Birth records are considered primary sources.

Birth records might seem like the first place to start your search, but experts recommend looking into death records first and marriage records second, and then birth records, because they are usually the most difficult to find.  Most states did not begin formally recording births until the 1900s.

Birth records usually give the child's name, sex, date and place of birth, and the names of the parents.  Newer records may have additional details, such as the name of the hospital, birthplace of parents, occupation of the parents, marital status of the mother, and the number of other children born to the mother.

A birth certificate is usually signed by the doctor or midwife who attended the birth.  Due to privacy laws, birth records are often the most difficult vital records to obtain.

There are 3 types of birth records:

Original - the record filed at birth
Amended - a birth record which has been revised from the original to reflect corrections or new information
Delayed - a certificate issued years after the birth because an original birth certificate was not filed.

Places to look for birth records and information

Family records including Family Bibles
Birth records including city and county civil registrations
Marriage records
Census records sometimes have the month and year of birth
Church records of births and christenings
Obituaries often give birth information
Death records often contain birth information
Cemetery records may give birth dates
Funeral home records
Military records
Newspapers may have lists of new births
Probate records
Immigration records
Land and Property records

To help find the government office holding the birth record you are interested in, you can perform a Google Search
enter this in search bar: "birth records" xxxxxx
Replace the "xxxxxx" with the name of the state you are researching.  i.e.   site:gov "birth records" Tennessee

Search Engine  -  All Vital Records  (may return information from subscription services)
U.S., Select Births and Christenings, 1867-1931  -  Ancestry ($)
U.S. Births in Newspapers  -  Ancestry  ($)

Texas County Birth Records -  USGenWeb Archives Project
County Websites -  TXGenWeb
Texas, Birth Certificates, 1903-1935  -  FamilySearch
Texas, Birth Index, 1903-1997  -  FamilySearch
Texas, Births and Christenings, 1840-1981  -  FamilySearch
Texas Birth Records 1927 - 2010   -  Archives  ($)
Texas Birth Index  1903-1997  -  Archives  ($)

Tennessee Department of Health  -  Government
Index to Nashville Birth Records 1881-1913     -   TSLA
Index to Davidson County Birth Records  1908-1912   -  TSLA
Tennessee County Birth Records  -  USGenWeb Archives Project
County Websites  -  TNGenWeb
Tennessee, Delayed Birth Records, 1869-1909  -  Ancestry  ($)
Tennessee, City Birth Records, 1881-1915  -  Ancestry ($)
Tennessee, Births and Christenings, 1828-1939   -  FamilySearch

Type of Information That May Be Found on in Birth Records

An address that would lead to the discovery of the family in a census or city directory
Ages of parents
Child’s birth order
Child's gender
Date of birth
Family’s home address
Full name of child
Maiden name for the mother
Names of both parents
Names of the previous generation
Newspaper birth announcement
Occupation of parents
Parents' approximate years of birth
Parents' birthplaces
Race of child
Religious affiliation
Place of birth
Hospital or name a medical attendant
Which children belong to which mother in the case of multiple marriages
Hidden Ancestors
Birth Records