnancy may also be more likely to end in miscarriage if you:
The "worst week" of pregnancy varies, but many women find the first trimester, particularly weeks 8-10, to be the most challenging due to intense morning sickness (nausea/vomiting peaking with hormone surges), extreme fatigue, and heightened emotional changes, though some experience severe symptoms like hyperemesis gravidarum (HG) requiring medical attention, while others face discomforts in later pregnancy.
If you miscarry naturally, even in the early weeks of pregnancy, you are likely to have period-like cramps that can be extremely painful. This is because the uterus is tightly squeezing to push its contents out, like it does in labour – and some women do experience contractions not unlike labour.
Caffeine. You can have caffeine, but no more than 200mg per day. Regularly drinking more than this amount can increase your risk of pregnancy complications, such as low birthweight, and even miscarriage.
Genetic factors
About half of all early miscarriages are caused by random, 'one-off' errors in the egg or the sperm, or in how the fertilised egg develops.
Uterine Abnormalities and Structural Issues
Another potential cause of miscarriage in the first 8 weeks is a structural abnormality within the uterus. These abnormalities can affect the shape or size of the uterus, which may prevent the embryo from properly implanting or growing.
Before 10 weeks, you may have a choice of taking medicine to end the pregnancy or having a procedure such as vacuum aspiration. After 10 weeks, surgical abortion is usually the only option. Abortions are rarely done after 24 weeks of pregnancy (during the late second trimester and entire third trimester).
You will have cramping and pain which can be severe for a short period time during a medical abortion. You may have some pain and cramping after a surgical abortion. This cramping may feel like period pains. The pain can also be in your back, thighs and tops of your legs.
A medical abortion ends an early pregnancy by using a combination of medicines. It's a safe procedure that works by stopping the growth of the pregnancy and then causing the uterine lining to shed. The mifepristone and misoprostol regimen can be used up through 12 weeks for an at-home abortion.
The "3-2-1 Rule" in pregnancy is a guideline for first-time mothers to know when to call their midwife or doctor for active labor: consistent contractions every 3 minutes, lasting 2 minutes each (or 1 minute long for some variations), for over 1 hour. It helps differentiate true labor from false labor (Braxton Hicks), signaling it's time to head to the birthing center, while subsequent pregnancies often follow the faster 5-1-1 rule.
Don't eat undercooked meat, poultry or eggs
There's no perfect time to share your pregnancy—do what feels right for you. Many wait until after the first trimester. Miscarriage risk drops after 13 weeks, but it's also OK to tell trusted loved ones earlier for support.