The truth is, vocally comparing bump sizes is a natural response. But you might be shocked to find out these seemingly harmless comments can actually hurt a mom-to-be. From a specific uterus position and a woman’s body structure to gestational age and even abnormal conditions, you never know what’s going on. Learn what causes different bump sizes, why you should never compare them, and some comments to avoid in this critical guide.

What Causes Different Bump Sizes?

Expecting moms can have different bump sizes for many reasons. Some you may have never even heard of. Let’s take a look at each reason below to help gain an understanding of why bump comments should be avoided.

Gestational age

The most obvious reason: women are at different stages in their pregnancy. Typically, someone 32 weeks pregnant will have a larger bump than a woman who is 17 weeks pregnant. This is because the baby, fluid, placenta, and weight gain gradually increase as a pregnancy progresses.

Baby’s position

How babies position themselves in the womb can have a significant impact on how a bump looks. A baby head-down and low in the pelvis usually presents a lower and more compact bump. On the other hand, if the baby is feet down, a bump may appear higher and wider. Also, keep in mind that the baby will change positions throughout the entire pregnancy, and the bump shape will follow right behind.

Pre-pregnancy size

An expecting mom’s frame plays a major role in how they carry the baby. “A woman with a slender build may have a more prominent bump, while a woman with a broader build might have a less noticeable one,” says Michael Green, MD, a board-certified ob-gyn in Lake Arrowhead, California. Essentially, every woman’s body is unique, and so are their bumps.

Number of pregnancies

In most cases, due to tighter abdominal muscles, first pregnancies tend to produce small baby bumps. That’s what my midwife told me at one of my prenatal appointments when I asked why I wasn’t showing yet. She advised me that women who’ve had multiple pregnancies will have more relaxed abdominal muscles and ligaments, making their bellies easier to stretch–hence a larger and more noticeable baby bump.

Number of babies

When a woman is expecting twins, triplets, or more, the uterus naturally expands further to accommodate the additional babies. This results in a larger and often more prominent bump. In contrast, moms expecting a single baby typically have a smaller, compact bump.

Uterus position

Some people don’t realize that uteruses aren’t created exactly the same, either. The position and specific tilt of a woman’s uterus can majorly affect the appearance of a baby bump. “For example, a retroverted uterus tilts backward, which may result in a smaller-looking bump,” says Green.

Abnormal conditions

Different circumstances like gestational diabetes, hyperemesis gravidarum, or other growth conditions can cause a deviation from the typical progression in pregnancy. In gestational diabetes, mothers can have a larger bump from the excess amniotic fluid. And with hyperemesis gravidarum, bumps can be much smaller due to excessive nausea and vomiting, leading to weight loss. In my case, doctors suspected a fetal growth restriction diagnosis–a condition where the placenta isn’t working well enough to provide the baby nutrients–resulting in a smaller baby bump.

Why You Shouldn’t Compare Bump Sizes

Making unsolicited comments on anyone’s body, pregnant or not, is something we should all avoid doing–even if it seems innocent. “You don’t know how anyone relates to their own body or if it makes them uncomfortable to receive comments about it,” says Green. 

And when it comes to comparing bump sizes, it’s best to say nothing during this sensitive and intimate time since you genuinely don’t know what’s going on in their pregnancy. When I received comments on how small my baby bump was, it reminded me my body wasn’t good enough to supply my small baby enough nutrients to grow.

Bump-related comments to avoid

Here are a few comments many expecting women hear throughout pregnancy that should be avoided. 

• “Wow, you’re getting huge!”
• “Are you sure you’re not having twins?”
• “You’re so big for only being __ weeks!”
• “You don’t even look pregnant!”
• “You’re barely showing!”
• “You’re so lucky you’re not gaining weight!”

When Should I Be Concerned With My Bump Size?

Although every bump is unique and grows at its own pace, there are some things you should look out for. “Rapid, significant changes in the size of the bump, whether it’s a sudden growth or shrinkage, should be evaluated by a healthcare provider,” says Green. 

Keep in mind that during your routine prenatal checks, your provider will monitor the progress by measuring your bump and assessing whether the baby is developing appropriately. Your healthcare team knows exactly what to look for in growing bumps and will speak up if they see anything abnormal. 

Experts in this article:

Michael Green, MD, is a board-certified ob-gyn in Lake Arrowhead, CA. He attended St. Louis University of Medicine, where he received his medical degree and has been in practice for over 30 years since. Dr. Green is now a Chief Medical Officer at Winona and an OB hospitalist and site director at Northridge Medical Center.