Previous studies have shown that women living with overweight or obesity face more difficulties getting pregnant and are at higher risk of pregnancy related complications when compared to women with normal weight. Recent studies have reported that, among women presenting with overweight or obesity and Polycystic Ovary Syndrome (PCOS, a hormonal condition affecting about one in every ten women), weight loss increased the chance of getting pregnant.
This study will look at all women presenting with overweight and obesity, irrespective of whether they have PCOS or not. We will use previously collected electronic health care records to investigate whether women who lost weight were more likely to get pregnant in the following three years and more likely to get pregnant faster, than women whose weight was in the stable and high end or increased in that period.
Among women with a record of pregnancy, we will also look at whether weight loss in the two years before pregnancy reduced the rate of pregnancy-related complications and adverse child outcomes, compared to women who maintained or increased body weight in that period.
The findings will improve the evidence available to health care providers when discussing family planning strategies with women who present with overweight or obesity.
In a recent study using data from the Clinical Practice Research Datalink (CPRD) and Hospital Episode Statistics (HES) we have shown that, among women living with Polycystic Ovary Syndrome (PCOS) and overweight or obesity, the chance of conception is increased with weight loss compared to high stable weight(1).
In this cohort study, we aim to examine the association between weight loss and reproductive outcomes among women with overweight or obesity, irrespective of their PCOS status. Specifically, we will estimate the association between different degrees of weight loss (3-9.9% and 10-25% of body weight) and time to first occurrence of pregnancy during follow-up, compared to women who maintained (+/-3%) or increased their body weight (>3%). In women achieving pregnancy, we also plan to estimate whether different degrees of weight loss are associated with fewer pregnancy related complications and adverse offspring outcomes. The primary analysis will be the comparison of time to pregnancy between women who experienced 10-25% weight loss and women who maintained their body weight during a 2-year baseline period.
We will include women (age 18-40 years) with a Body Mass Index (BMI) record from 01 January 2000 and a subsequent BMI record 12-24 months later. Exposure will be assigned based on the observed weight change in that period. For all exposure groups, follow-up will start 24 months after the first BMI was recorded. We will use Cox proportional hazards regression to compare time to pregnancy. We will use logistic regression to compare pregnancy related complications and adverse birth outcomes. Exposures, outcomes, and covariates will be ascertained from CPRD data linked to the pregnancy register, Hospital Episode Statistics Admitted Patient Care, and patient and practice level deprivation.
The outputs will improve the evidence available to health care providers when discussing family planning strategies with women presenting with overweight or obesity.
Primary outcome:
Time to first record of pregnancy
Secondary outcomes:
In subpopulation of women who achieved pregnancy:
Live birth; Miscarriage; Stillbirth; Gestational diabetes; Pre-eclampsia and other hypertensive disorders of pregnancy; Preterm birth; birth weight; small for gestational age/intrauterine growth restriction (SGA/IGUR); large for gestational age (LGA)); Shoulder dystocia; Congenital anomalies (any); Caesarean section (elective); Caesarean section (emergency)
Please note that for all conditions in this section, the condition is defined as present by the presence of a code in CPRD and assumed to be absent by the absence of a code. The exception to this is birth weight and gestational age which will be set to missing when they are absent in the presence of a recorded live birth.
For detailed definitions including specific International Classification of Disease (ICD) codes, please refer to Appendix A, which lists the code definitions used to define inclusion/exclusion criteria, exposures, covariates, and outcomes. Code lists were reviewed by clinician Dr Eva Winning Lehmann.
Maximiliane Verfürden - Chief Investigator - Novo Nordisk A/S
Maximiliane Verfürden - Corresponding Applicant - Novo Nordisk A/S
Adam Balen - Collaborator - Leeds Teaching Hospitals NHS Trust
Eva Winning Lehmann - Collaborator - Novo Nordisk A/S
Kasper Matthiessen - Collaborator - Novo Nordisk A/S
SHWETA UPPAL - Collaborator - Novo Nordisk A/S
Volker Schnecke - Collaborator - Novo Nordisk A/S
HES Admitted Patient Care;Patient Level Index of Multiple Deprivation;Practice Level Index of Multiple Deprivation;CPRD Aurum Mother-Baby Link;CPRD Aurum Pregnancy Register