During pregnancy, which form of estrogen predominates and may be useful in prenatal screening?

During pregnancy, which form of estrogen predominates and may be useful in prenatal screening?

• A. Estriol
• B. Estradiol
• C. Estrone
• D. Progesterone

Answer: (A)

In pregnancy the placenta becomes the main source of estrogen, producing estriol from fetal precursors. This causes estriol to be the predominant estrogen circulating in the mother as gestation progresses. Because of this placental origin, measuring estriol—specifically the unconjugated form, uE3—in prenatal screening is informative about fetal well-being and placental function, which is why estriol is used in screening tests. The other estrogens aren’t produced in the same dominant way during pregnancy: estradiol is the main estrogen in nonpregnant individuals, estrone is more prominent in certain conditions like postmenopause, and progesterone is a different class of hormone entirely.

In pregnancy the placenta becomes the main source of estrogen, producing estriol from fetal precursors. This causes estriol to be the predominant estrogen circulating in the mother as gestation progresses. Because of this placental origin, measuring estriol—specifically the unconjugated form, uE3—in prenatal screening is informative about fetal well-being and placental function, which is why estriol is used in screening tests. The other estrogens aren’t produced in the same dominant way during pregnancy: estradiol is the main estrogen in nonpregnant individuals, estrone is more prominent in certain conditions like postmenopause, and progesterone is a different class of hormone entirely.