Rhonda J. Pomerantz, MD is a practicing Dermatologist (Skin Specialist) in New York, NY. Dr. Pomerantz graduated from New York University School of Medicine in 1989 and has been in practice for 28 years. She completed a residency at Suny Health Science Center. Dr. Pomerantz also specializes in Internal Medicine.
Identical twins form when one egg has been fertilised by one sperm and the zygote splits into two. This happens at the very earliest stage of development, when the zygote is no more than a cluster of a few cells.
Multiple eggs are released or there is more than one ovulation. Both (or more) eggs are fertilized and this is how fraternal twins are made. This can happen with or without fertility drugs. One egg is released but splits in two. This is how identical twins are made. This can happen with or without fertility drugs.