Pregnancy tests: the complete trimester-by-trimester calendar

Irene · August 7, 2026 · 8 min

Between check-ups, blood tests, and ultrasounds, pregnancy has its own precise calendar, but the right time windows for each test are rarely explained clearly. Here's the full picture, trimester by trimester, with the dates each test should actually happen and why you can't just “get to it whenever.”

The two things that always get confused: exemption codes and the test calendar

Many articles online (even ones that rank well in search) call M50 “the pregnancy exemption code.” That's not correct: M50 only covers a high-risk pregnancy, threatened miscarriage, maternal-fetal conditions, and it needs a specific medical prescription to use.

An uncomplicated pregnancy, meaning one without complications, is instead entitled to the LEA tests (Livelli Essenziali di Assistenza, Italy's essential levels of care) through codes M00 (preconception phase) and M01-M41, each scheduled for a specific window of gestational weeks (DPCM of 12 January 2017, Annex C). This is the calendar that applies to most pregnancies, and the one we walk through below.

First trimester: the tests you shouldn't miss

The first trimester has the tightest time windows: missing them often means you can't recover the same level of reliability later on.

By week 10, the first prenatal visit, to date the pregnancy and schedule the following tests. Italian guidelines typically place it between weeks 6 and 8.
Week 11 to 13+6 days, the double test (measuring two proteins in the mother's blood) combined with an ultrasound measurement of nuchal translucency: this is the combined first-trimester screening, and its window is fixed and cannot be recovered later with the same precision.
Weeks 13 to 16, the triple test, the alternative for those who didn't make it in time for the combined screening.
Routine blood tests (blood type, complete blood count, blood sugar, infection screening) under the M01-M41 schedule.

Second trimester: the anomaly scan and the glucose test

The second trimester brings the two most anticipated tests (and often the most feared):

Weeks 19 to 21, the mid-pregnancy anomaly scan: the most detailed assessment of fetal anatomy, scheduled in exactly this window, when the organs are already clearly visible but there's still time for further follow-up if needed.
Weeks 24 to 28, the glucose tolerance test (OGTT), the screening for gestational diabetes: done fasting, with blood draws at fixed intervals after drinking the glucose solution.

Italy's updated ISS guidelines (2023-2026) confirm the ultrasound as the key test of the second trimester, but no longer recommend a routine ultrasound in the third trimester as well for uncomplicated pregnancies without risk factors, an update that many online sources, still stuck on the 2010-2011 document, don't mention.

Third trimester: the GBS swab and final checks

Weeks 36 to 37, a vaginal-rectal swab for Group B Streptococcus (GBS): if it comes back positive, it doesn't change the birth plan, but it does require an antibiotic during labour to protect the baby.
More frequent ultrasounds and monitoring from the middle of the third trimester onward, according to your own centre's guidance.
A pre-delivery consultation and, where offered, an assessment of fetal presentation (head-down or breech) ahead of labour.

What happens if a pregnancy becomes “high-risk”

If risk factors emerge along the way (maternal conditions, issues found on screening, multiple pregnancy), your OB-GYN can prescribe code M50, which gives access to additional, more frequent tests beyond the standard M01-M41 schedule. It's neither a permanent label nor, by itself, a reason for alarm: it simply means your monitoring is intensified to stay closer to a situation that needs watching.

How to keep track of everything without missing a deadline

Some test windows (particularly the double test/nuchal translucency) span only a few weeks: missing them often means giving them up entirely, not just doing them later. A simple method that works for most mothers-to-be:

Mark each test window in your phone's calendar as soon as you know your last menstrual period date; don't wait for the visit to calculate them.
Ask your OB-GYN, at the first visit, for a written sheet with the recommended dates for each test, many clinics already provide one, but it's worth asking if it doesn't come up on its own.
If you're unsure about the calendar you've been given, ask explicitly whether it reflects the most recent ISS guidelines: the three-part revision (2023, 2025, 2026) changed some recommendations compared with the previous document.

In summary

An uncomplicated pregnancy follows a precise test calendar, the double test between weeks 11 and 13+6, the anomaly scan between 19 and 21, the glucose test between 24 and 28, the GBS swab between 36 and 37, all under code M01-M41, not M50 (reserved for a high-risk pregnancy). Noting the right windows as soon as you know your last menstrual period date keeps you from chasing one down at the last minute.

Frequently asked questions

Which pregnancy tests are free in Italy?

For an uncomplicated pregnancy, the tests covered by Italy's LEA (Livelli Essenziali di Assistenza, the essential levels of care) are exempt from co-pay through codes M00 (preconception phase) and M01-M41, scheduled by gestational week under the DPCM of 12 January 2017.

What is exemption code M50, and who does it actually apply to?

It's a very common mistake to think M50 is the generic pregnancy exemption code: in reality it only applies to a high-risk pregnancy (threatened miscarriage, maternal-fetal conditions) and needs a specific medical prescription. An uncomplicated pregnancy instead follows the M01-M41 schedule.

When is the combined first-trimester screening (double test and nuchal translucency) done?

Between week 11 and week 13+6 days: this is the window for the combined first-trimester screening, and it can't be recovered later with the same level of reliability.

When is the mid-pregnancy anomaly scan done?

Between weeks 19 and 21 of pregnancy: it's the most detailed ultrasound for assessing fetal anatomy, which is why it's scheduled in exactly that window and not earlier.

When is the glucose tolerance test (OGTT) done?

Between weeks 24 and 28, to screen for gestational diabetes. It has to be done fasting, following the instructions of the centre performing it.

When is the Group B Strep swab done?

Between weeks 36 and 37, as indicated by Italy's ISS: it checks for Group B Streptococcus, which, if positive, only requires an antibiotic during labour, not a change to the birth plan.