Blood Type, Rh Factor and Pregnancy

Do you know your blood type? When you're pregnant, the Rh factor in your blood type is important because it could conflict with the baby's blood type. What determines a baby's blood type and Rh factor? At what point during your pregnancy can their blood type be determined? And how will your pregnancy change if your baby's blood is incompatible with your own?

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Episode Transcript

Preggie Pals
Blood Type, Rh Factor and Pregnancy

Please be advised, this transcription was performed from a company independent of New Mommy Media, LLC. As such, translation was required which may alter the accuracy of the transcription.


[Theme Music]

Damon Cobb : Every person has a blood type and Rh factor. When you're pregnant, your Rh factor may play a role in your baby's health. So it's important to know this information early in your pregnancy. I'm Dr. Damon Cobb, an OB/GYN with Poway Women's Care, and today we'll be discussing how blood types are determined and what happens if your blood types differs from your unborn child. This is Preggie Pals, episode 48.

[Theme Music/Intro]

Sunny Gault : Welcome to Preggie Pals, broadcasting from the Birth Education Center of San Diego. I'm your host, Sunny Gault. Have you downloaded our amazing Preggie Pals app? This is a great way to listen to our shows on the go, whether you're waiting on line at the grocery store or your next OB appointment. Did you miss an older episode of Preggie Pals? Then join our Preggie Pals Club, you'll get access to all of our archived episodes, transcripts and special bonus content after each show. Our club members even get a one year free subscription to Pregnancy Magazine. You can visit our website for more information and to sign up. And for all of our listeners local to San Diego, don't forget about the Your Natural Baby Fair coming up next month, April 27th. You can purchase your tickets online at, use promo code mommedia for 50% off. If you don't live in San Diego, we'll be broadcasting live from the event. You can visit the fair website for our scheduled interviews which includes Pennie Simkin, Doctor Bob Sears and more. OK, so we are joined by one of the panelists here in the studio, Amy, would like to introduce yourself?

Amy Askin : Hello! I am Amy Askin and I'm 39, I am the creator and writer for the Beloved Atmosphere blog, check it out. And I have three children, three girls in fact, and they were all born naturally. Olivia is 8, Serene is 3 and our newborn, Elysiana is one month today.

Sunny Gault : OK, and so the topic today is about blood types, Rh factor and you are Rh negative, correct?

Amy Askin : I am, all negative blood type.

Sunny Gault : All negative, OK, so we'll dive into what exactly that means in just a little bit.

[Theme Music] [Featured Segment: Designer Looks for Less!]


Sunny Gault : Before we begin today's show, here's some tips on how to keep your baby nursery on the budget, from Cynthia Kaiden,

Cynthia Kaiden : Hello Preggie Pals, I am Cynthia Kaiden, founder of Trick My Crib Nursery and Kids Room Design, where I help your nursery dreams come true. I'm excited to talk to you today about saving money in the baby's room by getting designers look for less. When you enter the world of nursery décor, you soon find that just because it's for a little baby, doesn't mean it has little price tag. Ideally, we all want our baby's room to be perfectly posh and it's totally possible without overspending. The key is shopping around and not buying the first thing you fall in love with, at the expensive boutique. Go to the upscale stores to get ideas. I recommend taking pictures of those special items you really love, or making a list with the details that made those items catch your eye. Then, go home and shop online. Websites like Ebay and Craig's list are invaluable to the bargain shopper. Usually, you can see pictures of the item, ask questions about the item and maybe even negotiate pricing. Sometimes, you can find the exact same expensive boutique item for a lot less. If you are unable to find the exact item, you can find something similar. It may not have the brand name, but if it has most of the characteristics of the expensive version, and it's a fraction of the price, does it really matter? Also, don't narrow your search to only baby items, I love to use home items in the nursery and often you can find them for less, because there are more sources. I also recommend visiting your local resell shops and garage sales. You will be amazed at the treasures you can find and the fun you will have. I do personal shopping as part of my design service. Please like Trick My Crib on Facebook, and visit my page often for decorating ideas. Thanks for listening to today's money saving tips, and be sure to listen to Preggie Pals for more great pregnancy tips in the future.

[Theme Music]


Sunny Gault : Knowing your blood type is important, and if you're pregnant, the type of blood you have could impact your pregnancy and your labor and delivery. Joining us here in the studio is Dr. Damon Cobb, he is an OB/GYN with Poway Women's Care, and he actually appeared on our show last summer, Dr. Cobb, welcome back to Preggie Pals!

