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28 Weeks Pregnant: The Third Trimester Begins

Medically reviewed by

Sarah Riffle, RN Jul 30, 2026

Line illustration of an aubergine: at 28 weeks pregnant your baby is about the size of a large eggplant, roughly 25cm crown to rump

Line drawing of a 28-week foetus with full rounded limbs as fat builds under the skin

Line drawing of a woman's torso at 28 weeks pregnant, showing the uterus inside a high rounded bump at the start of the third trimester

Your baby is the size of a

Aubergine

~1kg

~25 cm / ~9.8 in

Key Takeaways

At 28 weeks pregnant, your baby is about 25 centimetres (250mm) from crown to rump and weighs about 1,000 grams, according to Mayo Clinic. The eyelids can partially open, and the central nervous system can now control body temperature.

This is often the week of the Rh injection. If you have Rh-negative blood, SOGC says you will be given an injection of Rh immunoglobulin (also called RhoGAM, WinRho, or anti-D) at about 28 weeks, which prevents sensitization in 99% of women.

Movement awareness becomes routine now. SOGC advises being aware of any changes in your baby's usual activity level, especially in the third trimester, and says if you don't feel 6 movements in 2 hours, contact your provider as soon as possible.

Your Baby at 28 Weeks: Development & Growth

At 28 weeks pregnant, your baby is about 250 millimetres (roughly 25cm) long from crown to rump and weighs about 1,000 grams, according to Mayo Clinic. This week the eyelids can partially open, and the central nervous system can control body temperature and trigger breathing movements that can be seen on an ultrasound.

Your baby measures about 25cm this week — around the length of a large eggplant, and about a kilogram in weight. Mayo Clinic puts it as "nearly 10 inches (250 millimeters) long from the top of the head to the bottom of the tailbone, called crown to rump," and a weight of "about 2 1/4 pounds (1,000 grams)." Length is still measured crown to rump at this stage.

The headline change this week is the eyes. Mayo Clinic explains that at 28 weeks "your baby's eyelids can partially open." After weeks of being fused shut, they are starting to work.

The nervous system is taking on new jobs, too. Mayo Clinic notes that the central nervous system "can control body temperature" and "can trigger breathing movements, which can be seen on an ultrasound." Your baby is rehearsing the work of the outside world.

More is coming right behind this. Mayo Clinic notes that around week 29 your baby "can kick, stretch and make grasping movements" — the strong, unmistakable motions that will define these next weeks.

Your Body at 28 Weeks: Symptoms & Changes

At 28 weeks pregnant, many mothers feel the third trimester in their body — a growing bump, and the return or persistence of common discomforts. SOGC lists tender breasts, constipation, backaches, headaches, mood swings and leg cramps among them. This is also when movement awareness becomes routine, and when the Rh injection is given to Rh-negative mothers. Every pregnancy is different.

The Rh injection is the appointment many mothers have this week. SOGC explains that Rh status is checked early — "All pregnant individuals will be tested for Rh status during routine bloodwork taken early in pregnancy" — and that if you are Rh-negative without existing antibodies, "you will be given an injection of Rh immunoglobulin... at about 28 weeks gestation." It is a preventive step, not a sign anything is wrong.

Movement is the other theme of week 28. SOGC advises that it is "a good idea to be aware if any changes in your baby's usual activity level, especially in the third trimester," adding that "your perception of your baby's movements is one of the strongest indicators of your baby's wellbeing." You are the expert on your baby's pattern.

Symptoms may still come and go. SOGC lists tender or swollen breasts, constipation, gas and bloating, backaches, headaches, mood swings and leg cramps among the common discomforts of pregnancy. Any of these can still be part of your week, and, as SOGC puts it, "every pregnant woman is different."

Your shape is doing real work. SOGC explains that weight gain "isn't just the baby" — "your placenta, increased blood volume, larger breasts, and fat stores to support breastfeeding, also contribute." A rounding, heavier middle is your body doing exactly what it should this trimester.

What to Do at 28 Weeks Pregnant

NUTRITION AT 28 WEEKS PREGNANT

Add the third-trimester calories, and add them well. SOGC states: "In the third trimester, you need about 450 extra calories," noting this "generally equates to 2 or 3 additionally servings from any of Canada’s Food Guide’s food groups" — for example, a piece of toast and a cup of milk, or an apple and some yogurt. It is a modest increase, and quality counts more than quantity.
Stay on top of iron. SOGC advises increasing "your daily iron intake to 27mg daily during the final six+ months of pregnancy to support an increase in red blood cells and fetal tissues" — and notes that, "like most women, you may need a good supplement to meet this need." This is the trimester when iron demand is highest.
Mind your choline. SOGC notes that "choline intake above 450mg a day is linked to improved fetal stress responses and a reduced risk of neural tube defects," and adds that "this vitamin may not be found in your prenatal daily vitamin" — so it is worth checking your label.

WHAT SUPPLEMENTS TO TAKE AT 28 WEEKS PREGNANT

Keep taking 400mcg of folic acid daily. The Public Health Agency of Canada states that "a daily multivitamin with 400 mcg (0.4 mg) of folic acid is recommended for anyone who could become pregnant," and advises: "Continue taking folic acid throughout your pregnancy and while breastfeeding."
Don’t raise your folic acid dose on your own. The Public Health Agency of Canada advises: "You should not increase your dose of folic acid beyond 1 mg per day without talking to your health care provider." A higher dose is a conversation, not a decision for the supplement aisle.
Consider vitamin D. SOGC notes that "taking a vitamin D supplement of 2000IU in the last six months of pregnancy will enhance the vitamin D content of your breast milk towards meeting the daily needs of your breastfeeding infant." Check what your prenatal already includes.

