Month one Q&A
Q:
I’m delighted to be pregnant, and so was my boyfriend, until he made a calculation regarding the due date and how far along I am. He reckons the baby can’t be his, because he was away for a week when the doctor says we conceived. But it really is his baby! How do I explain this to him?
A:
Karin answers: The date your caregiver gives you is a gestational age based on the first day of your last period (if you can remember it!). This can be confusing because you are actually not pregnant for the first two weeks after your last period. However, doctors use this date as it is a day that can be pinpointed, unlike the day you conceive. Even if you know when you ovulated (and many women do) there’s no guarantee that this is the day that sperm met egg. In fact, actual conception can take place up to three days after ovulation or sex. So your boyfriend’s worry is unfounded, but the fact that he is suspicious is worrying in itself, and you may need to talk about trust issues. Based on the date of your last menstrual period, we have a 40-week pregnancy, when in fact you will only have a baby growing inside you for 38 weeks. A more accurate way to work out how pregnant you are is to have an early dating scan. A scan at nine weeks is considered the most accurate, as at this early point no genetic size factors influence the baby’s size (that only happens at around 20 weeks). At this stage foetuses follow the same developmental pattern, so an accurate gestational age can be given. It would be better if we change the way we think about the elusive due date and rather talk about an estimated due “period”: from two weeks before (38 weeks) your calculated due date to two weeks after (42 weeks). Your baby is considered full term from 38 weeks, which means he is fully developed and his lungs are mature enough for survival outside of the womb. With an estimated due period in mind, if you do reach your due date you are less likely to resort to medical intervention to speed up the onset of labour thinking that you are “late” or “overdue”. Rather tell people that you are due at, for example, the end of September, or in October.