Gestationsalter-Rechner

Was ist das Gestationsalter?

Gestational age refers to the age of a pregnancy counted from the first day of the last menstrual period (LMP), measured in Wochen and Tage. By convention, gestational age begins approximately two Wochen before conception actually occurs (at ovulation). A full-term pregnancy is 40 Wochen (280 Tage) from the LMP. Accurate gestational age determination is critical for timing prenatal screening tests, assessing fetal growth, planning delivery, and managing preterm or post-term pregnancies.

Naegele's Rule

Naegele's rule is the standard method for estimating the due date (EDD): add 280 Tage (40 Wochen) to the first day of the LMP. An alternative formulation is to add 7 Tage to the LMP date and subtract 3 months. This rule assumes a regular 28-day menstrual cycle with ovulation on day 14. For women with longer or shorter cycles, the EDD can be adjusted by adding or subtracting the difference from 28 Tage. Despite its simplicity, Naegele's rule remains a useful clinical tool when ultrasound dating is unavailable.

Ultrasound vs. LMP Dating

First-trimester ultrasound (measuring crown-rump length) is the most accurate method for dating a pregnancy, with a margin of error of ±5–7 Tage. ACOG recommends that if the ultrasound-based EDD differs from the LMP-based EDD by more than 7 Tage in the first trimester, 10 Tage in the second trimester, or 21 Tage in the third trimester, the ultrasound date should be used for clinical management. Once a dating method is established, it should not be changed later in pregnancy.

Wichtige Referenzen

• ACOG Committee Opinion No. 700. Methods for Estimating the Due Date. Obstet Gynecol. 2017;129(5):e150-e154.
• Whitworth M, et al. Ultrasound for fetal assessment in early pregnancy. Cochrane Database Syst Rev. 2015;(7):CD007058.