Week 4: Implantation

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This is your Pea in the Podcast for week four of your pregnancy. I'm Bonnie Petrie joined by Dr. Laurie Swaim, an obstetrician with Houston Women's Care Associates in Houston, Texas.

Week four is a big week for you and your baby. Your baby finds a comfortable home, it implants in your uterus and even though you haven't missed a period at the beginning of this week, Dr. Swaim says at some point you may get a positive home pregnancy test. "If it implants, let's say day ten, the HCG goes up about 66 percent over 48 hours, we call it doubling but it doesn't really have to double but most often it does, so it goes up relatively rapidly. So it's possible to have a positive pregnancy test before you miss a period."

Now some of you will still get what some call a false negative pregnancy test. All that really means is you've either tested too soon or your test isn't sensitive enough at this particular point in your pregnancy. Now if you really think you might be pregnant test again in a couple of days. A so-called false positive is more rare and usually indicates what is called a chemical pregnancy, "A chemical pregnancy is when there's a very low level of HCG such that fertilization, implantation has occurred but the pregnancy fails very early. Those are women who miss a period for three or four days, have a positive home urine pregnancy test, because those are very sensitive they'll detect HCG at a level as low as something like 25 million international units which is very low and then they start to bleed and there was never sort of a fetus that formed or what have you. Those are thought maybe to be due to what we call poor ovulation."

In fact, the sad fact of it is that many of these early pregnancies do not stick, "The miscarriage rate is very high, it's thought to be about 30% and that can differ given people's history and age, etc., etc. Unfortunately all pregnancies don't stick and if you think about it, it takes quite a bit to make a human being, there's a lot going on there. And the most common cause is that the chromosomes don't line up correctly and that's one thing that's really important: I say to people that when a miscarriage occurs it's never their fault." So if you do miscarry, you're not alone, be kind to yourself and Dr. Swaim says depending on your circumstances if you feel ready you do not have to wait to try again.

Now if 30% of these pregnancies don't stick, that means 70% of them will and in week four your baby is made up of about 500 cells and is now known as a blastocyst. The amniotic cavity is forming and the placenta, that organ that will nourish your little bean through the next 36 weeks, is starting to form. The beginnings of the connecting stock, for lack of a better term, it will become the umbilical cord has now appeared. Now your baby is developing with lightning speed and your body is working very hard to support it, "The ovaries are still in charge of the true hormone production, or a lot of the hormone production, until about six or eight weeks the ovary sort of conks out a little bit with the progesterone production because then the placental unit is able to take over and the HCG is still produced through out pregnancy by the placental unit. Then as the pregnancy progresses there's just a ton more estrogen too."

So your body is busy and there are some very subtle physical changes after implantation, "The uterus itself feels softer; the cervix actually changes color, at first it looks a little blue because there is increased blood flow to the uterus when a pregnancy is implanted. At term the blood flow to a uterus is something like 600 CCs a minute, it's very, very high. And there are probably some chemical changes in the muscle itself." Aside the obvious premenstrual symptoms, don't stress out if you still don't really feel pregnant, that is totally normal. "I don't think you would feel that different truly over the first four weeks, five weeks, around five or six weeks some women are nauseous, some women are very sick. And that's when sort of some of those other symptoms start to kick in, maybe constipation, maybe urinating frequently, a lot of women don't feel like having sex which sort of tends to get better, I don't know why that is." And some women report a metallic taste in their mouth during early pregnancy which may be associated with changing hormone level, experts don't really know. If you're carrying twins, some women report even the smallest symptoms are likely to be intensified.

But of course by the end of week four that big pregnancy symptom will occur or I should say won't occur, "Yeah you miss a period. You probably want to know when the last one was because it helps to date the pregnancy although now they're really all just known as imperative." So it's time to call your healthcare provider and make an appointment. Good prenatal care is essential to a healthy pregnancy and baby and the weeks of the first trimester are some of the most important for your baby's physical development. So get on the phone, you're four weeks pregnant. There are only 36 weeks to go until week 40.

That's your Pea in the Podcast for week four of your pregnancy. Dr. Swaim and I look forward to talking to you again next week. Enjoy this week and we'll talk to you then. I'm Bonnie Petrie, thanks for listening.