New Year's Baby
On April 7, someone somewhere hit it right romantically. That's the day, arithmetically speaking, that someone would have to be conceived to be born the following January 1st. This is based on the mother's last menstrual period beginning March 24 and ovulation occurring two weeks later, which is usually the way things go in regular cycles. The first baby of the last New Year has no doubt won a slew of diapers, a dash of formula, and a heap of gift certificates. And a cozy conception encounter in April will allow another contender to put his hat in the ring for the spot of the next coveted “New Year’s” baby. Of course, the fun is provided by arithmetic.
FAST FORWARDThe due date is called the estimated day of confinement (EDC), because traditionally women were confined to bed, “lying in,” from the day of delivery to convalescence was complete. The LMP (last menstrual period) is the only observable event from which to calculate a pregnancy without the aid of ultrasound.
EDC (LMP B 3 months) + 7 days
Yes, there are those early birds that like to come early, pushing themselves into the world as premature babies if they come before 37 weeks. At 36 weeks the lungs usually reach maturity, but we obstetricians feel a whole lot better about the 37-week mark if you want to know the truth. It's all arithmetic. The time-honored formula of subtracting three months and then adding seven days to the start of the last period still determines your official due date. Whether your baby actually has a birthday on that day may be nothing more than a sentimental notion for you and your husband, but it's a necessary temporal landmark for the obstetrician.
Importance of Due Date
Whether your baby is born exactly on her due date or not is unimportant if the discrepancy between the calculated arrival and the actual arrival isn’t great. But your due date becomes extremely important when it is used to determine the severity of preterm labor - whether your baby should be allowed to deliver with a reliable degree of safety or whether another week or two would guarantee mature lungs. In other words, we don't care if your baby is born at 38, 39, or 41 weeks. But we surely need to know when 40 weeks is so that we can be correct in stopping your labor at 33 weeks. The importance of the due date to the obstetrician is emphasized when your baby chooses a date remote from the calculated due date.
FAST FORWARDTerm is usually designated as the day forty weeks after the first day of the last regular menstrual period, but it’s not a due “date” because there is too much variation in the general population. Since term is anywhere from 38 to 42 weeks, it’s really a “due month.”
Now that we have that straight, everyone move up two weeks. Pay attention, because there’s a final in nine months.