Verified Clinical Literature

Verified Medical Sources & Literature

We never fabricate citations or research. All calculations, trimester divisions, and developmental milestones on Pregnancy Calculator are directly referenced from established obstetric governing bodies and peer-reviewed perinatology journals.

American College of Obstetricians and Gynecologists (ACOG)

Methods for Estimating the Due Date (Committee Opinion No. 700)

Obstet Gynecol. 2017; 129(5): e150–e154.

Authoritative clinical guidance on establishing gestational age using LMP and reconciling crown-rump length ultrasound scans.

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ACOG and Society for Maternal-Fetal Medicine (SMFM)

Definition of Term Pregnancy (Committee Opinion No. 579)

Obstet Gynecol. 2013; 122(5): 1139–1140.

Establishes the clinical definitions of early term (37w0d–38w6d), full term (39w0d–40w6d), late term (41w0d–41w6d), and postterm (42w0d+).

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Centers for Disease Control and Prevention (CDC)

National Vital Statistics Reports: Births in the United States

National Center for Health Statistics (NCHS), CDC.

Epidemiological distribution data on gestational age at delivery, spontaneous labor onset, and term birth outcomes.

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National Institutes of Health (NIH) / PubMed Central

The Length of Uncomplicated Human Gestation

Mittendorf R, Williams MA, Berkey CS, Cotter PF. Obstet Gynecol. 1990; 75(6): 927–932.

Seminal research analyzing median human gestation lengths in primiparous and multiparous populations.

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World Health Organization (WHO)

WHO Recommendations on Antenatal Care for a Positive Pregnancy Experience

Geneva: World Health Organization; 2016.

Global standards on gestational age assessment, nutritional guidelines, and routine antenatal visit scheduling.

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