Prenatal Screening Calculator

California Prenatal Screening Program

Time Windows for Prenatal Screening Tests

How It Works

Provide pregnancy dating and then click the "Calculate Test Date" button. Time Windows will be provided for drawing the First and Second trimester blood specimens and for obtaining a Nuchal Translucency Ultrasound.

Note: Your browser must be Java-enabled for the calculator to work. The calculations are estimates based on the pregnancy dating provided. Patients should consult their clinician about prenatal screening.

Patient Name

Today's Date

Dating Method Selection

Please select one of the dating methods below (dating methods are in order of preference):

Date of Ultrasound

First Day of Last Menstrual Period

Date of Physical Exam

Date of Ultrasound Information

Please fill in ultrasound date and either CRL mm or gestational age:

Date of Ultrasound

CRL (9.5 - 84.5 mm)

Gestational Age on Ultrasound

Weeks (0-40)

Days (0-6)

First Trimester Blood Specimen Time Window

First trimester blood specimen should be drawn between:

10 Weeks 0 Days

and

13 Weeks 6 Days

Draw a First Trimester blood specimen between 10 weeks 0 days and 13 weeks 6 days of pregnancy, using the California Program’s First Trimester Screening Lab test form.

Nuchal Translucency (NT) Time Window

Nuchal translucency ultrasound should be done between:

11 Weeks 2 Days

and

14 Weeks 2 Days

If you choose to have an NT ultrasound, schedule the NT appointment between 11 weeks 2 days and 14 weeks 2 days of pregnancy.

Second Trimester Blood Specimen Time Window

Second trimester blood specimen should be drawn between:

15 Weeks 0 Days

and

20 Weeks 0 Days

Draw a Second Trimester blood specimen between 15 weeks 0 days and 20 weeks 0 days of pregnancy, using the California Program’s Second Trimester Screening Lab test form

Prenatal Screening Test Calculator