13 weeks pregnant means 13+0 to 13+6 weeks from the first day of your last period: about 2 months and 30 days, as you move from the 3rd into the 4th month. This is the last week of the first trimester and the window for the nuchal translucency (NT) scan and combined screening is starting to close.
13 weeks pregnant (13+0 to 13+6 weeks) is about 2 months and 30 days from the first day of your last period, the week you move from the 3rd into the 4th month. By ACOG's definition the first trimester ends at 13 weeks 6 days.
The NHS says your baby is now around 7.4 cm long, about the size of a peach. The ovaries or testes have fully developed inside, with final changes happening on the outside. Your baby is moving: at first the movements are jerky and random, later they look more deliberate. Some babies suck their thumb, which helps develop the sucking reflex they will need to feed. You may not feel any movement until around week 17.
ACOG's summary for weeks 13 to 16 says the bones, especially the long bones, harden; the skin is thin and see-through but will soon thicken; toenails form; the neck is defined and the legs develop; hearing starts to develop; and the lungs begin forming the tissue that will exchange oxygen after birth.
A small bump may now show as your womb grows upwards and outwards. If you have needed to pee more often, this should ease as the womb moves away from your bladder. More blood flows to your pelvic area, which raises sex drive for some women and can make you thirsty, so drink plenty. Sex is safe in pregnancy unless your doctor or midwife has advised otherwise (NHS).
The NHS advice on infections: avoid contact with anyone who has chickenpox or rubella and tell your doctor straight away if you have been exposed; ask someone else to empty the cat litter (toxoplasmosis); and avoid undercooked meat, cured meats such as salami, and unpasteurised goats' milk and cheese.
Swollen, bleeding gums are common in pregnancy. Use a soft toothbrush and, if you are sick, rinse your mouth with water to wash away acid (NHS).
There is still time for combined screening, but the window is closing. The Turkish Ministry of Health guideline (2026) gives 11 to 14 weeks for the NT scan and combined test and recommends completing the first visit within the first 14 weeks. NICE NG201 screens at 11+2 to 14+1 weeks; ISUOG recommends 11+0 to 14+0 weeks and notes that fetal anatomy is best seen at around 13 weeks. ACOG offers first-trimester screening up to 13 weeks 6 days and gives a Down syndrome detection rate of 82% for measurements at 13 weeks.
Towards the end of the window, the baby's crown–rump length (CRL) may go beyond the required range (ISUOG: 45 to 84 mm); ACOG notes that some babies at the edge of the window may fall outside it. If you miss the combined test: the Turkish Ministry of Health offers the triple/quad test at 16 to 20 weeks, ACOG offers the quad test at 15 to 22 weeks, and cell-free DNA testing (NIPT) can be done from 10 weeks onwards (ACOG, 2025).
ISUOG's minimum checklist for the 11–14-week scan covers the head and brain, the neck (NT measurement), a heart beating regularly inside the chest, the abdomen (stomach, abdominal wall, bladder), four limbs each with three segments, and the appearance of the placenta. The guideline notes that details are best seen at around 13 weeks. This scan can show major structural problems early, but ISUOG points out that some major anomalies develop later in pregnancy or may not be detected at this stage even in the best hands.
| Symptom | Usually | Seek care if |
|---|---|---|
| Sharp pain on the sides of the bump (round ligament pain) | Round ligament pain from the growing womb is common from this week (NHS). | If the pain is severe, does not settle, or comes with bleeding, fever or leaking fluid. |
| Bleeding gums and nosebleeds | Both are common symptoms the NHS lists for this week. | See your doctor or dentist if the bleeding will not stop or keeps coming back. |
| Needing to pee often | This should ease as the womb moves away from the bladder (NHS). | If peeing burns or hurts, or you have a fever: urine infections are among the symptoms the NHS lists for this stage. |
These are danger signs or emergency referral criteria in the Turkish Ministry of Health guideline; contact your doctor or go to the nearest emergency department without waiting. NICE recommends a hospital review for any unexplained bleeding after 13 weeks, and anti-D for women who are RhD negative and at risk of isoimmunisation.
Days 91 to 97 from the first day of your last period, or about 2 months and 30 days. You are moving from the 3rd into the 4th month.
ACOG defines the first trimester as lasting until 13 weeks 6 days, with the second trimester starting at 14 weeks 0 days, so week 13 is the last week of the first trimester. The NHS week-by-week guide, however, places week 13 under the second trimester. The difference is one of definition and does not change your care.
No. The Turkish Ministry of Health guideline covers 11 to 14 weeks, ISUOG up to 14 weeks 0 days, NICE up to 14 weeks 1 day and ACOG up to 13 weeks 6 days. As the baby may grow beyond the measurement limit near the end of the window, do not put off your appointment.
Usually not reliably on ultrasound yet; UpToDate notes that ultrasound generally shows the sex at 17 to 20 weeks. A cell-free DNA blood test (NIPT) at 10 to 13 weeks can report the sex along with chromosome screening, but a failed result or a wrong sex assignment is possible (UpToDate, 2026).
Brief sharp pains on the sides of the bump (round ligament pain) are common now. Bleeding should always be checked: NICE recommends a hospital review for unexplained bleeding after 13 weeks, and recommends anti-D if you are RhD negative and at risk of isoimmunisation.
Last updated: . All sources have been confirmed with their latest versions. This content is for educational purposes and is not a substitute for a doctor's examination.