No, there's not necessarily anything wrong if your baby is small for dates. Babies grow at different rates and some are simply smaller than average. Measurements aren't always accurate either. Your midwife may offer you a growth scan though, to be on the safe side.
Can your pregnancy dates be wrong?
As pregnancy progresses, the accuracy of an ultrasound for predicting due dates decreases. Between 18 and 28 weeks of gestation, the margin of error increases to plus or minus two weeks. After 28 weeks, the ultrasound may be off by three weeks or more in predicting a due date.
What are the chances my due date is wrong?
In fact, only 6% of women deliver on their due date, Cackovic said. I tell patients that really, your due date is a date in the middle of almost a month-long period of time that you could have your baby. "The reality is that about 70% of women will have their baby within 10 days of their due date," he said.