First-Trimester Anaemia as an Independent Predictor of Preterm Birth: A Retrospective Cohort Study of 3,683 Singleton Pregnancies at a Tertiary Maternity Centre in Latvia

Every pregnancy is a race against time, a delicate biological countdown where the goal is to carry a baby to full term, defined as thirty-seven weeks or more. When birth happens before this milestone, the event is known as preterm birth, a condition that remains a leading cause of infant mortality and long-term developmental challenges worldwide. While modern medicine has made incredible strides in caring for premature infants, the rate at which these early births occur has not dropped significantly in decades, leaving scientists searching for the hidden triggers that cause a pregnancy to end too soon. One of the most common health issues affecting pregnant women is anaemia, a condition where the blood lacks enough healthy red cells to carry oxygen effectively to the body's tissues. In the context of pregnancy, doctors look at a specific protein called haemoglobin, which acts as the vehicle for that oxygen. If a woman's haemoglobin level falls below a certain threshold during the first three months of pregnancy, she is considered anaemic. The question researchers have long debated is whether this early drop in oxygen-carrying capacity is merely a side effect of pregnancy or a direct cause that pushes the body toward an early delivery.

A team of researchers at Riga Stradiņš University in Latvia decided to investigate this link by looking at thousands of real-world pregnancies. They conducted a retrospective study, which means they gathered and analyzed medical records from the past rather than following women forward in time. The team focused on 3,683 women who had given birth at the Riga Maternity Hospital, the largest obstetric center in the country, during the year 2024. They specifically looked for women who had a blood test measuring their haemoglobin levels during the first trimester, the first three months of pregnancy. The researchers divided these women into two groups: those whose haemoglobin levels were below 11 grams per deciliter, marking them as anaemic, and those whose levels were at or above that number, marking them as non-anaemic. The primary goal was to see if the women in the anaemic group were more likely to deliver their babies before the thirty-seven-week mark compared to the non-anaemic group.

The results of this large-scale review revealed a stark difference between the two groups. Among the women who were anaemic in their first trimester, nearly one in four, or 22.5 percent, gave birth prematurely. In contrast, among the women who were not anaemic, only about 6.4 percent experienced a preterm birth. This gap was so significant that the researchers could not attribute it to chance. Even after they adjusted their calculations to account for other factors that might influence birth timing, such as the mother's age and whether she had given birth before, the link remained strong. The study found that a woman with anaemia in her first trimester had more than double the odds of delivering her baby early compared to a woman with normal haemoglobin levels. This suggests that the condition is an independent predictor, meaning it carries its own risk regardless of other circumstances.

The researchers also looked deeper into the severity of the condition to see if there was a pattern. They found a clear dose-response relationship, a concept where the worse the initial problem, the worse the outcome tends to be. Women with mild anaemia had a preterm birth rate of 20.2 percent, while those with moderate anaemia saw that rate climb to 25.8 percent. This gradient provided strong evidence that the body's oxygen levels are directly tied to the timing of birth. Furthermore, the study noted that babies born to anaemic mothers were significantly more likely to be admitted to the neonatal intensive care unit, a specialized ward for sick or premature newborns. This outcome aligns with the higher rate of early births, as these infants often require extra medical support simply because they arrived before their bodies were fully ready.

The study offers a plausible biological explanation for why this happens. When haemoglobin is low, the uterus and the placenta receive less oxygen. This state of low oxygen can trigger a cascade of chemical signals in the body that prepare the cervix to open and the uterus to contract, essentially starting the labor process earlier than intended. The researchers noted that iron deficiency, the most common cause of anaemia, can also increase inflammation and oxidative stress in the body, which are known to play a role in triggering early labor. While the study was limited by its retrospective nature, meaning it could not prove cause and effect with absolute certainty, the consistency of the data and the biological logic make a compelling case. The authors emphasized that this is the first time such a large-scale estimate has been published for Latvia, filling a gap in medical knowledge for Northern and Eastern Europe.

Ultimately, the findings point toward a practical solution for improving birth outcomes. Because the study identified a clear link between early anaemia and early birth, it supports the idea that checking haemoglobin levels at the very start of pregnancy is crucial. More importantly, it suggests that treating anaemia aggressively and immediately upon diagnosis, rather than waiting, could be a modifiable way to reduce the number of preterm births. By ensuring that a pregnant woman's blood can carry enough oxygen from the very beginning, healthcare providers may be able to help the pregnancy reach its full, healthy term. This research adds a vital piece to the global puzzle of maternal health, showing that a simple blood test in the first trimester could hold the key to preventing one of the most serious complications of childbirth.