Baby measuring small for dates – what it really means

What does it mean if your baby is measuring small for your dates? Here’s what you need to know if a midwife or doctor says your baby’s looking small after your fundal height's been measured/you've had a growth scan…

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In a nutshell

Your baby measuring small for your dates means that your baby’s size is a little smaller than what’s considered average for the stage of your pregnancy. 

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However, you should try your best not to worry. These measurements don’t necessarily mean your baby will have a low birth weight, or that there’s anything wrong with your baby’s health. 

Easier said than done, we know! Hopefully, this article will help ease some of the worries you have…

How is my unborn baby’s size measured?

Your baby’s size is checked by your midwife measuring your bump (called ‘fundal height’) during a check-up. 

If they think you’re measuring small for your dates, you’ll likely be asked to go for what’s known as a wellbeing or growth scan.

What do the experts say about babies measuring small?

If you’re due to have a scan because your baby’s measured small, rest assured: the large majority of scans will be absolutely fine!

Professor Basky Thilganathan, a Consultant Obstetrician and spokesperson for the Royal College of Obstetricians and Gynaecologists (RCOG) also wants to make it clear that most small babies are totally healthy, and that size is simply used to help medical pros keep an eye on the baby’s wellbeing.

“Most women who have a small baby or a large baby are having a healthy small baby or large baby,” he tells MFM. “Part of the assessment of the scan is to look at the wellbeing of the baby irrespective of the size.

“It usually involves something called the dopplar assessment, so that’s a blood flow assessment, looking at the amniotic fluid around the baby, etc. Again, this is about the wellbeing of the baby irrespective of the size.

“The reason that is important [to note] is that most small babies are perfectly healthy. Most unhealthy babies are not usually small, either.

“Even though there is an association between being small and having problems, that association is quite weak. It is used as a signal for us to decide who needs special tests.”

“Often the scans are fine,” stresses MFM’s resident GP, Dr Philippa Kaye, too. “Essentially, if the baby is smaller than expected, they then check the blood flow in the placenta.”

Only in rare cases will there be something not quite right with the placenta. In that case, you’d monitored with more scans – and go from there. 

MFM mums share stories about their babies measuring small

Unsurprisingly, this is a BIG talking point on our forum. Loads of our MFMers have been told they’re measuring small for a variety of reasons – one of which is the fact they had small or petite bumps.

Reassuringly, most of them found that their baby’s actual weights were higher than the estimates from scans.

“I was told I was measuring small at 38 weeks,” says forumlady. “I was scanned at 38+4 and was told the baby had stopped growing and would be 5lb 10oz.

“I was to be induced at 38+5 so went home and rushed to the shops to buy newborn sizes… he was 6lb 12.5oz when born at 39 and he’s certainly not small now. 5 months and almost 17lb!”

“Please don’t worry (I know it’s hard),” advises wannanother. “I went through this exact thing with my daughter (1st child) who is 3yrs now.

‘Everyone thought I was only about 6/7 months when I was just about due, I had a small bump and anytime I saw a new consultant or midwife I was rushed for a scan because I was small for dates.

“They thought maybe my placenta wasn’t feeding the baby properly and were going to give me a C-section. But the scans always showed that everything was fine, there was enough fluid around the baby etc, and I was left to have the baby normally.

“Then she was overdue, so the day before I was due to be induced I was sent for yet another scan and they said the baby was just about 5lb so it would be ok to go ahead with inducing me the next day… the next day she was born at 7lb 2oz!!!

“So I don’t think she put on all that weight overnight! Anyway, everyone’s story is different, but I just wanted to reassure you you that just because you are small, it does not mean that your baby is too small or unhealthy or anything like that.

“It is hard – I remember crying my eyes out over it at the time – but my wee girl is a happy healthy wee thing with no problems.”

“I had exactly the same thing throughout my pregnancy, I was small and no one noticed I was pregnat until I left work at 36 weeks and still people didn’t know!!!” KirstyMacey adds.

“I started to measure small at about 36 weeks but baby’s head was engaged and far down so midwife said there was no need to worry about the 2-week [size] difference.

“I had my baby girl on 6 August and she weighed 6lb 14oz and she is now 8 weeks and 10lb 7oz so I would not worry about it. If midwife was concerned, she would let you know.”

What MadeForMums says

We know it’s so hard, but try not to worry too much if your baby is measuring small. Remember, most women will go on to have healthy babies. 

As many mums have found, growth scans/fundal height readings aren’t always 100% accurate. Keep that in mind, too!

And as always, if you’re really panicking, talk to your doc or your midwife and ask them to re-explain your scan to you, just for reassurance ?

Images: Stock image via Getty Images

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