Baby measuring small at 28 weeks (A weekly baby size guide)

In this article we will look at the milestones of the baby while in the womb, and how to check for its measurement.

Baby measuring small at 28 weeks

Babies at 28 weeks should be nearly 10 inches (250 millimeters) long from crown to rump, and weighing almost 2.22 pounds, according to Mayo Clinic. If the baby is small for gestational age depends on several factors and the progress of pregnancy. Small gestational simply means that the fetus is smaller than the average size that it should be. 

During your prenatal visits to your OB/GYN or midwife, they can get a rough idea of your baby’s size by gently pressing on your tummy, or called palpitation. This doesn’t hurt the baby as they are cushioned by the amniotic fluid in your womb.

Your baby’s development at 28 weeks:

At 28 weeks, your baby’s brain is in a period of rapid brain growth, and their brain tissue is developing the ridges and furrows that give the brain its well-grooved appearance.  Babies begin rapid eye movement at 28 weeks as well, though this starts as early as 14 weeks. The frequent eye movement is associated with REM sleep and healthy brain development.

The umbilical cord that carries the blood between the placenta and your baby was fully formed at week 12, between 30-100 centimeters long and and over 16 millimeters wide.

Survival of babies born at 28 weeks outside the womb go up and the risk of lifelong health impairments go down. With specialized neonatal care, a baby born prematurely at 28 weeks has 94% chance of survival outside the uterus.

How to measure your bump size?

Midwives start measuring your bump at 26 to 28 weeks. Babies can be smaller compared to other babies if their weight is below the 10th percentile. They are smaller than other babies only at the same gestational age.

A baby in the womb can be checked for a growth scan if you think the baby is smaller than expected. Just to be on the safe side. Many babies normally weigh more than 5 pounds, 13 ounces by the 37th week of pregnancy. And babies born less than 5 pounds 8 inches are considered low birth weight.

Your midwife or OB/GYN will ask you to lie down and measure the top of your pubic bone to the top of your uterus using a tape measure. This is also called the symphysis-fundal-height  measurement and used to monitor the growth of the fetus in your womb. This measurement starts at 26 weeks, or for some women who are high risk and have complications, this starts at 24 weeks.

How big should my baby bump be?

The symphysis-fundal-height  measurement should roughly correspond to the number of weeks into your pregnancy.  Although the bump size varies from person to person and may depend on the general body built of the pregnant woman as well.

If the measurement is small for the or outside the normal range, your doctor may ask you to get an ultrasound scan to get a better idea of your baby’s size. 

Here are the several factors that affects the bump size, which most of the time is nothing to be worry about:

  • Mother body built. Tall women with longer body size have more room for the baby to grow and may look smaller. The smaller framed women have less room for the baby thus may look plumper than the taller ones.
  • Number of babies. If you are carrying multiples or more than one baby, your bump will be bigger than the average size bumps of the singleton mothers.
  • Number of pregnancies. Uterine muscles are tighter on the first pregnancy, thus bumps are smaller. The next pregnancies will tend to be bigger due to the stretched muscles already.
  • Amniotic Fluid. The more amniotic fluids you have, the bigger the bump will be.
  • Baby’s position. The bump will be smaller if the baby’s back is in front of the mother’s tummy, wherein the arms and legs are hidden. The bump will show larger if the baby is facing front to mother’s tummy and the arms and legs are sticking out.

Smaller Gestational babies:

Babies with the issues are often diagnosed with intrauterine growth restrictions before birth. While pregnant, the baby’s size can be checked in many ways. The height of the top of the mother’s uterus can be measured from the pubic bone, and this measurement links to the number of weeks of pregnancy after the 20th week. 

Treatment for smaller babies depends on your child’s symptoms, age and general health at the time of birth and how severe the condition is. Babies with small size can be physically more mature than their size suggests. But they might be weak, take less feedings and unable to control their inner temperature.

Treatment for smaller babies are:

  • Temperature-controlled beds or incubators
  • Tube feedings or Orogastric tube (OGT), wherein a soft tube is passed through a child’s mouth into the stomach.
  • Blood test to check for low blood sugar
  • Oxygen level monitoring
  • Babies who are more premature may need more interventions or a breathing machine or ventilator.

Baby’s Weight and size by gestational weeks, according to

Gestational ageLength (US)Weight (US)Length (cm)Mass (g)
(crown to rump)(crown to rump)
8 weeks0.63 inch0.04 ounce1.6 cm1 gram
9 weeks0.90 inch0.07 ounce2.3 cm2 grams
10 weeks1.22 inch0.14 ounce3.1 cm4 grams
11 weeks1.61 inch0.25 ounce4.1 cm7 grams
12 weeks2.13 inches0.49 ounce5.4 cm14 grams
13 weeks2.91 inches0.81 ounce7.4 cm23 grams
14 weeks3.42 inches1.52 ounce8.7 cm43 grams
15 weeks3.98 inches2.47 ounces10.1 cm70 grams
16 weeks4.57 inches3.53 ounces11.6 cm100 grams
17 weeks5.12 inches4.94 ounces13 cm140 grams
18 weeks5.59 inches6.70 ounces14.2 cm190 grams
19 weeks6.02 inches8.47 ounces15.3 cm240 grams
20 weeks6.46 inches10.58 ounces16.4 cm300 grams
(crown to heel)(crown to heel)
20 weeks10.08 inches10.58 ounces25.6 cm300 grams
21 weeks10.51 inches12.70 ounces26.7 cm360 grams
22 weeks10.94 inches15.17 ounces27.8 cm430 grams
23 weeks11.38 inches1.10 pound28.9 cm501 grams
24 weeks11.81 inches1.32 pound30 cm600 grams
25 weeks13.62 inches1.46 pound34.6 cm660 grams
26 weeks14.02 inches1.68 pound35.6 cm760 grams
27 weeks14.41 inches1.93 pound36.6 cm875 grams
28 weeks14.80 inches2.22 pounds37.6 cm1005 grams
29 weeks15.2 inches2.54 pounds38.6 cm1153 grams
30 weeks15.71 inches2.91 pounds39.9 cm1319 grams
31 weeks16.18 inches3.31 pounds41.1 cm1502 grams
32 weeks16.69 inches3.75 pounds42.4 cm1702 grams
33 weeks17.20 inches4.23 pounds43.7 cm1918 grams
34 weeks17.72 inches4.73 pounds45 cm2146 grams
35 weeks18.19 inches5.25 pounds46.2 cm2383 grams
36 weeks18.66 inches5.78 pounds47.4 cm2622 grams
37 weeks19.13 inches6.30 pounds48.6 cm2859 grams
38 weeks19.61 inches6.80 pounds49.8 cm3083 grams
39 weeks19.96 inches7.25 pounds50.7 cm3288 grams
40 weeks20.16 inches7.63 pounds51.2 cm3462 grams
41 weeks20.35 inches7.93 pounds51.7 cm3597 grams
42 weeks20.28 inches8.12 pounds51.5 cm3685 grams


Generally speaking, if the baby is active in your tummy during your pregnancy, they are more likely to be fine. But if there is a doubt in your mind on the growth of your baby, it is best to have regular prenatal check ups to see the progress of your baby.

A smaller baby or fetus during pregnancy or at 28th week does not mean a serious problem will occur during pregnancy or at birth. It could be a symptom of intrauterine restrictions that is widely common to pregnant women. Most smaller babies catch up upon birth up to two years of age for a complete catch up.

FAQ’s on Baby Small Gestational Size (A weekly baby size guide):

What does it mean if your baby is measuring small at 28 weeks?

Your baby might be in the smaller range of size for the gestational age, or what is considered the average size at that stage of pregnancy. Try your best not to worry and seek your doctor’s advice.

What if my fetus is measuring small?

Babies that are small are diagnosed with intrauterine growth restriction (IUGR) if they appear to be smaller than expected on the average gestational size. An ultrasound can verify this and if the weight is below 10% percentile for their gestational age (week of pregnancy), it is called fetal growth restriction (FGR).

What is the average size of a baby at 28 weeks?

Your baby should be about 36 cm long and weighs at 1.13 kg. This will still be small, but during the succeeding weeks, the baby will pack up some more pounds in preparation of his/her birth.

Can a small fetus catch up?

The good news is that most IUGR babies catch up immediately after  birth, and the majority catch up growth from birth up until age two. If a catch up occurs, it generally happens during the 3rd to 6th month after birth and will complete on or before two years old.

Why is the 28th week of pregnancy crucial?

This is crucial due to the fact that you just entered the last phase or the beginning of the third trimester of your pregnancy. At 28th week, your baby’s brain is still developing, but the central nervous system has developed enough to allow your baby to begin controlling his temperature.