American College of Obstetricians and Gynecologists: 
http://www.acog.org/

Anesthesiology: 
http://www.cumc.columbia.edu/dept/anesthesiology/clinical-divisions/obstetric.html

Centers for Disease Control and Prevention, Reproductive Health: 
http://www.cdc.gov/reproductivehealth/

La Leche League: 
http://www.lalecheleague.org/

March of Dimes: 
http://www.marchofdimes.com/

Maternity Center Association: 
http://www.maternitywise.org/home.html

The National Parenting Center: 
http://www.tnpc.com

Neonatology/NICU: 
http://nicu-at-babies.org/

Pediatrics: 
http://cpmcnet.columbia.edu/dept/pediatrics/index.shtml 

Ultrasound: 
http://www.columbiaobgyn.org/patient-care-services/ultrasound.html

The What to Expect Foundation: 
http://www.whattoexpect.org/