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Study looks at the impact of fetal gender on the risk of preterm birth

Women pregnant with a boy are at higher risk for preterm delivery

In a study to be presented on Feb. 7 in an oral concurrent session at 8 a.m. PST, at the Society for Maternal-Fetal Medicine’s annual meeting, The Pregnancy Meeting™, in San Diego, researchers will report on the impact of fetal gender on the risk of and neonatal outcome.

Preterm birth, a delivery before 37 weeks of gestation, is one of the most serious obstetric complications affecting around 15 million pregnancies worldwide with more than one million newborn deaths each year due to complications of prematurity. So far, the underlying causes for preterm birth are still largely unknown.

Preterm birth can either occur spontaneously or can be induced for medical reasons. There are various risk factors for preterm birth, of which a previous preterm birth is one of the most important. The gender of the unborn baby also seems to play a role in the process of being born prematurely.

The study, titled Impact of Fetal Gender on the Risk of Preterm, a Dutch nationwide study, looked at 1,947,266 singleton births by Caucasian women between 1999 and 2010 with a fetus alive at the onset of labor. Cases with congenital anomalies or unknown fetal gender were excluded. The relative risk ratios for gender per week of gestation were assessed as well as gender related risk on adverse neonatal outcomes. These outcomes were perinatal mortality and a composite of neonatal morbidity (defined as neonatal intensive care admission, sepsis, meconium aspiration, necrotizing enterocolitis, respiratory distress syndrome or intraventricular hemorrhage).

The study concluded that male fetuses were at increased risk of spontaneous preterm birth as well as preterm premature rupture of membranes. There were no significant differences between male and female fetuses born at comparable gestational ages regarding neonatal mortality; however, males were at significantly increased risk of composite neonatal morbidity compared to females from 29 weeks onward with a peak at 37-38 weeks. So, if a boy and girl are born with comparable gestational ages, the boy is more at risk of becoming seriously ill than the girl.

“This study provides important insight into the differences in risk factors based on gender,” explained Myrthe Peelen, M.D. who is one of the researchers of the study and is also with the Academic Medical Center in Amsterdam. “Patients with a history of preterm birth should be monitored, particularly if they’re having boys now after a preterm birth of a girl,” added Peelen.

Source

Abstract 80: Impact of Fetal Gender on the Risk of Preterm Birth

Authors: Myrthe Peelen1, Brenda Kazemier1, Anita Ravelli1, Christianne de Groot2, Petra Hajenius1, Ben Mol3, Marjolein Kok1 1Academic Medical Center, Amsterdam, Netherlands, 2VU Medical Center, Department of Obstetrics and Gynaecology, Amsterdam, Netherlands, 3University of Adelaide, The Robinson Institute, School of Paediatrics and Reproductive Health, Adelaide, SA, Australia

Objective: To study the influence of fetal gender on preterm birth and neonatal outcome in Caucasian women.

Study Design: We performed a national cohort study using data collected in the Netherlands Perinatal Registry. The study population comprised 1,947,266 singleton births (25+0-42+6 weeks) from Caucasian women between 1999 and 2010 with a fetus alive at the onset of labour. Cases with congenital anomalies or unknown fetal gender were excluded. The relative risk ratios for gender per week of gestation were assessed as well as gender related risk on adverse neonatal outcomes. These outcomes were perinatal mortality and a composite of neonatal morbidity (defined as neonatal intensive care admission, sepsis, meconium aspiration, necrotizing enterocolitis, respiratory distress syndrome or intraventricular haemorrhage). Onset of labor was categorized in spontaneous onset with intact membranes, prelabor rupture of membranes (PROM) and induction of labor/elective caesarean section. We used a moving average technique covering 3 weeks per measurement to correct for possible fluctuations due to the small number of events.

Results: Male fetuses were at increased risk of spontaneous preterm birth with intact membranes compared to a female fetus with a peak between 28 and 31 weeks (RR 1.5 for male to female; 95% CI 1.3-1.7). In addition, male fetuses were at increased risk of PPROM between 26 and 37 weeks (RR 1.2; 95 CI 1.16-1.23). No gender effect was seen for medically indicated preterm birth. There were no significant differences between male and female fetuses born at comparable gestational ages regarding neonatal mortality. However, males were at significantly increased risk of composite neonatal morbidity compared to females from 29 weeks onwards with a peak at 37-38 weeks (RR 1.4; 95% CI 1.2-1.5).

Conclusion: Male fetal gender is an important risk factor for spontaneous preterm birth, both for intact membranes and for PPROM. In addition, males are at increased risk of neonatal morbidity mainly in the term period.

Society for Maternal-Fetal Medicine