My daughter is near her due date with her 1st baby. The hospital staff did a CTG and ultrasound and said the baby was in the 40th percentile. I am worried that there is something wrong with my grandson.
Our midwife Melissa says:
It is normal for women to remain pregnant for 37-42 weeks, and a baby born between 37 and 42 weeks is considered “term”, but we give women an estimated due date which is at the 40-week mark. That is not to say that this is the date that the baby will be born, and only about 2% babies arrive on their estimated due date. The majority of babies, however, arrive at a time around their due date, being 37-42 weeks. Therefore, we don’t consider a baby to be early unless he is born before 37 weeks, or late unless he is born after 42 weeks.
Some midwives and obstetricians will perform some monitoring of babies who are at or beyond 41 weeks of pregnancy, to ensure that all is well. There are two forms of monitoring that can be used, one being a CTG and the other being an ultrasound.
A CTG is a fetal monitor, and it can be used on women during pregnancy or labour. It involves two belts being placed around the woman’s belly. One measures and records the baby’s heartbeat, while the other records when contractions are occurring. This allows the heart beat to be recorded against the contractions, so that we can see how the baby is responding to contractions. This form of monitoring can tell us if the baby is healthy.
An ultrasound looks at the AFI, growth of the baby and flow of blood through the placenta. The AFI is the amniotic fluid index, or basically the amount of fluid around the baby. Amniotic fluid is formed by the baby’s urine after 12 weeks of pregnancy. We know that in a baby who is not getting enough blood through the placenta, the doppler flows will be affected and the baby will tend to put out less urine, and hence the AFI can fall. The other thing that can happen if the blood flow through the placenta is not optimal, is that the baby’s growth can slow down. The baby may still be growing, just not at the rate at which s/he was previously growing.
Normal growth percentiles are between 5% and 95%, so if your daughter’s baby is on the 40th percentile, that sounds perfectly normal, however your daughter should have discussions with the midwives and doctors who are looking after her, as they will be best –placed to provide advice.
This answer was written for Birth by midwife Melissa Maimann from Essential Birth Consulting.
Last revised: Thursday, 3 January 2013
This article contains general information only and is not intended to replace advice from a qualified health professional.