Question:

I just found out from a home pregnancy test that I'm pregnant for the first time. I'm concerned about causing harm to the baby because my blood type is O negative and my husband is O positive. I'll be seeing an ob-gyn soon, but can you tell me what I'll need to do?

Answer: Congratulations! What I believe you're worried about is Rh blood type incompatability, an Rh-negative mother and an Rh-positive father. Let me reassure you that any Rh blood type differences are of no concern in a first pregnancy.

When we refer to blood types like A, B and O, we're describing the presence or absence of A or B "antigens," protein substances found on the surface of red blood cells. A person who is type O has no A or B antigens on his red blood cells. Rh is another antigen that may or may not be on the surface of our red blood cells. If we have that antigen, we're Rh positive (+); if we don't, we're Rh negative(-). A, B, and Rh are the major antigens that may be present on red blood cells, but there are nearly 600 other minor antigens to which some folks might react during a blood transfusion.

Before the introduction of Rhogam, a preventive injection, in 1968, Rh blood type incompatibility between a pregnant mother and her developing baby claimed 10,000 babies in the United States each year.

In pregnancy, there are two separate blood circulations, mother and baby. If the mother's blood type is Rh negative (e.g., A negative, O negative, B negative, AB negative), and the baby's blood type is Rh positive, the mother's blood will produce antibodies against the baby's Rh-positive blood capable of causing life-threatening destruction of the baby's red blood cells (hemolysis). A Rhogam shot blocks the antibodies produced from an Rh-negative mother so as not to cause harm to a developing baby.

These antibodies are not usually formed in high numbers until after the first pregnancy. That means Rhogam isn't usually needed in a first pregnancy. You'll definitely need Rhogam as a precautionary measure in subsequent pregnancies, even if it turns out they're Rh negative like you.

nolead begins

An imaginary physical on Jolly Old St. Nick

Q:

Just for fun, could you speculate on what health problems Santa Claus might have?

A: Since I'm not the personal physician for the "jolly big guy," this is medical conjecture. But given his advanced age, occupational hazards, and obvious obesity, he might be dealing with a number of chronic medical conditions.

Starting at the head, he's probably already dealt with cataracts and has some degree of hearing loss. He probably also has a bit of age-related atrophy of the brain (which explains his need for numerous personal assistants at the North Pole).

Given his obesity, I wouldn't be surprised if his physician has him on medication for hypertension, diabetes, and high cholesterol. He also has probably dealt with benign prostate enlargement, and he's likely had a surgical procedure for that at some point. After all, it's a long trip around the world. Osteoarthritis of his knees, hips, and low back are likely given the weight of Santa's sack of toys and climbing from chimney to chimney all over the world. The extreme cold, dry air of the North Pole may cause asthma as well as a case of eczema.

But chronic health problems aside, he's a jolly old soul who never seems to fail to deliver on his promise of toys to children throughout the world. I expect him to be medically fit to conduct his Santa duties for as long as there are children who believe in the magic of Christmas.

Mitchell Hecht is a physician specializing in internal medicine. Send questions to him at: "Ask Dr. H.," Box 767787, Atlanta, Ga. 30076. Due to the large volume of mail received, personal replies are not possible.