Does size really matter Gestational size of baby


You find out that you are expecting and you see your life and body go through amazing changes. You start looking for ‘the Day’ when you would finally get to hold your baby in your arms. Being pregnant is definitely an exciting experience, but along with it comes this inherent fear/worry about the well-being/growth of your growing fetus, your baby.

In general, after 20 weeks, your fundal height (the distance from your pubic bone to the top of your uterus) should pretty much equal the number of weeks you’ve been pregnant. As a rule of thumb, your fundal height in centimeters should roughly equal the number of weeks you’re pregnant. For example, at 20 weeks, your fundal height should be about 17 to 23 centimeters. So, if you start measuring more than two centimeters off in either direction, your OB will probably schedule you for an ultrasound to check things out.

Possible reasons for measuring large:

  • You simply have a big, healthy baby
  • Your due date was wrong
  • You have uterine fibroids.
  • You’re carrying twins or more
  • You have too much amniotic fluid
  • You have looser abdominal muscles than most women, perhaps as a result of earlier pregnancies.
  • You’re obese, which can make it more difficult to get an accurate measurement.
  • Your baby is in a breech or other unusual position.
  • You have a narrow pelvis.
  • Your baby is much bigger than normal, a condition known as macrosomia. Risk factors for macrosomia include having type 1 or type 2 diabetes before pregnancy and gestational diabetes.

Possible reasons for measuring small:

  • You have a small baby
  • Your due date was wrong
  • There could be an intrauterine growth restriction which is when baby is below the tenth percentile for its age; it could be due to many reasons: placenta problems, heart disease in the mother, even high altitudes
  • You have too little amniotic fluid


If a mom-to-be has not been eating well, poor nutrition can affect your baby’s growth. Also excessive exercise or dieting can affect the baby’s nutrition causing the baby to be small for how far along the pregnancy is. The age of the mother could have some bearing on the growth of the fetus, especially in cases where the mother is under 18 or over 35, then they’re most likely to have a small baby. Statistics show that women who previously had a small baby have a higher chance of conceiving another small baby.

Steps to Be Taken with a Smaller Than Average Baby

The obstetrician/gynecologist or midwife can conduct an investigation to make sure all is well with the fetus and that the baby is growing well. For that, an ultrasound can be conducted to find out the accurate due date and to identify any possible causes for the measurements.

A rescan can be scheduled in a couple of weeks to oversee the cause and monitor the baby’s growth during that time if the first ultrasound scan measured the baby as small. It’s also done to rule out problems like less amniotic fluid and/or intrauterine growth restriction.

A ‘Doppler Ultrasound’ may also be suggested to measure the heartbeats of the baby and to see if the blood flow through the placenta and the umbilical cord is working fine. Frequent monitoring would thus be required to assess the well-being of your baby.

It’s common to see women measuring large as they’re nearing their delivery or are at the end of their pregnancy, as even a slight difference in size becomes more prominent and well-defined. No matter what stage of pregnancy, further investigations/scans can confirm due dates and check for twins or the presence of uterine fibroids.

As long as your baby is measuring consistently a week or two ahead or behind, it’s neither a matter of concern, nor does it imply that your due date is going to be affected. In all probability, the baby seems to be growing and developing just as any other baby would be and the disparity can sometimes be pinned down only when compared to any other average pregnancy.

Why You Shouldn’t Worry About the Size

Mostly, women who are at the same stage of pregnancy may sport bumps in a range of shapes and sizes. More often, the size of the bump, either large or small, is related to the body type of the mom-to-be. In fact, it does run in the genes depending on how tall or short either of you are parents. Race and ethnicity also does play its role.

Previous pregnancies causes the abdominal and uterine muscles to become more relaxed and less tight, this may cause the bump to show earlier, maybe comparatively bigger, earlier on in the pregnancy. Maternity clothes could make all the difference in appearance and that of the bump. Certain clothes may make the bump look bigger than others.

When Should You Worry About Your Baby’s Measurements?

If your baby is measuring 1 week, then 2 weeks, then 3 weeks behind, it shows that your baby may have a problem and you need to worry when:

  • Your obstetrician/gynecologist specifically says that he is worried.
  • Your baby is measuring further and further behind each time you go for your antenatal check-up, then this could mean that your baby has stopped growing. It means your baby has been diagnosed with Intrauterine Growth Restriction(IUGR) — specifically, if an ultrasound indicates that their weight is below the 10th percentile for their gestational age.
  • Other reasons when your obstetrician/gynecologist may consider for a further rescan include oligohydramnios (too little amniotic fluid), polyhydramnios (too much amniotic fluid) or when your doctor doubts your baby to be in a position such as breech or transverse.

Will having a Large or Small Baby affect the Birth?

Giving birth vaginally to a large baby–though quite difficult–can be possible. An assisted birth will be needed for the birth of a large baby. Almost two thirds of large babies (4.5 kg or more) are born vaginally. Complications like an increased risk of heavy blood loss after the birth and severe perineal tearing are most likely to happen. Rarely, a serious situation can occur if the baby weighs over 5 kg. There’s a one in 13 to one in 7 chance of large babies experiencing ‘shoulder dystocia’ during birth. Shoulder dystocia happens when the shoulder of the baby gets stuck while pushing his head out.

The doctor has it all looked after

There is a possibility that the doctor will recommended to induce early or schedule a caesarean if the baby is large and diabetic too. Labour and birth can be traumatic for smaller babies. Doctors may advise to go for a more managed delivery, such as a caesarean or forceps. Some small babies may require a ‘special care baby unit’ so that they can grow healthily and thrive better.

Whether the baby is small or large, chances are much higher that the scheduled due date is maintained, without medically inducing. And whatever the weight of the baby, getting to finally hold the baby will definitely be amazing and thrilling, no matter what!

So here’s to an easy delivery and a healthy and thriving baby!

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