Clarkson has spoken about the challenges during her second pregnancy ... an Instagram post last week that by 16 weeks she weighed less than before she was pregnant, had been taken to hospital ...

What Is the First Trimester of Pregnancy? The first trimester is the earliest phase of pregnancy. It starts on the first day of your last period -- before you’re even actually pregnant -- and ...

Low first trimester vitamin D concentrations are associated with risk for preterm birth; higher levels correlate with fetal growth.