Pregnancy due date ultrasound or LMP which is accurate?
Note: Ultrasound is more accurate, due date more than 7 days different use ultrasound (because of irregular periods)
ultrasound performed in the first trimester (up to 13 weeks and 6 days) is generally considered more accurate than relying solely on the last menstrual period (LMP),
LMP Accuracy: 28days ovulation cycle (regular periods assumption)
assuming ovulation and conception occurred on day 14 of the cycle, which may not always be true.
If LMP is 20th december 2024 (assuming 14days after egg release & sperm ready) conception. (tracking or remembering intercourse details gets another data)
Calculating EDD:
A common method for calculating the EDD is to add 280 days (or 40 weeks) to the first day of the LMP.
Variations:
It’s important to note that the actual delivery date can vary, with most pregnancies lasting between 38 and 42 weeks from the LMP.
pregnancy due date 40 or 42 weeks with LMP
Most pregnancies last 37 to 42 weeks About half of first-time mothers will give birth by 40 weeks and 5 days after the first day of their last menstrual period, with the other half giving birth after that time point.
due date different in ultrasound
if your menstrual cycles are irregular or if the ultrasound is done early in pregnancy(ideally before 13 weeks). Ultrasound measurements are generally considered more accurate . doctor uses ultrasound age.
2 weeks difference between lmp and ultrasound?
as per American College of Obstetricians and Gynecologists) guidelines
1st trimester ultrasound : if 1 week greater than 7 days difference use ultrasound, less than 1 week use LMP .
In the second trimester (22w0d–27w6d), redating is recommended if the discrepancy is greater than 14 days.
In the third trimester (28w0d and beyond), redating is recommended if the discrepancy is greater than 21 days.
Early ultrasound scans are more accurate for dating because they measure the fetus’s size directly.
Fertile Window Conception, and Pregnancy due date
After ovulation, an egg is typically viable for fertilization for a very short period, generally 12 to 24 hours.
Sperm Viability: Sperm, on the other hand, can survive in the female reproductive tract for up to 5 days.
three-day window for egg high chances.
sperm 3-5 days (7 days in some cases)
Fertile Window: 5 days.
any symptoms of conception date: In the first 72 hours after conception, you’re unlikely to experience noticeable pregnancy symptoms . so conception occurs on ovulation day (within the 12-24 hours following ovulation, if sperm are present. )
Ovulation day symptoms (temparature low, mucus slippery until ovulation, after that mucus thick, mood: want to stay with partner)
Baby Growth by week Ultrasound test
Due date calculation Last Missed period or LMP Last Menstrual Period
| Week | Date | Trimester | Important Milestones |
| Week 1 | Dec 21, 2024 – Dec 27, 2024 | first trimester |
|
| Week 2 | Dec 28, 2024 – Jan 3, 2025 | ||
| Week 3 | Jan 4, 2025 – Jan 10, 2025 | Baby conceived | |
| Week 4 | Jan 11, 2025 – Jan 17, 2025 | Pregnancy test positive | |
| Week 5 | Jan 18, 2025 – Jan 24, 2025 | ||
| Week 6 | Jan 25, 2025 – Jan 31, 2025 | Heartbeat detectable by ultrasound | |
| Week 7 | Feb 1, 2025 – Feb 7, 2025 | ||
| Week 8 | Feb 8, 2025 – Feb 14, 2025 | ||
| Week 9 | Feb 15, 2025 – Feb 21, 2025 | ||
| Week 10 | Feb 22, 2025 – Feb 28, 2025 | ||
| Week 11 | Mar 1, 2025 – Mar 7, 2025 | ||
| Week 12 | Mar 8, 2025 – Mar 14, 2025 | ||
| Week 13 | Mar 15, 2025 – Mar 21, 2025 (today) | second trimester |
Miscarriage risk decreases |
| Week 14 | Mar 22, 2025 – Mar 28, 2025 | ||
| Week 15 | Mar 29, 2025 – Apr 4, 2025 | ||
| Week 16 | Apr 5, 2025 – Apr 11, 2025 | ||
| Week 17 | Apr 12, 2025 – Apr 18, 2025 | ||
| Week 18 | Apr 19, 2025 – Apr 25, 2025 | Baby begins making noticeable movements, can hear sounds, and gender can be found out. |
|
| Week 19 | Apr 26, 2025 – May 2, 2025 | ||
| Week 20 | May 3, 2025 – May 9, 2025 | ||
| Week 21 | May 10, 2025 – May 16, 2025 | ||
| Week 22 | May 17, 2025 – May 23, 2025 | ||
| Week 23 | May 24, 2025 – May 30, 2025 | Premature baby may survive | |
| Week 24 | May 31, 2025 – Jun 6, 2025 | ||
| Week 25 | Jun 7, 2025 – Jun 13, 2025 | ||
| Week 26 | Jun 14, 2025 – Jun 20, 2025 | ||
| Week 27 | Jun 21, 2025 – Jun 27, 2025 | ||
| Week 28 | Jun 28, 2025 – Jul 4, 2025 | third trimester |
Baby can breathe |
| Week 29 | Jul 5, 2025 – Jul 11, 2025 | ||
| Week 30 | Jul 12, 2025 – Jul 18, 2025 | ||
| Week 31 | Jul 19, 2025 – Jul 25, 2025 | ||
| Week 32 | Jul 26, 2025 – Aug 1, 2025 | ||
| Week 33 | Aug 2, 2025 – Aug 8, 2025 | ||
| Week 34 | Aug 9, 2025 – Aug 15, 2025 | ||
| Week 35 | Aug 16, 2025 – Aug 22, 2025 | ||
| Week 36 | Aug 23, 2025 – Aug 29, 2025 | ||
| Week 37 | Aug 30, 2025 – Sep 5, 2025 | ||
| Week 38 | Sep 6, 2025 – Sep 12, 2025 | Full Term | |
| Week 39 | Sep 13, 2025 – Sep 19, 2025 | ||
| Week 40 | Sep 20, 2025 – Sep 26, 2025 | ||
| Week 41 | Sep 27, 2025 – Oct 3, 2025 | ||
| Week 42 | Oct 4, 2025 – Oct 10, 2025 |
gestational age vs fetal age
Gestational Age:
This is the standard way to measure pregnancy length, starting from the first day of the last menstrual period (LMP) and continuing until birth.
Fetal Age:
This refers to the actual age of the fetus, starting from the date of conception (ovulation).
The Two-Week Difference:
Because pregnancy is calculated from the LMP, which occurs before conception, gestational age is always about two weeks ahead of fetal age.
Ask a Question: