What do obstetricians mean by a “small” baby?
A baby whose birth-weight is in the lowest 10% of the population is called “small”. Or to put it another way, the baby weighed less than 90% of its newborn peers.
What causes a baby to be small?
1. About 2/3 of small babies are simply “constitutionally small”. These babies are absolutely healthy. They grew appropriately during the pregnancy but were always destined to weigh 6 pounds rather than 10 pounds. Just as there is a range of different heights for adults, there is a range of healthy sizes for babies.
2. A rarer cause, but potentially more serious, is calledfetal growth restriction (or intrauterine growth restriction). A growth-restricted baby is not thriving in the womb. Usually, this occurs because the placenta (which supplies blood to the growing fetus) is not working 100%. We monitor babies with fetal growth restriction very carefully, because they are at risk of serious complications.
3. In a small number of cases, babies can measure small because the mother picked up aninfection earlier in the pregnancy. Many infections (such as CMV or toxoplasmosis) cause only a mild flu-like illness for the woman but can have serious consequences for fetal development.
4. Rarely, babies are small because of an underlying chromosomal problem or genetic problem.
Do you often see couples who had a small baby in a previous pregnancy?
Yes – approximately 1-in-10 couples will have had a small baby in an earlier pregnancy. This is one of the common reasons that couples come to see me.
My previous baby was growth restricted – is my current pregnancy at higher risk?
Yes. You have an increased risk of fetal growth restriction in all future pregnancies. This is especially the case if the growth problem was severe enough to need early delivery of the baby. Women who needed early delivery in their last pregnancy should seriously consider seeing a Maternal-Fetal Medicine specialist.
I read that some medical problems are linked to small babies?
This is correct. Some underlying medical problems interfere with the development and function of the placenta. Conditions such as high blood pressure, kidney disease and some autoimmune conditions all increase the risk of fetal growth restriction, as do pregnancy complications like pre-eclampsia.
This risk can be reduced by optimising the management of your medical condition before pregnancy. Some women also benefit from low-dose aspirin started in early pregnancy.
For this reason, I strongly recommend pre-pregnancy counselling to any woman with a pre-existing medical condition, a history of pre-eclampsia or a previous small baby.
What additional tests do you recommend in my current pregnancy?
The most important test is regular ultrasound scanning to carefully monitor the baby’s growth. The ultrasound also allows us to measure the blood flow in the placenta (called fetal Doppler studies) and the amniotic fluid volume (waters).
Women with a previous small baby should at least have specialist growth scans at 28-30 weeks and 34-36 weeks. This is in addition to the routine scans at 12 and 19 weeks.
The bedside scans performed by most obstetricians are not specialist growth scans. General obstetricians do not have the training, experience or qualifications to perform diagnostic ultrasound scans. As a Maternal-Fetal Medicine specialist, I do have the training and experience to perform diagnostic growth scans and Doppler studies myself. I perform specialist scans for all my private patients at their antenatal appointments.
Depending on your circ*mstances and what we find on ultrasound, other tests may be recommended. This may include testing for pregnancy complications (like pre-eclampsia), specific infections, or a specialised chromosome test called an amniocentesis.
What else can I do to avoid my baby being small?
It’s important to avoid lifestyle choices that harm the placenta. Smoking in pregnancy is a very significant risk factor for fetal growth restriction. If you are a smoker, please talk to your GP as soon as possible for help quitting. The same goes for recreational drugs.
As always, this information is intended for general educational purposes only. It is not medical advice. Please discuss any medical issues with your own doctor. Read our full medical disclaimer here.
FAQs
About 2/3 of small babies are simply “constitutionally small”. These babies are absolutely healthy. They grew appropriately during the pregnancy but were always destined to weigh 6 pounds rather than 10 pounds. Just as there is a range of different heights for adults, there is a range of healthy sizes for babies.
Does having a small baby mean anything? ›
Most babies do not have any health problems but are just smaller than others and this is normal for them. However, sometimes babies are small because they have not grown as well as expected. This is called being 'growth restricted'. The smaller your baby is, the more likely they are to be growth restricted.
