**Abstract**

Assisted reproductive technology (ART) has been widely used for infertility treatment, but many people have concern about their baby's health. The objective of this chapter is to provide some detailed data about the effect of ART on human birth babies by analyzing the data from in vitro fertilization (IVF) centers in two countries. All recent records related to a baby's birth including mother's age, gestational days, baby's sex, and birth weight data were collected and analyzed according to fresh or frozen embryo transfer procedure. Normal delivery data without ART were used as control. The result showed that ART patient age is significantly older than non-IVF women; the gestation of fresh and frozen embryo transfer is the same as normal spontaneous conception gestation days, but women pregnant with multiple gestations have shorter gestational period and early birth rate as well as low birth weight; and there is no significant difference in the baby's weight between ART singleton babies and normal conception babies, but male babies weight is more than female babies, and multiple gestation's birth weights are significantly lower than singletons, while frozen embryo transfer babies have significantly heavier birth weight than fresh embryo transfer. Also, the frozen embryo transfer technique may significantly decrease premature birth rate. Thus, frozen embryo transfer may be recommended as a health strategy in ART.

**Keywords:** in vitro fertilization, frozen embryo transfer, baby birth, outcome
