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Better Late Than Never: Post-Date Delivery

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News flash: pregnancy is 40 weeks. Divide 40 by four ( ≈ four weeks to a month), and even we math novices know that equals 10. You heard it here first: pregnancy is actually 10 months! We know it’s like they just added a few more miles to the marathon once you thought you’d reached the end, but get out your Gatorade because, for some women, the race won’t end for another two weeks. Definition time: a post-term pregnancy is a pregnancy that is ≥ 42 0/7 weeks. The “start” line is first day of your last period, while a late-term pregnancy is one that falls between 41 0/7 and 41 6/7 weeks. Knowing your exact due date is super important because this will be the basis for all the D dates to come.

As OB/GYNs, we love to talk “dates.” And although we do appreciate hearing about the one you went on last night (did he or she really say that?), we want to focus on the date of your last period. The first day of your last menstrual period is probably the most frequently asked question to a pregnant woman. By the end of your 10 months (ugh, sorry to rub it in), your partner will be able to spit this number out in their sleep, it will be mentioned so many times! The reason we ask it over and over is because it determines what your due date is. It also determines if your baby is growing appropriately, if things are developing on track, and if a delivery must be planned or induced when it should or can be done.

Pregnancy and fetal development are based on “weeks.” You rarely ever hear an OB/GYN define a pregnancy in terms of months; our first and only language is weeks. Weeks of pregnancy correspond to the size and maturity of your baby’s organs, particularly the baby’s lung development. So, we will jump through hoops to make sure that your “dating” is accurate and that we know exactly how many weeks pregnant you are and how old your baby is!

Why some babies show up on time, some early, and some late is often very hard to figure out. There are risk factors for each, but most of the time, it’s sort of the luck of the draw. First-time moms, those carrying a male fetus, and women who are obese more commonly carry a baby past their due date. Additionally, if you went over with your first child, you are more likely to go the distance the second time around.

Other than discomfort and major ankle swelling, why do we care how long pregnancy continues? Well, several studies have shown that both late-term and post-term pregnancies have a higher risk of fetal complications. Factors like low amniotic fluid, stillbirth, admission to the NICU, passing meconium (babies’ first bowel movement) in the uterus and swallowing it (a.k.a. aspirating), and seizures occur at a higher rate in late-term and post-term pregnancies. In addition, the longer they cook, the bigger they get. Pregnancies that are past their due dates are more than two times likely to be macrosomic (a fancy way to say BIG!). You guessed it; a big baby is more likely to get stuck on its way out. This leads to a higher chance for an operative vaginal delivery (forceps or a vacuum) and a C-section.

So, when is it time to call it quits? A lot of this depends on your personal history: your age, how you got pregnant (fertility treatments), your medical history, your previous OB/GYN history (have you had a C-section before) and your baby’s development (size, fluid etc.). Not every delivery plan and timeline fits every pregnant woman. In most cases, labor induction cannot be planned prior to 39 weeks of pregnancy (one week before your due date). This is done to ensure that your baby is as ready as possible to take on the world when he or she makes that first appearance. While most OB/GYNs are okay with labor inductions after 41 weeks of pregnancy (the ACOG gives it the green light), they are almost all on board by 42 weeks. In fact, after 42 6/ 7weeks your baby is not only ready for preschool, but according to the ACOG, it is mandatory evacuation time.

There are ways to “get the party started,” including sex, dancing, a bumpy car ride, spicy foods, nipple stimulation (yup, we just said that), raspberry tea, and something called evening primrose oil (sounds super fancy, but really, it’s just a vaginal tablet). The cervix is the gate to the uterus. It will soften, become thinner, and ultimately open and dilate as labor gets closer. Depending on the readiness of your cervix, some of these home activities can help move the process along. Unfortunately, no matter how badly you want to meet your little one, labor often happens on its own schedule.

Once you hit the magic 40 and nothing is happening, your OB will likely initiate more fetal testing to ensure that the baby is just “chillin’ out” and is not stressed. Make sure to be in constant communication with your OB. The more surveillance you have at the end, the safer both you and your baby will be.

If things seem off (you are not feeling well or your baby is moving less), don’t stay silent. We want to hear from you, even in the middle of the night. Trust your intuition. Moms are usually right!

Funny Math: How Due Dates Are Calculated for Pregnancies Conceived after Fertility Treatments

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Does anyone recall sitting in math class and just staring at the blackboard thinking, “Nope, I just don’t get how X + Y * A = B.” Sure, you nodded to get Mr. Novick off your back, but in reality, you had no idea how he arrived at that answer. And while algebra and amusing are rarely used in the same sentence, that guy seemed to be doing some funny math! Much the same can be said about how we fertility doctors date (a.k.a. tell how pregnant you are and when you are due) pregnancies conceived with fertility treatments.

Most pregnancies (ART excluded) are dated based on the first day of a woman’s last menstrual period. And although you are technically not pregnant in the first approximately two weeks of the menstrual cycle (a.k.a. the follicular phase), you are growing the egg that will ultimately become half of your baby. Because the majority of menstrual cycles range between 25–35 days, the math usually works out. But when pregnancies are conceived with fertility treatments, the lead time (a.k.a. egg development) can be VERY variable. Weeks and even months may be added to get an embryo implant ready. For this reason, if you used fertility treatments to conceive, you can’t simply add a few days to your last menstrual period to calculate your due date. You may need some creative counting and a good doctor to get things sorted out.

As much as we love numbers, we can only count so high! Therefore, to make sure we are getting this equation right, we use pregnancy wheels (a fancy way to say pregnancy calculators) to figure out when you should plan to meet your plus one. Whether it be the day you ovulated, the day we performed your IUI, or the day your IVF ET was done, we can figure out exactly how far along you are. Given that the numbers will be less than transparent, it’s important to get a due date calculated by your fertility doctor before posting “We are expecting…coming March 24th” on your Facebook page. Additionally, you want to pass this info on to your OB and any other practitioner that participates in your care—they need to be in the know about when you will be ready to go!

Dates are not only numbers to an OB. We don’t break them, we don’t forget them, and we certainly don’t change them (unless we have a really, really good reason). They not only dictate when pregnancy-specific tests should be run (think genetic screening, diabetes screen, and GBS screening) but also when a fetus has what it takes to take on the world. Fetal lungs weren’t built in a day. In fact, they weren’t even built (for most babies) in nine months. They require those dreaded extra four weeks (remember, pregnancy is actually 40 weeks!) to get fully ready for a deep breath in and a deep breath out.

When most of us hear those words “You’re pregnant” (particularly after years of trying), we start to think about the end. And while it’s almost like planning for mile 26 before the race gun has even gone off, your due date is a big deal. But no matter how dynamite it is to know when D-Day is, your due date is NOT dynamic. It’s pretty dead set, especially after doing fertility treatment. IVF, IUI, and all the like leave little to the imagination. There is no questioning when your insemination or transfer was performed. Be mindful of these dates and the difference in how your due date is calculated after doing fertility treatment. While we love the web (#trulyMD), we want you to be careful when searching it for your due date. Make sure to use an IVF or fertility treatment calculator. This will save you a lot of calendar crossouts and changing-of-the-date chaos.