Pregnancy Week Calculator

Pregnancy is a 40-week journey divided into three distinct stages called trimesters. Understanding the math behind your timeline helps you prepare for major milestones and medical appointments.

The Three Trimesters

First Trimester (Weeks 1–12)

This is the period of rapid cellular division and organogenesis. By week 8, the embryo becomes a fetus, and all major organs have begun to form. This is often the period where "morning sickness" is most prevalent.

Second Trimester (Weeks 13–26)

Often called the "honeymoon phase," energy levels typically return, and the risk of miscarriage drops significantly. Around week 20, you will have an anatomy scan to check the baby's development and potentially learn the gender.

Third Trimester (Weeks 27–40+)

The baby grows rapidly in size and weight, preparing for life outside the womb. During this phase, the baby's lungs mature, and they begin to practice breathing and swallowing.

Key Development Milestones

• Week 4: Implantation occurs.
• Week 12: The heartbeat can usually be heard via a Doppler.
• Week 24: The "Viability Milestone"—where the baby has a chance of survival if born prematurely.
• Week 37: "Early Term"—the baby is considered fully developed but would benefit from more time in the womb.

Managing Your Health

Every pregnancy is unique. Regular prenatal checkups are essential to monitor blood pressure, glucose levels, and fetal growth. Always consult with your OB-GYN or midwife for medical advice tailored to your specific situation.