Few life stages reshape sleep as thoroughly, and as quickly, as pregnancy. Within the span of nine months, a woman’s body moves through several distinct waves of hormonal change, each with its own effect on how she sleeps, and the experience can shift dramatically from one trimester to the next. Understanding what is driving these changes, and why some women seem to sail through pregnancy sleep-wise while others struggle from the first missed period onward, involves both the shared biology of pregnancy itself and individual genetic variation layered on top of it.
Here we walk through what typically happens to sleep during each trimester and looks at some of the genetic factors that may help explain why the experience varies so much from person to person.
First Trimester: Fatigue and Fragmented Sleep
Exhaustion is one of the earliest and most universally reported symptoms of early pregnancy, and it has a clear hormonal driver. Progesterone rises sharply in the first trimester, and while this hormone has a sedative-like effect that can make daytime fatigue intense, it does not necessarily translate into deeper or more continuous nighttime sleep. Many women in early pregnancy report needing more total sleep while simultaneously experiencing more fragmented, lighter sleep at night, often compounded by increased urination frequency as the growing uterus places pressure on the bladder even at this early stage.
Nausea, another hallmark of early pregnancy for many women, adds its own layer of sleep disruption, since discomfort in the evening or during nighttime waking can make falling back asleep more difficult than it would otherwise be.
Second Trimester: A Relative Reprieve for Many
For a lot of women, the second trimester brings some improvement, as early pregnancy nausea typically eases and the physical size of the growing pregnancy has not yet reached the point of causing significant discomfort. Progesterone levels remain elevated, and some women describe this period as the most restful stretch of the entire pregnancy. This is not universal, and some women continue to experience disrupted sleep throughout, but as a general pattern, the middle trimester tends to offer more stability than the first or third.
Restless Legs Syndrome and Genetic Links
Restless legs syndrome, an uncomfortable urge to move the legs that tends to worsen in the evening, becomes more common during pregnancy, particularly in the second and third trimesters, and research has identified a genetic component that applies both inside and outside of pregnancy. Variants in genes such as BTBD9 and MEIS1 have been associated in research with increased likelihood of restless legs syndrome generally, and pregnancy itself, along with any related iron or folate changes, appears to interact with this underlying genetic tendency to bring symptoms to the surface for some women who may not have noticed them as strongly before becoming pregnant.
Third Trimester: Physical Discomfort Takes the Lead
By the third trimester, physical factors tend to overtake hormonal ones as the primary driver of disrupted sleep. A growing abdomen makes finding a comfortable position increasingly difficult, back pain becomes more common, and pressure on the bladder returns with force, often leading to multiple nighttime bathroom trips. Braxton Hicks contractions and fetal movement, particularly active periods late at night, add further disruption for many women during this final stretch.
Sleep-disordered breathing, including snoring and, in some cases, obstructive sleep apnea, also becomes more common in the third trimester, related to weight gain, hormonal effects on airway tissue, and increased blood volume. This is a symptom worth mentioning to a healthcare provider directly rather than dismissing as an ordinary part of pregnancy discomfort, since it can have implications for both maternal and fetal health that a provider is best positioned to evaluate.
Melatonin and Serotonin Shifts
Pregnancy hormones also interact with the same neurochemical pathways involved in sleep regulation more broadly, including serotonin and melatonin. Some research suggests that melatonin levels actually rise over the course of pregnancy, potentially playing a protective role related to fetal development, though this does not necessarily translate into improved subjective sleep quality given everything else happening physically during this time. Genetic variants affecting an individual’s baseline serotonin and melatonin pathway function, the kind reflected in a Serotonin and Melatonin Pathway report, may still play a role in how a given woman experiences these shifts relative to another woman with a different genetic profile.
Why Genetics Helps Explain Individual Differences
Given how much of pregnancy sleep disruption is driven by shared physical and hormonal changes, it is fair to ask what role genetics really plays here. The honest answer is that genetics does not override these universal pregnancy effects, but it does appear to modulate how intensely an individual experiences certain symptoms, restless legs syndrome being one of the clearer examples, and general sleep fragmentation tendencies being another. A woman who already carries variants associated with lighter, more easily disrupted sleep outside of pregnancy may find that pregnancy amplifies an existing tendency rather than introducing an entirely new one.
What to Discuss With Your Healthcare Provider
Sleep during pregnancy touches on maternal and fetal health in ways that make this a topic best navigated together with your obstetric care provider rather than through general information alone. This is especially true for anything involving supplements, medications, or significant sleep-disordered breathing symptoms, since safety considerations during pregnancy differ meaningfully from general adult guidance, and what is appropriate can vary by trimester and individual health history. If you are curious about genetic tendencies that might be relevant to your experience, such as a family history of restless legs syndrome or known melatonin pathway variants, reviewing relevant reports through a platform like SelfDecode before your prenatal appointment can give you useful, specific context to bring into that conversation. Any supplement, including something like Performance Lab Sleep, should only be considered during pregnancy with your provider’s explicit guidance, since ingredient safety and appropriate use can differ significantly during this time.
Frequently Asked Questions
Is it normal to have vivid or unusual dreams during pregnancy?
Yes, many women report more vivid or memorable dreaming during pregnancy, which researchers generally attribute to hormonal shifts and more frequent awakenings that make it easier to recall dreams upon waking.
Does restless legs syndrome during pregnancy usually go away after birth?
For many women it improves significantly or resolves after delivery, though this varies, and anyone experiencing ongoing symptoms after pregnancy should discuss it with a healthcare provider.
Can a family history of sleep problems predict how pregnancy will affect my sleep?
It may offer some insight, since genetic tendencies toward certain sleep patterns can persist across life stages, but pregnancy introduces enough unique physical and hormonal factors that family history alone cannot reliably predict your individual experience.
Should I mention snoring that started during pregnancy to my doctor even if I feel otherwise fine?
Yes, new snoring or breathing changes during pregnancy are worth mentioning at a prenatal visit, since your provider can assess whether further evaluation for sleep-disordered breathing is appropriate.