How to calculate pregnancy weeks
Pregnancy is a journey full of expectations and unknowns, and accurately calculating the number of weeks of gestation is crucial for expectant mothers. It not only helps to understand the developmental stages of the fetus, but also guides the arrangement of prenatal check-ups and due dates. This article will analyze in detail the calculation method of gestation weeks, and combine it with hot topics in the past 10 days to provide scientific and practical reference for pregnant mothers.
1. Basic concepts of gestation weeks
The number of weeks of gestation is calculated from the first day of the last menstrual period, usually in weeks. Medically, the pregnancy cycle is 40 weeks (about 280 days), which is divided into three trimesters: early (1-12 weeks), mid-term (13-28 weeks) and late (29-40 weeks).
2. How to calculate pregnancy weeks
There are two main ways to calculate gestational weeks:
(1) Last menstrual period method (LMP)
This is the most common method and is suitable for women with regular menstruation. The formula is as follows:
| step | illustrate |
| 1. Record the first day of the last menstrual period | For example: October 1, 2023 |
| 2. Calculate the interval between the current date and the last menstrual period | Assume today is December 10, 2023, and the interval is 10 weeks + 2 days |
| 3. Calculation of due date | First day of last menstrual period + 280 days (or 40 weeks) |
(2) Ultrasound examination method
For women with irregular menstruation or who are unsure about their last menstrual period, doctors will use early ultrasound (such as CRL measurement at 6-8 weeks of pregnancy) to more accurately determine gestational age.
| Ultrasound indicators | Applicable gestational age |
| Gestational sac diameter (GS) | 5-6 weeks |
| Crown-rump length (CRL) | 6-12 weeks (error ±5 days) |
| Biparietal diameter (BPD) | After 12 weeks |
3. Related topics of popular pregnancy topics in the past 10 days
Based on recent hot discussions on social platforms, the following topics are closely related to the calculation of pregnancy weeks:
(1) Precautions during early pregnancy
Topics such as #Early Pregnancy Bleeding# and #Morning Sickness Relief# emphasize the sensitive period of the fetus from 1 to 12 weeks, and the need to avoid strenuous exercise and drug abuse.
(2) NT inspection time window
The hot search #NT Examination Guide# points out that 11-13 weeks + 6 days is the prime time to screen for fetal malformations, and it must be arranged strictly according to the gestational age.
(3) Nutritional supplements during pregnancy
The recent popular video "Nutrition Table for Various Stages of Pregnancy" shows that calcium/iron intake needs to be increased in the second trimester (from 13 weeks onwards) and blood sugar needs to be controlled in the late trimester.
4. Common misunderstandings and answers
| Misunderstanding | scientific explanation |
| "The date of intercourse is the day of conception" | Actual conception occurs after ovulation (about the 14th day of menstruation), and the gestational age needs to be calculated 2 weeks in advance. |
| "The older the gestation period, the healthier the fetus will be." | Postterm pregnancy (>42 weeks) may cause placental function degradation |
| "The due date must be accurate" | Only 5% of mothers give birth on the day of their expected delivery date, and ±2 weeks is considered normal. |
5. Recommended practical tools
The "Pregnancy Calculator", which has recently been on the download list of health apps, can automatically complete the following calculations:
| Function | Sample data |
| Current gestational age | Enter last menstrual period: 2023-10-1 → Current: 12 weeks + 2 days |
| Important prenatal check-up points | Tang screening: 16-20 weeks | Major ovarian cancer: 20-24 weeks |
| fetal development control | 12 weeks ≈ lemon size (about 6cm long) |
Mastering the correct method of calculating pregnancy weeks can help expectant mothers plan their pregnancy life more scientifically. It is recommended to have regular prenatal check-ups and adjust the calculation method based on the doctor’s advice to ensure the health of mother and baby. The recently hotly discussed #pregnancy management# also confirms the importance of scientific calculation of gestational age. I hope every pregnant mother can enjoy this wonderful journey with peace of mind.
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