In the early stages of pregnancy, the placenta grew at a far greater rate than your baby. Your baby has now caught up and from now on will be larger than the placenta.
The structure of the placenta will change over the course of the next few weeks as the second wave of cells move into the spiral arteries in the uterus (see You are 14 Weeks and 4 Days). The placenta is currently at its thickest but as it continues to grow, albeit at a slower rate for a time, it thins out.
Your baby's more rapid growth means that at 2.5 oz (70 g) she is now heavier than the placenta and by the time she is full term she will be six or seven times its weight. Nutrients supplied across the placenta provide your baby with energy for growth, but growth is in part regulated by her own insulin production and insulin-like growth factors.
Although your baby has relatively high concentrations of growth hormone, which is responsible for growth after birth, this does not seem to play an important role in her growth during pregnancy.