What is my gestational age given my last menstrual period (LMP) was March 31, 2025?

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Last updated: May 12, 2025View editorial policy

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From the Guidelines

You are approximately 2 weeks pregnant based on your last menstrual period starting on March 31,2025. To determine this, we calculate the time elapsed since your last menstrual period, considering that pregnancy typically lasts about 40 weeks (or 280 days) from the first day of the last menstrual period (LMP) 1. Given that conception usually occurs about 2 weeks after the start of your period, you would be considered approximately 2 weeks pregnant in gestational age, with fertilization having occurred very recently. It's essential to note that the exact date of conception and gestational age can be confirmed through ultrasound measurements, such as the crown-rump length in the first trimester or biparietal diameter (BPD) in the second trimester, which provide accurate estimates of gestational age to within 7 and 10 days, respectively 1. If you suspect you are pregnant, I recommend taking a home pregnancy test or consulting with a healthcare provider for confirmation and proper prenatal care guidance. Some key points to consider when estimating gestational age include:

  • The first day of the last menstrual period is the most common method for assessing gestational age 1
  • Ultrasound measurements can provide a more accurate estimate of gestational age 1
  • Factors such as abdominal distention can affect the accuracy of fundal height measurements 1
  • Gestational age can be estimated using symphysis fundal height, with the height in centimeters approximately corresponding to the gestational age in weeks between 16 and 36 weeks of gestation 1

From the Research

Pregnancy Calculation

To determine how pregnant you are, we need to calculate the number of weeks since your last period.

  • Last period: 3/31/25
  • Current date: assumed to be the date you are asking the question, which is not provided. For the purpose of this calculation, let's assume the current date is 5/12/25.
  • Number of weeks since last period: approximately 6 weeks

Folic Acid Supplementation

According to the studies 2, 3, 4, 5, folic acid supplementation is crucial for preventing neural tube defects and other congenital anomalies.

  • The recommended daily dose of folic acid is 0.4-1.0 mg for women of reproductive age who are planning or not avoiding conception 4.
  • Women who have had previous pregnancies with neural tube defects, those who did not plan their pregnancy, and women with low intake or impaired adherence to daily folic acid supplementation may benefit from higher daily doses of folic acid 4.
  • Folic acid supplementation should be taken as part of a multivitamin, and women should be advised not to take more than one daily dose of vitamin supplement, as indicated on the product label 2.

Prenatal Care

The studies 2, 3 emphasize the importance of prenatal care in preventing pregnancy-associated morbidity and mortality.

  • Care initiated at 10 weeks or earlier improves outcomes 3.
  • Women should be screened for asymptomatic bacteriuria, sexually transmitted infections, and immunity against rubella and varicella, and should receive tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap), influenza, and COVID-19 vaccines 3.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

The use of folic acid for the prevention of neural tube defects and other congenital anomalies.

Journal of obstetrics and gynaecology Canada : JOGC = Journal d'obstetrique et gynecologie du Canada : JOGC, 2003

Research

Prenatal Care: An Evidence-Based Approach.

American family physician, 2023

Research

Folic acid in obstetric practice: a review.

Obstetrical & gynecological survey, 2011

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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