18th week: The second ultrasound is coming soon

Weeks and days
17+0 to 17+6
Month
5
Trimester
2

This week, the fetus grows from about 130 to 142 millimeters and weighs around 220 grams by the end. In Germany, the time window for the second ultrasound paid for by health insurance opens next week.

A single large pomelo lies in an open palm on beige linen
Pomelo132 to 154 mm, the size of your baby at the end of the week

Week 18 of 40

Calculate your week
1st trimester2nd trimester3rd trimester

How big is the fetus?

020406080100120140160 mm16th week101 to 11617th week116 to 13018th week130 to 14219th week142 to 153Pomelo at the same scale

130 to 142 mm

By the end of the week, the fetus is about the size of a pomelo. Its sex organs are developed enough that the labia or penis can be seen on ultrasound if the baby is in a favorable position.

Crown-rump length according to the UNSW Embryology table, weight according to the WHO growth charts. A large pomelo measures 132 to 154 mm.

This week

Your baby

  • In girls, the first follicles form in the ovaries.
  • A new phase begins in the lungs, in which the fine airways form.
  • By the end of the week, the head circumference grows on average to about 148 mm.

Your body

  • The median hCG level is 20,860 mIU/ml; 8,175 to 55,868 is normal. More in the hCG levels chart.
  • Your belly is now clearly rounded, and others can also see that you are pregnant.
  • A pulling feeling in the groin often comes from the round ligaments, which stretch as the uterus grows.

What matters now

  • For the second ultrasound in Germany, you decide whether you want the basic ultrasound or the extended basic ultrasound with a more detailed examination of the organs.
  • In Austria, the time window opens for the second Parent-Child Pass (Eltern-Kind-Pass) examination and the second ultrasound, now with measurement of the cervical length.
  • If you do not want to know the sex, say so before the ultrasound.

Get checked right away: heavy bleeding, severe or persistent abdominal pain, fever, pain when urinating, or vomiting where you cannot keep anything down.

Gestational sacPlacentaFetus with heartbeat

On ultrasound

  1. 17+0

    Head circumference is on average about 135 mm, and about 148 mm at the end of the week.

  2. 17+0

    Thigh bone (femur) measures on average about 22 mm, and about 26 mm at the end of the week.

  3. 18+0

    Second screening is scheduled in Germany from this day.

From 18+0, the window for the second ultrasound paid for by health insurance opens in Germany. Before then, you should decide whether you want the basic or the extended basic ultrasound.

Frequently asked questions about the 18th week of pregnancy

Where is the baby in your belly in the 18th week of pregnancy?

The top of the uterus is between the pubic bone and the navel. According to the Merck Manual, it reaches the level of the navel around the 20th week.

Is it normal not to feel any baby movements in the 18th week of pregnancy?

Yes, even in a later pregnancy. In one study, women who already had a child felt the first movements on average at 16+1 to 17+5, and first-time mothers at 18+0 to 19+0. If the placenta is at the front, you usually feel them later.

What is the risk of miscarriage in the 18th week of pregnancy?

Small. In large comparison groups without a procedure, about 6 in 1,000 pregnant women still lost their baby before the 24th week.

Which month is the 18th week of pregnancy?

The 5th month of pregnancy, in the 2nd trimester. Figures such as 17+2 weeks also belong to the 18th week of pregnancy.

Sources

Updated on 30 October 2026 · Fertilio Editorial Team