Superfetation and twins are two distinct phenomena related to pregnancy. Superfetation occurs when a woman becomes pregnant again while already pregnant, resulting in two fetuses of different gestational ages in the womb. This rare occurrence happens when a woman continues to ovulate after becoming pregnant, leading to the fertilization of a second egg by sperm from a separate instance of sexual intercourse.

On the other hand, twins refer to the simultaneous development and birth of two offspring from the same pregnancy. Twins can be either monozygotic (identical), resulting from the fertilization of a single egg by a single sperm that later splits into two embryos, or dizygotic (fraternal), resulting from the fertilization of two separate eggs by two different sperm.

One example of superfetation is the case of a woman who became pregnant with twins of different gestational ages. In this instance, she ovulated after becoming pregnant with the first baby, leading to the conception of the second baby at a later point in time.

Understanding the differences between superfetation and twins is important in the field of obstetrics and reproductive health. It highlights the complexities of human reproduction and the potential for unique and rare occurrences during pregnancy.