Pregnancy Week Calculator & Timeline

About the Pregnancy Week Calculator & Timeline

Enter the first day of your last period — or the due date from your scan — and this calculator shows how many weeks and days pregnant you are, your trimester, the due date and how many days are left. Pick a different date to plan ahead, for example for a trip or an event.

Below that it dates a timeline of standard antenatal checks for your pregnancy under the schedule you follow: the US windows for screening tests and vaccines (first-trimester screening, anatomy scan, glucose test, Tdap, GBS swab), the WHO 2016 eight-contact model, or India’s MoHFW schedule with the four ANC visits, Td vaccine, GDM tests and your PMSMA days (the 9th of every month). Download it as a printable PDF or add every check to your phone calendar. Nothing you enter leaves your browser.

How the weeks are counted

Pregnancy is dated from the first day of the last menstrual period (LMP), so you are about two weeks pregnant at conception. The due date is LMP + 280 days (40 weeks). If you enter a due date, the calculator counts back 280 days. “12w 3d” means 12 completed weeks and 3 days. The first trimester runs to 13 weeks 6 days, the second from 14 0/7 to 27 6/7 weeks and the third from 28 0/7 weeks (as used by ACOG); full term is 39 0/7 to 40 6/7 weeks. If an early scan gave a different due date from your period, the scan date is usually the one your care team uses — see the pregnancy due date calculator for the rules.

The US schedule (ACOG, CDC)

• Cell-free DNA screening (optional): from 9–10 weeks, any time after.
• First-trimester screening (nuchal translucency scan + blood test): 10 0/7–13 6/7 weeks; a quad screen at 15–22 weeks if that was not done.
• Anatomy ultrasound: usually 18–22 weeks (ISUOG allows about 18–24), recommended whatever screening was chosen.
• Gestational diabetes screening: 24–28 weeks.
• Tdap vaccine: one dose in every pregnancy, preferably early in weeks 27 through 36 (CDC).
• Group B strep swab: 36 0/7–37 6/7 weeks — not needed if GBS was found in your urine this pregnancy or a previous baby had GBS disease, because antibiotics in labour are given anyway.

The WHO 2016 model

WHO recommends at least eight contacts: the first up to 12 weeks, then at 20 and 26 weeks, and at 30, 34, 36, 38 and 40 weeks, returning at 41 weeks if the baby has not arrived. It recommends one ultrasound scan before 24 weeks, daily iron and folic acid, tetanus vaccination depending on earlier doses, a blood count for anaemia and a urine culture, and gives 24–28 weeks as the usual window for diagnosing gestational diabetes.

India: MoHFW antenatal visits and PMSMA

• At least four ANC visits: the first within 12 weeks (as soon as pregnancy is suspected), then 14–26 weeks, 28–34 weeks (ideally with the Medical Officer at the PHC) and 36 weeks to term.
• Td vaccine: dose 1 at registration and dose 2 four weeks later, or a single booster if you had two doses in a pregnancy within the last three years — the second dose or booster before 36 weeks.
• GDM tests: 75 g glucose, fasting or not, with a 2-hour value of 140 mg/dL or more meaning gestational diabetes — at the first visit and again at 24–28 weeks if the first was negative.
• Iron–folic acid and calcium tablets for 6 months in pregnancy, starting after the first trimester.
• PMSMA: on the 9th of every month, designated government facilities give women in the 2nd and 3rd trimesters a free check-up by a doctor, tests and medicines, including one ultrasound in the second trimester. The calculator lists your 9ths from 14 weeks to the due date.

Sources

• Society for Maternal-Fetal Medicine. Consult Series #74: Cell-free DNA screening for aneuploidies, Table 1 (adapted from ACOG Practice Bulletin 226)
• ISUOG. Practice Guidelines (updated): performance of the routine mid-trimester fetal ultrasound scan. Ultrasound Obstet Gynecol 59:840-56
• ACOG Practice Bulletin 190, Gestational Diabetes Mellitus; CDC. Pertussis vaccine recommendations
• ACOG Committee Opinion 797, Prevention of Group B Streptococcal Early-Onset Disease in Newborns, as summarised in Devabhaktuni A et al. in O&G Open and in Microorganisms (PMC9780959, Table 1)
• WHO. Recommendations on antenatal care for a positive pregnancy experience, Box 5 and recommendations A.2.1, B.1.1, B.1.2, B.1.4, B.2.4, C.5
• MoHFW. Guidelines for Antenatal Care and Skilled Attendance at Birth by ANMs/LHVs/SNs and Diagnosis & Management of Gestational Diabetes Mellitus; National Health Mission, Maternal Health; PMSMA

Limitations

• Typical windows for planning, not a care plan: your doctor, midwife or ANM decides your actual tests and visits, and some depend on your history or test results.
• Dating from a last period assumes a regular 28-day cycle; with irregular cycles or an IVF pregnancy, enter the due date your clinic gave you.
• PMSMA days are listed as the 9th of each month; check with your facility, especially if the 9th is a holiday.
• Dates within 44 weeks of the last period are accepted. The calendar file holds what is still ahead as all-day events without reminders; windows longer than three weeks appear as their first and last day.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.