My husband and I decided to have a baby in the 2nd/3rd year of my PhD. As I am studying on a Tier 4 Visa, I was entitled to up to 60 days off. I have had a great level of support from the faculty and my advisor, so there was no trouble in pausing my studies. Additionally, the school was generous in providing a stipend for me for the two months I took off, which extended my total funding to 3 years and 8 months. I share an office with several other students, so on my return I was given access to a small room and fridge to express and store milk.
The biggest difficulty in having a child here while on a visa was the cost of childcare after returning to work. The prices at the University childcare center and other centers in St Andrews are extremely high, and because of our status we are ineligible for childcare vouchers to help pay for the costs. Fortunately my husband is in full-time employment, but even so we had to find a childcare service out of town and only are able to have 4 days a week. Because I am a student I am able to easily take that time to spend at home, but it does require me to put in extra time at nights and weekends to stay on schedule for graduation (the visa end-date is non-negotiable, so an extension would much difficult to orchestrate).