Damon Cobb : Thank you, it's an honor to be here.

Sunny Gault : So let's talk about blood types and Rh factors. As a disclaimer, I know this can get confusing, so let's try to break this down as simply as possible.

Damon Cobb : Sure, it's going to be a confusing topic no doubt, so hopefully we can lay it out to pretty basic, so you can have a firm understanding of blood types in general.

Sunny Gault : OK. So what are blood types?

Damon Cobb : Blood types are just antigens within your blood. Antigens are basically substances that evoke a response from our immune system or our antibody system. Our blood types are basically based on that antigen system as well.

Sunny Gault : OK, then what's an Rh factor?

Damon Cobb : Rh factor is the rhesus factor. What that determines is, as you probably have heard of your blood type, the positive and negative aspect of that. Again, the Rh factor is just genes or protein that's attached to the red blood cell surface.

Sunny Gault : So it totally changes the type of blood you have by adding a negative or positive to it, right?

Damon Cobb : It does. There are generally 30 different subsets or blood groups when we talk about blood. The most common that people know of are what we've mentioned, the AB and O. However there's 600 different genes, so it can be a little confusing, for the sake of this talk, we will just talk about the most common that we hear of, the AB, O group.

Sunny Gault : I didn't even know that there were extra ones, D, Z, F?

Damon Cobb : Yes, alphabet soup a little bit.

Sunny Gault : But that's obviously very rare.

Damon Cobb : Right, exactly.

Sunny Gault : Since we're on the track of blood types, let's talk a little bit more, just in general, about them. What are the most common blood types and what are the most rare? Not the really really rare ones, but of the common ones.

Damon Cobb : Interestingly, it depends on where you are in the world. In the United States, O positive is the most common. In other parts of the world, it differs. The least common in the United States is AB negative.

Sunny Gault : AB negative. OK, and so, Amy, what are you?

Amy Askin : O negative, and I believe my mom is AB negative, I think that's how I got my Rh negative.

Damon Cobb : We talk about just blood types in general, how do we get our blood types, like most of our characteristics, they are passed down from our parents through genes. A subset or a special code to the gene is something called an oleyl, we each have two of those, so we get half of our blood type from each parent. To break that down a little bit, one parent may be AO, and the other father may be B and O. And when we talk about oleyls, we talk about dominant and recessive factors as well, they may sound familiar to some of you. A and B are the dominant aspects of the blood types, O is considered the recessive. So based on genetics, that's how we ultimately determine what blood type a baby is going to be.

Sunny Gault : I was doing some research for this, I actually found sites where they would have you enter what's your blood type, what's your partner blood type and it would predict what your baby's blood type would be. Is it that scientific that this is always recessive, this is always dominant, so you can always predict what the baby's blood type is going to be?

Damon Cobb : You can predict a certain percentage. Let's say that A O and B O, the likelihood is going to be greater that baby is going to have more of a dominant blood type. So you have about a 25% chance that that baby may have just an O blood type. It's all based on percentages connected with the genes.

Sunny Gault : So for women out there that know their blood type, I actually don't know how many people know their blood types, but let's say you do know, you know that it's negative, and you become pregnant. What are some of the precautions that are typically taken to ensure a succesful pregnancy?

Damon Cobb : The first step would be, in a woman who knows her Rh factor is negative, is finding out what they're partner blood type is. If her partner also has an Rh negative factor, than nothing needs to be done. After that, if you confirm that the father's blood type is positive, then usually I sit down and discuss what that means in relation to the pregnancy. The big factor that you are trying to avoid is anytime there is any crossover of fetal blood with maternal blood, whether it would be through several different factors – delivery is the most common factor where you get a little bit of that crossover, what can happen is that the mom's immune system will recognize baby's positive Rh factor as foreign. When that happens, like with anything that our body recognizes is foreign, our immune system develops antibodies, substances that fight that foreign object. When that occurs and those antibodies develop, then the woman's subsequent pregnancy is in danger of having bad effect because of those antibodies, assuming that the next baby will have an Rh positive foreign blood type.

Sunny Gault : How or what point in a pregnancy does a baby develop its own blood type? Is it immediately? When does this become an issue for pregnant women?

Damon Cobb : Around day 30 is when we have been able to determine the Rh factor on the surfaces of fetal red blood cells. So pretty early.

Sunny Gault : So the testing process, that's one of the first blood test you take, as a pregnant woman, right?

