How long should a pregnancy really last?
FROM this point on, the concept of months should be thrown out of your mind and lost for eternity. A pregnancy does not last for nine months, and the basic reason for this is that some months have 31 days, some have 30, while February has 28. The actual length of a pregnancy is actually 40 weeks from the first day of the last menstrual period until the expected due date (that’s 280 days).
The menstrual cycle
The menstrual cycle is a complex play of hormones which leads to the release of an egg from the ovary, which when a sperm meets same, results in conception — a magnificent event that only God could create. When conception is not achieved, the lining of the uterus is shed and this results in menstruation — an unfortunate reminder for a couple actively trying to conceive.
For a woman with a regular 28-day cycle and who is not on any form of hormones, her pregnancy can accurately be dated from the first day of the last menstrual period by adding 40. Yes, a pregnancy is dated from even before conception actually occurs! This is confirmed with a pregnancy test, which some tests can actually detect up to nine days after conception.
Ultrasound
Accuracy of the ultrasound depends on when it is done. Ultrasounds done within the first 12 weeks of pregnancy are extremely accurate (up to 7-10 days) in dating a pregnancy, especially in a woman who is unsure of her last menstrual period. Second and third trimester ultrasound datings are not as accurate, and can be up to 14-21 days off.
Why is it important to date the pregnancy?
Babies who are born too early (premature) and babies who are born too late (post-date) are at risk for adverse outcomes. Dating a pregnancy allows the obstetrician to manage the pregnancy properly and to intervene when necessary to improve the overall outcome of the mother and baby. Premature babies have poor lung development. If delivery is unavoidable for a premature foetus, the obstetrician can administer medication to the mother to help strengthen the foetus’ lungs so that it can have a better chance of survival when born.
With regards to post-date pregnancy, these babies tend to have a larger birth weight and can be a potentially more difficult to deliver. In addition, the placenta (afterbirth which provides nutrients to the foetus) can suddenly shut down, resulting in stillbirths.
When do most women deliver?
Most women usually deliver at around 38 weeks of gestation before the actual expected due date. Obstetricians will agree that most babies tend to make their debut in the early morning hours; however, labour can occur at any time — like a thief in the night — and it is important for women to be made aware of the warning signs of labour.
Dr Daryl Daley is a medical officer in OBGYN at the May Pen Hospital and a consultant OBGYN at Gynae Associates, 23 Tangerine Place, Kingston 10 and Shops 46-50, Portmore Town Centre, Portmore. He can be contacted at 929-5038/9 and 939-2859 or drdaryldaley@gmail.com.