What is the meaning of a small baby? ›
A small baby is a baby whose estimated weight puts them in the lowest 10% of babies at that stage of pregnancy. That means their weight is below 90% of other babies.
What does "constitutionally small baby" mean? ›
The constitutionally normal infants have normal birth weight less than 10th percentile because of inherent factors such as maternal height, weight, ethnicity, parity, and in these infants, there is no increased risk of perinatal mortality and morbidity.[1] SGA and fetal growth restriction (FGR) are used interchangeably ...
What does it mean if your baby is measuring small? ›
Some babies are small because their parents are small. But most babies who are small for gestational age have growth problems that happen during pregnancy. When the unborn baby has trouble getting oxygen or nutrients during pregnancy, they don't grow as much as expected. The condition is often suspected before birth.
Is a 5 pound baby healthy? ›
Nearly all low birthweight babies need specialized care in the Neonatal Intensive Care Unit (NICU) until they gain weight and are well enough to go home. Fortunately, there is a 95 percent chance of survival for babies weighing between 3 pounds, 5 ounces, and 5 pounds, 8 ounces.
What is the meaning of tiny baby? ›
a very young child, especially one that has not yet begun to walk ... See more at baby. (Definition of tiny and baby from the Cambridge English Dictionary © Cambridge University Press)
What are the signs of a small baby? ›
Some signs of being born too early include:
- Small size, with a head that's large compared with the body.
- Features that are sharper and less rounded than a full-term baby's features due to a lack of cells that store fat.
- Fine hair that covers much of the body.
Informal words that refer to a child's small size are ankle-biter, nipper, squirt, and, in UK English, tiddler. The park was full of ankle-biters. He has a little nipper that follows him around everywhere. He's just a little squirt.
Does a small baby mean a small adult? ›
Some small babies remain small as adults and others are within the normal range. Infants whose growth was restricted because their mother used alcohol while pregnant are likely to have long-term developmental and behavioral problems (see also Alcohol Use During Pregnancy).
Genentics. What the researchers discovered was surprising when they looked at the reasons behind this correlation. They found a genetic link between maternal height and a baby's birth weight and length. That was expected—small parents make small babies.
What is small baby syndrome? ›
Intrauterine growth restriction, or IUGR, is when a baby in the womb (a fetus) does not grow as expected. The baby is not as big as would be expected for the stage of the mother's pregnancy.
Can a small fetus catch up? ›
Do growth-restricted babies catch up? Yes, most babies with IUGR will reach the size of full-term children their age by age 3. It's important to note that all children grow differently and that you shouldn't attempt to overfeed your child. This could unintentionally cause other conditions like obesity or diabetes.
What does it mean when the doctor says your baby is small? ›
Small for gestational age is a term that can be used to refer to your baby before birth or when they are born. It is when your baby's birth weight is less than the 10th percentile for their sex and gestational age, or your doctor predicts they will be based on your pregnancy ultrasounds.
Is it OK if my baby is small? ›
Many babies are otherwise healthy except for being small, so it is likely safe to try vagin*l delivery. Babies that are severely growth restricted or that have abnormal Doppler patterns may not do well with labor, so C-section may be indicated. A discussion with your doctor is always recommended.
Can stress cause you to have a small baby? ›
High levels of stress that continue for a long time may cause health problems, like high blood pressure and heart disease. During pregnancy, stress can increase the chances of having a baby who is preterm (born before 37 weeks of pregnancy) or a low-birthweight baby (weighing less than 5 pounds, 8 ounces).
Can a small baby still be healthy? ›
Should I be concerned if my baby is small? Most small babies will be healthy. However, if your baby has fetal growth restriction, this increases the risk of complications and, sadly, also the risk of stillbirth.
Do small babies mean small adults? ›
Some small babies remain small as adults and others are within the normal range. Infants whose growth was restricted because their mother used alcohol while pregnant are likely to have long-term developmental and behavioral problems (see also Alcohol Use During Pregnancy).
Is it Genetic to have a small baby? ›
Although some babies are small because of genetics (their parents are small), most SGA babies are small because of fetal growth problems that occur during pregnancy.
