Hello,

One of the most common questions patients ask in the clinic is:

“My pregnancy seems further along than I expected—why is that?”

Today, I’d like to explain how pregnancy weeks are calculated in a simple way.

When you see two lines on a home pregnancy test and visit the clinic,

an ultrasound will usually show a gestational sac,

and you may be told,

“You are about 5 weeks pregnant.”

At this point, many patients wonder:

“It has only been about 5 weeks since my last period—

why am I already considered 5 weeks pregnant?”

Pregnancy is calculated based on the first day of your last menstrual period (LMP).

For someone with a regular 28-day menstrual cycle,

if your period started on Day 1,

ovulation typically occurs around Day 14,

and pregnancy occurs around that time.

So, when we say “5 weeks pregnant,”

it means counting from the first day of your last period.

In reality, conception likely occurred about 3 weeks ago

(approximately 2 weeks after the start of your last period).

For example,

if your last period began on November 1,

you may be confirmed to be 5 weeks pregnant in early December

when you visit the clinic.

This is because pregnancy is calculated from the start of your last period,

which may differ slightly from the actual time of conception.

In summary,

pregnancy weeks are calculated based on your last menstrual period,

and the early weeks (weeks 1 and 2)

do not reflect the actual moment of conception.

For the most accurate assessment of your pregnancy stage,

we recommend visiting the clinic

and confirming it through an ultrasound examination.

Thank you.

• 목록