Yellow skin is a phone call
Yellow is not a colour you rank at home. Newborn jaundice is very common. It is rarely serious.
And the page still says a nurse, midwife or doctor should check and monitor every case. Common plus rarely serious is not the same as you deciding.
The signs are yellowish skin, yellowish whites of the eyes, drowsiness, and feeding that is hard. The colour tends to begin on the face and head. If bilirubin climbs, it moves down the body. You look in daylight if you can, not under a warm lamp that flatters everyone.
There is more than one cause, which is why guessing is useless. Feeding problems can dehydrate a baby, and fluid is part of clearing bilirubin. Delayed cord clamping, which doctors may recommend, lets more red cells in and can lead to jaundice because the liver has more to process.
Bruising from forceps or another birth intervention can do a similar thing. Those versions often need watching by you, and usually do not mean a long hospital stay. They often settle over 1 to 2 weeks.
Blood type incompatibility is rarer and more serious, and those babies need treatment. You will not sort that taxonomy in the kitchen.
Take the baby to a GP if they are unwell, feeding poorly and not gaining, if the poo is pale or the wee is dark, or if they look jaundiced. Pale poo and dark wee are also the flag for a rare problem, biliary atresia, which tends to show from 2 to 8 weeks and needs surgery. Do not file dark wee as a nappy quirk.
Measurement is a machine on the skin for a moment, or a heel prick if they need a blood level. High levels or a worry about something rarer means more tests. Treatment follows cause and how bad it is.
Phototherapy is the light treatment. Most babies handle it. A mild rash and runny poo can show up for a few days.
Some babies lose fluid and need extra feeds. You can do extra feeds. You can sit with them under the lights and not treat it as a failure of the birth.
If it is breastmilk jaundice, keep breastfeeding. That type is usually mild and improves with time. Talk to the child health nurse or GP rather than stopping feeds because a forum scared you.
Your role is eyes and logistics. You notice the colour in the morning light. You say it.
You get the appointment. You write wet nappies and feeds so the clinician is not working from adjectives. You do not announce it is just the mild one because your sister's baby was yellow and fine.
Source: Raising Children Network