We’ve all heard stories about someone who didn’t realize they were pregnant for months. While it might sound hard to believe, Dr. Yolanda Kirkham, an obstetrician and gynecologist at St. Joseph’s Health Centre of Unity Health in Toronto, says she's seen it in her own practice. “I have personally had a patient roll into labour and delivery in full labour and not realize they were pregnant,” she says. This person was experiencing what's called cryptic pregnancy.
A cryptic pregnancy is a pregnancy that goes undetected for a longer time than usual, for a variety of reasons. Kirkham says a cryptic pregnancy is also commonly referred to as an unknown pregnancy, or a case where the mother is late to prenatal care.
Cryptic pregnancy happens more often than you might think. Kirkham says that a study out of Australia found that one in 475 pregnancies was diagnosed after 20 weeks, and only one in 2,500 pregnancies was discovered during labour. She adds that rates may vary in different countries, or even in different regions within the same country. “There’s such variability in where people live," she says. "If they’re in more rural areas or part of a more siloed cultural group, they may have different experiences.”
While some pregnancies do remain unknown right through until the moments before birth, the vast majority of cryptic pregnancies are simply discovered late.
The symptoms of cryptic pregnancies aren't necessarily different from any other pregnancy. But it's easy to miss early signs of pregnancy if you aren’t looking for them. For example, the nausea and vomiting that's common in early pregnancy could be mistaken as viral gastroenteritis. Kirkham notes that fluctuating weight is normal for some women and that the physical changes that occur during pregnancy like a bulging tummy and bigger breasts may be attributed to weight gain.
The most obvious sign of a pregnancy is a missed period, but even that is not as clear-cut as you might imagine. Some women don't have super regular cycles to begin with, so for them, Kirkham says, “they could see a little bit of spotting, which can happen in early pregnancy, and think, Oh, that's my period.” Even fetal movement—those first kicks that are usually experienced between 16 and 24 weeks of pregnancy—can be very subtle for some people and mistaken for cramps or indigestion, says Kirkham.
So while there may be pregnancy symptoms in cryptic pregnancy, some women may downplay or misattribute them to other causes.
Kirkham says that cryptic pregnancies are generally most common among people who don’t get regular periods for any number of reasons. One example of this is polycystic ovarian syndrome (PCOS), a metabolic and endocrine syndrome that can cause several missed periods in a row. “If people with PCOS don't have a period, that's normal for them, rather than being a sign of pregnancy,” says Kirkham. “Plus, a lot of patients with PCOS are told that their fertility is decreased. And while that may be true, it doesn't mean they can't get pregnant.”
Others who may not have regular periods include those with relative energy deficiency in sport (REDS), also known as hypothalamic amenorrhea or athlete’s triad. "These are individuals who often are athletes or in competitive sports and the amount of energy they take in is not sufficient, so the body sacrifices the ability to reproduce in order to send energy to other areas of your body to survive.” Fertility returns to people with REDS once they stop being as active, and they might be caught off guard.
Newly postpartum moms also might not have had their periods return. “New moms are busy and don't expect their period to come back," says Kirkham. "While we always say that you can get pregnant again before you see that first period, it may not be on their mind that this could happen.” Likewise, those who are perimenopausal, in their mid-to-late 40s, start having skipped periods and don't ovulate all the time. “Some perimenopausal people forget that they might need contraception and can miss a pregnancy too.”
Finally, cryptic or missed pregnancies can occur when there is denial on the part of the mother, Kirkham says: “There can be a psychiatric or mental health illness component, but it can also be a subconscious survival and coping mechanism for dealing with conflict.” She explains that any number of bad consequences can result from pregnancy, causing someone to be in a state of denial. “Unfortunately, domestic or intimate partner violence increases a lot during pregnancy. Or there can be financial instability, immigration consequences and trouble at work or school.” There can even be religious or cultural taboos or legal obstacles to a full spectrum of reproductive care that come into play.
While a home pregnancy test might produce a false negative very early on, tests repeated over a number of days will generally tell you if you are pregnant. If you have pregnancy symptoms, but a negative test, Kirkham recommends seeing your doctor for a pregnancy blood test.
They'll request an ultrasound if there remains any uncertainty, but bloodwork that looks for HCG should be reliable, as you cannot be pregnant and not have the HCG pregnancy hormone in your blood. “Pregnancy hormone levels follow a predictable pattern and rise exponentially quite quickly," says Kirkham. "Abnormal pregnancies like ectopic pregnancies rise slower, but they are still able to be confirmed by a blood test—which is fortunate as they can be life-threatening. But bloodwork can almost always determine if someone is pregnant.”
If a pregnant person is unaware that they're pregnant, that means that some, if not all, of the standard prenatal care hasn't happened. “For example, picking up rare genetic abnormalities during early ultrasounds and bloodwork can be missed,” says Kirkham. Other risk factors of an unknown pregnancy include less than ideal nutrition, lack of prenatal vitamins, and use of alcohol, cigarettes or other substances discouraged during pregnancy, which Kirkham notes can lead to small birth-weight babies who are at greater risk for other complications.
Maternal health issues such as a fibroid disorder, high blood pressure or irregularities with the uterus will also be missed without prenatal care. And there can also be significant trauma for the mother. “If you have no preparation mentally and physically for the birth process, and you don't have a support network or all the physical things like strollers and bottles that you need to support a baby, that can be very hard to deal with,” says Kirkham.