4 Weeks Pregnant

Exciting things are happening this week, Mama!
Now that baby has officially arrived inside your uterus and implanted into the uterine lining, she’ll begin transitioning from a blastocyst to an embryo. (Which is a fancy way of saying, your little one is growing up!)
Meanwhile, the amniotic sac is forming and filling with fluid. The sac will rupture roughly 36 weeks from now (when your water “breaks”), but from now until then, it will serve some important purposes: to cushion baby from bumps, to regulate her temperature, and to encourage her lung formation. Because, yes, she will swallow and “breathe” the amniotic fluid while in utero.
The “yolk sac” has started coming together now, too. Not entirely unlike the yolk of a chicken egg, the yolk sac will nourish baby until the placenta is fully formed, nearer the start of the 2nd trimester.