Naegele's rule

Jump to navigation Jump to search

WikiDoc Resources for Naegele's rule

Articles

Most recent articles on Naegele's rule

Most cited articles on Naegele's rule

Review articles on Naegele's rule

Articles on Naegele's rule in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on Naegele's rule

Images of Naegele's rule

Photos of Naegele's rule

Podcasts & MP3s on Naegele's rule

Videos on Naegele's rule

Evidence Based Medicine

Cochrane Collaboration on Naegele's rule

Bandolier on Naegele's rule

TRIP on Naegele's rule

Clinical Trials

Ongoing Trials on Naegele's rule at Clinical Trials.gov

Trial results on Naegele's rule

Clinical Trials on Naegele's rule at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Naegele's rule

NICE Guidance on Naegele's rule

NHS PRODIGY Guidance

FDA on Naegele's rule

CDC on Naegele's rule

Books

Books on Naegele's rule

News

Naegele's rule in the news

Be alerted to news on Naegele's rule

News trends on Naegele's rule

Commentary

Blogs on Naegele's rule

Definitions

Definitions of Naegele's rule

Patient Resources / Community

Patient resources on Naegele's rule

Discussion groups on Naegele's rule

Patient Handouts on Naegele's rule

Directions to Hospitals Treating Naegele's rule

Risk calculators and risk factors for Naegele's rule

Healthcare Provider Resources

Symptoms of Naegele's rule

Causes & Risk Factors for Naegele's rule

Diagnostic studies for Naegele's rule

Treatment of Naegele's rule

Continuing Medical Education (CME)

CME Programs on Naegele's rule

International

Naegele's rule en Espanol

Naegele's rule en Francais

Business

Naegele's rule in the Marketplace

Patents on Naegele's rule

Experimental / Informatics

List of terms related to Naegele's rule

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Naegele's Rule is a standard way of calculating the due date for a pregnancy. It is named after Franz Karl Naegele (1778-1851), the German obstetrician who devised the rule.

History

Franz Karl Naegele was born July 12, 1778, in Duesseldorf, Germany. In 1806 Naegele became ordinary professor and director of the lying-in hospital in Heidelberg. His "Lehrbuch der Geburtshuelfe," published in 1830 for midwives, enjoyed a successful 14 editions.

The rule estimates the Expected Date of Delivery (EDD) from the first day of the woman's Last Menstrual Period (LMP) by adding a year, subtracting three months and adding seven days to that date. This approximates to the average normal human pregnancy which lasts 40 weeks (280 days) from the LMP, or 38 weeks (266 days) from the date of fertilisation. Example, if LMP was 8 May 2007, then +1 year = 8 May 2008, -3 months = 8 February 2008, +7 days = 15 February 2008; whereas precisely 280 days would be 12 february 2008.

Assumptions

This method is a fairly good estimation of the due date, but makes a number of assumptions.

An average menstrual cycle
The rule is based on ovulation and fertilization happening on cycle day 14 with a cycle length of 28 days. It is less accurate when ovulation happens earlier or later in the cycle, and for women with irregular menstrual periods. Sometimes women may have a light bleed of a threatened miscarriage in early pregnancy, which adds to this confusion if it is mistaken for a period.
Average lengths of calendar months
The rule assumes an average length for all months in the Gregorian calendar year of just over 30 days (365 / 12 = 30.416). The rule, on average, therefore equates to 280.75 days. However the unequal length of the Gregorian calendar's months results in Naegels's rule overestimating the EDD by 3 days for all LMPs in May, and depending on the effect of leap years gives precise dates on only either 2, 5 or 7 months of the year.
Average gestation
The rule assumes 40 weeks, or 280 days from LMP. Recent studies have suggested that the EDD would be better estimated using 282 days from the LMP date (40 weeks and 2 days),[1] this is not though current accepted clinical practice.

Other estimation techniques

The effects of varying lengths of the calendar months may be overcome by use of hand operated pregnancy wheel devices, or the use of electronic computer pregnancy calculator programs.

Ultrasound confirmation of gestational age

Since the estimation is based on the LMP date, Naegele's rule can easily be a week or more off, it should be used to calculate a range of due dates and confirmed with ultrasound in the first trimester. Since the 1970's ultrasound scans have allowed measurement of the size of developing embryos directly and so allow for an estimation of gestation age. Ultrasound dating is most accurate if undertaken in the first trimester (first 12 weeks of pregnancy) with a 95% error margin of 6 days. Scans performed in the second trimester have an error margin of 8 days and those in the third trimester a margin of 2 weeks.

Most obstetric departments in Australia, United Kingdom and United States use a combination of LMP and ultrasound based estimates for the EDD using either 10-day or 7-day rules, so that if LMP dates and ultrasonographic dates are in agreement within 7 (or 10) days, then the LMP dates are accepted.

References

  1. Nguyen T, Larsen T, Engholm G, Møller H (1999). "Evaluation of ultrasound-estimated date of delivery in 17,450 spontaneous singleton births: do we need to modify Naegele's rule?". Ultrasound Obstet Gynecol. 14 (1): 23–8. PMID 10461334.

de:Naegele-Regel


Template:WH Template:WS