From the Guidelines
Miscarriages occur in approximately 10-20% of known pregnancies during the first trimester, with the majority happening before the 12th week of pregnancy, as supported by the most recent guidelines and studies, including the Society of Radiologists in Ultrasound consensus conference recommendations published in the American Journal of Obstetrics and Gynecology in 2025 1.
Key Factors Influencing Miscarriage Rate
- Maternal age is a significant factor, with the rate increasing to about 25% for women in their late 30s and potentially exceeding 50% for women over 45.
- Previous miscarriages, certain chronic conditions like uncontrolled diabetes or thyroid disease, smoking, alcohol consumption, and excessive caffeine intake are also risk factors.
- Chromosomal abnormalities account for about 50-60% of early pregnancy losses, representing natural selection against non-viable embryos.
Diagnosis and Classification of Early Pregnancy Loss
The Society of Radiologists in Ultrasound consensus conference recommendations provide a lexicon for first-trimester ultrasound, categorizing early pregnancy loss into five main categories: concerning for, diagnostic of, in progress, incomplete, and completed 1.
- Concerning for early pregnancy loss (EPL) is defined by specific criteria on transvaginal ultrasound (TVUS), including embryonic crown-rump length (CRL) <7 mm and no cardiac activity, or mean sac diameter (MSD) 16-24 mm and no embryo.
- Diagnostic of EPL is determined by the absence of embryo with cardiac activity 7-13 days following visualized gestational sac (GS) and no yolk sac.
Outcome and Recurrence
Most women who experience a single miscarriage have excellent chances of a successful subsequent pregnancy, with approximately 85% going on to have a healthy pregnancy afterward.
- For recurrent miscarriages (three or more consecutive losses), specialized evaluation is recommended to identify potential underlying causes, as indicated by the guidelines 1. While no proven interventions exist to prevent most first-trimester miscarriages, maintaining a healthy lifestyle before and during pregnancy may help reduce risk, emphasizing the importance of prenatal care and risk factor management.
From the Research
Miscarriage Rate in First Trimester
- The miscarriage rate in the first trimester is estimated to be around 10 to 15% of all pregnancies 2.
- A study published in 2021 estimated the pooled risk of miscarriage to be 15·3% (95% CI 12·5-18·7%) of all recognised pregnancies 3.
- The population prevalence of women who have had one miscarriage is 10·8% (10·3-11·4%), two miscarriages is 1·9% (1·8-2·1%), and three or more miscarriages is 0·7% (0·5-0·8%) 3.
Risk Factors for Miscarriage
- Advancing maternal and paternal age are known to be associated with increasing chance of miscarriage 2.
- Other risk factors include being underweight or overweight, smoking, and high alcohol consumption 2.
- A study published in 2021 identified additional risk factors, including very young or older female age, older male age, very low or very high body-mass index, Black ethnicity, previous miscarriages, stress, working night shifts, air pollution, and exposure to pesticides 3.
Management of Miscarriage
- Expectant management is the first-line approach for miscarriage, and is encouraged for 7-14 days after diagnosis 2.
- Medical management of miscarriage can be offered using misoprostol 2, 4.
- Surgical management may be chosen by a woman if she has had a previous adverse or traumatic experience associated with pregnancy 2.
- A study published in 2020 found that misoprostol is most effective in the setting of retained products of conception if the primary treatment for miscarriage was expectant management 4.
Consequences of Miscarriage
- The consequences of miscarriage are both physical, such as bleeding or infection, and psychological 3.
- Psychological consequences include increases in the risk of anxiety, depression, post-traumatic stress disorder, and suicide 3.
- Miscarriage, and especially recurrent miscarriage, is also a sentinel risk marker for obstetric complications, including preterm birth, fetal growth restriction, placental abruption, and stillbirth in future pregnancies 3.