In plain words
Human chorionic gonadotropin, or hCG, is a hormone made by the placenta soon after an embryo implants. Home pregnancy tests detect it in urine. In early pregnancy, the level often doubles every two to three days, though the pace varies widely between people. It peaks around the end of the first trimester and then falls. hCG keeps the corpus luteum active, which keeps progesterone high until the placenta takes over. Because hCG rises at the same time as nausea, it is often named as a possible cause of , but that link is not proven. hCG is not a measure of how the pregnancy is going on its own. Clinicians use serial levels, together with ultrasound, when they check on an early pregnancy or a pregnancy loss.
The deeper version
hCG is a heterodimeric glycoprotein of alpha and beta subunits. The beta subunit confers specificity and is the target of most immunoassays. It is produced by syncytiotrophoblast, peaks around 8 to 11 weeks of gestation, and declines thereafter. It acts on LH/hCG receptors on the corpus luteum to sustain progesterone production until the luteal-placental shift near 8 to 10 weeks. Its proposed role in hyperemesis rests on peak timing and on the association between very high levels and severe symptoms, as in twin and molar pregnancies (ACOG Practice Bulletin 189, 2018). Causality is unestablished. has been proposed as a stronger candidate for severe nausea (Fejzo and colleagues, Nature Communications, 2018). Serial hCG is used clinically to assess early pregnancy viability.
Where it comes up
- Nausea and vomiting in pregnancyPregnancy: Your Body
- Cravings and food aversionsPregnancy: Eating
- Eating when nothing sounds goodPregnancy: Eating
- Your body and heart after a miscarriageLoss and Complications
What mothers here say about human chorionic gonadotropin
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Sources
- American College of Obstetricians and Gynecologists — Practice Bulletin 189: Nausea and Vomiting of Pregnancy, 2018
- Fejzo MS et al. — Placenta and appetite genes GDF15 and IGFBP7 are associated with hyperemesis gravidarum. Nature Communications, 2019