A number of things could keep a woman from noticing the changes in their body:
Fear or stress. The thought of becoming a mother is so stressful for some women that they go into deep denial — so deep that they don’t know they’re pregnant. “Denial is a very powerful defense mechanism, making it possible to talk yourself out of every symptom you may have. The movement in your abdomen is ‘just gas,’ for instance,” Cackovic says.
For example, a teenager may deny or ignore a pregnancy because they don’t want their parents to know they have had sex. A married woman may do the same because they got pregnant by someone other than their partner. Some women may have a denied pregnancy because of a mental health problem, like bipolar disorder or schizophrenia.
No symptoms. For some women, the physical tip-offs of pregnancy, like weight gain, morning sickness, heartburn, or fatigue, don’t happen. Or they’re so mild that a woman just doesn’t notice them. Depending on their body type, “it’s reasonable for a woman to make it to 30 weeks without looking pregnant,” Cackovic says.
Weight changes. If a woman is overweight or their size often goes up and down, they might not notice the extra baby weight. If they’re obese, Cackovic says, they may not “have the physical feelings of being pregnant” that non-obese women feel.
Period problems. A woman can have irregular periods because of stress, some medications (like birth control pills or drugs for epilepsy), obesity, or health problems like polycystic ovary syndrome (PCOS), uncontrolled diabetes, or an eating disorder. So when their period is a no-show, their first thought may not be pregnancy.
They can’t feel the baby move. Usually a mom-to-be will start to feel their baby kicking or rolling between 18 to 20 weeks of pregnancy. But if the placenta happens to be in the front of their uterus, they may not feel those movements, Cackovic says.
Research suggests a well-adjusted woman can have a denied pregnancy and still go on to be a good mother, especially if they’re able to come to grips with the fact that they’re going to have a baby, Cackovic says. For example, some women understand and accept it when they see an ultrasound image of their child. But doctors usually recommend a mental health evaluation to figure out what caused them to deny their pregnancy. It’s also an important step to prevent child abuse and neglect, which are more common after denied pregnancies than normal ones.