Should a parent stay at home for below kindergarten toddler or send the toddler to a day-care/pre-school

I have a  lot of thoughts on this question and wondered at how it is a common practice to send the toddler to a day-care during the pre-school time. Having read a relevant book and found some researched and cited study on this topic, I wanted to share it with all. Here is goes....
Its from the book "Beyond Intelligence: Secrets for raising happily productive kids"

The authors of this book quote a research done by the National Institute for Child health and Human Development (NICHD). This study began in 1991 with over a 1000 infants from a variety of family backgrounds, locations through the US. Its findings showed that children who were cared for by stay-at-home mothers didn't develop differently than those who were primarily cared for by others like nannies, extended family, day care personnel. What mattered was the parental and familial characteristics they experienced, including warmth, responsiveness, and the right kinds of stimulation. Researchers did find some differences across different circumstances. Children who participated in better care settings showed higher levels of language, cognitive, and social development than those who experienced a lower-quality care. Another study by Megan Gunnar et al found that children's stress levels rise when they are in settings where they don't receive ample attention, support, guidance from the care provider. Children in the NICHD study who spent more time in non-maternal care in their first 4.5 years of life had more behavioral problems like aggression, lack of cooperation as well as minor illnesses of upper respiratory system and stomach, as compared with those with fewer hours in care. On the same lines, findings of Gunnar include that children in daycare situations have higher levels of cortisol (a stress hormone) than children being cared for at home by their parents, and this increased with the number of hours in the care.

Lastly, a child attending care-child centers do better socially and cognitively in the early years, but also have more minor illnesses upto an age of 3 and more behaviorial problems when they enter kindergarten. Gunnar's concludes that center-based care is inherently more stressful than home-based care for children younger than 3 and parents should keep tp a minimum the number of hours their infant or toddler spends in the care-based daycare.


I appreciate the importance of giving relevant citations of such an important study.

Megan Gunnar's article: "The Rise in Cortisol in Family Daycare: Associations With Aspects of Care Quality, Child Behavior, and Child Sex"
NICHD research: Backgrounder: The NICHD's 16-Year Study of Child Care & Development