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"Pregnancy is a process that invites you to surrender to the unseen force behind all life."

- Judy Ford

Pregnancy Dating Program

Download the AMOR-IPAT Dating Program:

        Pregnancy Dating Program (MS Access .mdb file)

How to use the AMOR-IPAT Dating Program:

This program may be used to determine three things:

1. The EDC (Estimated Date of Confinement, or DUE DATE) based on the first day of the last menstrual period (LMP).
2. The EDC (Estimated Date of Confinement, or DUE DATE) based on an ultrasound study.
3. Gestational Age on any given day (including “today”) based on an established EDC.

The AMOR-IPAT Dating Program has three main parts:

1. EDC based on LMP:
   • Enter the LMP (month-day-year) into the “LMP” box.
   • The EDC based on the entered LMP automatically appears in the “EDC-by-LMP” box.
2. EDC based on ultrasound (room for four ultrasounds):
   • Enter the date of the ultrasound (month-day-year) into the “Ultrasound-date” box.
   • Enter the best estimate of the fetus’ gestational age as determined by the ultrasound into the gestational age boxes (“Weeks-of-gestational-age” box and “Days of gestational-age” box).
   • The EDC based on the entered ultrasound information appears in the “EDC-by-Ultrasound” box.
3. GESTATIONAL-AGE-on-Specific-Day based on any given date and EDC information:
   • Enter an established EDC into the “EDC” box.
   • Enter a date into the “Specific-Day-in-Question” box.
   • The gestational age of the pregnancy on the specified day appears in the “Gestational Age” box.

Caveats:

1. Generally speaking, the first ultrasound provides the most accurate dating.
2. However, dating by crown-rump-length proves better dating than gestational sac measurement. Dating by CRL is generally better than dating by BPD (biparietal diameter) measurement.
3. Per ACOG recommendations, if EDC-by-LMP and EDC-by-first-trimester-ultrasound are within 7 days, then keep EDC-by-LMP. Otherwise, use EDC-by-first-trimester-ultrasound.
4. Per ACOG recommendations, if EDC-by-LMP and EDC-by-second-trimester-ultrasound are within 14 days, then keep EDC-by-LMP. Otherwise, use EDC-by-second-trimester-ultrasound.
5. Per ACOG recommendations, if EDC-by-LMP and EDC-by-third-trimester-ultrasound are within 21 days, then keep EDC-by-LMP. Otherwise, use EDC-by-third-trimester-ultrasound.
6. The isolated use of ultrasound dating, i.e., by ignoring LMP information, moves the EDC ahead in time in most pregnancies. This makes the pregnancy look less far along, and has been used by some as a way decrease the need for post-dates induction. However, the pregnancy is not really younger; it is just made to appear so. However, Randomized Clinical Trials have shown that pregnancy outcomes are better if labor is induced at 41 weeks 0 days of gestation rather than allowing the pregnancy to continue to a later gestational age. Hence using ultrasound data to change the EDC so as to avoid labor induction is not advised.
7. Third trimester ultrasounds that suggest that the EDC is sooner than previously established EDC (an “encroaching EDC”) may mean that the fetus is growing faster than usual (this increases the risk of cephalo-pelvic disproportion (CPD) during term pregnancy – especially late term pregnancy).
8. Third trimester ultrasounds that suggest that the EDC is later than previously established EDC (a “receding EDC”) may mean that the fetus is growing slower than usual (this increases the risk of utero-placental insufficiency (UPI) during term pregnancy – especially late term pregnancy).