Monique Rainford

For the next few weeks, I plan to devote my articles to answering some of the readers' questions.

Dear Doctor,

I am engaged to this wonderful woman who lives in another country. We are planning to get married. The problem is that she met this guy had sex with him around November 6 and again on November 23, 2006. Now I went to see her on November 28, 2006 and we made love. Her period was late and when it came, it wasn't her normal. Around December 20, 2006, she realised that she was pregnant. She did an ultrasound and showed her a few weeks pregnant.

Base on the ultrasound, I don't believe that the baby is mine and she agrees. Now she is about 11 weeks pregnant. I want her to have an abortion, but she won't, saying it will kill her. Can you tell me if it is too late to have one, plus she is asthmatic. Also how accurate is the ultrasound?

Dear Reader,

Thank you for your honest and open question. A pregnancy is dated by the first day of a woman's last menstrual period that is, the menses before her missed period. Let us assume that a woman's last menstrual period fell on November 15, 2006. Her due date can be estimated by a simple rule in which she adds seven days to the day, subtracts three months from the month and adds one year. Therefore, in this case, her estimated due date is August 22, 2007.

However, this calculation is based on a woman having an average cycle length of 28 days. This means that 28 days elapse from the first day of one period to the first day of the next. However, many women do not have a 28-day cycle. If a woman has a 28-day cycle she will ovulate (release an egg) about14 days after her period starts and if the egg is fertilised by a sperm, this occurs within 12 to 24 hours of ovulation. Therefore, in your situation, the timing of your friend's period and the average length of her cycles are important pieces of information in estimating when she conceived.

Based on the information that you provided, she was about eleven weeks on January 31 of this year. Therefore, assuming she has a 28 day cycle I would calculate that her last menstrual period was mid November of last year and she could have very well conceived around the 28th of November and the baby could in fact be yours.

About abortion

Abortion is currently illegal in Jamaica, but in the United States of America where it is legal, all states allow abortion up to at least 12 weeks of pregnancy the medical procedure can be performed safely during this time period, even in women with asthma, there are potentially serious emotional and psychological consequences of an abortion which cannot easily be measured. Therefore, it is very important to listen to your friend's views because if she feels as strongly against it as you have described, these consequences could be very severe.

The earlier that an ultrasound is done in pregnancy, the more accurate it is in dating a pregnancy. A first trimester (first three months) ultrasound can determine the age of pregnancy to within seven days. If an ultrasound is done during the second trimester (the next three months) it will have a possible error of up to two weeks and a third trimester ultrasound may have an error of up to three weeks.