If I Get Pregnant in December, When Am I Due?

Due dates for a December 2026 conception

A pregnancy lasts about 266 days (38 weeks) from conception, so a December conception leads to a due date in August or September. The table gives the estimated due date for each possible conception day, and the date a home pregnancy test is usually reliable — about two weeks after conception, around when the next period would be due.

Dates for 2026. In other years the due date is the same or one day different, depending on leap years.

A winter conception: what it means for you

A December conception leads to a due date in late August or September. If you conceive around the holidays, you may get your positive test in early January. Your second trimester falls in spring, and the final weeks come at the end of summer. A September baby is often one of the oldest in their school year.

Seasons and timing

With conception in December, the first trimester runs until about February, the second trimester covers the months after, and the third trimester begins around June. In the northern hemisphere, that puts the last weeks of pregnancy in summer and the birth in summer (the seasons are reversed in the southern hemisphere). Late pregnancy in hot weather can be tiring: plan for shade, light clothing, plenty of fluids and rest with your feet up.

Because most babies arrive between 37 and 42 weeks, a baby conceived in December could be born in the month before or after the due month. Your baby’s birthday is most likely to fall between Aug 3, 2027 and Oct 7, 2027.

Conception dates are estimates

Few people know the exact day they conceived. Conception happens within about a day of ovulation, which can be up to five days after sex. If you know the first day of your last period, the Due Date Calculator is the standard method. For any month at a glance, see the Conception Due Date Chart.