What should be investigated if a pregnancy test is initially positive, followed by a negative test one week later, and the menstrual period is now late?

From the Guidelines

If a pregnancy test is positive and then negative a week later with a delayed period, this situation should be investigated by a healthcare provider as it could indicate a chemical pregnancy or early miscarriage. Contact your doctor or gynecologist promptly for evaluation, which will likely include blood tests to measure human chorionic gonadotropin (hCG) levels and possibly an ultrasound, as recommended by the most recent study 1. These tests can determine if there was a pregnancy that ended naturally or if there's another explanation for the conflicting results. Chemical pregnancies occur when fertilization happens but the pregnancy doesn't progress, often due to chromosomal abnormalities. Other possibilities include testing errors, ectopic pregnancy (which requires immediate medical attention), or hormonal fluctuations causing both the positive test and delayed period. While many chemical pregnancies resolve without complications, medical assessment is important to rule out serious conditions and provide appropriate care, as highlighted in the study 1. Most women can try to conceive again after one normal menstrual cycle following this experience. Key considerations in the evaluation include:

• The sensitivity of pregnancy tests and the potential for false negatives or positives, as discussed in 1
• The importance of ultrasound in diagnosing pregnancy of unknown location (PUL) and early pregnancy loss (EPL), as outlined in 1 and 1
• The need for follow-up care and potential further testing to confirm the diagnosis and rule out complications, as recommended in 1 It is essential to prioritize the patient's health and well-being, considering the potential risks and complications associated with early pregnancy loss and the importance of timely medical evaluation and care.

From the Research

Possible Causes of Positive then Negative Pregnancy Test

• A positive pregnancy test followed by a negative test a week later, along with a late period, can be caused by several factors, including:
  • Early miscarriage or chemical pregnancy 2
  • Ectopic pregnancy 3, 4
  • Molar pregnancy 5
  • Incorrect test results due to low beta-hCG levels 3, 4

Investigation of Possible Causes

• If a pregnancy test is positive and then negative a week later, with a late period, the following should be investigated:
  • Beta-hCG levels to determine if they are rising or falling 3, 2, 4
  • Pelvic ultrasound to check for an intrauterine pregnancy or ectopic pregnancy 3, 4, 6
  • Serum progesterone levels to help differentiate between normal and abnormal pregnancies 2
  • Transvaginal ultrasound to evaluate the presence of a gestational sac or embryonic structures 3, 4, 6

Importance of Ultrasound and Beta-hCG Levels

• Ultrasound and beta-hCG levels are crucial in diagnosing and managing early pregnancy complications 3, 4, 6
• A combination of ultrasound and beta-hCG levels can help identify patients at risk of ectopic pregnancy or other complications 4, 6
• Pelvic ultrasound performed by emergency physicians can be used to rule out ectopic pregnancy and make an accurate diagnosis in most patients with complicated first-trimester pregnancies 6