When are abortions typically

1. When “how far along” is measured: gestational age versus fertilization age

Medical and legal systems usually measure pregnancy in gestational age from the first day of the last menstrual period (LMP), a convention that places conception roughly two weeks later; some laws, however, use fertilization or post‑fertilization language, which shifts numeric cutoffs by about two weeks and can create confusion about “when” an abortion occurs ^{[6] [7]}. Research that reports by fertilization date will therefore show different percentage breakdowns than studies using LMP, and analysts warn that translating between the two is essential to compare statistics and laws accurately ^{[2] [7]}.

2. The typical distribution: most abortions are very early

Surveillance and survey data show the bulk of abortions occur in the early weeks of pregnancy: CDC reporting found 80.8% of abortions in 2021 occurred at ≤9 weeks’ gestation and 93.5% at ≤13 weeks ^[1], while analyses of earlier years and Guttmacher data put about two‑thirds at eight weeks or earlier in the United States ^{[8] [2]}. International reviews of high‑income countries likewise confirm early timing as the dominant pattern, a fact health authorities cite when recommending timely access to safe medical and surgical options ^[9].

3. Later abortions: uncommon but clinically and logistically distinct

Abortions after the first trimester (second trimester and beyond) are uncommon: CDC and other datasets find single‑digit percentages occur in later weeks, and procedures at or after about 21 weeks gestation are rare and concentrated among specialized providers and facilities ^{[3] [1] [4]}. These later procedures often involve different methods — for example, dilation and evacuation becomes the predominant surgical technique after mid‑pregnancy — and typically require more time, resources and, in many cases, inpatient care ^{[10] [4]}.

4. Why some abortions happen later: medical, access, and diagnostic reasons

When abortions occur later in pregnancy, the reasons documented by clinical studies are often medical (fetal anomalies or maternal health risks), delays related to access and referrals, or late diagnosis of conditions such as structural abnormalities, for which median gestational ages have been reported at or above 20 weeks in some specialty series ^{[11] [4]}. Policy changes, travel burdens and state‑level gestational restrictions can also force delays that push care later, with disproportionate impacts on people with fewer resources ^{[12] [13]}.

5. Legal cutoffs and the practical effect on timing

State and national laws set a patchwork of gestational limits — some states ban abortion at 15 weeks, others at roughly 20–24 weeks, and a few impose no gestational limit at all — and those legal lines shape when abortions can practically be obtained, sometimes creating chilling effects because dating is not exact ^{[6] [5] [13]}. Analysts note that legal definitions (LMP vs. fertilization), variable exceptions, and enforcement risk mean that statutory week numbers do not always map neatly onto clinical practice or individual cases ^{[7] [13]}.

6. What “late‑term” means and how rare it is

The term “late‑term” is not a standardized medical label; publications and policy discussions use varying thresholds — often 20 weeks, 21 weeks, or the start of the third trimester around 28 weeks — but data consistently show that abortions at or after about 21 weeks constitute a very small share of all procedures and are concentrated among a few providers and circumstances ^{[3] [4] [10]}. Given the diversity of definitions, reporting sources advise caution in using “late‑term” without specifying the gestational cutoff and the dating method used ^{[3] [7]}.