Fetal Development Timeline (by Gestational Week)

Fetal Development Timeline (by Gestational Week) | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Health
Input types: select, number, date
Output type: html
Sample coverage: 4
API ready: Yes

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.

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

1Select your input mode: either enter your known gestational weeks directly or input the date of your last menstrual period (LMP).
2Adjust the decimal precision setting if you want to customize how measurements are displayed.
3Click 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.

Examples

1. Tracking Mid-Pregnancy Milestones

An expecting mother at 20 weeks

Background

A mother wants to know the developmental milestones and average size of her baby at the exact halfway point of her pregnancy.

Problem

She needs to quickly find the baby's length, weight, and key physical developments for week 20.

How to use

Set the mode to 'Known gestational weeks', enter '20' in the gestational weeks field, and set the decimal precision to '0'.

mode: "weeks", weeks: 20, precision: 0

Outcome

The timeline highlights Week 20 (Trimester 2), showing the fetus is approximately 16 cm long, weighs about 300 grams, is roughly the size of a banana, and has vernix covering the skin.

2. Calculating Gestational Week from LMP

A newly pregnant individual

Background

A user recently took a positive pregnancy test and knows the date of their last menstrual period, but not their exact gestational week.

Problem

They want to determine their current week of pregnancy and see what milestones are forming at the end of the first trimester.

How to use

FAQ

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.

mode: "lmp", lmp: "2026-01-01", precision: 0

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Continue with connected tools and hubs

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Tracking Mid-Pregnancy Milestones

2. Calculating Gestational Week from LMP

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