# Fetal Development Timeline (by Gestational Week) See week-by-week fetal development from conception to birth (40 weeks). Enter your LMP date or a known gestational age and the tool highlights the current week with size, weight and milestones. > Canonical page: https://elysiatools.com/en/tools/fetal-development-timeline - **Category:** Health - **Keywords:** fetal development, pregnancy week by week, gestational age, fetal growth, trimester, lmp, baby size, obstetrics ## Overview The Fetal Development Timeline tool provides a week-by-week visual guide of pregnancy from conception to birth, highlighting key milestones, fetal size, weight, and trimester phases. By entering either your known gestational age or the date of your last menstrual period (LMP), you can instantly pinpoint your current week of pregnancy and view detailed developmental progress. ## Inputs - **How is gestational age given?** (select) - **Gestational weeks** (number): e.g. 20 - **Last period date** (date): Select the first day of your last period - **Decimal places** (number) ## When to use - When you want to track your baby's weekly growth milestones, weight, and length during pregnancy. - When you need to calculate your current gestational week using the date of your last menstrual period (LMP). - When you want to visualize which trimester you are in and compare the fetus to common fruit size equivalents. ## How it works - Select your input mode: either enter your known gestational weeks directly or input the date of your last menstrual period (LMP). - Adjust the decimal precision setting if you want to customize how measurements are displayed. - Click calculate to generate the interactive timeline, which highlights your current week, trimester, and fetal milestones. ## Use cases - Expecting parents tracking weekly fetal milestones and size comparisons at home. - Doulas or pregnancy educators demonstrating trimester transitions and developmental stages to clients. - Quickly converting a last menstrual period (LMP) date into a specific gestational week for reference. ## Frequently asked questions ### How does the tool calculate my current gestational week? It either uses the exact number of weeks you enter or calculates the weeks elapsed from the first day of your last menstrual period (LMP). ### What measurements are provided for the fetus? The timeline displays estimated crown-rump length (or head-to-heel length in later weeks), weight in grams, and a familiar fruit size comparison. ### Can I see milestones for other weeks besides my current one? Yes, the tool generates a complete 40-week timeline, allowing you to scroll through past and future weeks while highlighting your active week. ### What is the difference between gestational age and fetal age? Gestational age is measured from the first day of your last menstrual period, whereas fetal age is the actual age of the growing fetus from conception (usually two weeks later). ### How accurate are the fetal weight and size estimates? They represent average ranges based on standard obstetrical growth charts; individual fetal development can vary naturally. ## Related tools - [Blood Alcohol Content (BAC) Estimator](https://elysiatools.com/en/tools/bac-calculator): Estimate your BAC from sex, weight, drinks and time using the Widmark formula. 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