Big or small for dates
During the course of your pregnancy you may well be told by your OB-GYN or nurse-midwife that you’re ‘big’ or ‘small’ for dates. So what does this mean, and should you be worried?
As your pregnancy progresses, your caregiver will assess your baby’s growth by measuring the distance from your pubic bone to the top of your uterus – it’s known as ‘fundal height’. It’s measured in centimeters and should roughly equate with how many weeks pregnant you are – so, if you’re 23 weeks pregnant your fundal height might be 21-25cm.
A more accurate assessment can be done by ultrasound scan, and you may be given one of these if you appear to be significantly over or under where you should be in terms of size.
Why might I be small for dates?
Small for dates is defined as being more than 2cm below the average fundal height for your stage of pregnancy. There are many reasons why you might measure as small: it may simply be because you’re not as far along as you thought. Other reasons can include strong abs or being small yourself – in which case your baby might just be naturally small too.
But measuring small could also indicate a more serious problem, such as too little amniotic fluid or intrauterine growth restriction because your baby isn’t getting the oxygen and nutrients he needs to grow. This could be due to a deficient or low-lying placenta (placenta previa), high blood pressure, pre-eclampsia, a poor diet or even certain medications. Chromosomal abnormalities such as Down syndrome can also affect your baby’s size.
If your OB-GYN or nurse-midwife is concerned, you’ll be referred for further tests to determine the cause.
Why might I be big for dates?
Big for dates is when your fundal height is more than 2 centimeters over the average for your stage of pregnancy. Again, this could be due to a number of factors. Many women on their second and subsequent pregnancies appear large for dates because their abdominal muscles are often looser than those of first timers. It may also be because you’re carrying a lot of amniotic fluid or because your baby is simply sitting high above your pelvis. A high position can sometimes indicate problem such as a breech presentation, and your midwife will want to investigate this further.
Other causes could be a multiple pregnancy, or a condition known as gestational diabetes, which can be diagnosed with a simple test. And again, it may simply be that your due date has been wrongly calculated, and you’re more pregnant than you think. Of course, you may just also be carrying a very big and healthy baby!
Have you tried out our due date calculator to check when you’re baby might be born? Simply type in the first day of your last period and how long your cycle usually lasts and our calculator will give you an estimated due date.
The information in this feature is intended for educational purposes only. If you have any concerns about your health, the health of your child or the health of someone you know, please consult with a doctor or other healthcare professional.
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Last Modified: 06/06/2008
Related Chat 9
i was told my baby was big for his dates from 24 weeks and as my first baby was 9lb 2oz it was suggested that i was induced at 38 weeks , i ended up having an emergency c-section and a baby boy who weighed in at 10lb 12oz !!!! no wonder he did not want to come out naturally .
my first was 10lbs 60z so im dreading the weight of this next one due in 7 wks time
Hi I had such a tiny bump with my first all the experts said i would be lucky if he made 4lbs etc..well he turned up a healthy 8lbs 2ozs....the opposite happened with my second child i was ginormouse experts said oohh yr baby will be at least 10lbs ( yep i did cry lol) but she came out 7lb 9 ozs..my third who was early popped out weighing 4lb 5ozs so no idea what this one is gonna be although they have said ( smirk) that she is very long...so might be having a giraffe lmao...
I was told around the 32nd week that everything was looking a bit too small so I was closely monitored, had appointments at my gyno every week. In the 36th week I was sent to another gyno for a second opinion and he, too, said I was small-for-date but that everything was developed well. The following week my gyno said "see you next week or later" and she was right: 37 weeks into the pregnancy my waters broke and we rushed to hospital. 5 hours later my little boy arrived weighing 1900g (just under 4lbs). He was rushed to special care almost straight after arrival where he spent two weeks. He's now grown his way up to an average weight and size for his age and we're happy to see that even small-for-date babies can catch up and there's no need to worry. It's a bit weird at first watching him wired up in intensive care but you get used to it fast. The nurses there are trained to help you cope and give you all the advice you need.
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