Weeks Pregnant Calculator NHS

NHS Pregnancy Weeks Calculation:

\[ \text{Weeks} = \lfloor \frac{\text{Current Date} - \text{LMP}}{7} \rfloor \]

Weeks Pregnant:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Weeks Pregnant Calculator NHS?

The Weeks Pregnant Calculator NHS estimates gestational age based on the last menstrual period (LMP) according to NHS guidelines. It calculates the number of weeks pregnant by determining the time elapsed since the first day of your last period.

2. How Does the Calculator Work?

The calculator uses the NHS standard formula:

\[ \text{Weeks} = \lfloor \frac{\text{Current Date} - \text{LMP}}{7} \rfloor \]

Where:

\( \text{LMP} \) — First day of last menstrual period
\( \text{Current Date} \) — Today's date or specified date
\( \lfloor \rfloor \) — Floor function (rounding down)

Explanation: Pregnancy is calculated from the first day of your last period, not from conception. This method follows standard NHS obstetric dating practice.

3. Importance of Pregnancy Dating

Details: Accurate pregnancy dating is essential for monitoring fetal development, scheduling prenatal tests, determining due date, and making important clinical decisions throughout pregnancy.

4. Using the Calculator

Tips: Enter the first day of your last menstrual period and the current date (or any date you want to check). The calculator will determine how many weeks pregnant you are on that specific date.

5. Frequently Asked Questions (FAQ)

Q1: Why does NHS calculate from LMP instead of conception?
A: LMP is typically more reliably known than conception date, and this method provides a standardized approach used across healthcare systems.

Q2: What if I don't know my exact LMP?
A: If uncertain about LMP, an ultrasound scan in early pregnancy can provide more accurate dating based on fetal measurements.

Q3: How accurate is this calculation?
A: For women with regular 28-day cycles, this method is quite accurate. Variations in cycle length may affect precision.

Q4: When should I contact my midwife or GP?
A: Contact healthcare providers as soon as you know you're pregnant to begin prenatal care, typically around 8-10 weeks.

Q5: Does this work for IVF pregnancies?
A: For IVF pregnancies, dating is typically based on embryo transfer date rather than LMP for greater accuracy.