Dear doctor,
I am five months pregnant, and worried because these days I pass black stool and yet I do not eat millet porridge. What is the problem?

Dear Hanifa,
Though the colour of stool may tell one’s type of diet, black stool may actually mean that one is bleeding higher up in the alimentary canal or even in the nose and the blood is finding its way into the alimentary canal where it’s partially digested only to colour stool black. Additionally, bleeding peptic ulcers are a common cause of black stool and an almost exclusive red meat diet or soft drinks containing black currant can also lead to dark stool. At five months of pregnancy, it is likely that you are taking iron supplements which also lead to dark stool. Since dark stool can be caused by bleeding, which is likely to lead to anaemia in pregnancy (a serious health problem), it is necessary that your antenatal clinic checks out the likely cause.

Dear Doctor
I had sex with a woman who was in her periods. Doesn’t this put me at a greater risk of getting HIV?

Dear KB,
Whenever anyone has unprotected sex with a partner whose HIV status is unknown to him, he risks getting infected with HIV. This risk increases further under certain conditions, say how one has been exposed to the HIV virus, type of sex (oral, vaginal or anal) or the amount of viruses in the fluids one has been exposed to. Blood has the highest number of HIV viruses, with semen and vaginal fluids following closely. Therefore, your exposure to both vaginal fluids and blood could have exposed you to a greater risk of getting HIV. That said, one may not get HIV from the very first exposure but if one is unfortunate, he can get infected, requiring that one always protects himself at all times whether it is the first encounter or not.

Dear doctor,
I have a wife whose blood group is AB, Rh-positive and I am O, Rh-positive. Surprisingly, we are both saved and trust each other, but our son is blood group A, Rh-negative. I am devastated because I trusted my wife.
Rev TK

Dear Rev TK,
Blood groups are types of blood based on inherited substances called antigens. These substances can lead to production of other substances that can damage one’s blood in case a different blood type is introduced into one’s circulatory system, such as by a blood transfusion. The blood groups A, B, AB, and O are very important in blood transfusion. The other blood type which was found in rhesus monkeys and hence its name rhesus group is more important in pregnancy. If a mother who is rhesus negative is pregnant with a rhesus positive baby and the baby’s blood leaks into the blood system of the mother, subsequent pregnancies may suffer blood damage with grave consequences for those babies. These blood groups being inherited, before the advent of DNA testing, have been

used with varying successes to determine parenthood and as such have today been rendered less significant except in a few obvious cases. A person who is blood group AB with another who is blood group O can have offspring who are blood group A or B! A parent who is rhesus positive, has inheritance substances + + or + -. If both parents who are rhesus positive are + -, then there is a likelihood of getting offspring who are - - (rhesus negative), meaning that there is a possibility that the offspring is your son. Many times when a man is suspicious about the paternity of a baby, other factors leading to the suspicion are at play, requiring that DNA tests become the final arbiter.

Dear doctor,
What happens when someone with HIV is bitten by a mosquito and it bites another person? I am told we get malaria because the mosquito has bitten a person who had malaria and before it feeds again, it regurgitates (vomits) the old blood with the malaria into a victim. I am scared because I shared a mosquito-infested room with a friend who is HIV-positive. Help.

Dear Aliena,
Malaria is spread by mosquitoes because malaria parasites, once taken in during a blood “meal” from a person suffering from malaria, multiply in the abdomen of the mosquito, only to be taken to the salivary glands from where they are released into a victim as the mosquito feeds, leading to malaria. If a mosquito is feeding, the blood goes to its stomach, not to the salivary glands, and will hence not be release into the blood system of the next victim as the mosquito seeks satisfaction.

Even if the mosquito’s feeding tube had some traces of blood injected in a new victim, this is so little and unlikely to lead to infection. Killing the mosquito on oneself after it has bitten another person is also unlikely to lead to infection.
Please do not be scared that you once shared a room once with an Aids victim because mosquitoes do not transmit HIV. What you should be worried about however is whether you had unprotected sex with that person. Since you are worried about whether you have HIV, please visit an Aids counsellor who will arrange proper HIV tests for you after counselling.

Answers by Dr Vincent Karuhanga