If either you or your partner was a “big” baby, you might have an increased likelihood of giving birth to a big baby yourself, a brand new study by researchers from the University of Bergen, Norway, shows. This might potentially improve prenatal care and interventions by identifying pregnancies at higher risk of obstetric complications during labour and delivery.

The study from Norway explored the connection between parent’s own birthweight and the chance of getting an enormous baby, and to what extent maternal body-mass index (kg/m2) (BMI) in early pregnancy also contributes to this risk.

Exploiting the Medical Birth Registry of Norway, the oldest on the planet, the researchers combined information on parent’s own birthweight to pregnancies they parented. Parents and offspring born during a 50-year period were included, leading to information on 647,957 births with available information on each parents’ birthweight. The study included only singleton newborns carried to term.

Macrosomia, the scientific word for a “big” baby, was defined as a newborn weighing 4500 grams or more, and was more common among the many offspring generation, with 4.0% in comparison with 3.2% among the many parent generation.

The danger of giving birth to a macrosomic infant was much higher if the parents themselves were big at birth. In comparison with each parents weighing below 4500 grams, greater than 6-fold increase if each had been big! Even with just one parent being macrosomic, the chance was greater than double if the daddy had been macrosomic (relative risk 2.2) and greater than 3 times if the mother only had been macrosomic (3.4).

The researchers also explored whether maternal BMI in the beginning of pregnancy contributed to the chance of birthing a macrosomic baby. The proportion of macrosomic newborns varied substantially by maternal BMI. Among the many group where each parents had been born macrosomic, the proportion of babies also being macrosomic ranged from 17% when born to women who were normal weight before pregnancy (BMI 18.5-24.9), to 31% amongst women who was obese (BMI of 30 or more).

– Birthing a baby who’s macrosomic comes with an increased risk of obstetric complications, researcher Cathrine Ebbing says.

– One could speculate that through evolutionary mechanisms if the parent was big, this might protect the mother and child against macrosomia-related complications. Nonetheless, we didn’t find that this risk was substantially diminished if the parents had also been born macrosomic, Ebbing says.

This study adds one other piece to the puzzle regarding the generational effect of birth outcomes, in addition to the contributing effect of maternal BMI. The brand new insight may result in recent opportunities to detect pregnancies vulnerable to giving birth to a macrosomic child, and thus result in more targeted prenatal care and interventions. Nonetheless, further studies are required to look at the clinical usefulness of those predictions.