In the U.S., any loss after 20 weeks is usually considered a stillbirth) (In Anderson’s study, stillbirth was defined as a loss after 28 weeks. Rates of ectopic pregnancy also rose with age: Risk of ectopic pregnancy by the mother’s ageĪs did the chances of a stillbirth: Risk of stillbirth by the mother’s age at conception Risk of pregnancy loss by the mother’s age at conception.
What did she find? Miscarriage risk rises sharply during a woman’s late 30s and reached nearly 100% by age 45. Anderson tracked every “reproductive outcome”– every pregnancy, miscarriage, birth, stillbirth, or abortion–in Denmark between the years of 19–ultimately tracking outcomes of over a million pregnancies. Risk of Miscarriage by the Woman’s AgeĪnne-Marie Nybo Anderson, of the Danish Epidemiology Science Centre led the largest population-based study ever conducted on age and miscarriage. The man’s age matters too, especially after they turn 40. The most important risk factor, as is well known, is the woman’s age: Miscarriage rates climb as women age, especially after the late 30s. Your personal characteristics and behaviors alter your miscarriage risk. Rates hovered around 2% per week until week 13, when chances of a miscarriage dipped below 1% Their rate of miscarriage was 4-5% in week 6. In a large prospective study of 4,887 women trying to conceive, 4070 became pregnant. What are their chances of a miscarriage before that crucial piece of news? Many women will not have an ultrasound and fetal heartbeat confirmation until sometime between 8-10 weeks. Miscarriage Risk by Week Before Confirmation of a Heartbeat Up to 6 weeks 2 days gestation: Chance of miscarriage by fetal heart rate up to 6 weeks 2 days of gestation.īetween 6 weeks 3 days and 7 weeks 0 days: Chance of miscarriage by fetal heart rate at 7 weeks gestationĪfter 7 weeks, the fetal heart rate was at or above 120 beats per minute for almost all ongoing pregnancies. (Normal fetal heart rates change with fetal age, so these tables break down the risk by pregnancy week.) The lower the heart rate, the higher the miscarriage risk. The chance of a first trimester miscarriage varies by fetal heart rate, according to a study of 809 pregnancies. But a fetal heart rate that is too slow can instead signal an impending miscarriage. Miscarriage Risk by Fetal Heart RateĪ fetal heartbeat often indicates a healthy, viable pregnancy. Women who entered the study later, and who therefore had a normal ultrasound and heartbeat at 7-10 weeks, had a risk under 10%. Women who entered the study in their 4th to 5th week of pregnancy had about a 35% risk of miscarriage. Chance of miscarriage by 12 weeks but after confirmation of a fetal heart rate by the mother’s age.ĭespite the higher risk for this age group overall, a normal ultrasound result from 7 weeks remains a promising sign. Miscarriages rates declined between 6 to 10 weeks, according to a study of 697 pregnancies with a confirmed fetal heartbeat:Ī similar study of 668 pregnancies with a confirmed fetal heartbeat between 6 and 10 weeks, found a similar decline in miscarriage risk by week:īut for women in their mid to late 30s and early 40s, these studies understate the risk. E ven after confirmation of a fetal heartbeat, miscarriage risk remains high for women 40 and older through 12 weeks, according to a study of 384 women 35 and older. Fortunately, for most women by 14 weeks their chance of a miscarriage is less than 1%. The risk is highest early in the first trimester. Miscarriage risk drops as pregnancy progresses. Where possible, I break down the risk by…Įdit: I also have a new post on how morning sickness signals a lower risk. So I have compiled a summary of the best research on risk of miscarriage. The lack of good information frustrated me when I was pregnant, and I bet it frustrates you too. Problem 3: Nearly all these sites derive their statistics from just two small studies, one which tracked 222 women from conception through just the first 6 weeks of pregnancy, and another which tracked 697 pregnancies, but only after a fetal heartbeat had been detected–a key point, because heartbeat detection dramatically lowers the chances of a miscarriage.
Problem 2: These sites do not breakdown miscarriage risk by other known risk factors, like the mother’s age. Problem 1: These sites rarely provide their sources, so you cannot tell whether their information is reliable. Many websites claim to tell you your risk of miscarriage, citing statistics that look like these : Commonly reported chances of miscarriage by pregnancy week Trying to figure out your chances of miscarrying? Sadly, you are going to have a hard time finding good information.
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