Damon Cobb : It is, along with several other tests, one of the most important is looking at your blood type. And then also along with that your Rh factor. We also screen for antibodies that we talked about a little bit early that could be positive at that point early in pregnancy. Obviously, you'd want that antibody screen in best case scenario to be negative early on.

Sunny Gault : Just to be very clear, 'cause I know we've talked about positives and negatives, and find out what your spouse is, it really starts with the mom. If the mom is positive, has an Rh factor positive, than this really isn't a concern.

Damon Cobb : It's not a concern at all and some people will ask about the paternal aspect, that doesn't matter. From a standpoint of early testing, the only time we're concerned is when the Rh factor is negative. And really, thankfully, that's very little population, at caucasian population it's about 15%.

Sunny Gault : You're special, Amy.

Amy Askin : Always.

Damon Cobb : African-Americans are between 5-8% and the Asian about 1-2%.

Sunny Gault : Amy, knowing that you are negative, did you have any concerns going into your pregnancy, have you heard about the Rh factor and how that could impact pregnancy? I don't know that a lot of pregnant women know that this could be an issue.

Amy Askin : You don't have to deal with it too much. Because I was under care with really experienced, great people, they did my initial test and I found out that I was negative, I have always thought that I was O positive, because in my 7th grade science class you do that blood on the test, obviously that was not correct. So I was a little shocked, but it was not a big deal and I am not much of an alarmist. So I said, “OK, what does that mean?” and he said I get a shot of RhoGAM at 28 weeks and then you get another one, I can't remember how many. But you get shots of RhoGAM and its just a shot in the behind or whatever and it's not a big deal. So because of modern medicine, I didn't feel in any way alarmed.

Damon Cobb : You mentioned RhoGAM a little bit earlier, what RhoGAM is, it's basically a blood product that's taken from the plasma of donors that helps prevent – if there is that chance of crossover between Rh positive and Rh negative – it helps prevents an immune reaction generated by mom.

Sunny Gault : And that's given at what point?

Damon Cobb : Generally, if the pregnancy is gone textbook, no issues, we'll usually get that around 28 weeks. RhoGAM has a life span of about 12 weeks, so some practitioners, if that pregnancy goes over 40 weeks, will give another dose. We'll also usually give a postpartum dose within 72 hours, depending on baby's blood type, because as I mentioned before, the highest risk of that crossover is during birth. In order to protect against that immune response, within 72 hours we'll give that second dose.

Sunny Gault : Are there any complications that could result from this shot?

Damon Cobb : Thankfully, there is not. It is a blood product, but the process that occurs to make RhoGAM is very safe. The viral – as we think about any type of blood product, we think about different viruses, hepatitis and HIV and the process is really absent when we talk about RhoGAM and how they process it.

Sunny Gault : Amy, this was not a big deal for you as far as getting the shots.

Amy Askin : Just another shot.

Sunny Gault : Did you only have one? You had two?

Amy Askin : I had the protocol that he was describing, 28 weeks and then after 72 hours, both times, with baby number 2 and 3.

Damon Cobb : That is the general standard dose but there are several factors that can occur throughout pregnancy where you may need to get a little bit early. Those would entail, unfortunately, women who have miscarriages early – they may need to get an earlier dose, and usually in the first trimester, before 13 weeks or so, we'll usually give a lower dose of RhoGAM, because the fetal crossover would be much smaller than you experience at birth. Other examples would be abdominal trauma, some women unfortunately get hit in the stomach for whatever reason, abruptions.

Sunny Gault : I want to take a quick break and when we come back we are going to dive more into some of the concerns during labor and deliveries. So we'll be right back.

[Theme Music]


Sunny Gault : Welcome back everybody, today we are talking about blood types, Rh factors and pregnancy and our special guest expert is Dr. Cobb, he is Poway Women's Care, he is an OB/GYN. So let's talk about the concern with crossover, Dr. Cobb, with labor and delivery. What are some of the concerns that OBs have?

Damon Cobb : As we've mentioned a little bit earlier, the thing we worry about is the crossover and mom developing those antibodies from the foreign Rh type. Generally, that wouldn't affect that initial pregnancy, it's the subsequent pregnancies that we worry about. What happens, basically, is when mom does create those antibodies, with the next baby, if the baby happened to be Rh positive again, then mom's immune system recognizes that as foreign, and those antibodies are able to crossover to the placenta and affect baby.

