18 weeks pregnant means 18+0 to 18+6 weeks from the first day of your last period: about 4 months and 4 days, so you are in the 5th month. You have reached the weeks of the detailed (anomaly) scan, and many mothers feel the first flutters around now.
18 weeks pregnant (18+0 to 18+6 weeks) is about 4 months and 4 days from the first day of your last period. You are in the 5th month.
The NHS says your baby is now around 14.2 cm from head to bottom, approximately the size of a bell pepper. Hearing, feeling, swallowing and sucking reflexes are developing this week, and your baby is wriggling a lot and moving arms and legs.
ACOG's summary for weeks 17 to 20 says the part of the brain that controls movement is fully formed, the digestive system is working, and the ears, nose and lips can be recognised on ultrasound. In girls, the uterus and vagina start to form.
You may feel a bit clumsier as your bump grows, and your breasts may have gone up a size, especially in a first pregnancy. Your blood pressure is probably a little lower than before, so do not leap up from the sofa or you may feel dizzy (NHS).
Your baby has been moving for months, but you may only now notice it as bubbling or fluttering inside your belly. A dark line may appear down the middle of your tummy (linea nigra): the NHS says this is normal pigmentation that usually fades a few months after the birth.
Turkish Ministry of Health guideline (2026) – second visit (18 to 24 weeks): weight gain is reviewed; if the height of the womb is 4 cm larger or smaller than expected you are referred to a specialist; the urinalysis and full blood count are repeated and a urine culture is taken if not done before. The fetal anomaly scan is done at 18 to 24 weeks; placental position and attachment problems are especially important to check after previous womb surgery. Women who have had a preterm birth have their cervical length measured by vaginal ultrasound. Women not in a high-risk group are told about the 50 g glucose screening test due at 24 to 28 weeks. A woman with dental or gum complaints at 18 to 20 weeks is referred to a dentist.
Whooping cough (Tdap) vaccine: the Turkish Ministry of Health guideline recommends it at 18 to 24 weeks; if this window is missed, one dose can be given until the end of week 32. The NHS offers it from 16 to 32 weeks, usually around 20 weeks. The US advice reported by UpToDate is ideally 27 to 36 weeks.
When is the detailed scan? The Turkish Ministry of Health gives 18 to 24 weeks, NICE 18+0 to 20+6 weeks, and ACOG and UpToDate 18 to 22 weeks. ACOG says the scan looks for major structural problems in the brain and spine, face, abdomen, heart and limbs; NICE also asks for the position of the placenta. The NHS says the scan can pick up a range of conditions but not all of them; it does not hurt, though the sonographer may press on your tummy for a clear view. UpToDate notes that cervical length can be measured at the same scan; a cervix of 25 mm or less at 16 to 24 weeks signals a higher risk of preterm birth.
| Symptom | Usually | Seek care if |
|---|---|---|
| Dizziness when standing up | Blood pressure dips a little in these weeks; getting up slowly helps (NHS). | Straight away if it comes with fainting, chest pain, difficulty breathing or bleeding (Turkish Ministry of Health emergency referral criteria and danger signs). |
| Dark line on the tummy (linea nigra) | It is normal pigmentation and usually fades a few months after the birth (NHS). | It needs no action; get help for unexplained itching of the skin (a Turkish Ministry of Health danger sign). |
| Not feeling movements yet | In a first pregnancy, movements may not be felt until after 20 weeks (NHS). | The Turkish Ministry of Health guideline treats no movements after 20 weeks as a reason for referral; the NHS says to tell your midwife if you have felt nothing by 24 weeks. |
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. The NHS says to call immediately if your baby's movements change, without waiting until the next day, even in the middle of the night.
Days 126 to 132 from the first day of your last period, or about 4 months and 4 days. You are in the 5th month.
The Turkish Ministry of Health guideline recommends 18 to 24 weeks, NICE 18+0 to 20+6 weeks and ACOG 18 to 22 weeks. UpToDate notes that although many anomalies can be seen in the first trimester, the second-trimester scan is more sensitive.
Often yes. UpToDate notes that ultrasound generally shows the sex at 17 to 20 weeks. The NHS says the sonographer may be able to tell you at the 18 to 20 week scan, but not every hospital's policy is to reveal it; say beforehand if you do not want to know.
In Turkey, the Ministry of Health guideline gives 18 to 24 weeks, or up to the end of week 32 if that window is missed. The NHS gives 16 to 32 weeks (usually around 20), and the US advice (UpToDate) ideally 27 to 36 weeks.
According to the WHO fetal growth charts (2017), the median (50th percentile) estimated fetal weight at 18 weeks is 222 g, and the 10th to 90th percentile range is 192 to 255 g. These are reference values from ultrasound measurements in low-risk pregnancies in ten countries; the authors note differences between countries, with maternal factors and with fetal sex, and say the charts may need adjusting for local use. UpToDate adds that ultrasound weight estimates are generally not useful before about 24 weeks. The NHS gives a length of about 14.2 cm from head to bottom.
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.