Mom with Vibe TeamSeeing your tiny baby wrapped up for the first time is one of life’s most precious moments. You may feel perplexed if your child is smaller than you anticipated, though. But why are some infants born smaller than expected? In this article, we’ll look at some of the most prevalent causes.
If your child is described as being small for gestational age (SGA), or if you’ve noticed that they’re not as robust as the other babies you’ve seen, you may wonder why. To begin, here are seven of the most common causes of small babies:
7 Reasons Why Your Baby Could Be Born Small in Size
1. Premature Birth
Premature birth is the most prevalent cause of a small baby at birth. This term refers to babies born before the 37th week of pregnancy, rather than the 39th to 40th week, which is typical for full-term pregnancies.
When born early, a baby has less time to develop in the uterus and, as a result, will be smaller than a baby born at term. The earlier the birth, the lower the birth weight, as the baby hasn’t had as much time to grow in the womb.
There are various reasons why a pregnancy may be preterm, including maternal illnesses or infections, as well as pregnancy complications. However, with advanced medical care, preterm newborns often thrive, though they may require special care in the first few months of life.
Related: 7 Things You Need to Know About Your Baby’s Weight
2. Genetic Factors
Just like adults, babies inherit their size from their parents. In many cases, they receive genes that determine their stature. If parents are smaller or shorter in stature, there’s a higher likelihood that their baby will also be smaller than average. The chances of this are especially high if there is a family history of smaller infants.
Genetics play a significant role in how much weight a baby will gain during pregnancy. Some babies are naturally born small due to their genetic makeup.
Certain ethnic groups tend to produce smaller newborns compared to others. This isn’t a sign of illness or a problem; instead, it’s a genetic trait passed down through generations.
Genetics also influence how a baby grows during pregnancy. A baby may be smaller than expected due to genetic factors but still be healthy.
3. Placental Insufficiency
The placenta is responsible for the growth and development of your baby during pregnancy. It supplies oxygen and nutrients to the baby while in the uterus and disposes of waste. If the placenta isn’t functioning properly, your baby may end up being smaller than expected.
Placental insufficiency can impede the baby’s growth, causing them to be born underweight.
Various conditions can cause placental insufficiency, including preeclampsia, gestational diabetes, and infections. The placenta’s role is to transfer nutrients from the mother’s blood to the baby, and if blood flow is compromised, the baby may not receive the necessary nutrients for proper growth.
Babies born to mothers with placental insufficiency may need special care immediately after birth and for several weeks to ensure they are healthy and gaining weight as they should.
Related: Placenta’s Role in Pregnancy: 7 Key Functions
4. Infections During Pregnancy
Infections during pregnancy can significantly affect the baby’s development and may lead to low birth weight. In some cases, the infection may directly harm the placenta, while in other cases, it may prevent the baby from absorbing nutrients, slowing their growth.
Common infections that may result in a baby being born underweight include:
-
Toxoplasmosis: A parasitic infection that can cause miscarriage, preterm birth, or low birth weight.
-
Rubella: A viral infection that can lead to birth defects and impaired growth.
-
Cytomegalovirus (CMV): A common virus that can cause various health problems, including developmental delays and low birth weight.
-
Urinary tract infections: Common during pregnancy, UTIs can lead to complications such as premature labor, miscarriage, and low birth weight if left untreated.
If you have an infection during pregnancy, it’s essential to follow your healthcare provider’s treatment plan to minimize the impact on your baby.
5. Poor Maternal Nutrition
A mother’s nutrition plays a crucial role in the size of her baby at birth. If a mother is malnourished or doesn’t eat enough nutritious food during pregnancy, her baby may not develop to their full potential. Essential nutrients like proteins, vitamins, minerals, and others are required for fetal development, and deficiencies in any of these can impact the baby’s growth.
For example, a lack of folic acid during pregnancy can result in neural tube defects, and insufficient iron and protein in the mother’s diet can restrict the baby’s muscle and organ development. Mothers who are underweight or have eating disorders are also at risk of having small babies.
Pregnant women should consume a balanced diet rich in essential vitamins and minerals to ensure the healthy development of the baby. Prenatal vitamins may also be recommended to ensure adequate nutrition throughout pregnancy.
Related: Nutrikids Food Nutrition DHA+ Orange
6. High Blood Pressure (Hypertension)
High blood pressure during pregnancy can impact both the mother and the baby. When a mother experiences high blood pressure, it can restrict blood flow to the placenta, reducing the oxygen and nutrients the baby receives. This decreased blood flow can cause the baby to grow at a slower rate, resulting in low birth weight, a condition known as intrauterine growth restriction (IUGR).
Pre-eclampsia is a more severe form of high blood pressure that can also affect the baby’s size. Women with pre-eclampsia may experience placental insufficiency, which, as mentioned earlier, can restrict the baby’s growth.
If left untreated, high blood pressure can lead to preterm delivery, low birth weight, and various complications for both mother and baby. Regular monitoring of blood pressure is crucial during pregnancy to manage and control hypertension effectively.
Related: What Is Food Cravings During Pregnancy?
7. Multiple Pregnancies (Twins, Triplets, etc.)
Multiple pregnancies, such as twins or triplets, often result in smaller babies. Preterm births and intrauterine growth restriction (IUGR) are more common in multiple pregnancies because each baby must share the limited space and nutrients in the uterus. This can lead to smaller babies at birth.
While multiples tend to be smaller than singletons, they are generally healthy and, with proper care, grow well. However, multiple pregnancies require additional monitoring and care to ensure that each baby is developing properly.
Conclusion
Small babies are not always unhealthy or a sign of a problem. While smaller babies may be underdeveloped, they can still be healthy and thrive with the appropriate care and attention. Various factors, including preterm birth, genetics, placental insufficiency, maternal nutrition, infections, and multiple pregnancies, can contribute to a baby’s size at birth.
It’s natural for parents to be concerned about their baby’s health and development, but with the right medical care, most small babies will grow up to be healthy. If you’re pregnant and worried about your baby’s size, discuss your concerns with your healthcare provider to ensure the best possible outcome for you and your baby.
Save the pin for later
- 10 DIY Sensory Play Activities for Toddlers - March 12, 2026
- 12 Family Organization Systems for Busy Moms - March 12, 2026
- How to Change a Diaper: A Step by Step Guide - March 11, 2026
