Concerned about size of baby's head at 31 weeks pregnant

Patient

Q: Hello,

I am 31 weeks (+1 day) pregnant. It has been a complicated pregnancy - initially I had twins but we sadly had to stop the heart of one twin at 23 weeks due to severe ventriculomegaly and other abnormalities. The remaining twin has appeared perfectly normal throughout and has been shown to be growing well.

However, today I went for a reassurance scan and was told that baby's head is measuring slightly smaller and is on a lower percentile than previously. Her head (BPD and HC measurements) is now around the 25th percentile whereas before it was around the 50th (five weeks ago at the last scan). The doctor did not seem worried by this as it is still within the normal range and she is in a breech position which he said can 'squash' the head.

However, I am extremely worried and anxious and did not feel reassured by him. I am worried that the growth of the head has slowed down and that could indicate some developmental problem. Perhaps I am over-worrying because of my history with the other twin, but I would greatly appreciate a second opinion/more information.

Could the breech presentation give inaccurate measurements (the head could actually be bigger than it looked on the scan)? If not, I don't understand why it's not more concerning that her head isn't growing at the same speed as before!?

I would be extremely grateful for your help.

Symptoms:  Baby's head measuring on a lower percentile than previously
Doctor

A:   Hi,
Thanks for the query.
I understand your concern.
Usually the fetus is considered as normal if the measuring parameters are within 10th to 90th percentile.
The points to be considered in your case are:
-As the baby is in breech position, sometimes accurate measurement of the BPD and HC can become difficult.
-If other parameters like AC and FL are also corresponding the head parameters, there is possibility of generalized growth retardation compared with previous scan.
-If only head parameters are at lower level, developmental anomalies should be ruled out.
-Sometimes demise of one fetus in twins can affect the other one.
So, please try to rule out factors which can lead to fetal growth retardation like pregnancy induced hypertension, less liquor, placental insufficiency etc with your doctor's help.
If all these factors all normal, as now the fetal parameters are within normal percentile, you can continue the pregnancy with regular antenatal checkups and ultrasound examinations to monitor the growth and well being of the baby.
Continuing the medicines prescribed by your doctor, adequate healthy diet and rest are important to maintain the normal growth of the baby.
Take care.

Comments / Follow Ups

Patient: Thanks for your response. The AC and FL are measuring along the same centiles as at previous scans. It is just the HC and BPD measurements which have dropped from about the 50th percentile to the 25th (it doesn't say exactly on my report, it is just plotted on a graph so I am estimating).
My blood pressure is normal and so is the volume of amniotic fluid.
I am concerned now about placental insufficiency causing the head to have slowed down in growth? Is there a way to know whether this is the case? Also, I am still confused about whether the breech/squashed position is making the head look small (when it actually isn't) - is this possible? I would have thought that the head circumference would not be affected by whether or not the head is squashed??
The doctor I saw today did not request a repeat scan as he was so convinced everything was fine. But do you feel I should insist on this? I don't know what my next step should be and I am getting very distressed. Thank you.
Doctor: Hi,
Sometimes because of breech presentation, taking accurate head measurements may become difficult as I told previously.
As other parameters are normal, as the exact percentile of the head parameters are not mentioned in report and as your doctor is not much concerned, there may not be major problem.
But better to be careful and next time means after two to three weeks please go for ultrasound along with doppler to rule out uteroplacental insufficiency.
If everything thing is normal, there may not be any problem with continuation the pregnancy.
Take care.

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