17 weeks pregnant

Your baby at 17 weeks

Week 17 sits at the start of a stretch that ACOG groups as weeks 17 to 20. In its week-by-week guide, the part of the brain that directs movement is fully formed by the end of that stretch, the digestive system is working, and the ears, nose and lips can be recognized on an ultrasound picture. A soft, fine covering of hair called lanugo begins to form over the body. These changes build up across the four weeks rather than landing on a particular day.

For size, your baby is compared to a pear. The length of about 13 cm is measured crown to rump, because the legs are still tucked up and are hard to measure straight. The fruit and the length are the comparison used in the ProbaBaby app's size guide, a rough picture rather than a scan standard. From week 21 the guide switches to crown-to-heel, which is why the number will jump. The baby does not suddenly grow; the measurement simply changes.

The weight is a different kind of number. At 17 weeks the middle estimated fetal weight on the WHO charts is 179 g, and 8 in 10 babies fall between 155 g and 207 g. Nobody weighs your baby in the womb. A sonographer measures the head, tummy and thigh bone on a scan, and a formula turns those into an estimate. The same charts put the middle head circumference at 135 mm. Because the range is wide, being above or below the middle line says little on its own, and your care team looks at the trend over several scans.

One thing makes week 17 special: you are now inside the window when movement can first be noticed. The NHS says people usually start to feel their baby between 16 and 24 weeks, and describes the first sensation as a gentle swirling or fluttering. In a first pregnancy you might not feel anything until after 20 weeks.

Your body at 17 weeks

With 23 weeks still to go, your uterus keeps expanding and your waistline is changing. Some people show clearly by now, others do not, and both are typical. Clothes tend to get snug around the middle first.

Your routine care is quiet this week. The NHS appointment schedule has a visit at 16 weeks, where the midwife goes over earlier screening results and checks your blood pressure and urine. The next routine visits are at 25 weeks if this is your first baby and at 28 weeks for everyone, so it is worth writing down questions in the gap. The big event ahead is the mid-pregnancy scan, which the NHS offers between 18 and 21 weeks.

Energy often improves. The NHS describes tiredness as most typical in the first trimester, and later fatigue as more to do with carrying extra weight and disturbed sleep. If you feel better than you did a few weeks ago, put that energy into movement. The NHS suggests 150 minutes of moderate activity a week, such as walking, swimming or yoga, at a level where you can talk but not sing. If you are new to exercise, it suggests starting with about 10 minutes a day.

Common symptoms around 17 weeks

• Lower back ache. Your ligaments soften and stretch in preparation for labor, and that loads the joints of the back and pelvis. The NHS suggests flat shoes, keeping your back straight and supported when you sit, and bending your knees rather than your back to lift. Gentle exercises for the tummy muscles and antenatal yoga or swimming classes can also help.
• Itchy stretching skin. Around 8 in 10 pregnant women get stretch marks, says the NHS, and itching around thinning skin can be the first hint. They are not harmful, and after the birth they may fade to paler lines. The NHS says there is no reliable evidence that creams remove them.
• A first flutter, or none yet. Early movements are light and easy to miss. The NHS says they later turn into kicks and jerky movements, so they usually become easier to recognize.
• Leftover queasiness. The NHS says morning sickness usually settles by weeks 16 to 20. If it is still with you, small frequent plain meals, cold food and regular sips of fluid are the NHS suggestions.

Tips for this week

• Choose your scan preferences now. Decide whether you want to be told the baby's sex, and whether anyone can come with you, so the conversation at the scan is short.
• Note down your questions. The mid-pregnancy scan looks for 11 conditions and also checks the placenta, so it is a good moment to ask about anything you have been wondering.
• Use the energy. Pick an activity you enjoy and can keep up, and build slowly if it is new to you.
• Tell your instructors. If you go to a gym or class, say you are pregnant. The NHS also advises avoiding sports with a risk of falls or knocks.
• Begin noticing your baby. You do not need to count anything. Just pay attention to when your baby seems most active as the movements become regular.

When to call your doctor or midwife

How quickly to call depends on what you notice. Ring your local emergency number now if you are bleeding heavily, in severe pain, feel faint, or have pain in the tip of a shoulder. If you have light spotting or mild cramps, contact your midwife or doctor the same day. Until 20 weeks an early pregnancy unit may be the right place, and your local non-emergency health line can advise if you cannot reach your own team.

• Call the same day if you see light vaginal bleeding or spotting, even if it does not hurt or comes only with mild cramps. Call your emergency number now instead if the bleeding is heavy, soaks a pad quickly, or comes with severe belly pain, shoulder pain, or feeling faint or dizzy.
• Call now if you cannot keep food or fluids down for 24 hours, if your pee is very dark or you have not peed for over 8 hours, or if you feel weak or faint.
• Call now if you are vomiting and also have belly pain, a high temperature, or blood in your vomit.
• Call now if peeing hurts or burns, or if back pain comes with a fever, bleeding or pain in your side.
• Call your emergency number if back pain comes with loss of feeling in your legs, buttocks or genitals.
• Tell your midwife if you have felt no movements by 24 weeks. Once you have a regular pattern of movements, call your midwife or maternity unit straight away if they slow down, change or stop; do not wait until the next day.