Difficulty getting pregnant after a previous successful pregnancy is called secondary infertility, and it is surprisingly common. About 1 in 5 couples in the U.S. struggle to conceive after a year of trying, and many of them already have at least one child. The fact that you’ve been pregnant before doesn’t guarantee it will happen easily again, because several things in your body (and your partner’s body) can change between pregnancies.
Your Eggs Have Changed Since Last Time
Even a gap of two or three years between pregnancies can make a measurable difference in egg quality and quantity. Fertility drops noticeably after age 35 and becomes steep after 40, with natural conception nearly impossible for most women by 45. This decline isn’t just about having fewer eggs. The eggs that remain are more likely to carry chromosomal errors, which can prevent implantation or lead to early miscarriage. Chromosomal abnormalities affect roughly 2% of pregnancies in a woman’s twenties but jump to about 30% in her forties.
If your first pregnancy happened at 30 and you’re now trying at 34 or 35, you may be crossing a biological threshold you didn’t face before. This doesn’t mean pregnancy is impossible, but it helps explain why something that happened naturally the first time now feels stalled.
A Previous C-Section Can Interfere
If your first baby was delivered by cesarean section, the scar left on your uterus may be part of the problem. One of the most common complications is a defect in the scar called an isthmocele, where the tissue doesn’t heal evenly. This creates a small pocket in the uterine wall that can fill with fluid. That fluid buildup can interfere with a fertilized egg trying to implant, and it can also cause spotting between periods, heavier menstrual bleeding, and pelvic pain.
The good news is that this is treatable. In one study of women with secondary infertility linked to a C-section scar defect, 80% of those who had the defect surgically repaired became pregnant within two years. Even among women who had already failed multiple rounds of IVF before the repair, about 43% conceived afterward. If you had a cesarean delivery and are now struggling to conceive, this is worth discussing with your doctor, especially if your periods have changed since the surgery.
Breastfeeding Can Still Suppress Ovulation
If you’re breastfeeding your current child, your body may not be ovulating yet. Nursing triggers elevated levels of prolactin, the hormone responsible for milk production. High prolactin disrupts the chain of hormonal signals your brain needs to send in order to trigger ovulation each month. Specifically, it suppresses the pulsing release of hormones that drive your menstrual cycle forward, which can leave you without a period entirely or with irregular cycles that make conception unlikely.
This effect is strongest when you’re nursing frequently, including at night. As you reduce feeding sessions or wean, prolactin levels drop and ovulation typically returns. But the timeline varies widely. Some women start ovulating again within a few months postpartum even while breastfeeding, while others remain anovulatory until they stop completely. If your period hasn’t returned or is irregular and you’re still nursing, that’s likely the primary factor.
Your Partner’s Fertility Matters Too
It’s easy to assume the issue is on your side since you’re the one trying to get pregnant, but male factors contribute to roughly half of all infertility cases. Your partner’s sperm quality can change meaningfully over time. Men over 40 show higher rates of DNA damage in their sperm compared to younger men, along with reduced semen volume and lower motility. But age isn’t the only variable. Weight gain, new medications, increased alcohol use, smoking, exposure to environmental chemicals, and even infections can all reduce sperm quality between one pregnancy and the next.
A semen analysis is one of the simplest and least invasive fertility tests available, yet it’s often overlooked when a couple already has a child together. If your partner’s health or lifestyle has changed since your last pregnancy, testing his sperm early in the process can save months of focusing on the wrong problem.
Weight and Lifestyle Shifts After Pregnancy
Retaining weight after your first pregnancy can directly affect ovulation. A BMI of 30 or higher reduces fertility by disrupting the hormonal signals that trigger egg release each month, and the higher the BMI, the longer it typically takes to conceive. This isn’t about appearance or willpower. Excess body fat actively changes hormone levels in ways that can prevent ovulation from happening reliably.
Other postpartum lifestyle changes play a role too. Sleep deprivation, higher stress levels, and less frequent sex (a practical reality with a child in the house) all reduce your chances in a given cycle. Couples trying for a second child often have sex less often than they did while trying for their first, which narrows the window of opportunity each month.
New Conditions That Develop Over Time
Some conditions that affect fertility develop or worsen between pregnancies. Endometriosis, for example, is progressive and can cause more damage to the reproductive organs over time, even if it wasn’t a factor during your first conception. Thyroid disorders, polycystic ovary syndrome (PCOS), and uterine fibroids can also emerge or become more significant after a first pregnancy. Pelvic infections, sometimes related to delivery or postpartum complications, can cause scarring in the fallopian tubes that blocks the egg from reaching the uterus.
These conditions aren’t always obvious. You might have regular periods and feel perfectly healthy but still have a structural or hormonal issue silently interfering with conception.
When to Get Evaluated
The standard recommendation depends on your age. If you’re under 35, seek evaluation after 12 months of trying without success. If you’re 35 or older, that timeline shortens to 6 months. If you’re over 40, earlier and more immediate evaluation is warranted. These aren’t arbitrary cutoffs. They reflect how quickly fertility declines with age and how much time-sensitive treatment options can matter.
A typical workup will check your ovarian reserve (how many eggs you have left), confirm that your fallopian tubes are open, look at your uterine lining and structure via ultrasound, and test your partner’s sperm. If you had a C-section, your doctor should specifically examine the scar area for defects. Blood tests will check hormone levels including thyroid function and prolactin. Most of these tests are straightforward and can be completed within a single menstrual cycle, giving you a much clearer picture of what’s actually going on rather than continuing to wonder month after month.