How Big Will My Baby Be? The Answer Will Help You Prepare For Childbirth

As your pregnant belly grows larger and your baby's due date approaches, it's natural to wonder just how this whole pregnancy things ends. So, if you're wondering, either silently or out loud, "How big will my baby be?" know that you're far from atypical. I'd say it's more than common to worry about your baby's size when they're charged with exiting your body via the birth canal (or via a C-section scar, of course). At the very least, and if the whole "human being leaving your body through a small hole" thing doesn't freak you out, you might want to know what size clothes to buy for your new baby. It would be great if there was a way to know in advance how big your baby will be, to make plans and put your mind at ease. Enter: science.

According to experts, you will have to wait until your baby is born to find out your newborn's exact weight. However, there are risk factors, signs, and symptoms of carrying a big baby, according to What To Expect. There's an equation you can use to predict how big your baby will be. And, of course, there are tests your doctor can do to estimate your baby's size, according to the Mayo Clinic. But it's important to note that these tests often aren't reliable and shouldn't be the only thing you and your health care provider considers when making decisions about labor and delivery.

According to the Mayo Clinic, determining how big your baby will be is pretty important when planning your childbirth experience. The site reports that having large baby (over 8 pounds, 13 ounces) is called fetal macrosomia, and can cause health complications for both you and your baby, including your baby getting stuck in the birth canal — requiring forceps and/or a vacuum during delivery — or having a birth injury. It can also cause injuries to you during childbirth, including tearing, postpartum hemorrhage, and uterine rupture. The same site notes that having a higher than normal birth weight can cause your baby to have low blood sugar at birth (which may require medical treatment), or lead to childhood obesity and other health issues.

So, how can you know what to expect when it comes to your soon-to-be baby's size? According to What to Expect, certain conditions can put you at risk for having a big baby, including gaining a large amount of weight during your pregnancy, having gestational, Type 1, or Type 2 diabetes, having had a big baby before, or going past your baby's due date. If you are at risk for a baby with fetal macrosomia, your doctor may measure your fundal height — the distance from your pelvic bone to the top of your uterus — or order an ultrasound to measure your fetus and the amount of amniotic fluid. According to the same site, if you are at risk for fetal macrosomia, your doctor might recommend that you eat a healthy diet and exercise to help keep your weight gain stable. If you have gestational, Type 1, or Type 2 diabetes, controlling your blood sugar with medication or diet can help prevent your baby from growing too big.

It's also important to remember that even if your baby is suspected to be big, they might not be. According to the American Congress of Obstetricians and Gynecologists, determining your babies' size via an ultrasound can be difficult, is often inaccurate, and can have consequences. As one study published in the Maternal Child Health Journal reported, almost one third of American pregnant women are told that they are having large babies, resulting in birth interventions like induction of labor and C-sections, but only one fifth of those women actually had large babies, which might have made those interventions unnecessary.

So if your baby measures big, are you destined for a C-section? According to the American Congress of Obstetricans and Gynecologists, not necessarily. Their practice guidelines state that having a large baby usually isn't a reason to induce labor or perform a C-section, unless your labor stalls, there are other pregnancy complications, or your baby is estimated to be over 10 pounds. So, while you might opt to schedule a C-section, if your baby is estimated to be big, it's just fine to wait to see what happens in the delivery room, if your doctor gives you the go-ahead.

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