catellington You have done the right thing with regard to drops for baby, particularly in Winter.
You could stop the drops IF you are sure that baby is getting the required amount of Vit D from milk. The baby needs about 300 - 400 IU per day , (from all sources diet, supplement, sun etc. ,) increasing as weight goes up.
In an ideal world, breast milk, should contain at least 400 IU Vit D per litre, . Unfortunately this is unlikely in the UK , unless you are taking supplements , ( a lot more than the 400 IU found in pregnacare would be necessary). You may be regularly sunbathing and receiving UVB, but in Britain , that is pretty unreliable. That is why the gov recommend drops. It is a disgrace that most babies don't receive that supplementation. It would cost only a pound or two for each baby. The government's "Healthy Start Programme " of vitamin uptake is pitiful.
I highly recommend you watch the Hollis video above. He is a highly respected medical Professor. The level in your milk will go up IF you yourself get enough Vit D , but 400 IU is not enough for you.
Sunlight , without sunscreen, will work, for you, and will make a great deal of difference.
If you are breastfeeding only, and you are taking daily supplements , in the range of thousands of units, (3000 -6000 say ) then you can expect your baby to reach a good blood level, without baby drops.
Now: a blood level achieved by baby, by the gov recommended supplementation of approx 300 IU , to baby, will be in the order of 80 - 100 nmol/litre. This is perfectly good and proper.
You should aim to maintain this. It is somewhat of a mystery that officialdom does not maintain that recommendation of blood level throughout life , at least right through infancy and junior years. BUT, to maintain that blood level your child needs to get more Vit D from all sources. ( diet, sun, supplement) as she grows and increases in weight.
It would not be unreasonable to check vit d levels in March , every year, to make sure good levels are achieved.
A human being requires approx 65 -75 IU per day per kilogram of weight,( from all sources- sun,supplement,food, sunbed etc . ) for optimum vitamin D levels , to promote optimum health , at least from the vitamin D point of view.
UK recommendations for Vit D supplementation of babies under 6 months is out of line with other countries. We say " start after 6 months " , whereas others start at birth. For instance , the USA says supplement by 400 IU within a few days of birth. The gap that we have in this country is not a good thing . IF the mother is breastfeeding only , and she is not taking sufficient supplements, then the child's blood level will not be optimum in most cases, unless mum takes the baby out in the summer sunshine, for a few minutes. DO NOT BURN. NO SUNSCREEN . Winter babies may be at risk, as the sunlight is not strong enough to generate Vit D. Formula milk does contain vit D , but breast milk in UK is often low in Vit D ( possibly just 25 IU per litre in winter) , but breast is best in most other respects.
Circumstances are different for almost every baby , every mother, every ethnicity , every latitude that you live. A Glasgow mother won't get much sunshine , a family living in Southern Spain will. The important thing , is how much vit D is the baby getting.
I'm afraid that there is so much information now available, recent research etc , it is difficult to convey it in a few lines of text in a chatroom. However I hope this helps.
BTBHealthy.