Healthy Pregnancy: What's Blood Mixing?

July 20, 2018 4 min read
Healthy Pregnancy: What's Blood Mixing?

There are an estimated 128,845,000 babies born each year at a rate of 350,000 per day, with the global population expected to reach 9.8 billion by the year 2050.


And while thankfully medicine has come a long way since the days when forceps were considered the apex of obstetric technology, sorting through the cacophony of information on potential pregnancy health mishaps can be bewildering. RingMD’s series on pregnancy health aims to straighten out misconceptions and address your pressing concerns so that you can focus on what’s most important--taking care of yourself and preparing for the birth of your baby.

pregnant woman with flowers

Blood Type

A particularly prevalent worry--sparked by the essentiality of matching compatible blood types during blood transfusions and donation--is that the baby will not have the same blood type as it’s mother, leading to a potential ABO or Rh incompatibility reaction when their blood mixes in utero. An ABO incompatibility reaction is a rare occurrence that can take place when a blood donation recipient is matched with the wrong type of blood. There are four main blood types--A, B, AB, and O--which each have a specific set of antibodies. A and B each have specific A and B antibodies respectively, AB has both A and B antibodies, and O has none at all. This means that AB types are universal recipients and can receive any type of blood, while A can receive A and O, B can receive B and O, and O (although it is the universal donor) can only receive O blood. In rare instances, when an incompatible form of blood is used for a transfusion, the recipient’s immune system will mark the new red blood cells as a threat and begin destroying them, which triggers excessive clotting and may block the blood supply to vital organs.

ABO incompatibility reactions, however, do not typically take place during pregnancy despite the mother and baby’s potentially having different blood types. This is because their blood doesn’t actually mix during pregnancy, but is instead separated by the placental membrane. The placenta is the organ which forms in utero and through which oxygen and nutrients pass from the mother to the baby. Blood, however, does not usually pass through the placental membrane during the pregnancy unless there is a miscarriage, but blood mixing can occur during childbirth. If a placental breach occurs and the two blood types mix, the destruction of red blood cells can cause the waste product bilirubin to accumulate, giving the baby a yellow color and leading to the condition commonly known as jaundice in the hours immediately after birth. Jaundice, however, is a treatable condition that normally does not pose any long-term harm to the infant. Severe conditions caused by extremely high bilirubin levels, such as acute bilirubin encephalopathy and kernicterus, only ensue if jaundice is left untreated and are fairly rare given that the signs of jaundice--yellowing of the skin and the whites of the eyes--are easy to spot. Although there is a slight risk that anaemia may occur following ABO incompatibility reaction, the infant will usually be monitored for low red blood cell count at the first sign of jaundice.

blood mixing

Protein Incompatibility?

Rh incompatibility reactions, although more common, poise a similarly low level of concern. Rh stands for ‘Rhesus factor,’ a specific protein found on the surface of blood cells, and its presence is indicated by either a positive or negative sign which accompanies the letter of your blood type (i..e, AB+, O-). Like ABO incompatibility reactions, Rh incompatibility reactions are relatively rare occurrences that only occur during a placental breach--but there’s a slight twist involved.  Most people (about 85%), are Rh+, and therefore there most women have no risk of health complications if there is a breach in the placental membrane. Potential problems arise, however, if the mother is Rh- and the baby is Rh+. In this case, if there is a breach and a mixing of Rh+ and Rh- within the mother’s body, she may develop Rh antibodies. These antibodies pose no risk to the mother following the birth of her first child, but if a second pregnancy occurs and blood mixing occurs once more, these antibodies will attack the red blood cells of the fetus and lead to anaemia. Fortunately, this can be prevented through injections of anti-D gammaglobulin (or simply ‘anti-D’) if the mother has not yet started to produce the antibodies. If she has, the fetus can be monitored and if necessary, receive a blood transfusion through the umbilical cord while in utero.

What does this mean for you?

In short, while blood mixing (either in utero or during childbirth) is possible, it is unlikely--and any potential consequences can most often either be prevented or properly monitored by hospital staff. If you have more questions on this topic, particularly with regard to how it applies to you, we recommend that you consult a doctor. Here are some tips on how to find a doctor or therapist in Singapore. You can also speak to a doctor online on RingMD from wherever you are (just click the button below).

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