HCG is produced almost exclusively in the placenta. At which week of gestation HCG is maximum?

The intact hCG molecule is detectable in plasma of pregnant women 7 to 9 days after the midcycle surge of LH that precedes ovulation. Thus, it is likely that hCG enters maternal blood at the time of blastocyst implantation. Plasma levels increase rapidly, doubling every 2 days, with maximal levels being attained at 8 to 10 weeks. Peak maternal plasma levels reach about 100,000 mIU/mL. At 10 to 12 weeks, plasma levels begin to decline, and a nadir is reached by about 16 weeks. Plasma levels are maintained at this lower level for the remainder of pregnancy. Ref: Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 3. Implantation, Embryogenesis, and Placental Development. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e.