Sunny Gault : So what is it about the labor and delivery process that could trigger something like that?

Damon Cobb : Higher chance because of placenta issues, placenta separation, bleeding during labor, the chance is just so much greater than not having any issues throughout the pregnancy. Plus the fetal volume of blood is much greater at that point, as compared to someone who is unfortunately had a miscarriage 8-10 weeks.

Sunny Gault : So the concern is that somehow, through all of this stuff that's going on in the labor delivery process, the blood is somehow going to get into the baby? Through the umbilical cord?

Damon Cobb : Basically through mom's system, so through the placenta, if there is any crossover of those fetal cells into mom's blood supply, because the placenta is attached directly to the uterus and to mom's blood supply, although fetal and maternal blood don't mix through the placenta, if there's trauma or if there is just the natural brith process, that can happen. The big thing we worry about is that those antibodies will cause red blood cell destruction of the fetus, causing severe anemia, which can, if it is indeed severe, can lead to heart failure and something called highdrops.

Sunny Gault : And how quickly can that happen? We were talking earlier about the first 30 days of the pregnancy, when you can detect Rh factor, but is that too late to know if there has been any damage?

Damon Cobb : Well, every pregnancy is a little bit different, and the severity can be different. We can start testing generally as early as 18 weeks. Interestingly enough, the subsequent pregnancy, the initial subsequent pregnancy is generally less effective than pregnancies after that, so with each pregnancy after that, the attack can get a little bit more severe and anemia can be a little more severe.

Sunny Gault : At what point can you test to see the fetus, or what you have to test to find out what blood type they are carrying? Can you do that, and at what point?

Damon Cobb : You can. Initially, start again with the prenatal profile, we look at the blood type, Rh factor, and then look at the antibodies. The antibody is going to be important within that pregnancy because we look at how high that level is and that gives us an idea how severe tha crossover and that attack of the fetus would be. Generally, what we'll do is first test dad again, again, when we go back to our initial discussion of just those two different oleyls, we talked about the dominant and recessive. If that has two of the same dominant genes, than all of his offspring are going to have that positive Rh factor. If there is a dominant and a recessive, than you've got a 50% chance that that fetus is going to have an Rh negative factor. If that fetus has an Rh negative factor, than again it's nothing to worry about. So once we determine the paternal testing, there's a couple of other ways that we can look into the fetuses Rh type. There is a test that's actually newly available in the US, that is able to extract that information from maternal serum, but it's very new, they use it over in the UK more often. If that is not available, then what we do is amniocentesis and generally we can start testing at around 18 weeks to determine the fetal Rh type.

Sunny Gault : And then, if it's determined that it's incompatible with mom than that's when the shot would be administered?

Damon Cobb : Interestingly enough, you would assume that the RhoGAM would help, but once the mom has been sensitized, and has developed those antibodies, that shot no longer is effective. So generally what we do after that point, once we determine that the baby could be affected, then we start following those tighter levels. We look at those level pretty frequently, every couple of weeks or so, starting around 20 weeks, and if that tighter gets to a certain critical level, where we would assume because of that level that the severity of the attack is increasing, we would look at the blood level of the baby through something called a cordocentesis. So basically putting a needle in the cord, drawing off some of that blood and looking at the severity of the anemia. Based on that, if it falls in a decent range, we continue to follow, if it fell on a more critical range, than the next step would be a transfusion.

Sunny Gault : Transfusion for baby or for mom?

Damon Cobb : For baby. To try to resolve that anemic status.

Sunny Gault : This sounds really big, it sounds like it's really involved.

Damon Cobb : It is, and generally, once a mom has become sensitized, then they really need to be seen by a specialist in high risk pregnancies, because of the severity that can escalate relatively quickly, and the treatment that needs to occur if that does happen.

Sunny Gault : Is there anything moms can do preventively to assist in those processes? Or if they know that they have the Rh negative factor, does diet, does lifestyle, does anything like that play a part? Or we're just talking about pure genetics? If you got it you got it and you may have to go through some testing?

Damon Cobb : Exactly, we talk about cholesterol, something like that. We can diet, exercise, do all we can, but there is still the genetic aspect of that. And we're talking about blood factors, it's purely genetics. Unfortunately, there's not a whole lot moms can do, other than just being pretty vigilant if there's any issues, concerns with heavier bleeding in your Rh negative factor mom, obviously letting your provider know what's occurred.