LIFESTYLE TIPS AT 28 WEEKS PREGNANT

Keep moving — aim for at least 150 minutes a week. SOGC advises that "pregnant women should accumulate at least 150 minutes of moderate intensity physical activity each week," spread across "at least 3 days a week, and up to 7 days a week." Walking, swimming and stationary cycling remain good options in the third trimester.
Build in pelvic floor exercises. SOGC notes that "pelvic floor muscle training (e.g., Kegel exercises) can be performed every day to reduce the risk of urinary incontinence." Easy to fold into a daily routine, and useful now.
Get to know your baby’s movement pattern. SOGC notes that movements "tend to be consistent for any one baby, in any one pregnancy," and suggests that if you count, "try to do it at the same time each day" — often in the evening, lying down, when babies tend to be more active.
Keep caffeine to 300mg a day. Health Canada recommends a maximum daily caffeine intake of 300 mg for people who are pregnant. For reference, Health Canada puts one 8oz (237ml) cup of brewed coffee at about 135mg — so roughly two cups is the ceiling, and that total includes tea, cola and chocolate.

When to Contact Your Doctor or Midwife

Most of week 28 is a steady new beginning, not an alarm. But some symptoms should always be checked. Contact your doctor, midwife or other health care provider if you experience:

A change in your baby's movements, or fewer movements than usual. SOGC advises being aware of any changes in your baby's usual activity level, especially in the third trimester. To do a kick count, SOGC says to count the baby's movements for 2 hours — and if you don't feel 6 movements (such as kicks, flutters, or rolling movements) in 2 hours, you should contact your health care provider as soon as possible. SOGC adds that if you ever have concerns regarding your baby's movement pattern, you should have the baby assessed as soon as possible, and that mothers should always trust their intuition.
Signs of preterm labour. SOGC advises contacting your health care provider right away if you are having any of the following: backache that comes and goes; regular contractions less than 10 minutes apart; cramping in your lower abdomen; fluid leaking from your vagina; pressure in your pelvis or vagina; vaginal bleeding. SOGC stresses that it is very important to go to the hospital if you have regular contractions at any time before 37 weeks that don't go away when you change your activity, and warns that staying home thinking this couldn't possibly be labour because it is too early is dangerous.
Any vaginal bleeding. SOGC lists vaginal bleeding in the 2nd or 3rd trimester among situations that need medical attention. Contact your health care provider promptly, and if bleeding is heavy or you feel very unwell, seek emergency medical care immediately.
Signs of a possible infection. SOGC notes that you may have an infection in your vagina or cervix if you notice an unusual vaginal discharge, have pain in your pelvis or groin area, or a fever, and advises notifying your health care provider. A bladder or kidney infection can show up as pain when you urinate or needing to go often.
Persistent low mood or disruptive mood swings. SOGC advises that "depression or disruptive mood swings are not normal and it is important to seek help for these more serious concerns."

Frequently Asked Questions

How big is my baby at 28 weeks pregnant?

At 28 weeks pregnant, your baby is about 250 millimetres — roughly 25cm — from crown to rump and weighs about 1,000 grams, according to Mayo Clinic. Mayo Clinic describes it as "nearly 10 inches (250 millimeters) long from the top of the head to the bottom of the tailbone, called crown to rump," weighing "about 2 1/4 pounds (1,000 grams)." Length is measured crown to rump at this stage.

What is the injection at 28 weeks of pregnancy?

For mothers with Rh-negative blood, it is the Rh immunoglobulin (anti-D) injection. The Society of Obstetricians and Gynaecologists of Canada (SOGC) explains that if "you have Rh-negative blood and do not already have antibodies for Rh-factor, you will be given an injection of Rh immunoglobulin (also called RhoGAM, WinRho, or anti-D immunoglobulin) at about 28 weeks gestation." SOGC says this "prevents sensitization in 99% of women so that your body will not form antibodies to the baby’s Rh factor." Rh status is checked with routine bloodwork early in pregnancy, so you will usually know beforehand whether you need it.

How do I do a kick count in the third trimester?

The Society of Obstetricians and Gynaecologists of Canada (SOGC) advises: "To do a kick count, count the baby’s movements for 2 hours. If you don’t feel 6 movements (such as kicks, flutters, or rolling movements) in 2 hours, you should contact your health care provider as soon as possible." SOGC adds that "if you have a pregnancy with risk factors (e.g., high blood pressure, gestational diabetes, etc.), you should do a kick count every day, starting at 26-32 weeks." Evening, lying down, at the same time each day tends to work best.

How many extra calories do I need in the third trimester?

The Society of Obstetricians and Gynaecologists of Canada (SOGC) states: "In the third trimester, you need about 450 extra calories." SOGC notes this "generally equates to 2 or 3 additionally servings from any of Canada’s Food Guide’s food groups" — for example, a piece of toast and a cup of milk, or an apple and some yogurt. It is a modest, quality-focused increase, not a large one.

How much caffeine is safe at 28 weeks pregnant?

Health Canada recommends a maximum daily caffeine intake of 300 mg for people who are pregnant. Health Canada puts one 8oz (237ml) cup of brewed coffee at about 135mg, so roughly two cups a day is the ceiling — and that total should include tea, cola and chocolate, which also contain caffeine.

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