Baby at 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.
You at 4 Weeks Pregnant 🚺
Your body has (finally!) started producing hCG, but it’s still a wee bit early to detect baby via a home pregnancy test. About 1/3 of women, however, will experience a bit of bleeding or spotting this week. (During implantation, baby may disrupt a few blood vessels in the endometrium, causing some of your uterine lining to shed.)
Though implantation bleeding is typically very light—potentially as light as a drop or two—many women may mistake the sight of blood for their regular menstrual period.
How to tell the difference? Implantation bleeding will start light and remain light, whereas a menstrual flow typically gets heavier over the first day or two of your period. The blood may also appear darker and/or more brownish in color during implantation, and light cramping is fairly common, too.