Sunny Gault : Amy, is there anything that you would like to say to the women out there that know that they've got Rh negative, anything you want to warn them about or tell them about the process? Or share about your own experience?

Damon Cobb : I think that as long as you're sure that you are with a care provider who is aware of everything Dr. Cobb has discussed, I think that's your number one preventive means of getting through it. Because I have had zero issue whatsoever, I've been under excellent care. I knew about all of the research that he was talking about and all the things that he said, but I never for a moment questioned anything. It is a little bit scary with your first experience, but if you are in good care and you make sure that you take care of yourself often and have good care, you should be fine. It's not a big deal though, that shot is like... in fact, this time I got my flu shot and this one, I got one in the arm and another one. It's not a big deal at all.

Sunny Gault : Alright, well thank you Dr. Cobb for joining us today, for more information about Dr. Cobb and his practice as well as information about all of our panelists, you can visit the episodes page on our website, for members of our Preggie Pals Club, the conversation continues as we explore how blood types and Rh factor can change if you're pregnant with twins.

[Theme Music] [Featured Segments: The Best Online Pregnancy Resources]


Robin Kaplin : Hi Preggie Pals listeners! I'm Robin Kaplin an, international board certified lactation consultant, owner of the San Diego Breastfeeding Center, and the host and producer of Preggie Pals' sister show, the Boob Group. I'm hear to offer some advice on what you can do during pregnancy to prepare for a positive breastfeeding experience, such as locate a local, welcoming breastfeeding support group. Yes, we all know that breastfeeding is natural and normal, yet many of us first time moms have never really been around other breastfeeding mothers. Plus, many of the children we see breastfeeding in public maybe covered up with a blanket. So we actually don't even know what breastfeeding looks like. A few years ago, after I set up my first breastfeeding support group, I overheard a group of new moms talking about how they wished they had gone to a breastfeeding support group while they were still pregnant. This shocked me a little bit; as I wasn't sure why they thought this would have been helpful. As I listened to their reasons, it began to make complete sense. And now I recommend it to all of the first time moms that I meet. And this is what they said. First of all, these moms mentioned that after they had their babies, they were a little bit anxious to go somewhere they had never been before, they didn't know where they would park their car, they didn't know where to park their strollers, and visiting the support group while they were pregnant, they felt they will be able to figure out all of these details, as well as taking the vibe of the group to see if it was somewhere they felt they would belong. Once seeing new moms with a group of babies under two years old, they felt it would help them to come sooner after their babies were born. They thought they would also be less intimidated.

Secondly, they would have liked to see what a breastfeeding woman really looks like, without the cover. How does she sit, how does she latch her baby, did she use a breastfeeding pillow, did she wear one of those nursing tanks? All these little things they could just gain just by checking around the room. And they though that that would have been incredibly helpful. Lastly, they would have liked the opportunity to ask these new moms questions about what life was like with a newborn. Many of the women who attended the support group were not from San Diego. So they didn't have many friends or family around who had young children. The support group became their village, where they could seek advice from new friends. Pregnant moms have the opportunity at the support group to interact with moms, ask them questions about local resources and then just get a general sense of what life may look like after they have had their baby. Seeing breastfeeding moms, especially those who have overcome challenges, can be just enough inspiration for a new mom to persevere to meet her personal breastfeeding goals. Especially if you make a connection with another mom who can encourage you during any of this challenges that you may have. It's definitely worth the hour during your maternity leave while pregnant, to visit a local breastfeeding support group. So I highly recommend finding one that you really enjoy. For more great information about what you can do during pregnancy to prepare for a positive breastfeeding experience, check out my blog, at, and be sure to listen to Preggie Pals and the Boob Group for fantastic conversations about breastfeeding and breastfeeding support.

[Theme Music]

Sunny Gault : That wraps up our show for today, we appreciate you listening to Preggie Pals, don't forget to check out our sister show, Parent Savers, for parents of newborns, infants and toddlers, and our show the Boob Group for moms who breastfeed their babies. This is Preggie Palls, your pregnancy, your way!


This has been a New Mommy Media production. Information and material contained in this episode are presented for educational purposes only. Statements and opinions expressed in this episode are not necessarily those of New Mommy Media and should not be considered facts. Though information in which areas are related to be accurate, it is not intended to replace or substitute for professional, Medical or advisor care and should not be used for diagnosing or treating health care problem or disease or prescribing any medications. If you have questions or concerns regarding your physical or mental health or the health of your baby, please seek assistance from a qualified health care provider.


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