Constipation is a common side effect of iron tablets in pregnancy. Duphalac contains lactulose, a laxative doctors commonly use for this. It works inside the gut instead of being absorbed into your body. That makes it generally safe for regular use in pregnancy, including daily.
Next Steps
The exact amount and frequency that suits you is best decided by whoever prescribed your iron and multivitamin. Meanwhile, drinking more water, adding fibre to your meals and staying gently active through the day will all help too.
Health Tips
See your obstetrician if the constipation doesn't improve. Go in sooner if you notice cramping, bleeding or pain along with it.